CA1337440C - Detector and localizer for low energy radiation emissions - Google Patents

Abstract

A detector particularly suited for use in immuno-guided surgery capable of detecting very faint gamma emissions and thereby localizing cancerous tumor. The detector employs a hand manipular probe within which is contained a crystal such as cadmium telluride which is secured in a light tight compressively restrained environment employing compliant yet conductive components which also serve to exhibit varying accoustical impedance to impinging microphonic effects. A preamplifier is incorporated within the probe device itself which employs an integrator stage front end combining a field effect transistor and bipolar device with a very small feedback capacitance of less than one picofarad. A bootstrap technique is utilized to enhance the amplification of the bipolar amplification stage.
Pulse related signals outputted from the device are normalized and compared to produce pulse data which are analyzed. In one mode of operation a siren effect is employed to guide the surgeon towards emission sources.

Description

DETECTOI~ l~ND LOCALI7,ER
FOR LOl~7 ENERGY R~DIATION EMISSIONS

~is application is a divisional of application Serial No. 561,451 filed M~rcn 15, 1988.
Back~round The detection and treatment of cancerous tissue has been the subject of intense investigation for many years. One among the many approaches to its detection has concerned the identirication of tumor specific antigens.
Where these antigens can be identi~ied, radionucleid labeled antibodies have 5 been employed which tend to collect at tumor sites. ~Yhen so concentrated, somewhat elaborate radiation dctection equipment then is employed to record, for example, by imaging tlle concentrations of the emissive substances and thus to locate neoplastic tissue. Important advances in this procedure have been evidenced through the use of monoclonal antibodies or l0 fragments thereof with a variety of radionucleides. Typical techniques for carrying out imaging of tllese antibodies have involved, for example, tomographic scanning, irnmunoscintigraphy and the like. The particular choice Or radionucleid for labeling antibodies is dependent upon its nuclear properties, the physcial halr life, the detection instrument capabilities, the 15 pharmacokinetics of the radiolabeled antibody, and the degree of difficulty of tile labeling procedure. The most widely used Or these radionucleides in nuclear medicine imaging include technetium, Tc99m, iodine 1l25, 1131, and indium, INlll. Of the above, for localizing tumors of the gastro-intestinal tract, the radionucleid ll3l is used as tlle marlcer or label in conjunction 20 Witll imaging gamma cameras and the like which are relatively large and elaborate devices positioned nbove the patient during the imaging process.
In spite of its somewhnt extensive utilization, Il3l is not an ideal rndionucleid for use in diagnostic medicine. The high energy gamma-photon emitted from Il3l is poorly detected by classic ~amma camera and like 25 instrumentation. ln addition, the particular admissions of emissions deliver a high radiation dose to the patient. ~urther, the imaging definition of these external imaging devices llave not been satisfactory for many reasons.
As tumor sites becorne smaller, the radionucleid concentrations thereat ~ill tend to b-e lost, ~rom an imaging standpoint, in the background or blood pool 30 radiation necessarily present in the patient.

- I 3374~

Over the recent past, a surgical procedure has been developed concerning the difrerentintioll nnd removal of such neoplastic tissue tllrough the use of rnuch lower energy gamma emission levels for example, I125 (27-35 kev). While SUCIl a radiolabel cannot be employed with conventional 5 external imagillg or scallrlillg devices, it llas been found that when employed witll a probe type detcction structure, a highly effective differentiation techniquc can be evolvec3. More particularly, the longer llalf life of this type of radiolabel coupled with a surgical methodology involving the waiting of appropriate intervals from the time of introduction of the radiolabelled 10 antibody to the patient to tlle tirne of surgery, can evolve a highly accurate dif~erentiation of cancerous turnor. This improved method of localization, differelltiation and removal of cancerous tumor involves a surgical procedure wherein the patient suspected of containing neoplastic tissue is administered an effective alnount of a labeled antibody specific for 15 neopl~stic tissue and labeled with a radioactive isotope as above-noted exhibiting photon ernissions of specific energy levels. Next, the surgical procedure is delnyed for a time interval following such administration for permitting the labeled antibody to preferentially concentrate in any neoplnstic tissue present in the patient so as to increase the ratio of photon 20 ernissions from tlle neoplastic tissue to the background photon emissions.
Thereafter, an operative field of the patient is surgically accessed and tissue within the operative field to be examined for neoplastic tissue has the bncl~ground photon emission count determined. Once the bacl~ground photon emission count for the tissue within the operative field has been determined, 25 this hand-held probe is manually positioned within the operative field adjacent tissue suspected of being neoplastic. Readouts then can be achieved from probe counting for differentiation. In the above regard, reference is made to the following technical publications:

3~
I. "CEA-Directed Second-Lool~ Surgery in the Asymptomatic Patient after Primary I~esection of Colorectal Carcinoma", E.W.
Martin, Jr., MD, J. P. Minton, MD, PhD, Larry C. Carey, MD. I~nnals of Sur~ery 202:1 (Sept. 1985 301-12.
II. "Intraoperative Probe-Directed Im-munodetection Using a Monoclonal Antibody", P.J. O'Dwyer, MD, C.M.

Mojzsik, RN MS, G.H. Hinkle, RPh, MS, M.
Rousseau, J. Olsen, MD, S.E. Tuttle, MD, R.F.
Barth, PhD, MO, Thurston, PhD, D.P. McCabe, MD, W.B. Farrar, MD, E.W. Martin, Jr., MD.
Archives of Surqery, 121 (Dec. 1986) 1321-1394.
III. "Intraoperative Radioimmunodetection of Colorectal Tumors with a Hand-Held Radiation Detector", D.T. Martin, MD, G.H. Hinkle, MS
RPh, S. Tuttle, MD, J. Olsen, MD, H. Abdel-Nabi, MD, D. Houchens, PhD, M. Thurston, PhD, E.W. Martin, Jr., MD. American Journal of surqerY~ 150:6 (Dec. 1985) 672-75.
I~. "Portable Gamma Probe for Radioimmune Localization of Experimental Colon Tumor Xenografts", D.R. Aitken, MD, M.O. Thurston, PhD, G.H. Hinkle, MS RPh, D.T. Martin, MD, D.E. Haagensen, Jr., MD, PhD, D. Houchens, PhD, S.E. Tuttle, MD, E.W. Martin, Jr., MD, Journal of Surqical Research, 36:5 (1984) 480-489.
V. "Radioimmunoguided Surgery: Intraoperative Use of Monoclonal Antibody 17-lA in Colorectal Cancer'l, E.W. Martin, Jr., MD, S.E. Tuttle, MD, M. Rousseau, C.M. Mojzisik, RN MS, P.J.
O'Dwyer, MD, G.H. Hinkle, MS RPh, E.A. Miller, R.A. Goodwin, O.A. Oredipe, MA, R.F. Barth, MD, J.O. Olsen, MD, D. Houchens, PhD. S.D.
Jewell, MS, D.M. Bucci, BS, D. Adams, Z.
Steplewski, M.O. Thurston, PhD, Hybridoma 5 Suppl 1 (lg86) S97-108.
The success of this highly effective differentiation and localization technique is predicated upon the availability of a probe-type detecting device capable of detecting extremely low amounts of radiation necessarily developed with the procedure. In this regard, low energy radionucleides are used such as I12s and the distribution of radiolabeled antibody with the nucleid is quite sparse so that background emissions can be minimized and the ratio of tumor-specific counts received to background counts can be maximized. Conventional radiation detection probe-type devices are 1 33744~
~- ineffective for this purposc. Generally, because a detection device is required for the probes whicll is capable of performing at room temperatures, n detection crystal such as cadmium telluride is employed.
The probe using such a crystal must be capable of detecting as little as a 5 single gamma ray emission WlliCh may, for example, create electron-hole pairs in the crystal of betwecn about 2,000 and 4,000 electrons. Considering that an ampere generates 6.25 x 1013 electrons per second, one may observe that extremely smnll currents must be detectable with such probe.
Ilowever, tlle probc system also must be capllble of discriminating such 10 currents from any of a wide variety of electrical disturbances, for example which may be occasioned from cosmic inputs, room temperature molecular generated noise and capflcitively induced noise developed from the mere mnnipulation of the probe itself. Whilc being capable of performing under these extreme criterin, the same probe further must be capable of 15 performing undcr the rcquiremetlts of the surgical theater. In tllis regard, it must be sterilizable and rugged enougll to withstand manipulation by the surgeon within tlle body cavity of the patient. Furtller, the system with whicll the probe is ernployed, must be capable of perceptively apprising the surgeon of when neoplastic tissue is being approached such that the device 2~ may be cmployed for the purpose of guiding the surgeon to the situs of cancer. I~inally, for sugrical use, tlle probe instrument must be small, so as to be effectively manipulated through surgical openings and tlle lilce. Such dimunitive size is not easily achieved under the above operational criteria.
This technique llas beell described as "radioimmuno-guided surgery", a 25 surgical approach developed by E:.W. Martin, Jr., MD, and M.O. Tllurston, E"lD.

Summary The present inventi~n is addressed to apparatus and system for 3~ detecting and locating sources of emitted radiation and, particularly, sources of gamma radiation. Detection is achieved under room temperature conditions using a crsytal SUCIl as cadmium telluride and with respect to very low energy emissions. To achieve the extreme sensitivity capabilties of the apparatus, an instrumentation approach has been developed in which 35 the somewhat fragile crystal is securely retained in isolation from externally induced incidents otherwise creating excessive noise. In this regard, micropllonic effects are minimized through employment of a sequence of materials exhibiting divergent acoustic impedances.
Capacitive effects occasioned by the most minute of inter-component movements are controlled to acceptable levels.
The probe instrument design incorporates a preamplifier with an integrator structure which resides in substantial adjacency with the crystal within the probe instrument and which achieves very substantial amplifying gain of relatively minute crystal derived charge signals. This sensitivity permits medical uses of the instrument, for example, in immuno-guided surgery where low energy gamma emissions are located to differentiate cancerous tumor. The system of the invention employs an audibly perceptible output in conjunction with a count rate analysis of detected emissions to guide the surgeon to tumor sites with a siren effect wherein the frequency of the audible output increase as the count rate increases and vice versa.
Broadly, the invention provides an apparatus for detecting and evaluating sources of gamma radiation having given energy levels including detector means for deriving induced charges in response to interactions of the radiation therewith to provide detector signals of given levels and exhibiting noise charac-teristics of given levels; noise averaging means responsive to the given noise characteristics for deriving a noise signal corresponding with an average level of the given noise characteristics levels; normalizing circuit means responsive to the detector signals and given noise characteristics and to a control input for adjusting the level of the noise charac-teristics and corresponding the detector signal given levels to provide composite signals of normalized values; comparator means responsive to the composite signals for comparing the amplitude thereof with presettable upper and lower threshold levels for providing pulse data outputs corresponding with the comparisons;
logic circuit means responsive to the pulse data outputs for deriving valid pulse signals; output means controllable for < _ 1 33~440 providing a valid pulse signal related perceptible output; and control means responsive to the noise averaging means noise signal for deriving the control input to the normalizing circuit means and to the valid pulse signals for controlling the output means.
A feature of the invention is to provide an apparatus for detecting and evaluating sources of gamma radiation having given energy levels. The apparatus includes a detector for deriving induced charges in 5a response to intcrnctiorl~ of rlldintion therewith to provide detector signals atgiven levcls nnd exhibi~irlg noise characteristics of given level. ~ noise averaging nctwor!~ is provided whicll is respollsive to the given noise characteristics for derivillg a noise signnl corresponding with an average 5 level of the given noise chnracteristics. /~ normali~ing circuit is provided which is responsive to tlle detector signals nnd given noise characteristics and to a control input for adjusting tlle level of the noise characteristics andcorresponding detector signal givcn levels to provide composite signals of normalized values. A cornparator arrangement responds to the composite 1() signal for comparing tlle alnplieude tllereof with presettable upper and lower tilresllold levels for providing pulse data outputs corresponding with the compnrisons. A logic circuit responds to the pulse data outputs for deriving valid pulse signals and an output is incorporated which is controllable for providing a valid pulse signal related perceptible output. Finally, a control 15 is included which is responsive to the noise averaging noise signul for deriving the control input to the normaliæing circuit and to valid pulse signals for controlling the output arrangement.
Otller objects of tlle invention will, in part, be obvious and will, in part, appear hereinnfter.
2~ Tlle invention, nccordh~gly, comprises the apparatus and systern possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure. For a fuller understanding of the nature and objects of the invention, reference should be llad to the following detailed description taken in connection with 25 the accompanying drawings.

Brief Description Or the Drawings Fig. 1 is a perspective view of the probe instrument and associated console representing tlle instrumentation system of the invention;
3(~ Fig. 2 is a side elevationnl view of the probe instrument shown in Fig. 1 with portions brol~en away to reveal internal structures;
Fig. 3 is an exploded view of one embodiment of the forward assemblage of the instrument of Fig. 2;
Fig. 4 is a sectional view of the forward portion o the instrument of 35 ~ig. 2;
Fig. 41~ is a sectional view of an alternate embodiment of the forward portion of the instrument ns described in conjunction with Fig. 4;

Fig. 5 is an electrical schematic diagram of a preamplifier incorporated within the instrument of Fig. 3;
Fig. 6 is a layout drawing of the component positioning on a circuit board implementing the circuit of Fig. 5;
Figs. 7A and 7B combine as labelled to form a block diagram of the functional components of the system of the invention;
Figs. 8A-8C combine as labelled to provide an electrical schematic diagram of the analog signal treatment components of the 10apparatus of the invention;
Fig. 9, which is on the same sheet of drawings as Fig.
8A, is an electrical schematic diagram of the volume control and audio amplification components of the apparatus of the invention;
Figs. lOA and lOB combine as labelled to provide an electrical schematic diagram of the digital components of the apparatus of the invention;
Fig. 11, which is on the same sheet of drawings as Fig.

4, is a side view of the probe instrument of Fig. 2 showing its emplo,vment with a sterile cover;
20Fig. 12, which is on the same sheet of drawings as Fig.
4, is a partial side view of the probe instrument of Fig. 2, showing its association with a check source insert;
Fig. 13, which is on the same sheet of drawings as Fig.
4, is a top view of the check source insert represented in Fig. 12i Fig. 14 is a flow chart showing the main program of ~he apparatus of the invention;
Fig. 15 is a flow chart showing an interrupt routine employed with the control features of the invention;
Fig. 16, which is on the same sheet of drawings as Fig.
301, is a schematic representation of a readout provided with the console shown in Fig. 1;
Fig. 17 is a flow chart showing a count rate determination carried out with the interrupt update routine of the control of the inventioni Fig. 18 is a flow chart showing the display update routine employed with the control features of the apparatus of the invention;
Fig. 19 is a flow chart showing the programming interface features of the control components of the apparatus of the invention;
Fig. 20 is a flow chart showing the self-diagnostic routine carried out by the control features of the invention;
Fig. 21 is a flow chart showing the technique for carrying out siren type audio outputs employed as part of the control features of the apparatus of the invention;
Fig. 22, which is on the same sheet of drawings as Fig.
1, is a schematic representation of a display which may occur at the readout of the console shown in Fig. l;
Fig. 23 is a flow chart showing the remote display update routine employed by the control features of the apparatus of the invention;
Fig. 24 is a flow chart showing the calibration routine carried out by the control features of the apparatus of the invention;
Fig. 25 is an exploded view of another embodiment of the forward assemblage of the instrument of Fig. 2; and Fig. 26 is a sectional view of the forward portion of the instrument embodiment represented in Fig. 25.
Detailed Description of the Invention Referring to Fig. 1, an embodiment of the instrument of the invention particularly designed for employment in the medical-surgical field is represented generally at 10. This instrument includes a hand-manipular probe represented generally at 12 which is coupled by a triaxial cable 14 to a console 16. The probe 12, which preferably is retained by the surgeon within a disposable polymeric sheath or cover is maneuvered about the region of surgical interest to locate tumerous tissue for resection. When used in conjunction with colonic surgery, for example, the probe 12 `_ 1 337440 is maneuvered through a surgical opening in the body cavity and essentially brought into contact with organs under study by the surgeon. When employed in a radioimmuno-guided mode, a loudspeaker or annunciator within the console 16 may be employed to provide a "siren" form of output which apprises the surgeon that the probe 12 is nearing a site of cancer. Thus, it is necessary that the device 12 be of convenient length and comfortable to grasp. The probe 12 is seen to include a window 18 located at the tip of an angularly oriented portion thereof 20. Portion 20 extends from a hand-grippable portion 22 at an angle of about 30 to facilitate itsmanueverability about the back or hidden side of organs.
Because the assemblage 10 is used in a surgical theater, the console 16 also is readily cleaned, having a smooth, one-piece touch sensitive polymeric surface 24 surmounting a relatively large LCD readout or display 26, a dual colored LED readout 28 and a sequence of finger-actuated switches having a tactile feedbac~.
These switches or keyboard as represented generally at 30 permit the microprocessor driven console 16 to carry out an instructive or "user friendly" dialogue witl1 the practitioner. l~or purposes of safety, the device is powered by a rcch~rgeable battery.
In addition to convclltioIlnl on and off switches shown, respectively, at 32 and 33, the switches provided on tl1e console 16 include a count mode SWitCIl 34, a sound switch 35, a reset count switch 36, a range function switcll 37, a calibration function switch 38, and up and down incrementing switches for adjustment within certain of the switch generated modes as shown, respectively, at 39 and ~0.
The probe 12 must be cnpable of performing essentially at room temperature. Thus, the device employs a cadmium telluride crystal and, because of the preferred low energy levels of radiation which it may detect, must be capable of operatively reacting to low energy gamma ray interactions. The interaction of gamma rays with such crystals is primarily through three processes, namely tlle pl1oto-electric effect, Compton scattering, and pair production. In the photo-electric effect, a photon of energy, l1v, interacts with an atom as a whole. Its energy is completely transferred to an electron, usually in the innermost shell. The electron is ejected Witll a Icinetic energy: ekin = hv - Eb, wllere Eb is the binding energyof tl1e orbital electron, h is Planck's constant, and v is the frequency associated with tl1e wave nature of the gam ma radiation. In Compton scattering, the primary photon may interact with any one of the orbital electrons. The electrons are considered essentially as free electrons under the condition that the primary photon energy is large compared with the electron binding energy. The interaction may be analyzed as the elastic collision between the primary photon and the electron. Energy is shared between the recoil electron and the secondary photon. This secondary photon travels in a direction different from that of the primary photon, and is referred to as the scattered photon.
Thus, as an incorning gamma ray is absorbed by the crystal, it transfers some or all of its encrgy to electrons, which as charged particles pass through the semi-conductor produchlg electron-hole pairs and, therefore, the capability of charge-transfer within the crystal medium.
When a charge particle produces electron-hole pairs in the semi-conductor, the electric field causes these charge carriers to move toward and accumulate at the appropriate electrodes. As these charges are collected at the electrodes, they induce a charge or electrical pulse signal in the circuit external to the detector. It is then necessary to pre-amplify 1 33~440 these signals and feed them to the electronics of the control unit or console 16.
For effective pcrformance, the probe 12 must be capable of generating and discerning signals representing gamma ray strikes which are 5 of extremely low energy. In this regnrd, a gamma ray interaction with the cadmium telluride crystal may produce two to four thousand electrons. It being recognized that G.25 x 1018 electrons per second represent one ampere of current, the relative sensitivity of the instant device will become apparent. As a consequellce, the mechanical structuring of the mounting 10 arrangement for the crystal within the probe 12 is of critical importance as is the technique for detecting and treating these significantly small charges representing gamma ray interactions.
Looking to Fig. 2, a more detailed representation of the probe device 12 is revealed. Tlle angular orientation of the front portion 20 is shown 15 having the noted 30 cant witll respect to the central axis of the hand gripped portion 22. J~evice 12 is small llaving an overall length of about 19 cm and portion 22 having a length of about 12.7 cm. The overall diameter of tlle cylindrical structure 12 is about 1.9 cm. Front portion 20 is formed having a groove 42 for retaining a collimator which optionally may 20 be positioned over the portion 20 and window 18 to provide a higher directional aspect for the device. The hand grip portion 22 carries a preamplifier on an elongate circuit board as represented in general at 44.
Depending upon the energies of radiation encountered, the probe 12 structure is formed of an electrically conductive and thus shielding material 25 which further functions to attenuate radiation.
Cable 14 supplies power to the preamplifier of the probe, as well as bias to the crystal and functions to transmit the preamplifier treated output signals. Callle 14 includes tin copper cladding components 46 and 48 which are mutually insulated and spaced by a silicon rubber tube 50 which is 30 somewhat loose to permit flexure. The innermost leads of the arrangement at respective lines 52 and 54 carry the output signals from the preamplifier 44 and a bias signal, for example 30 volts, for application to the rear side of the crystal within tlle device 12. Clad 46 carries a 12 v power supply for the preamplifier circuit, while outer clad 48 carries ground for the system. An 35 outer silicon rubber cover then is provided at 56.
Loolcing to Fig. 3, an exploded detail of the nose or forward portion 20 of probe 12 is provided. This portion 20 retains the cadmium telluride crystal in a ligl~t-tigl~t nnd mechanically secure orientation while maintaining neccssary ground nnd bias conditions upon it. Generally, such crystals as at 58 will llave a rigidity or physical consistency somewhat simliar to chalk and are forrncd having very light gold coatings on their 5 surfaces. Device 58 is retained within an outer electrically insulative c~ating 60 of U-shaped cross section. The forward or front surface 62 is grounded and, in efrect, represents the most negative electrode in the system. Its rearward face G4, on the other hand"~as a bias, for example 30 v, applied to it, an available bias range of lOv to lOOv generally being 1~ desired. Thus, these electrical parameters are required Witll respect to the crystal 58 while it is maintained in a carefully electrically shielded, acoustically dead and light-tigllt environment. The outer surface of front portion 20 is an electrically conductive tube or collar 66 formed, for example, of copper so as to provide an electrical shield as well as an 1~ attenuator for radiation of the energy range contemplated. The forward edge of tube 6G is closed by the- window 18 whicll is formed of a silicon-aluminum alloy about 0.015 in. thick soldered thereto.
Crystal 58 and various components associated with its mounting are assembled within the cup-shaped structure including window 18 and shell 66 20 in a sequellce represcnted in ~ig. 3 which includes a foamaceous, electrically conductive insert G8 having a diametric extent such that it is in contact with ground, here the internal electrically conductive surface of shell 66. Generally, the insert 68 may be provided as a carbon impregnated foam whicll functions to assist in the compression of the components under 25 final assembly. Insert G8 is shown in ~ig. 3 exhibiting its expanded, pre-assembly cross-sectional configuration.
Next in the assembly sequence is a dislc-shaped insert 70 formed of carbon filled silicon rubber having a thickness, for example, of 0.020 in. ~he diametric extent of the insert 7~ is such that it is in c~ntact witll electrical30 ground about the internal periphery of the tube portion 66. Marketed, for example, by Tecknit Company of Cranford, New Jersey, insert 70 is both pliant and exhibits an adhesive-like surface which, in final assembly, tends to adhere to the forward surface 62 of the crystal 58. It has been found that the use of this disk, substantially improves the noise immunity of the device.
35 Thin aluminum foil has been employed in place of the carbon filled rubber for insert 7~, however, any slight rubbing of the foil insert against the face 62 will create a static electricity build-up and, thus, noise. ~Yhile considerable improvernerlt was found in cmploying the aluminum dis1<, it also was found tllat thc probe runctiolled only whell held motionless during a count, tlle mere sliding Or n fingertip across the surface of the probe causing unacceptable noise levels witll the latter arrangement. A similar disk of the conductive silicon rubber material but of lesser diametric extent is positioned for engagemcnt witll the rearward surface 64 of the crystal 58 as represented at 72. The noted crystal bias voltnge is asserted through tllis adhesive surfnce insert 72 from a disk-shaped copper electrode 74. Provided having a thickness, ~or e:cample, of about 0.050 in., the electrode 74 may be gold-plated at least on its contact surface to improve conduction and avoid corrosive effects. l he rearward side of the insert 74 carries a bead of solder 76 to effect a union with a short lengtll of insulated wire 78. The asselnblage of crystal 58, illsert 72, and electrode 74 is configured to nest within an insulutive cup 80 formed, for example, of Teflon or the like. Cup 80 is configured having a hole 82 at the center point thereof for the purpose of receiving wire 78 and accommodating solder bead 76. To assure removal of all ionic contaminants, cup 80, shell G6 and window 68 are boiled repeatedly in distilled water prior to assembly.
Cup 80 nnd its internested components are slideably retained within a cylindrical cavity 84 bored within a slug or blocking component 86. Formed llaving a principal diameter which is slideable witllin tlle tube 66, tlle slug 86 is fasllioned of copper or tungsten or the lil(e and functions botll to provide a secure support for the crystal mounting components and to assure radiation blockage with respect to any radiation impinging from the rearward portion of tlle probe 12. Component 8G is counterbored at 88 to accommodate for the solder bead 76 upon assembly. Communicating from counterbore 88 is a bore 90 of small diameter selected to receive the small wire 78 which extends to an electrical connector 92. Connector 92 is covered with an electrically insulated material and is slideably inserted into bore 90, the outer llead portion thereof at 94 residing witllin a counterbore 96 within component 86. Blocking or backing component 86 additionally is configured having a coupling portion of lesser outer diameter 98 which is configured to be slideably received within the internal diameter of a supporting tubular portion 100. The forwardly disposed tubular region of portion 100 at 102 is configured having a diameter to, in turn, coincide with that of the main diametric component of slug 86 so as to slideably receive tubular portion 66 upon assembly. Upon such assembly, as shown in Fig. 2, an additional retainer groove ns nt l ~ is developcd. ~or assembly, additionally, a conrlector wire ~s at 10G provides elcctrical connectiorl between connector 'J2 nlld the preampliricr ~ (l ig. 2).
Tlle sub-assemblntJc of electl ode 74, cup 80 and slug componcnt 8G
5 along with connector 92 is provided prior to a final combination of the forwurd probe part. In tllis regard, it is dcsired tllat the wire 78 be rnaintained in te~lsion to assure no mecllanical movement in the sub-rlsseml)ly. I`o providc tllis thc wir e is couplcd to thc connector 92 and supported so as to extcnd ~htollgll bore 80 and into contact with the solder bead 7G within the cup 80. Cup 80 will have been positioned along with the electrode 74 within cavity 8~. The disk electrode 74 then is heated such that a sweat soldering of tlle wire tal~es place and connection is made with the componerlts in a heated state. Upon cooling, the resultant assemblage pr ovi~es ror tllc wirc r crnrlinillg in tensiorl to sccure ag~ins~ componcnt 15 motion. An nvoidance Or any relative rnotion of t~le components is importarlt becausc of thc cnpacitive effect developed with any relative motion between thc cornponcnts of the assemblage. The noted sub-- assemblage along wilh thc remaining components described in connection with l~ig. 3 thell are "slid" togcther under a dry nitrogen atmosphere.
2~ I.ool<ing to I~ig. 4, the components shown in expanded form in E;ig. 3 are represerlted in their post-assembly orientations. Note that the roamaceous insert G8 has been compressed to aid in securing the remaining - components from ally motion. The roarn material is compliant in this regard to assure a uniforrn compression of all components into the crystal 58.
25 Similarly, the slightly adhesive and compliant silicon rubber inserts 70 and 72 aid in this securernent. Components 10û and 6G may be retained together, ror exarnplc, using an epoxy adhesive. As noted earlier, the mildest of vibrational rnovemellt may create a capacitive alteration on the order of a gamma stril<e for the very delicate instrument. Thus, the 30 arrangement shown serves to provide mechanical securement. There also is a potential for vibration and the noise dif ficulties that ensue due to the microphorlic effects occasioned by the occurrence of noise or the mildest of disturbance at the window 18. I; oamaceous material 68, as well as the inserts as at 70 provide a protection for such effect due to the cllange of 35 acoustic impedance. I;or example, any microphonic effects at the window surface 18 will be damped by the change of acoustic impedance at the junction between window 18 and foamaceous material 68. A similar alteration occurs betwcerl thc insert G8 and tlle next subsequent silicon rubber insert 70. Tllis alteration Or acoustic impedance is analogous to the difficulties in vocnlly commullicating froln the atmosphere to a listening position benenth the surface of water. Generally, the principal source of 5 microphonics effects is occasioncd with rubbing at the surface of window 18, a condition to be erlcountered in normal operations. Of course the maintaining of tubular portion ~6 and the entire housing of tlle probe including components 100 and llandle 22 at ground reference functions to provide an electrical shieldillg. It has been found helpful to dampen acoustic 10 vibration of window 18 by applying a polymeric coating to its outside or inside surface, i.e. Teflon or the like.
Rererring to ~ig. 4A, an alternate and effective arrangement of the forward portion 20 of the instrument 12 is portrayed in similar fashion as I~ig. 4. In tlle rigure, a disk of the earlier-described electrically conductive15 silicon rubber 71 is positioned against the inner surface of window 18. The opposite face of this insert 71 then confronts a dead air space 73 which, in turn, extends to an assembl~ge comprising the earlier-described electrically conductive foamaceous material G8, rubber insert 70 and crystal 58. Tllese components are retained compressively together by a band 75 which is 20 structured of a material permitting the transmission of gamma radiation therethrougll but whicll, preferably, additiomllly is electrically conductive.
i~luminum, for exnrnple, may be used for the band 75. The remainder of the structure is identical Witll tlle structure of Fig. 4 as labelled witll the samenumeration. Providing a uniform resistance from the forward surface of 25 crystal 58 to ground is an irnportant aspect of each of the embodiments shown in Figs. 4 and 4f~.
Referring to ~ig. 25, a preferred structuring for the forward portion 20 of the instrument 12 is portrayed in similar fashion as Fig. 3. The embodiment shown has been found to be more readily fabricable, while 30 maintaining requisite perforrnance characteristics. ~ig. 25 shows the hand-graspable portion as at 22 extending to earlier-described supporting tubular portion 100. The forwardly disposed tubular region of portion 100 including surface 102 are configured having an internal diameter defining a cavity 1232 for receiving a generally cylindrically shaped slug or blocking 35 arrangement 1230 along with an elastomeric retainer layer which retains the slug 1230 witllin the cavity 1232 while spacing its outer cylindrical surface from the interior wall of portion 100 an amount sufficient to provide a shock mountillg arrangernent. Ihis elastomer may l)e proYided, for example, as a rul)bcr cE)oxy malel inl. I`o acl-ievc spacing from thc noted interior wall and fncilitnle mounting, an clnslolneric ring such as an O-ring is provided as at 1234 which serves to hold the slug 123() in an appropriate position while the 5 elastomeric rubber epoxy sets. The O-rhlg 123~ is slid over the copper outer cylindrical surfacc Or slug 1230 so as to nest in a rectangular groove 1236 formed lhereilI. J,ooking a ldiliollally to ~ig. 2G, the O-ring 1234 is seen in assembled position and tl~c clnslolneric retaining Inyer is shown at 1238. As before, slug 1230 is formcd of copper or tungslen to attenuate radiation 10 impinging from a rearward direclion and furlher includes a V-shaped groove 1240 extending thercal)out. A central bore 1244 extends through the slug 1230 to carry insulative lead 106. The forwardmost face of slug 1230 provides a l)ase support surface as at 12~G which is counterbored at 1248 so ns to provide an improvc(l connection witl~ a plastic elec~rically insulative cup or support 1250 l1aving a rearwardly disposed cylindrical portion 1252 whicll is nestable witl~in tllc bore 1248. Cup 12S0 may, for example, be form ed Lcxan or the like nnd, preferably, are adhesively attached to the base support surface 12~G and counterbore 12~8 by a compatible adhesive.
Cup 1250, as before, includes a central cylindrical cavity 1254 which receives and supports an assemblage including a resiliently compressible shoclc cusl-ion layer 125G as an initial component. Layer 1256 may, for eYample, be forrned a non-woven Teflon clolll marl~eted under the trade designation "Gortex" havillg a thicl(llcss, for example, of about 0.020 in. The layer 125G is provided having an opening in the middle thereof for receiving the lead 106. In general, this lead 106 is formed of a multi-strand type lead and the strands thereof are attached to a small disc 1258 of adhesive copper tape. This dislc 1258 servcs to electrically couple lead 106 to and apply a biasing voltage to the rearwardly disposed face 1260 o~ a gamma radiation responsive cryslal 12G2 forrned, as described above, of cadmium telluride or the equivalent. The forward face of crystal 1262 as at 1264 is electrically grounded by a copper ground strap 126G which extends rearwardly to provide electrical grounding communication witll the exterior of copper slug 1230.
Tl~e asseml)lage of crys~al 12G2, copper adl~esive tape or disl< 1258, shock cushion layer 1256, and cup 1250 are compressively retained together by an elastomeric retainer 12G8 which may be provided, for example, as a common finger cot. This sheatll o~ electrically insulative elastomeric material is rolled over the assemblage and retained in position by a resilient band such 1 337~
as a resilient O-rh~g 1270. This O-ring nests in the earlier-described V-shaped circumfercntial groove 1240 to retain the sheath 1268 in position.
The entire assemblage Or slug 1230 and those parts compressively retained in position by thc sheatll 1268 and O-ring 1270 may be maneuvered during 5 the assemblnge employing rubber epoxy layer 1238 to provide appropriate spacing accommodating for variations in component thicknesses, for example the thickncss variations wllic11 may be eneountered with erystal 1262. The forward assemblage ineluding tube G6 and window 18 then is positioned over surfaee 102 and cemented in plaee, for e:cample, Witll a 10 conduetive silver epoxy cement. Note in Fig. 26 that the assemblàge is so oriented that a dead space 1272 is ereated between the forwardly disposed surface 1264 of crystal 12G2, as associated with retainer sheath 1268, and window 18. Tllis dead air sp~ee provides an enhaneement of aeoustic isolation of the crystal 1262.
As represented at circuit board 44 in Fig. 2, in order to carry out the treatment of the very faint eharges which are evolved due to gamma interaction with crystal 58, it is important that the preamplification function talce place as close as possible to the situs of the interaction.
Because of the operational need in surgery for the 30 eant of the eentral 20 axis of the forward portion 20 with respect to the eorrespondblg axis of the rearward support portion 22 of the probe 12, some small length of transmission wire as at 1~6 is required. Beeause extremely small eharges of eurrent are involved in the range of 300-600 atto eoulombs, a preamplification stage whieh performs to aehieve a very high gain is ealled 25 upon but one whieh performs with low noise generation. In effect, the preamplification stage of the instant apparatus is one achieving a voltage ampli~ication, for example on the order of about 25,000. Correspondingly, if one eonsiders the eurrent amplifieation funetion numbers of eleetrons constituting very faint charges are eonverted to about a milliampere at the 30 output of the preamplifieation stage, an enormous gain eondition (about three trillion). The resultant power gain is about 8 x 10 6.
Lool(ing to ~ig. 5, a preamplifier cireuit represented generally at 110 employed with the instrument 12 is revealed. In the figure, earlier described input line 54, earrying tlle bias for assertion at the rearward faee 35 of crystal 58 again is reproduced as extending to one side of crystal 58 through resistors Rl and R2. Resistor Rl in eombination with a capaeitor Cl provides a loeal filter to remove any spurious noise whieh may be -- engendered in the line transmitting the noted bias signal. The opposite face of cr~sytnl 58 is coupled to ground as represented at lines 112 and 114. In gener~l, the preampli~ier circuit 110 includes an integrator st~ge represented gcnerally at llG which is followed by a voltage amplification and line driver stage represented generally at 118. Integration stage 116 is formed of three transistors identified at Ql-Q3 performing in conjunction with a capacitor C3.
The input to stage 116 from crystal 58 includes a crystal bias resistor R2 of very large resistance value, for example about 50 megohms, a level selected to avoid absorbing current disturbances from crystal 58. Generally, the resistance for this component will be selected between about 10 to 20n megohIns. The input signal to the integration stage 116 at line 120, typically about 300-G00 atto coulombs, is asserted through coupling capacitor C2 to the gate input terminal of an N-channel junction field effect transistor (JI rT) transistor Ql. Line 120 also is coupled via line 122 and bias resistor R3 to ground at line 112. The resistance value at resistor R3 is selected commensurately with the selection of resistance for resistor R2, preferably at about 200 megohms to avoid signal absorption. Generally, the resistance for this component will be selected between about lO to 10,000 megohms, tlle component supplying bias for transistor Ql. ~lso extending from line 120 at the input to the integrator stage is line 124 leading to a coaxial capacitor C3, the opposite side of which is coupled to integrator stnge feedback line 126. Capacitor C3 is very small, typically having a capacitance of 0.25 picofarads and, in general, having a capacitance less than one picofarad. To create this capacitor C3, copper tubing having a 0.050 in. outside diameter is employed in conjunction with an insulated wire inserted in its center. Wire 126 is soldered to close the opposite side of the tube. Thus, by moving wire 124 inwardly snd outwardly of the surrounding tube coupled to wire 126, the capacitive value at capacitor C3 may be altered. Capacitor C3 may be tuned in the above manner to adjust the preamplification stage 110 for gain. Such construction of capacitor C3 may be referred to as "coaxial".
JFET transistor Ql functions, in effect, as a "source follower" charge amplifier, its purpose being to achieve an impedance transformation from a very high impedance gate suited to low current and low noise. In general, the J~ET structure exhibits lowest current noise at the room temperature operating conditions contemplated for the instant instrument. Further, these devices exhibit high frequeney response (wide bandwidth) as well as a high ampli~ication factor or high transconductance. In view of the latter aspect, the device tends to create a large current disturbance at its source terrninal at line 128. Line 128 extends through a source load resistor R4 to 5 ground line 112. Tlle resistor I~4 functions as a d.c. current return device.
The drnin terminnl of transistor Ql is coupled to +12v supply via line 130, while the same terminal is decoupled or isolated by a filter comprised of capaeitor C4 and resistor R5 connected with line 130.
The signnl relnted voltnge at line 128 is coupled via line 132 to the 10 base of NPN, bi-polar transistor Q2. Transistor Q2 performs a voltage amplificntion and a singular bi-polar component is eleeted for this function inasrnucll as sucll devices exhibit low voltage noise characteristies at room temperatures. Additionally, the devices have a higher amplification factor availability tharl corresponding field effect transistors. The use of such a 15 bi-polar device in conjunction witll the input field JFET device was evolved following signifieant experimentation and represents a lowest noise cornbination which was achieved in conjunction with room temperature operation.
The degree of amplification achievable with the stage Q2 is related to 20 the impedance exhibited witll respect to its emitter and eolleetor, i.e. the value of the collector load irnpedance divided by the emitter impedance. In the arrangement shown, the emitter of transistor Q2 is coupled via line 134 to ground through resistor I~6 and, importantly, the emitter is by-passed to ground via lines 134 and 136 througll eapaeitor C5. The latter eomponent 25 exhibits relatively lo~ impedanee on the order of 25 ohms at the frequeneies of interest. Looking to the eollector to supply arrangement at line 138, there is a relatively higll resistance value resistor R7, for example of 3 l~ohms and, in series, a resistor ~8 having a 1.5 I~ohms resistanee to provide a total resistance of 4.5 Kohms. To achieve t11e most effective 30 amplifieation or highest gain, NPN transistor Q3 is so eoupled within the integrator stage 116 as to provide a "boot strap" eireuit to raise the ef~ective collector irnpedance to transistor Q2. In this regard, the base of transistor Q3 is coupled via lirle 140 to line 138, while the collector thereof at line 142 is coupled to supply line 130 in eonjunetion with a deeoupling 35 filter eomprised of resistor R9 and capaeitor C7. The emitter of transistor Q3 is eoupled to line 126 as well as to line 144 to ground through resistor R10. Line 126 is seen to extend to linc 146 ineorporating eapaeitor C6 and ~~ coupled intermediate resistors n7 and R8. Transistor stage Q3 functions as an emitter follower, feeding the noted junction between resistors R7 and R8 through capacitor C6 in boot-strappillg fasllion. The result is to raise the effective impedance at the collector of transistor Q2 due to the alteration 5 of net current rlow tllrougll resistor R7. This provides a much higher voltage gnin achieved at the integrator stage 116. Note that a portion of tlle signal from the emitter Or transistor Q3 returns to the coaxial capacitor C3 of the integrator stage.
Voltage amplifier and line driver stage 118 is seen to be comprised of 1(~ an a.c. voltage amplifier configured as the combination Or NPN transistor Q4 and PNP transistor Q5. Such an arrangement comprises desirably few components and exllibits high gain and very broad bandwidtll. Because the gamma ray interaction of crystal 58 will exhibit a frequency disturbance spectrum ranging from about 50 l~l~z to 200 l~l~z the frequency response of 15 tlle stage 118 is tailored accordingly. I;or example, the high end roll off of this response is cstablislled by resistor R10 within line 144 and capacitor C8 within line 148. The output of the integrator stage is asserted througll resistor Rll and capacitor C9 to the base of transistor Q4. A voltage bias to tlle base of transistor Q4 is provided via line 148 from supply following its20 division by divider resistors R12 and R13. This bias input, amounting to about one-fourth of the supply voltage also is treated by the filter combination of resistor R9 and capacitor C7.
The 12 v power supply additionally is filtered by a pi filter comprised of capacitors C10 and C12 along witll resistor nl4 connected within line 150. Line 150, in turn, is seen to extend via line 152 to the emitter of transistor Q5 and througll resistor R15 to the base thereof as well as to the collector of transistor Q4. Correspondingly, the emitter of transistor Q4 extends via lines 154, 156 and 158 to resistor R16 and the collector of transistor Q5 as well as to resistor n29. The output of stage 118 is provided at line lG8 incorporating resistor R17. The gain of this output stage is set by resistor R18 witllin line 154 in conjunction with resistor R16, while capacitor Cll in that line aids in the setting of low frequency roll-off of the stage. The high frequency roll-off characteristic is further aided by the combination of resistor Rll and capacitor C13, the latter component being coupled between line 145 and ground via line lG2. Low end roll-off characteristics for the stage further are aided by the combination of capacitor C5 and resistor R6.

In view Or tlle extreme sensitivity of tlle type of preamplifier at hand and tlle tcndency of such circuitry to oscillate, tl)e layout Or the circuit witllin llousillg portion 22, ror cxnmple on a circuit board a~ at 44, also becomes nn importnllt nspect in tlle dcsign of tlle instrument. Tllus, loolcing 5 to I; ig. 6, a layout for the preamplifier circuit showing component orientations and relative positioning is revealed. In general, the most sensitive cornponents are grouped to the left in tlle figure, a position corresponding Witll n left orientation in conjunction with ~ig. 2. As a consequerlce, tllesc comporlerlts are closest to the crystal in the system.
In ]3ecause of tlle very large resistance values ror resistors 1~2 and ~3, theseresistors are to tlle left in tlle circuit orientation and are mounted vertically upwardly froln tlle board or l~ase, one side of them being attaclled at such base. 1 he opposite sides of tllese resistors extend in space to couple to capacitor C2. Thus, c~pacitor C2 is off tlle surface of tlle printed circuit 15 bo~rd to avoid leakage conditions. The most sensitive transistor in the system is JI I~T transistor Ql wllose source and drain terminals are coupled to the printed circuit board, wllile its gate electrode extends to the common junction in space of capacitor C2 nnd resistor n 3. Thus, this sensitive terminal also resides in space in close proximity to the crystal itself.
2~ Coa:~ial capacitor C3 is mounted upon the board in a vertical orientation SUCIl tllat it.s tunillg Yire line 124 is coupled from its coaxial location witllin the component to the common juncture of the gate of transistor Ql and the upstnnding common junction of resistor n3. The above-described are the most sensitive of the components and their mounting in the manner shown 25 has been found to be important to successful operation of the device.
Capacitor C18 is a radial-lead device and is seen coupled to the left side of - tlle circuit board for convenierlce as may be observed by loolcillg to its corresponding position in ~ig. 5. Note that tlle component developing the llighest amplification effect, transistor QS, is furthest to the rigllt on the 30 circuit bonrd away from the sensitive gate at transistor Ql. The remaining components are shown in their orientations on the circuit board 44 along witll small lines representillg tlle "hair pin" type mounting orientations.
Referring to l~igs. 7A and 7B, a block diagrammatic representation of the instrumentation circuitry is revealed. ln ~ig. 7A, the cadmium telluride 35 crystal 58 again is sllown having one ace coupled to ground through line 17~, wllile tlle opposite, biased face thereof is coupled via lines 172 and 174 to a bias filter represerlted at block 176. As noted above, tllis filter, for exarnple, includes rcsislor I~2 as well as capacitor Cl and resistor Rl. The input to the filter components 17G is represented at line 178 as being applied througll the triaxial cable as described earlier at 14 and represented by that numeral herein. I,ine 178 corresponds with the earlier-described line 52 in 5 I;ig. 2. This bias emanates from a power supply shown at block 180 in Fig.
7B and represented at line 182.
Line 172 from tlle crystal 58 is shown extending to the earlier-described integrator stnge Or the prcampliîier 110. Tlle integrated valuation of detected radiation disturbance then is shown directed, as represented by line 184, to the driver-amplification network described generally at 118 in Fig. 5 and identified by that numeration in block form in Fig. 7A. ~ 12 v power supply is provided from tlle power supply 180 (Fig. 7B) as represented at line 186 whicll, as showrl in Fig. 7~, is directed to a probe current nctwork represerlted by block 188. Under microcomputer control as represented by line 190, the network 188 develops signals, for example, determinillg whether the probe instrument 12 llas been properly connected to the console 16. Delivery Or the 12 v power supply for the preamplifier stage 110 is represented at line 192 as extending to the driver amplifier from cable 14 via line 194. l,ine 194 corresponds with the clad 46 described in conjunction with cable 14 in I: ig. 2.
Ground to the instlument 12 also is developed from the power supply block 180 as represented at line 196 shown in ~ig. 7A as extending to cable 14 and via line 198 to the instrument and preamplification components 110.
Line 198 corresponds with the earlier-described clad at 48 in Fig. 2.
The output of the preamplification circiut 110 is represented at line 200 extending through the cable representation 14 corresponding with the enrlier-described line 54 in Fig. 2. Line 200 extends from the cable 14 as line 202 to the input of a normalizing amplifier represented at block 204.
The network represented by block 204 functions to amplify or attenuate, i.e.
3û scale the noise characteristic of any given instrument 12 and normali~e the value thereof or render it consistent for later comparison stages. Generally, for example, the 27 kev energy level gamma ray generated pulses in the system will be about five times higher than noise levels. Normalizing arnplifier network 204 will establish those noise levels at some predetermined level, for example, 200 millivolts and the resultant proportional valid gamma related pulses will become about one volt high for purposes of ensuing comparison functions. It may be observed that the 1 3374~0 amplifier nctwork at block 20~ is shown controlled from a digital-to-analog converter network represented at block 206 via line 208. Network 206, in turn, is controlled from line 210 extending, as shown in ~ig. 7B to block 212 representing a microcomputer network. The normalized output developed from network 20~ is presented along lines 214 and 216 to a noise averager circuit as represented at block 218. This network, represented at block 218 determines an average amplitude value for the noise of a given system with a given instrument 12 and provides a corresponding signal as represented at line 220 (noise amp) wllich is emplt)yed as above-described as information - 10 used by tlle microcomputer 212. This information in addition to being employed with the normali%ing amplifier network represented at block 204, may be employed to develop a low window valuation for the comparison f unc tion.
Line 216 also e~tends via line 222 to a pulse acquire network represented at block 22~. This network functions, when activated by the microcomputer represented at block 212, to acquire the value of the highest pulse amplitude witnessed at line 222. Periodically, this information then is transmitted to the microcomputer at block 212 as represented by line 226.
Representing n form of pcak detector, the network is sometimes referred to as a "snapsllot circuit". ~lso produced from line 216, as at linc 228 and block 230 is a bufEer amplifier which will provide at line 232 an output representing received pulses which may be made available at the rearward portion of console 16 for conventional radiation evaluation purposes.
Line 214 extends, as shown in Fig. 7B at line 234, to one input of an upper window comparator represented at block 236 and a lower window comparator illustrated at block 238. The threshold levels for comparative purposes employed by the network at block 238 is shown asserted from line 240 and, prererably, is developed by the logic of microcomputer network 212 at a level just above the noise amplitude signals generated from line 220.
Of course, manunl setting of such windows can be carried out. In similar fashion, the upper window of acceptance for valid gamma ray interaction is established rrom a corresponding line 242. This threshold setting may be made from the information taken from pulse acquire network 224.
Returning to ~ig. 7A, the threshold upper window and lower window threshold selections are made under the control of the microcomputer network at block 212 as controlled from the digital-to-analog network shown at block 206. It is the characteristic of such networks as at block 206 to provide an output whicl- is comprised, for example, of 256 steps of varying arnplitude. The percentage o~ incrementation from step-to-step will vary somewhat over the range of voltage values provided. ~ccordingly, the outputs flom this conversion network at block 206, as at lines 244 and 24~
are directed to sguurer networks shown, respectively, at blocks 248 and 250.
These networks function to square the current outputs at lines 244 and 246 - and thus achieve a uniform percentage incrementation of the threshold defining outputs at lines 240 and 242.
Returnillg t~ 1: ig. 7B, the outputs of the comparator net~orks shown at blocks 236 and 238 represent candidate pulses which may be above or below the given thresllolds and are identified as being presented as a "UW pulse"
and an l'LW pulse" along respective lines 2SG and 258. These lines are shown directed to a real time pulse discriminator network represented at block 260 whicll carries out Boolean logic to determine the presence or absence of valid pulses. Valid pulses are introduced to the microcomputer network 212 as represented by line 262.
The microcomputer represented at block 212 performs under a number of operational modes to provide both audio and visual outputs to aid the surgeon in locating and differentiating tumorous tissue. In the former regard, as represcnted at line 264 and block 266, a volume control function may be asserted with amplitude variations controlled from a solid-state form of potentiometer as represented at line 268 and block 27~. Further, a "siren" type of frequency variation may be asserted as represented at line 272 to an audio amplification circuit represented at block 274 for driving a speaker as represented at 276 and line 278. With the noted siren arrangement, the ~requency output from speaker 276 increases as the instrument 12 is moved closer to the situs of concentrnted radiation. Of course, conventional clicks and beeps can be provided at the option of the operator.
The microcomputer network 212, as represented by arrow 274 and block 276 also addresses an input-output network which, as represented at arrow 278, functions to rrovide a pulse count output of varying types as well as outputs representing volume levels, pulse height, noise levels and battery status. Visual readout is represented in Fig. 7B as a block with the same display 26 numeration as described in conjunction with Fig. 1. Similarly, the input-output function represented at block 276 provides appropriate scanning of the keyboard or switches described in conjunction with Fig. 1 at 30 and represented by the same numeration in Fig. 7B. During a counting operation, the microcomputer network 212 functions to control a light emitting diode drive network represented by block 282 from line 284. The drive network reprcsented at block 282 is shown providing an input, as 5 represented by line 28G to the dual LED display as described at 28 in Fig. I
and represented in block form with the same numeration. This readout provides a red light when a gamma ray is detected and a green light during the counting procedure in general. 1~ serial output port of conventioanl variety also is provided on tlle console lG, such ports being represented at 1(~ block 288 being addressed from the microcomputer at block 212 from line 290 and having output nnd input components represented by arrow 292. ~
real time cloclc-calendar having a non-volatile memory also may be provided in conjunction with the functions of the microcomputer network 212 as represented by bloclc 29~ and arrow 296. I;urther, the microcomputer may be employed to monitor the performance of the power supply represented at block 180. This is shown being carried out by the interaction of the microcomputer nctwol k witll a multiplexer represented at block 298 and having an association represented by arrows 300 and 302. It may be observed that the power supply also provides +5 sources for the logic level components of the circuit as represented by line 304; a -5v source at line 306, as well as a -9v reference at line 308 for display 26 drive and, finally, a2.5 v reference as represented at line 310 to provide reference input to the analog circùitry described later herein.
Returning to I~ig. 7A, the microcomputer network as represented at block 212 also provides an input to the digital-to-analog conversion network represented at block 206 whicll corresponds with the instantaneous pulse rate and this information is conveyed to a pulse rate amplifier network represented at block 312 via line 314. The resultant output as represented nt line 316 may be provided, îor example, at the rear of the console 16.
This circuit represented at block 312 also may be employed to generate a calibrating pulse for testing the downstream components of the system.
Thus, the microcomputer applies a predetermined pulse level through the digital-to-analog conversion network at block 206 for presentation to the amplifier network represented at block 312. The resultant output at line 318 is selectively switched as represented by block 32~ to define pulse width from the microcomputer input at line 322 to generate the calibrating pulse at line 324.

- ~ Referring to l; igs. 8t~-8C, pulse treating analog eireuits as are maintained in console lG are revcaled. In I;ig. 8A, the output of a 10 pin ribbon eable which, in turn, is coupled to triaxial eable 14 is revealed generally at 330. Ofthe tcn connecting pitlS and lines of tllis ribbon cable, 5 five are at ground for sllieldirlg purposes as represented by ground line 332.The bias supply is provided îrom the earlier-deseribed power supply as at block 180 and shown again at line 182 extending througll resistor R20.
Correspondingly, the +12v power supply earlier deseribed at line 186 again is reproduced as extending to the terminal 330through resistor R21. Lines 182 and 18G are seen coupled to respeetive filtering eapaeitors C16 and C17.
I; inally, tlle preampli ried deteetor pulse output is reeeived from the connector 330 from along line 332 and is applied to the analog downstream cireuitry tllrougll blocking capacitor C18.
The probe curren~ dctector described earlier in con~unction with block 188 in Fig. 7A again is represented in general by that numeral in Fig. 8A.
This detector employs resistor R21 within +12v supply line 186. The opposite sides of resistor R4 are tapped at lines 334 and 336 whieh, in turn, are direeted to a resistor network comprised of resistors R22-R25 and thence are directed to the inputs of an operational amplifier 338. A
20 filtering e~pacitor Cl9 additionally is eoupled to one side of resistor R21.
The resistor network 1~22-R25 and amplifier 338 form an instrumentation amplifier which measures the voltage difference across resistor R21 and further functions to perform a level shift of 12v to ground. Following sueh level shifting, the resulting probe eurrent responsive signal at line 340 is direeted to the non-inverting input of a seeond amplifieation stage 342.
Stages 338 and 342 are shown eoupled to ~12v as filtered by eapaeitor C20 via line 344 and to -12v supply as filtered by eapaeitor C21 via line 346.
The inverting input to amplifier 342 at line 348 ineorporates resistor R26 and, additionally is coupled to t~le output of stage 342 at line 350 via resistor R27. Amplifieation stage 342 funetions to amplify tlle signal from stnge 338 by a factor, for example, of 10 to provide an analog signal representative of probe eurrent (PROBE 1) at line 352. This analog signal is directed to the microcomputer function earlier described at bloek 212 in Fig. 7B.
Line 202, earrying the preamplified gamma reaetion pulses is direeted, as shown in ~ig. 8B, to the input of the normalizing amplifier network represented in Fig. 7A at bloek 204 and shown in general by that 1 337~40 numeration. Tl~e signul at line 202 is filtered by a capacitor C22 while a re.~istor R27 supplics bills to PNP transistor Qfi. These filter components provide a higll freqllcllcy roll-off avoiding n~ interference which may be encountered. The collector Or trnnsistor QG is coupled via line 352 and resistor R28 to -5v supply, while the emitter thereof at line 354is coupled tllrougllresistols R29alld R30 to +5vsupply. Resistor R30 provides a supply bypass filter ~unction hl conjunction with a capacitor C23 coupled witll Line 354 via line 356, while resistor R29 providcs emitter bias for transistor QG.
I;urther filtering for line 35Gis provided by capacitor C23. This relatively stable supply at line 356is directed via line 358 to line 360 extending in one direction to the collector of NPN transistor Q7 and in the opposite direction througll collector load resistor R31 to the collector of NPN transistor Q8.
Transistors Q7 nnd Q8 are coupled as a difrerential pair, having ~ common emitter connection at line 3G2 which extends via line 364 to the collector of NPN transistor Q9. The base of transistor Q9 is coupled by line 364 to line 352, while the ernitter thereo~ is coupled via resistor R32 to -5v. The high pass filter comprised of capacitor C24 and resistor R33 additionally is coupled from the emitter of transistor Q9 to -5v.
The base Or transistor Q7is coupled to ground via line 366, whilet11e corresponding base o~ opposite transistor Q8 is coupled via line 368 to tlle digital-to-analog control described in connection with block 20G in ~ig. 7A.
Line 368 will receive a controlUng current as directed by the microcomputer network 212 to carry o~lt a normalization process. Line 368 additionally is coupled with a voltage dividing network comprised of resistors R34 and R35, the former resistor being positioned within line 370 and the latter within line 372. Note that line 370 is directed to ground. I~s a consequence, a slight bias voltage is applied to the base of transistor Q8 as is further filtered by capacitor C25. Capacitor C26 within line 374 functions to filter ground line 370 from -5vsupply.
The collector of transistor Q8 is coupled via line 376 and coupling capacitor C27 to the inverting input of an operational amplifier 378. The non-inverting terminal of the amplifier is coupled to ground, while power input to the device 378 is developed from +5vsupply via line 380 and from -5vsupply via line 382. ~ capacitor C28 filters the latter line. The gain set and higll frequency roll-off chQracteristic of amplification stage 378 are derived by the feedback path shown at line 384 incorporating resistor R40 and cnpacitor C31 to provide an output at line 386. With the arrangement shown, the a.c. signnl npplicd to the base of transistor Q6 becomes a fluctuating current at its collector wllicll is referenced against -5v supply.
Tllere develops in consequence an a.c. sign~l across transistor Q9 which creates a.c. current in its collector. Tllat a.c. current is split along two paths associated with differential transistors Q7 and Q8. By controlling the current input from the digital-to-analog converter at line 368, the d.c.
voltage at the base of transistor Q8 may vary above or below ground. Where it varies below ground, the a.c. signal into the collector of transistor Q8is diminished and, conversely, if that value is above ground tlle current is starved from tlle collector of transistor Q7 and accentuated at transistor Q8. Operationnl amplifier 378 buffers the resultant signal conditioning and applies it as raw pulse data to line 386. In operation, tlle microcomputer function described in conjunction Witll block 212, evaluates tlle noise amplitude at line 22~ (Fig. 7~) and adjusts the signal at line 368 such that the noise condition achieves a nominnl consistent value, notwithstandillg that different probe instruments as at 12 may be employed. This assures - performance at the upper and lower window comparator functions describedin conjunction with blocks 236 and 238 in Fig. 7B which is consistent and proper from probe-to-probe.
The raw pulses at line 38G are directed, inter alia, through frequency shaping elements including resistor R41 and capacitor C33 in line 388 to a buffer stage described in conjunction with blocl~ 230 in Fig. 7A which is formed of an operational amplifier 390. Tlle non-inverting input of the amplifier is coupled to ground while additional frequency sllaping in gain elements thereof are provided in feedback fashion from the output line 392 of the amplifier via line 394 to line 388. Tllis feedback path incorporates resistor R42 and capacitor C34. The amplifier stage 390iS powered from +5v via line 396 coupled to -15v whicll is filtered by capacitor C35 and is coupled to -5v supply froln line 398 which is filtered by capacitor C36. The resultant output, as presented througll resistor R43, may be employed for peripheral devices such as oscilloscopes and the like wherein the buffered raw pulse data may be analyzed.
Line 386 extends additionally via line 400 to the input of comparator stages described in conjunction with blocks 236 and 238 in Fig. 7B and identified in general by the same numeration in ~ig. 8B. These stages nre essentially identically structured and thus, identical numeration is employed in their dcscription but with primed notation in eonjunction with the cireuit ~t 238.
The compnrator stage 236is formed of a type LTlOllCN8 comparator as at 4~4 into which the negative going raw pulse data from line 400 is asserted througll a resistor R44 to the inverting input. Note that the non-inverting input terminal of the comparator is coupled to ground via line 4~G
and is thus at 0 volts. As a consequence, the assertion of signals more positive than 0 voltage on the inverting input will cause the output at line 25G to assume a low value, and signals more negative than ~ on this inverting input will cause the output at line 256 to transition to higher value. The reference signals which are applied to stage 236 are presented from line 408 and extend through resistors R45 and R46 to the inverting input to create a current to the input of the system that is essentially balanced by the current from raw pulses at line 400. Any time these currents sum at point 410 to a voltage more negative than 0, a positive pulse will be outputted from the comparator 404. This arrangement is provided, inasmuch as comparators perform more effeetively where a small common mode range is involved. Capacitor C37 of the stage provides a 5v by-pass to accommodate digital noise. Resistor R47 provides a pull-up function via line 412 ror the open colleetor output of the comparator, resistor R48 and eapaeitor C38 provide a hysteresis for snap action as threshold switch-over is approached by the comparator 404 and eapaeitor C39 provides a by-pass for the -Sv supply. Capacitor C4 1 provides additional filtering of the window potential from tlle squaring circuits 250.
As noted above, the configuration of eomparator stage 238 providing an output at line 258 is identieal to that of comparator stage 236 and thus its eomponents are identi~ied with the same numeration in primed fashion.
Now looking to the squarer cireuit earlier deseribed in eonjunetion with block 250 in Fig. 7A and represented in general by that numeration in Fig. 8B, a eurrent is supplied from the digital-to-analog converter network as represented at bloek 20G in Fig. 7A under the eontrol of the microcomputer function represented in Fig. 713 at block 212. This current establishes the threshold level for the operation of comparator stage 236 and is shown herein as line 242 whieh is directed to the inverting input of operational amplifier stage 414, the non-inverting input of which is eoupled to ground via line 41G. Amplifier 414 is eoupled to +Sv at line 418 through line 420 and capacitors C42 and C43 eoupled with the former line provide a 1 33~ 440 filtering function. l`he output of st~ge 414 at line 422 is coupled to the base of PNP transistor Q10, the emitter of which is coupled through line 424, incorporatirlg resistor ~49, to the inverting input at line 242. Thus current is caused to rlow ~rom the output of the amplifier 414 through the feedback line 424 WlliCIl develops a ncgative voltage at the lower end of resistor R49.
Generally, this control current at line 242 will vary from O to 250 microamps and the volklge corresponding therewitIl across resistor R49 will vary from zero volts to -150 millivolts. The 250 microamps required at tlle output is derived from the negative voltage supply at line 426 coupled to transistor Qll of a current mirror comprisecl of transistors Qll and Q12 operating in conjunction with capacitor C44. In tlle arrangement sllown, the emitters of NPN transistors Qll and Q12 are coupled to -Sv at line 426, while their bases sre itl common as represented by line 428. The collector of transistor Q10 is shown coupled to line 428 via line 430, while the corresponding collectors of transistors Q10 and Qll are coupled in common through line 432. Correspondingly, the collector of transistor Q12 is coupled via line 434 to the common emitter outputs of differential pair transistors Q13 and Q14.
In general operation, mirror structures as shown perform such that a current which flows into transistor Qll will be split between lines 430 and 432, most of the current flowing into the collector and out of the emitter and a fraction thereof flowing into the base and out the emitter. That current which flows into the base of transistor Qll will cause a base-to-emitter potential to be developed proportional to the currents flowing at the collector base combination, i.e. proportional to the Beta of the transistor.
Transistor Q12 is identicial to transistor Qll having a common base therewitll and thus the same voltage will be exhibited at the base of transistor Q12 and an identical collector current will be caused to flow.
Thus, the collector current to transistor Ql 1 is matched by a corresponding collector current at line 434 with respect to transistor Q12 to evolve a currrent mirror operation. In the present configuration, current is flowing out of the collector of transistor Q12 and into the differential transistor pair Q13-Q14 common emitter junction. The base of transistor Q14 at line 436 is at a fixed voltage, for example -lOOmv by the combination of resistors R50 and R5 1 wllich function to form a voltage divider between ground and -5v supply. This permits the varying voltage (Ov to -150mv) at the base of transistor Q13 as coupled to the emitter of transistor Q10 via -line 438 to be botl~ rnore positive nnd Inore negative tllan the base value voltnge at line 43(i. Tl~ls, tllc amount of current available at the source line434 is changed as well as the proportion of current that flows througll the transistor Q14, a capal)ility being present to divert a greater or lesser amount of current out of the collector of transistor Ql2 effecting a deviation of current from the transistor Q14. This creates an analog squaring activity. If the asserted current at line 242 is quite small, then the current reflected to line 434 would be quite small and the voltage at the base of transistor Q13 will l)e negative but more positive than the base of transistor Ql4 which is rixed at -lO0 millivolts. /~s a consequence a small step in the output is recogni%ed. As the input currents at line 242 elevate in vulue, the reflected c~lrrents at line 434 become ]arger and, simultaneously, transistor Q13 is more ~nd more turned off to provide more and more available current at transistor Q14. Power supply filtering is provided by the parallel coupled capncitors C45 and C46, while the d.c. level at line 436 is filtered to nssure stability by capacitor C47.
The squaring current output at the collector of transistor Q14 is directed via line 440 to the inverting input of an operational amplifier 442.
The non-inverting input to the amplirier is coupled via line 444 to ground and the output thereof at ]ine 44G is coupled to line 408 as well as through resistor R52 to input line 440. A capacitor C48 performs a filtering function. Resistor R52 develops the voltage range output for the stage 442 in correspondence with squared circuit inputs thereto. The maximum value for this output voltage will be, for example, 5v.
Looking to E;ig. 8C, the squarer circuit identified in Fig. 7A at block 248 again is represented under the same general numeration. Inasmuch as this circuit is identical to that described at 250 above, the identification of components thereof is identicnlly presented in primed fashion. Thus, control is asserted via line 240 for the lower window as a positive-going current and the resultant squared output at line 408' is asserted to comparator stage 238 (Fig. 8~3) for summing at summing point 410'.
I;ig. 8C shows tlle extension of line 400 carrying raw pulse data to line 450, wllich, in turn, is directed to the +A input terminal of a peak detector configured to derive the pulse acquire function described at block 224 in Fig. 7A and identified by the same general numeration herein. The pulse acquisition stage 224 is provided as a type PKDOl~P device 448 configured by coupling to +5v at line 452 and with -Sv at line 454. Filtering of the -supplies is provided by respective capncitors C51 and C52. Capacitor C53 providcs a hoold fullction. Thc output of device 448 at lines 456 and 45B will represerlt the last and lat gest pealc vnlue for a given pulse detected.
Commellcelnent Or mensuring of the pulse heigllts is controlled from the 5 microcomputer, as represented at block 212 in Fig. 7B, by input frorn lines 460 and 462. Tllese inputs selectively reset the device 448 to zero valuation to commence collecting pulse heights, as well as to capture the resultant last largest puIse heigllt for assertion at line 458 to the microcomputer for evaluation. This evaluation may be used, for example, to establisll the 10 threshold level of the upper window comparator input at line 242 (Fi~. 7B, Fig. 8B). It also provides an hlput to the display 26 Line 450 additionally extends to the +A terminal of a peak detector device 4G~ r~presenting the princpal component of the noise averager stage described generally at block 2l8 in Fig. 7A and represented in general by 15 that numeral in the instant ~igure. Device 460 is coupled to +5v from line - 4G4 and to -5v from line 4G6 wllich, respectively, are filtered by capacitors C54 and C55.
The device 4G0 contilluQlly operates to acquire and reset applied inputs to a peak detector component thereof at gates +A, -A. This oscillation is 20 provided by the configuration of a multivibrator in conjunction with a comparator stage whicll is extant at terminals C+, C-, and CMP. In effect, the device functions to "dither" the npplied input in an essentially imperceptible manner to establish an average noise level valùe at line 468.
With the arrangement shown, a 2.5v reference is established at line 470 25 leading to the +C input to the compnrator function of device 4G0. This 2.5v reference is developed by a voltage divider comprised of resistors R53 and n54 in conjunction with ground and +5v supply. The output of the comparator is provided at line 472, the oscillatory period of which is controlled by the R-C cornbination of resistor R55 and capacitor C56, the 30 common junction of wIlic}l is coupled by line 474 to the -C input of the comparator function. The comparator output is seen directed via lines 476 and 478 to the DET termine~l of device 460 which, in turn, is coupled to +5v through resistor It5G as well as via line 480 to the reset input terminal. A
resistor R57 provides hysteresis performance. Capacitor C57 provides an 35 averaging function for tlle average noise input signal while resistors R58 and R59 provide a gain, for example, of 2 for the peak detector function at the +~ terminals. ~ buffered output is provided at line 468.

Returrling to ~ig. 8A, tl-e rate amplification function as well as self-test circuit discussed in conjunction with blocl(s 312 and 320 in ~ig. 7A are illustrated nt nn enllarlced level Or detail and identified with the same general numeratiom nate output or count rate information is derived by the S microcomputer networl~ described in conjunction with Fig. 7B at block 212 and, as described in conjunctiorl with ~ig. 7l~ is presented to the stage 312 via line 314 e~tending, in tUrn, from tlle VAC network 200. Line 314 leads to the non-inverting input of an operational ampUfier 486 and the current value thereof which, for example, will range from 0 to 250 microamps is directed to a I l~ohln resistor R60 witllin line 488 shown coupled to ground from line 314. The output of amplifier 486 at line ~190 is directed to the base of NPN transistor Q15, the emitter of which is coupled by line 492 to ground and whicll incorporates gain scaling resisitors R61 and R62. The inverting input of the amplifier 48G is connected by line 494 to a position 15 intermediate the latter resistors to carry out this function. The output fromamplifier 486 will, for example, range from 0 to 2.75v and is directed via line 496 to the norl-illvel ting output of buffer amplifier 498, the output of wllicll is provided at the earlier-noted line 316 (7A) incorporating resistor RG3. The opposite input to buffer stage 498 is coupled to output line 316 via 20 feedbaclc line 500 and the resultnnt output of the device is shown QS labelled "RATI~ OUT" which rnay be used for a variety of analysis purposes.
Collector current at transistor Q15 at line 502 leads to a current mirror comprised of transistors Q16 and Q17 having common bases as represented by line 504, which bases additionally are coupled to tlle 25 collector of another PNP transistor Q8, the emitter of which is coupled to +12v supply at line 50G as asserted through resistor R64 and line 508. As before, n line 5 10 extends rrom line 502 to line 504. With the arrangement, positive current can be produced out of transistor Q17 and into tlle input of tlle normali%ing amplifier via line 202. Note that the emitters o~ respective 30 transistors QIG and Q17 are coupled to line 5~6 through respective balancing resistors RG5 and R66 and that the supply is filtered at line 506 by capacitor C58. Resistors RG5 and RG6 serve to balance out any differences of performance parameters Witll respect to transistors Q16 and Q17.
Transistor Q8 serves the switching function for the self-test and can 35 be turned on upon rnicrocomputer command to sink away the available current to the base of transistors Q16 and Q17. in this regard, the base of transistor Q8 is coupled via line 512 to the collector of NPN transistor Q9.

~ 337440 Linc 512 is couplc~ to ~lus supply at linc 50G througll resistor RG7. The putsc amplitudc ~or thi~s simulatcd pulse is developed by adjusting the voltage across resistors I~Gl and IIG2 to scnle t~le resulting current frorn transistor Q17. Tllcll, upon quite rapid command, as a matter of nanoseconds,trallsistor Q8 can be turned off and on to enable transistor Q17 and produce the resullallt pulse, the combined control, in effect, making tlle pulse any width and heigllt desired for a testing procedure. The rnicrocomputer runction will produce levels on the order of O to Sv into line 322. These pulses are lcvel shifted to operate in conjunction witlI the +12v 10 supply at line 50G by NPN transistor Q19, the collector of which is coupled to line 512 and tlIc emitter of whicll is coupled to line 322 via resistor R68.
Two and one-half volts are applied to its base from divider resistors RG9 and R7~), the formct being coupled to ~5v su~[)ly and the latter being coupled to ground.
TurnilIg to l; ig. 9, the volume control and audio amplifier stage described in conjunction with respective blocks 2GG and 274 in Fig. 7B are represcnted in cnharlced levels of detail along with general identification with the same numerntion.
The microcomputer described in conjunction with block 212 in Fig. 7B
will develop a volume output signal ranging from +5v to -5vthrougll a solid-state form of potentiometer as described in conjunction with block 270 of the latter figure. This signal is applied, as earlier described, via line 268 througll scaling resistor R73 to a current mirror comprised of NPN
transistors Q20 nnd Q21. /~s before, the emitters of these transistors are coupled in common to -5v supply at line 514, while their bases are in com rnon as represented by line 51~. A filtering capacitor C59 provides stability at the common bnses of these transistors while a current splitting line 518 is coupled between the collector and base of transistor Q20. The output of the current mirror at the collector of transistor Q21 at line 520is connected to the common emitter connection of differential paired transistors Q22 and Q23. The base of transistor Q23 is coupled to ground througll resistor I~74, wlIile tlIe corresponding base of transistor Q22 at line522is modulated by an audio squarewave of controlled, variable frequency generated from tlle microcomputer function at block 212 and presented along line 264througll coupling capacitor C60 and resistor ~75. Line 522is seen to extend to ground through resistor n76. Thus, modulation of the current mirror controlled volume signals is provided. In this regard, the collector Or transistor Q23 is coupled to ~ 12v and tl-e rcsultant volume controllhlg sigmll gcnerated tht ough resistor R77. Correspondingly, tlle 180~ phase separated e(luivlllerlt sigrlal at tlle eollector of transistor Q22 is provided nt lirle 526 and is provided ~s the opposite drive control in put at resistor n78. These differential inputs are used in a push-pull drive arrangement of the audio amplification stage shown generally at 274.
Looking to one side, it rnay be observed that the signal at line 524 is coupled to the invcrting input of operational amplifier 528 through line 530 and eoupling cnpncitor CG1. Tlle opposite input to the amplifier 528 is coupled IU via line 532 and resi.stor R79 in line 534 to ground as part of a voltage divider networlc including resistor R82 and capacitor C64. l~mplifier 528 fullctions to operate respective PNP and NPN power transistors Q24 and Q25 in clas~sic push-pull fnsllion. In this regard, the bases of these transistors are coupled to the output at line 536 of amplifier 528 via feedbaclc line 538 incorporating resistor I~79 and line 540. The collector of transistor Q24 is coupled to +12v at line 542, while the emitters thereof are conneeted by line 544 to output line 536. The collector of transistor Q25 is coupled to ground. T,ine 53G is shown to incorporate resistor R80 which, in turn, is coupled to line 5~4. The output of the drive transistor is coupled via 2() line 546 to one input of the loudspeal~er or annunciator 276.
The corresponding differential drive signal is presented through resistor R78 and capacitor C63 within line 548 to the inverting input of operational amplifier 55~. The non-inverting input to amplifier 55~ is coupled to line 532 wllicll, in turn, is coupled through resistor R8() to +12v supply. The output of amplifier 550 at line 552 extends through resistor R81 to line 554 eommonly coupling the emitters oE respective NPN and PNP
power transistors Q2G and Q27. Transistor Q27's collector is eoupled to ground, while the corresponding eollector of transistor Q26 is eoupled to line 542. The output of amplifier 550 at line 552 is coupled to feedbaek line 556 3~ incorporating resistor R83 and, the arrangement funetions to provide push-pull or differential power to the loudspeaker 276 through eoupling capacitor C65 and resistor R84 within line 558.
Control over frequency and volume thus provided permits a broad flexibility in developing an audibly perceptive eueing to the surgeon using the probe device 12. In particular, it is this eontrol over loudness and frequency which perrnits the "siren" type output whieh inereases in _ 1 337440 frequency and volume as the situs o~ tumor containing more concentrated radiolabel is npproached.
I~eferring to ~igs. 10~ and 10B, the digital or microcomputer driven functions oE the control fentures-of the invention are represented at an enhanced level of dctail. Looking to ~ig. 10A, the principal logic control for the instrumentation seen to be provided by a microcomputer 570 which may be provided, for example as type MC68~ICllA8 as marketed by Motorola, Inc. This single-chip microcomputer employs HCMOS technology and includes on Cllip memory systems including an 81~ byte ROM, 512 bytes of electrically erasable programmable ROM (EEPROM), and 256 bytes of static RAM. TlIe device also providcs on chip peripheral functions including an eight channel analog-to-digital (A/D) converter, a serial communications interfsce (SCI) subsystem nnd a serinl peripheral interface (SPI) subsystem.
~nother feature of the device employed with the instant instrumentation is a pulse accumulutor which can be used to count external events (gamma ray related pulses) in an event counting mode. Port groupings on the device are shown labeled as "PA, PB, PC, PU, P~". Clock input for the microcomputer is provided from a four Mllz crystal 572 performing in conjunction ~ith capacitors C70 and C7 1 as well as resistor R90. Device 570 interfaces througll an address bus coupled to its P~ port at 574 and branching as shown at 576 and 578 with an erùsable programmable read only memory (EPROM) 580 having 321~ bytes of memory. The corresponding data ports of the device 580 are coupled to data bus 582 shown branching as at 584 to extend to the PC terminals of microcomputer 570 (Fig. 10~). Memory 580 is shown coupled to +5v at line 58G as filtered by capacitor C72 and is enabled from along line 588 extending to a terminal of an erasable programmable logic device (EPLD) 590 described in conjunction with Fig. 7B at block 260 as a real time pulse discriminator, that numeration also being provided in the instant drawing. J~evice 590, a type EP600 marketed by ~ltera Corp.
incorporates a large compilation of 600 logic gates which are programmable to develop desired Boolean functions within a single component. It is shown coupled to +5v supply as followed by capacitor C77.
Data bus branch 584 is seen branching as at 591 for connection with an array of pull-up resistors 592 coupled, in turn, to +5v.
Branch 584 further extends via branch 594 to the Y outputs of a type 74541 input buffer 596. This device is shown coupled to +5v supply as filtered by capacitor C75. The lead array extending from the A ports of the _.
device at 598 is coupled to pull-up resistors from the array thereof at 600, whcrcupon thc deviccs nre coupled to ports 0-7 of a connector N3 leading to thc kcyboard type switchcs 32-40 at console 16. Data bus branch 584 also extends via branch G02 to tlle 1) input tcrrninals of type 74574 output latches 604 and G~G shown coupled to +5v as respectively filtered by capacitor C73 and C74. These latches provide general purpose outputting at 16 locations as labelled at connector N3.via respective lead groupings 616 and 618.
/~ supplementary branch 608 of the data bus extending from branch G02 is employed for drivillg the LCD display 26, the outputs being represented as Al)0-7 in connector N3. Similarly, read/write information to tlIe display is provided to the connector from line 620; the display clock is driven from line 622; tlIe display reset is provided frotn line 624; the display select signal is provided from line 626 rrom device 590; and the l/O port selection of tlle display is made by signal from line 628, all of the above leac3ing to connector N3 as labeled. Devices 596, 604 and 606 are enabled, rcspectively, from lines G10, G12 and G14 extending from logic device 590.
Drives to the dual L~D at 28 of the console 16 as described in Fig. 1 are provided at connector N3 throllgh lines 634 and G36. The latter lines lead to tlle dif~erential transistor pair of a transistor array component represented at 638. These transistors are selectively actuated from the output ports 4 and 5 of lead array grouping 616 through respective resistors R91 and R92.
l he transistors of componcnt 638 also may be employed to buffer raw pulse data representing the output of device 590 at line 640 (I;ig. lOB). Such an input may be provided from the device 590 at line 640 for assertion through resistor R93 to the base of a buffer transistor within component 638. The emitter Or that transistor is coupled via line 642 to ground and resistor R94 to line 64(~ and the output thereof at line 644 is coupled to +v througll resistor n95. ~ line G46 carries the raw pulse signals to connector N3 for providing availability to them through the back panel of console 16. In similar fashion, the apparatus is capable of receiving serial data in for inputs from a remote facility nt connector N3 as attached to line 648. Such inforrnation is fed througII resistor R96 and directed to the base of a level shifting transistor within component 638 for presentation to the microcomputer input line PD0. The latter line is shown coupled at +5v through resistor R97. The emitter of the subject transistor within component 638 is coupled to ground and a diode Dl is coupled from the emitter to line 648 for protecting the transistor.

Microcomputcr 570 adclitionally receives a reset from the circuit represented gcnerully at G50 nnd comprised of capacitor C76, diode D2, resistors n98 nnd Tl99. The resct function extends via earlier-described line 624 to connector N3 for purposes of resetting the display 26. Output from 5 the networlc G50 is througll line G52 extending to the reset terminal of microcomputer 570.
Three of the leads of bus ~rray 616 are tapped at line array 654 and directed as represented by bus 65G to the input of an EEPO T described earlier at block 270 in connection with Fig. 7B and shown with lil~e nulneration in Fig. 101~. Coupled between +5v and ~5v, the device 270 provides a solid-state election of impedance values with memory under the control of the microcomputer 570 from input G5G. The resultant output, wIlich may vary between -5v and +5v, is directed along line 658 for output~irlg at conllector Nl leading to line 2G8 as described in conjunction witll ~igs. 9 and 7B. Similarly, the audio squarewave input to line 264 of that volume control function is provided from one PE port of microcomputer 57~ via line 6G0.
Microcomputer 57~ is programmed to monitor the power supplies as described at blocl~ 180 in l~ig. 7B, employing a multiplexing approacll as represented by block 298 in that figure. Connector N2 is shown itl Fig. lOB
calrying the inputs rrom the various aspects of the power supply. These power inputs are both used by the instant circuitry and monitored by the microcomputer 570 through the noted multiplexer function 298. In this regard, it may bc observe(3 that line GG2 functions to monitor battery status, while line GG4 monitors a voltage reference. These lines are directed to two of the inputs of the multiplexer shown at 678 in Fig. IOA. The bias supply for the crystal 58 of the instrument is monitored from line 666 following a level shi~ting procedure which, lool~ing to ~ig. lOA is provided from one stage of a quad operational amplifier component shown at 682. Note that line 66G extends througll resi~tor R98 into this stage, the latter resitor beingcoupled with a divider resistor R99 and the output of the level shifting stage being provided at line GG7 which extends to another input of tlle multiplexer 678. ln similQr fashion the +12v power supply is coupled througll resistor R100 by line 6G8 and is additionally coupled to ground through resistor R101 and line 676. Line 668 is seen directed to another input of multiplexer stage 678. The +Sv supply is adjusted by resistors 102 and 103 and submitted via line 670 to a multiplexer stage 678. The -5v supply is monitored from line G72 which is seen to extend through resistor R104 to another level shifting stnge of component G82. Tl)c shifting furtller is affeeted by feedbaek resistor R105 and tllc resultnnt output to multiplexer stage 678 is provided at line 673. I;inally, the -9v supply introduced at connector N2 is monitored 5 by line G74 whicll e~tends through resistor nllO to another level shifting stage of eomponcnt 682, the level shifting further being eontrolled from feedbaek rcsistor R 112 to provide an output to the multiplexer stage 678 from line 675. Note that line 676 eouples intermediate components of connector N2 to ground.
I;ig. 10~ furtller reveals tllat the fourth amplirier stage of eomponent G82 is used to provide a serial output port, the stage receiving the noted reference signal as provided at connector N2 and being presented with pulse data as an input througll resistor R114 at line 684. The level shifted signal tl~en is asserted at line 68G througll resistor Itll6.
rig. lOA also reveals the prescnee of a quad digital-to-analog eonverter component deseribed earlier in conjunetion with bloclc 206 in Fig.
7l~ and represented in general by the same numcral. The component, shown at 688 is coupled to +5v at line 690 as filtered by capacitor C80 and is controlled rrom microcomputer 570 via address bus 584 and branch 710 as 2û well as bus G92 and lead grouping 700. Read/write commnnds are nsserted from the microeomputer 570 through a cireuitous arrangement ineluding lines 694, 696 and G98, while the ehip seleet input thereto is provided from 711 extending from deviee 590 (1;ig. lOB). The four ehannels of output from deviee 688 are shown at line grouping 702 leading to eorresponding conneetors withill the eonneetor eomponent Nl. These deviees extend, for example, to the two squarer networks deseribed at bloeks 248 and 250 in Fig. 7A as well as the rate amplifieation networlc 312 described in that figure and the normali7ing amplifier deseribed at bloek 204 in that figure.
Also shown entering the eonnector N 1 are the upper window pulses and 3() lower window pulses respeetively developed at lines 256 and 258 (Fig. 8B) whieh are direeted as labeled, to the eorresponding inputs at eomponent 590 (~ig. lOB). Additionally, tlle probe current monitored output at line 352 - (I;ig. 8A) enters for assertion at a Pr. terminal of microcomputer 570 via line 704. Further, the output of the noise averager networks shown at block 218 in Fig. 7A and developed at line ~20 are presented to conneetor Nl and conveyed to microcomputer 570 via line 706. The corresponding pulse acquisition output, as described in conjunetion witll bloek 224 in Fig. 7A, is shown entering tlIrougll connector Nl for presentation to the microcomputer 570 via line 708. Address bus 574 is seen to extend to the Q input terminals of an address latclI 712. Provided as a type 74573, the latch functions as a portion of a memory interface saving lower data bits and converting tlIem to addresses. The output of the latch 712 as coupled to the branch 714 of data bus 710. Latch 712 is coupled to +5v as shown which is filtered by capacitor C81.
~ddress bus 574 also is seen being directed to the A terminal input of a real time cloclc and calendar component described in conjunction witll block 29~ in Fig. 713 and shown with the same numeration herein. Marketed as a type DS121G component by Dallas Semi-Conductor, Inc. the device hIcorporates an embedded lithium energy cell such that CMOS static ~AMs associated tllerewitII can be converted to non-volatile memory. The device Iceeps track of hulIdreds of seconds, seconds, minutes"lours, days, date of the montII, months and years. These data may be of considerable value in maintaining researclI statistics in conjunction witIl the instrumentation 10.
The device as represented at 71~ is coupled to +5v as filtered by capacitor C82 and the O terminals thereof are coupled to data bus via branch 718.
~s indicated earlier herein, for surgical utilization, it is necessary that the instrument 12 be maintnined in a clean and sterile condition prior to its implementation within the surgical theater. Thus, the outer surface of the device is polished for ease in cleaning contaminants therefrom and the assemblage is suitable for sterilization preferably by gaseous treatment.
/~ technique whicll both simplifies cleaning the instrument and maintaining its sterile condition involves the use of a disposable plastic cover which fits over the probe device 12 and which is formed of a polymeric material which is readily produced in a sterile state. Thus, prior to an operation, the surgical personnel will slide the probe within the cover or sheath. The addition of the polymeric surface aids in the control of vibration induced noise as well as representing an ideal technique for maintaining tlle requisite sterile condition for the device. Looking to Fig.
11, the instrumerIt 12 is shown in dashed line fashion within a polymeric cover 730. The cover 730 includes a nose portion 732 formed of a tough plastic having a thickness, for example, of 0.020 inch. This will protect the cover 730 from tearing or the like when used in the rigorous activities of surgery. From the nose portion 732 the sheath may extend rearwardly a `~ sufficie1It Icngth to cover the signal transmission components as at 14 for a su~ficient distnncc to nssure sterile integrity.
Periodic caIibratioIl is nn important aspect of operating the apparatus 10. In this regard, a check source is employed preferably which is readily 5 positionable over the forward portion 20 Or the probe instrument 12.
I~dditionally, n noise adjustment fixture is employed whicll is structured to temporarily shield the detector components from local sources of radioactivity, i.e. within the surgical theater. Turning to Figs. 12 and 13, such a noise adjustmellt fixture is represented generally at 734. Looking to 10 ~ig. 13, the component 734 is seen to be formed having an outer cup-like portion 736 formed of a radiation attenuating material such as lead having a thickness, for example, of 0.125 inch. Within the outer cup 736 is a center cup 73~ faslIioned oî n smooth, soft washal)le material such as teflon, nylon or the lilce. A loose fit over the portion 20 of the instrument 12 is desired.
15 This arrangement functions to block such local sources. A check source retainer is formed in similar fashion as the inner cup 738 to fit over forward portion 20 of the instrUmeJIt. Again using cup 738 as exemplary of this checlc source fenture, within the center portion 740 (l~ig. 13) of the cup ~34 there would be positioned a check source of radiation of relatively low 20 energy but extensive half life. ~or example, lodine 129 represents a viable material for this purpose.
The general program under which the microcomputer 570 performs is represented in flow chart format in Fig. 14. Referring to the latter figure, the start of the main program is represented at node 750 which is shown 25 directed via line 752 to the self-diagnostic and initialization procedures represented at bIock 754. Following such initialization, as represented at line 756, the main program proceeds to display screen information to the operntor as represented at block 758. The particular information displayed is determined witl1 respect to the particular type of utilization being made 30 of the instrument 12. In general, however, the main program reacts to an interrupt generated from the "keyboard" represented by the switches on the console lG represented in general at 30. Accordingly, the program progresses as represented at line 760 to the inquiry at block 762 determining whether or not a l(eyboard switch has been depressed. The l(eyboard 30 is 35 sampled on about 10 millisecond intervals for a valid character, i.e. one whicll pnsses a simple "debounce" test. In the event tllere is no valid I(eyboard switch depression, then as represented by loop line 764, the main prograrn returns to line 7G0 to again await the depression of a switch by the operator. In the cvent a vali(l l(ey or switch dcpression has been detected, thcn as rcpresented at line 7GG, tlle main prograrn perrorms in accordance with the function of the key so depressed. This will include the depression 5 Or up-down arrow switches as at 39 and 40, alteration of mode count techllique 34, and the like. Following the carrying out of the function associated with the noted switch, as represented by line 770, the program returns to line 75G again to display screen information corresponding with tlle keyec3 instruction and agaill to await a key interrupt.
I,oolcing to 1; ig. 15, tlle main or general interrupt routine of the program is revealed as starting at node 772. As represented at line 774, the interrupt routine initially saves register information, as represented at block 776. Then, as represented at line 778 and block 780, an inquiry is made as to whether the key information received is valid. For example, for a valid switch depression to be recognized, at least two interrupts are required. In the event that a valid key or switch depression is detected, then as represented at line 782 and block 784 a filtering function is carried out to determine whether or not the Orr switch 33 has been depressed. In that event, then there is no rationale for continuing witll the active program.
Thus, assuming that the off button has been depressed, as represented at line 786 nnd block 788 a checl~ sum is prepared to assure that the data in memory are valid and the information is then saved in non-volatile memory (EEPROM), it being recalled that the microcomputer 57~ has 512 bytes of such non-volatile memory. The program then proceeds, as represented at line 790 and at block 792 to turn off the system, whereupon as represented at line 794 and node 79fi, the interrupt routine is ended.
Assuming that the off button was not actuated, then as represented at line 798 and bloclc 800, the interrupt routine determines whether the reset count switch 3G of console 16 has been depressed. Generally, the pulse 3~ counting procedure is onc having several modes of operation. In its most simple performance, an event count which is identified at display 26 as "mode count" provides a straight-forward accumulation of counts in incrementation Or the displuy. Loolcing momentarily to Fig. 16, the display is revealed for this orientation. The LDC output of large numbers at 802 provides the numeric readout of the accumulated counts. Actuating the reset count button or switch 36 resets this published count to zero on the fly, is it were. This particular mode is sometimes used for checking or adjusting the instrulTlellt. lhe mode count identification in the display is publislIed ns rcvcrse vidco readout at region 804. Note additionally on the display tllat n "SOUNI) VOL" readout is supplied above the numerals at 806 whicll, wllen active, will be represented in reverse video. The particular 5 audio volume is selected by the operator by pushing switch 35 and manipulating up-down buttons switches and 40 in conjunction therewith.
lhe display 26 provides a bnr graph representation of selected volume as shown at 808. T~isplay 26 nlso will portray upper (U) and lower (L) compnrator window settings as a chart shown at 810. The lower portion of 10 this chart at 811 shows noise level, the above which pulse height is portrayed at 812. l~indow limits (U,L) are represented by labelled horizontal dashes. Additionally, display 2G will show batttery charge status in bar chart form as at 813.
The count modes which are selected by actuating SWitCll 34 in 15 conjunction witlI up-down switches 39 and 40 includes a time count which is a str~ight-forward accumulation oî counts for a specified interval. A next count in this mode is initiated by depressing reset count 36. Counting intervals of 1, 2, 5, 10, 20, 30, 50, 60 and 100 seconds are selectable in the count mode using switches 39 and 40. 1~ rate mode also is selectable within 20 the count mode election at switcll 34. For that mode arrangement, the display at 804 will read "MOI)l R~TE CPS". Correspondingly, where the noted timed modes are available, the display at region 804 will read "MODE
COUNT/SEC" (see ~ig. 22). Two seconds is a default value for tllis feature in the event the operator has picked no others. The count mode switch 39 25 actuation also provides Q time to preset function which is a useful constant accuracy mode of operation. In this mode, preset counts of 100, 200, 500, 1,000, 2,000, 5,000 and 10,000 are selectable, 100 counts being a default value. The counter and readout 802 increments from zero to the selected preset value and holds. Thus, the display SllOWs the number of gamma rays 30 counted until it reaclles that preset number, whereupon it switches to show the number of seconds required to reach the preset count. The reset key 36 resets tlle display to zero and initiates any next counting sequence.
I~ccordingly, the count mode switch 34 initiates this count mode and the up/down arrow switches 39 and 40 may be actuated by the operator to 35 develop "COUNT", "TIMI~ COUNT", "R~TE", I'TIME TO PRESET" and "OF~"
displays and modes of performance.

-- ~eturning to I~ig. 15, in tlle event tlle reset switch 36 has been actunted, tllen as rcpresentcd at line 822 and block 824, the data count is reset to zero, the L~D 28 is illuminated green and the collect mode recommenccs as thc program continues as represented at line 826.
In the event tllat no reset actuation has been observed, then as represented at line 828 and block 830, switch information is saved and the program continucs ns represcnted at line 832 to the inquiry at block 834 to determirle wllether it is appropriate to update the display 26 and real time clock in~ormation. I~lso associated with line 832 is the path line 836 frorn 1() block 780 showing that the program defnults to this position in the event no valid switch actuation has been detected. In the event the appropriate timing is at harld to update the real time information, then as represented at line 838 and block 840 a substantinl amount of updating occurs.
l~ desirable aspect of the operation of the instant instrumentation resides in its capability for accumulnting pulses such that the microcomputer 570 is not called upon to sample periodically to look for received count. /~s a consequence, no "dead time" between sampling is present within which any counts might be lost. An 8-bit register within the device 570 permits a gathering of up to 255 events or counts before it must be read or overflows. Thus, the register may be read at a 10 millisecond interrupt rate witllout rcsort to time critical subroutines attempting highly rapid polling procedures. I~s shown in block 840, the updating includes the display 26 data, sound information in terms of volume and the like, the real tilne cloclc, the time spent counting and all counting modes and information.
Following such update, as represented at line 842, the routine returns to line 844 also representing a deterrnination that the time` for updating has not occurred as developed at the inquiry at block 834. The program then turns to tlle instructions at block 84G where the registers are stored and the interrupt routine is terminated as represented by line 848 and end node 850.
3~ I~s part of the interrupt updating, the program also evolves count rate information which has particular utilization in the surgical guiding feature of the instrumentation oî the invention. Looking to Fig. 17, this interrupt update routine is revealed as commencing at block 852, the program commencing as represcnted by line 854 and block 856 to read the count 3S register. ~s represented at line 858 and inquiry block 860, a determination is made as to whether a one second cpllection interval llas elapsed. If such is the case, then as represented at line 862 and block 864, the count total .. _ then is made equal to tlle previous counts and the counts in tlle register. As represented then at line 8GG and bloclc 8G8, the rate is computed as the total counts divided by time which may be either a one second interval or a G0 second interval. The program then progresses as represented at line 870 and S block 872 to display the updated information us to rate.
In the event the determination at block 860 is in the negative, tllen as represented at line 874 and block 876, an inquiry is made as to whether 1/10 second has elapsed. If 1/10 second hns not elapsed then, as represented at Ible 878 and block 880, no number of count~s is saved and the register is updated. /~s represented at line 882 and node 884, this portion of the update routine then is concluded. On the other hand, should thc inquiry at block 876 determin that 1/10 second has elapsed, then as represented at line 886 and block 888, the previous number of counts is added with the new b~formation frorn tlle count register and, the routine continues as represente(l at line 890 and block 820, the rate is computed with respect to the 1/10 second intervnl. The program then progresses to earlier described block 872 as represented by line 894. Upon completion of display update, then as represented at line 896 and block 898, the rate information as developed by tlle 0.1 second incrementation is saved for purposes of updating the siren audio output of the system which is used in immuno-guided surgery. As represented at line 900 and node 902, the routine then is completed.
Turning to ~ig. 18, another portion of the update display routine described in connection with Fig. 15 is represented, the latter display updating function being represented at block 904. This routine progresses as represented at line 906 and bloclc 908 to a determination as to whether the diagnostic mode has been called for. This mode is accessed by a combination of switch actuations at array 30 and is used mostly by maintenance and factory personnel, for example, to establish selected bias for the crystal 58. The mode derives readouts for various voltage levels which can be adjusted in conjunction with observing the readout. Thus, if the diagnostic mode is detected, then as represented at line 910 and block 912, the voltage and other diagnostic information is displayed. The routine thèn exits as represented at line 914 and node 916.
l~1here the diagnostic inode is not present, as represented Qt line 918 and block 920, the program then reads the real time clock and updates the main display information. The program then proceeds as represented at line 922 and block 924 to dis~tlay tllc inrormation so updated and further updates grapll displays, for cxample, such as tllat shown in ~ig. 16 at 808, 810 and 8 13 showing nudio volume level for the readout, pulse and noise levels and battery condition. Tlle routine then proceeds to end as represented by line 926 leading to node 91 G .
Turning to I; ig. 19, the programming interface routine which cssentially is part Or the routine of Eig. 14 is represented as commencing at block 928 and line 130 to the determination as to whether a calibration as cnlled for by switch 38 o~ console 16 has been called for. In the event that it has, as represcnted at line 934 and block 936, the display 2G commences to read out instructions in a user friendly manner for the attachment of the noise adjustment fi~ture as described at 734 in Figs. 12 and 13 and subsequent adjustrncnt of the device. Following such adjustment and completion of the instructions displayed, then as represented at lines 938, 940, and 942, the programming interface rnode ends. 1~ the calibration mode has not been called for, thell as represented by line 944 and block 946 the program then inquires as to whether the sound mode has been called for by actuation of SWitCIl 35. If that is the case, then as represented at line 948 and block 950, the display 2G shows graphic information as to volume level as shown at 808 in I ig. 16 and updates the particular sound state called for.
In particular, the up/down switches 39 and 40 may be employed to elect a "click" type sound reminiscent of a Geiger counter, a "beep" sound of longer duration, the earlier-noted siren tone, the frequency of which varies with the radiation level detected. This tone enables the user to detect evidence oE variations in radioactivity levels while watching the position of the probe itself. I;inally, Mn OE~ election may be made in tllis mode. Eollowing the updating of information elected by the user, then as represented at line 952, the routine e~its as represented by lines 940 and node 942.
In the event the determination at block 946 is that the sound mode was not entered, then as represented by line 954 and block 956 a determination as to what mode for counting has been elected. This mode is entered by the actuation of switcll 34 upon console IG. In the event the mode is elected, then as shown at line 958 and block 960, the various options for this mode are displayed at display 2G. The options will include the earlier-discussed "TIME COUNT", "RATE", and "TIME TO PRESET" which, in turn, lead to additional dialogues with the user. As before, the up/down switches 39 and 40 adjust rates within the count mode election; they adjust volume; and they carry out calibration adjustlnents. In effect, these switches provide a change o~ value or adjustment within a current function within which the system is operating. ~ollowing tlle ndjustment and display as represented at block 960, as shown at lines 9G2 and 940 and node 942 this routine ends.
In the event the determination at block 956 is in the negative, then as represerlted at line 964 and block 9G6, the system then considers the above-described actuations o~ switctles 39 and 40 witll the up/down functions.
Where those switches have been actuated, then as represented at line 968 and block 970, a deterrnination is made as to whether by so actuating either of these switchcs, the resultant election should be displayed SUCtl as the counts per second or counts per minute rate and the like. Where such display should be made tllen, as shown at line 972 and block 974 the new information is displlyed and as represented at line 976 and line 940, the routine exits as represented at node 942. Where no new function may be displayed, as determincd at 970, then as shown at line 978 and line 940, the routine exits as represented at line 942. Similarly, where tllese switches 39 or 40 have not been actuated, then as represented at line 9~0 leading to node 942, the routine ends.
Turning to ~ig. 20, a self-diagnostic routine is represented as commencing at block 982. This self-diagnostic routine may be used a number of tirnes during the main program, its most important application being at the commencement of any given use. The program commences as represented at line 984 to the inquiry at blocIc 986 wherein a determination of the appropriateness o~ the operating voltages is made. This activity includes tlle monitoring evaluations made in conjunction with connector N2 as described in conjunction with Fig. lOB, and includes an update on battery charge status. In the event that these conditions so monitored are incorrect, then as represented at line 988 and block 990, the user is advised ut display 26 that tlle operating voltages are incorrect, and as represented at line 992, the program is brought to a hault as represented at node 994.
Where nll monitored parameters are correct and the probe 12 is appropriately mounted or attached to console 16 then as represented at line 996 and block 998, the background is evaluated and this background will include cosmic disturbance, normal electrical noise and the lilce. ~ecall that this adjustment is made ~rom the digital-to-analog converter ~unction described at block 206 in I;ig. 7A. Following setting of this background noise level, as shown at line 1000 and block 1002, a determination is made as to whether adjustrnent can be macle within specification. In the event that the noise adjustment is without ~specification values, then as represented at line 1004 and block IOOG, the diagnostic digital-to-analog converter input is set as descril)ed at lhlc 314 in Fig. 9, the self-test pulsing at line 322 is carried out and, the "front end" analog circuit including ~ig. 8~-8C is tested wilh a diagnostic pulse. Then, as represented at line 1008 in block 1010, a determinEItion as to whetl~er analog circuitry (front end) was performing correctly with the test pulse is made. Where that is correct, then as represented at line 1012 and block 1014, a determination is made that the preamplirication stage witllin tlle instrument 12 is defective and the user is so advised at display 26. /~s represented at lines 1016 and 992, leading to node 994, the program then halts. Where the indication of the front end test at blocl~ 1010 shows that the analog circuitry was not functioning properly, theIl as represented at line 1018 and block 1020, the user is advised at display 2G tllat the annlog circuitry or "front end" is defective. The routine then proceeds as represented at line 1022 to halt as indicated at node 994.
Where the indication that the noise is adjustable to specification is made, then the program proceeds as represented at line 1024 and block 1026, the unit is ready for operation and as represented at line 1028 and node 1030, the routine ends.
/~s describcd in conjunction with the flow chart of I; ig. 17, the microcomputer 570 continuously updates the value of the count rate. This feature is used to update the status of the sound output function of the instrument. Looking to Fig. 21, the routine under which the siren perceptive output is achieved for immuno-guided surgery is portrayed as "Update Noise Maker" represented at blocl( 1032. This routine commences at line 1034 to the inquiry at block 103G whereill a determination is made as to whether the current pulse rate has changed. ~lhere that is not the case, then no alteration takes place in the sound output parameters and the routine exits as represented at line 1038 and end node 1040. IIowever, where the current rate has changed as determined at block 1036, then as represented at line 1042 arld block 1044 an increasing (up) or decreasing (dn) rate condition is evaluated. If the rate has gone down, then as represented at line 1046 and block 1048, the frequency applied at line 264 (Fig. 9) is diminished and, as represented at lines 1050 and 1038, the routine ends as represented at node 1040. Ilowever, where the rate llas gone up, then as represented at line 1052 and block 1054, the frequency is altered to rise and, as represented at line 105G and node 1040, the routine exits. Witll this routine, the so-called siren tone may move from a "growl" on and off sound essentially near background radiation levels to a siren tone QS tlle target area is encountered, the sound witnessed usually represents a dramatic increase in 5pitch as increasing radiation levels are encountered. As shown in Fig. 22, the siren indication is provided at region 806 of display 26, while the range mode is displayed at readout 804 in conjunction with the range graphics at region 814. When the range switch 37 is actuated, or held down, the siren tone will be elected, a bar graph 814 displaying threshold of the siren tone 10being shown. The range function adjustment permits adjustment of the device by switches 39 and 40 so as to be silent for background levels but to com mence siren audil~les whell a more radioactive area is scanned. In practice, the range function is often adjusted with the up/down switches 39 and 40 in conjunction with this siren operation.
15Turning to ~ig. 23, a remote display update routine is shown commencing at block 1058 and the routine is designed with respect to the Ilitaclli type LM21313 display device 2G which is operated in a graphics mode both for characters and graphics. The routine commences at line lOG0 wherein the x,y position of the display cursor is located. Where such 20location is determined, then as represented at line 1064 and block 1066, the display address register is set and the x,y coordinates of the cursor are retained in memory. The routine then exits as represented at line 1068 and node 1072. Ilowever, where an ongoing cursor activity is not present as represcnted at line 1074 and block 1076, a determination is made QS to 25whether the display has been cleared. If that is the case, then as represented at line 1078 and block 1080, the cursor is homed to its initial 0,0 position and zeroes are written to all pixels to erase the display 26. ~s represented at lines 1()82, 1068 and node 1072, the routine then ends. Where the display is not cleared, then as represented at line 1084 and block 108G, a 30determination is made as to whether it is necessary to draw lines on the display. If that is the cnse, then as represented at line 1088 and block 1090, the starting and end positions of any given line are located and the cursor x,y coordinate orientations are such as to fill in the lines between tllose two end locations in horizontal and vertical orientations. The routine then exits 35via lines 1092, 1068 and node 1072.
Where the draw lines routine is not called for, then as represented at line 1094 and block lO9G, an inquiry is made as to whether a box or 1 33744~

rectangulur drawing is reguested. In the event that is the case, then as represented at line 1098 and box 1100, the start and end positions oE the rectangular structure are located and four lines defining the rectangular form are rilled in. The routine then exits as represented by lines 1102, 1068 .5 and node 1072. Whcre the box drawing is not called for, then as represented at line 1104 and block I IOG, an inquiry is made as to whether a character is to be displayed. 1~ that is the case, then as represented at line 1108 and block 1110, ù deterlninatioll is made as to whetller a large or small character is to be displnyed, such variation character size being observable from ~igs. 16 and 22. Where a l~rge character is appropriate, then as represented at line 112 and block 114, a mernory accessed appropriate address for the elected character o~ large format and the character is displayed. The routine then e.Yits as represented at lines 1116 and 1068 to node 1072. Where a large character is not elected as at block 110, then as represented at line 1118 and block 1120, the regular character table is accessed and such character is displayed of smaller format. The routine therl exits as represented at lines 1122, 1068 and node 1072.
Where no characters are to be displayed, then as represented at line 1124 and block 1126, inquiry is made as to whether a line should be erased.
In the event that is the case, then as represented at line 1128 and block 1130 the start and end positions of the line in question are accessed and zeroes are written at tlle specified locations. The routine then exits as represented at lines 1132, 1068 and node 1072.
Where no line is to be erased, then as represented at line 1134 and block 1136, the equivalent inquiry is made as to whether a box or rectangle is to be erased. Where that is the case, then as represented at line 1138 and block 1140, the starting and end positions for the box or rectangular figure are located and zeroes are written at the starting and end points appropriate to carry out erasure. The routine then ends as represented at lines 1142, - 30 1068 and node 1072.
Where no rectangle erasure is at hand, then as represented at line 1144 and block 1146, a determination is made as to whether any shading is required within a box, i.e. to show a bar graph or the like. ln the event that is the case, then as represented at line 1148 and block 1150, start and end positions of the box with respect to this shading are determined and ones are written to form the shading. The routine then ends as represented at lines 1 3374~

1152, 1068 and 1()72. As represented further at line 1154, this is the Einal inquiry in the displ~y updnte, the latter line leading to end node 1072.
Turning to ~ig. 24, the calibration routine is represented commencing at bloclc 1156 with the actuation by the user of the calibrating switch 38 5 upon console lG. At the commencement of this routine, as represented at line 1158 and block 1160, a determination is made as to whether the probe instrument 12 is properly connected. This is carried out through the earlier-described mellsurement of probe current as described in Fig. 7~ in conjunction block 188. In the event the probe device 12 is not properly 1~ connected, then as represented at line 1162 and block 1164, the display 26 advises the user to install the probe and the routine recommences as represented by loop line 1166.
Where the probe is appropriately connected, then as represented at line 1 lG8 and block 1170, a determination is made as to whether the power supply voltages are correct. As discussed above, this involves the monitoring of the input supply voltages including bias to crystal 58 as described in conjunction Witll Fig. IOB at connector N2 and E ig. lOA in conjunction with multiplexer 678. If the determination as to voltage levels finds crror, then ns represcnted at line 1172 and block 1174, the display 26 advises the user of dif~iculty with system voltages and, as represented at line 1176 and node 1178, the system llalts until correction can be effected.
Where the test for supply voltages shows them to be at valid levels, then as represented at line 1180 and block 1182, the lower window of acceptance is adjusted for the lowest noise level above background, the latter values, ~or example, being attainable from the noise averager network as described at block 218 in conjunction with Fig. 7A. Following the attempted adjustment, as represented at line 1184 and block 1186, a determination is made as to whether adjustment of the lower window can be made to an appropriate value. In the event that it cannot, then as represented at line 1188 and block 1190, the display 26 is employed to advise the user that the instrument cannot be calibrated and the routine exits as represented lines 1192 and 1194 to node 1178 to halt.
Where lower window settings can a~L-ropriately be developed, then as represented at line 1196 and block 1198, the user is instructed via display 26 to install the check source as described above in conjunction with Figs. 12 and 13. The routine then continues as repesented at line 1200 and block 1202 to determine whether or not the counting carried out with tlle check source, for e:cnmplc using Iodine 129, is nppropriate, this internal counting will take place over an interval, for example, selected as 5 or 10 seconds.
Where the counts or pulses detected are without proper tolerances, then as represented at line 1204 and block 120G, tlle display 2G is employed to advise 5 the user that tlle counts received are out of tolerance and, as represented atlines 12n8 and 1194 leading to node 1178, the system Jlalts. ~Iowever, wllere the counts using the checlc source are witllin tolerance, then as represented at line 1210 and bloclc 1212, the user is advised through the display 26 that the calibration is complete and the unit is ready for operation. The routine th-en ends as represented at lines 1214 and node 121G.
Since certain chang~es may be made in the above-described system and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the description thereof or shown in the accompanying drawings shall be interpreted QS illustrative and not in 15 a limiting sense.

Claims (4)

1. An apparatus for detecting and evaluating sources of gamma radiation having given energy levels, including:
detector means for deriving induced charges in response to interactions of said radiation therewith to provide detector signals of given levels and exhibiting noise characteristics of given levels;
noise averaging means responsive to said given noise characteristics for deriving a noise signal corresponding with an average level of said given noise characteristics levels;
normalizing circuit means responsive to said detector signals and given noise characteristics and to a control input for adjusting the level of said noise characteristics and corresponding said detector signal given levels to provide composite signals of normalized values;
comparator means responsive to said composite signals for comparing the amplitude thereof with presettable upper and lower threshold levels for providing pulse data outputs corresponding with said comparisons;
logic circuit means responsive to said pulse data outputs for deriving valid pulse signals;
output means controllable for providing a valid pulse signal related perceptible output; and control means responsive to said noise averaging means noise signal for deriving said control input to said normalizing circuit means and to said valid pulse signals for controlling said output means.

2. The apparatus of claim 1, in which said control means is responsive to said noise averaging means noise signal to preset said lower threshold level at a value at least as high as said noise signal.

3. The apparatus of claim 1, including:

pulse acquire means responsive to said composite signals to provide a peak signal values corresponding with the instantaneous highest given level of said detector signals; and said control means is responsive to said peak signal values to preset said upper threshold level in correspondence therewith.

4. The apparatus of claim 1, including:
pulse generating network means actuable for generating a diagnostic pulse of controlled amplitude and width; and said control means is configured for selectively actuating said pulse generating network means and diagnostically monitoring said noise averaging means, said normalizing circuit means and said comparator means.