DE2819186A1 - Determination of direction of radiation source - uses collimator with number of optical slits combined with photoconducting detectors - Google Patents

Abstract

The position of a source of radiation is determined by detection using a number of detectors of radiation which passes through a collimater with a large number of optical slits. The instrument is for detecting the position of the source of radiation and comprises a collimator (12) with a large number of optical slits each with a photoconducting detector (14) which closes the remote end of the slit. These slits receive components of radiation on a direct line from the source. A positioning motor (64) modifies the transverse position of the slits w.r.t. the source.

Description

Device for obtaining information about a through their

Location Specific Source The invention relates to an apparatus according to the preamble of claims 1 and 3. It relates generally to devices to obtain information about radiation sources.

Visible light can be reflected as well as refracted.

The ordinary camera takes advantage of the refraction by using a optical lens for refracting and focusing the visible coming from an object Light to create an image of the object on film. However, electromagnetic radiation of higher frequencies than vacuum ultraviolet (such as x-rays and gamma rays, hereinafter collectively referred to as gamma rays) are not effective either reflected or refracted. Hence the creation of an image a gamma radiation source achieved using a collimator, which on somewhat similar to how the old pinhole camera works. The pinhole camera enables that the light from an object in a straight beam through a hole in the camera body passes through to produce an inverted image on the film.

Collimators with an array of parallel channels such as those shown in Figure 1 were used in imaging gamma radiation sources. When the axes of the channels are directed towards a source of gamma radiation, the channels have generally the same size in both dimensions perpendicular to the axis; are common the channels circular, triangular or square in cross section. In Figure 1, in which is the walls or septa of each lead channel for absorbing gamma radiation and with a radiation detector (not shown) on top of that of the source opposite side of the collimator is arranged, the radiation is which pass from a point source through a special channel and the Detector can be defined by the solid angle A under which the The base of the parallel channel 2 pulls in. The spatial resolution of a Such a collimator is improved by reducing the solid angle.

However, the sensitivity of each channel * depends on the The amount of radiation passing through the channel increases by increasing the solid angle improved. It is of course desirable to have spatial resolution as well to improve the sensitivity, in particular the latter in such a way that the time required for observation is reduced can be.

With regard to the radiation detector, it is known to use the photoconductor to be used as the base element of such a detector. However, with known The photon absorption path corresponds to fields of photoconductor detector elements and inter-electrode spacing are the same photoconductor dimension and are thus general same length. It is desirable to make the photon absorption distance large with reference on the interelectrode distance, since the greater the absorption distance, the better the sensitivity, because a larger fraction of the incident Phions are collected, and the smaller the inter-electrode spacing, the larger the power as well as the speed of the collection of electrical signals at the electrodes, which are generated in the photoconductor body by incident photons will.

The present invention is based on the object of a simple and to create effective devices of the genre standing by, which the corresponds to the above mentioned Erfoffierniæsen.

This object is achieved in a device according to the preamble of Claims 1 and 3, according to the invention, are solved by their characteristic features. Further Features of the invention emerge from the remaining claims.

The invention creates a sensitive, stable, high resolution comprising and conveniently usable device for obtaining information about the distribution of and also provides a source of gamma radiation Device useful radiation detector.

The information obtaining device according to the invention has high sensitivity without sacrificing resolution. The device has a collimator which is easy to manufacture without the need an intricate honeycomb of separate channels, and the walls of the collimator can suitably consist of tungsten foil, tungsten being a better radiation-absorbing one Material is considered lead and therefore thinner than lead walls, which makes it effective Collimator transparency is improved. The output of the device can be easily and quickly converted to high-resolution by suitable computer techniques Generate images of gamma radiation sources. The device is in the field widely applicable in nuclear medicine and is also industrially useful.

The detector according to the invention is easy to manufacture and has an improved one Resolving power and signal / interference ratio.

It has a high uniformity of response to a given one Photon impingement energy, so that interference and suppressed signals, which through the scattered Compton effect, and lower energy photons, which arise in places remote from the primary radiation source are rejected can be. It also has a high photon collection efficiency because of improved Sensitivity and a short output pulse due to improved temporal resolution.

In one aspect, the invention includes obtaining information via a source determined by its location, for example a gamma radiation source, through slit collimation and the detection of bundle components from the source in one Variety of different gap arrangements, as well as using the resulting ones Data for recording the source position.

Preferred embodiments of the invention include in this aspect a collimator having a frame having an axis of rotation and a plurality of has flat plates of gamma radiation absorbing material, which through the frame in a parallel, spaced-apart arrangement with respect to one another and held parallel to the axis of rotation, with adjacent pairs of plates define the gaps therebetween and each of the gaps has an opening at one end and has a base at the opposite end and for allowing passage unhindered by gamma radiation through it in a first correctly parallel to the axis of rotation and within the frame in a second direction perpendicular to the axis of rotation and is unobstructed parallel to the panels; Means for positioning the Collimator for keeping the axis of rotation adjusted to a source of gamma radiation in such a way that that the gaps are arranged to receive gamma radiation therefrom while the eollimator is rotated around its axis, with each of the gaps being in the through the first and second directions defined the plane at a much larger angle draws towards receiving the radiation passing through it to the base from the Source, compared to an angle at which it is in a second plane perpendicular to the second direction; a detector connected to the frame for a common rotation connected to the collimator and the bases of the column adjacent is for tracing those passing through each gap to the base of it Radiation and to generate an output which is responsible for the intensity of the detected Radiation over the entire base of each gap as a function of the angle of rotation of the collimator is representative; and means for accumulating a matrix such output values, the matrix being ordered according to the particular Slit in which the radiation generating the output was detected, and corresponding to the particular angle of rotation of the collimator at the time the Radiation has been detected and the matrix is capable of conversion into a matrix that corresponds to the image of the radiation source.

In another aspect, the invention comprises a detector for Detecting gamma radiation and generating an output variable as a function of the radiation, the detector having a plurality of gamma radiation sensitive Photoconductor material has existing detector elements that are parallel and with Spaced strips are, for exposing a generally planar, surface of the incident gamma radiation formed by an area of each of the elements from a source of these, and each of the elements having a pair of attached thereto Has electrodes, each pair of which is arranged between adjacent elements is, the electrode planes perpendicular to the planar, exposed to the incident radiation Surface runs and the thickness of each detector element, measured from that of the incident Position exposed surface along a line perpendicular to this, is large with respect to the distance between each pair of electrodes.

Certain preferred embodiments include a detector which a plurality of detector elements corresponding in number to the slots which are operatively connected to the frame such that they are their associated Bases remain adjacent while the collimator is rotated about the axis will; a processing circuit with an amplifier for amplifying the detector outputs and an amplitude discriminator for eliminating any components which have an amplitude below a minimum amplitude, from the Baseline values; a housing as a holding device, which comprises a tube, a rotatably mounted in the tube plate means for rotating the plate, which includes an opening for receiving the frame such that upon rotation of the plate the frame is rotated together with it; a switch motor to rotate the disk in separate angular steps as a rotating device. Tungsten foil collimator plates; a detector element which has a scintillating plate and one with the plate connected photo amplifier to produce an electrical output ate; optical Fibers connecting the scintillating plate / its photo intensifier; as Detector elements located between the collimator plates at the base of the slots and held there by the frame0 Other preferred embodiments include detector elements made of photoconductive material; Cadmium tellurite detector elements; Photoconductor detector elements in which the planes of their electrodes are parallel to the collimator plates are ordered and the route through the photoconductor element in the first direction is large with respect to the distance between each pair of Electrodes in a third direction perpendicular to the first and second directions, wherein a distance through the photoconductor element in the first direction is not less than 5 mm and the distance through the photoconductor element in the third direction is not is larger than 0.75 mm and the photoconductor elements are in the form of strips.

Briefly summarized, the invention relates to the holding of information via a source determined by its location, for example a gamma radiation quile, by slit collimation and tracking of bundle components from the source in one Variety of changing gap arrangements, as well as using the resulting ones Data for plotting the location of the source The invention is described below on the basis of exemplary embodiments shown schematically in the drawing explained.

The figures show: FIG. 1 a section along a vertical plane a typical known channel collimator, Figure 2 is a perspective view an embodiment of the invention, Figure 3 is an enlarged plan view of a part the embodiment according to Figure 2, Figure 4 is a section 4-4 from Figure 3, wherein various parts are broken away, Figure 5 shows a section 5-5 from Figure 3, wherein various parts are broken away, Figure 6 is a perspective view in an exploded view of a part of the embodiment according to FIG. 3, FIG. 7 is a schematic representation the embodiment according to Figures 2 to 6 with associated switching devices, FIG. 8 shows a greatly enlarged section along a vertical plane of a part a second embodiment of the invention, Figure 9 is a section along a vertical Plane that runs perpendicular to the plane of Figure 8, the second embodiment, whereby various parts broken away and associated switching devices schematized FIG. 1o is an exploded perspective view of part of the second Embodiment.

In Figure 2, a camera 10 which includes the invention is shown. The camera 1o has an integrated collimator 12 and detector 14, which are rotatably mounted together in a housing 16. The collimator 12, which shown more clearly in Figures 3 to 6 comprises one made of steel Frame 18 and a series of fifty-one parallel plates 20 of tungsten foil, which are held taut in the frame 18 The frame 18 has two opposite Pages 22 that are 80mm by 55mm by 15mm.

A group of three rods 24 made of steel with a diameter of 5mm connects the sides 22 to the ends of these via drilled through the sides 22 Bores 26. Screws 28 hold when tightened in bores 30, which the bores Cut 26 across, rods 24 in place in sides 22 and form a square with an outside dimension of about 80 mm by 80 mm. The plates 20 have likewise a group of three bores 32 (FIG. 6) at their ends for receiving of the rods 24, which thereby hold the plates 20 clamped with the aid of spacers 34 made of lead, which separate adjacent plates 20 at the ends of the plates and held in place by rods 24 passed through bores pass in the spacers 34. Each plate 20 is 0.15 mm thick, 30 mm wide and 80 mm long. The lead spacers 34 are 0.85 mm by 15 mm plates mm by 30 mm.

The spacers 34 and rods 24 together form the two other sides of the frame 18 in addition to the sides 22.

The plates 20 are arranged at the same distance of 0.85 mm from each other, to form fifty gaps 36 which are 50mm by 30mm by 0.85mm. That Tensioning the plates 22 described above maintains these slot dimensions.

The detector has fifty detector elements 38, the scintillating Plates of commercially available scintillating plastic are mainly ofyvinyltoluene and made by Nuclear Enterprises of San Carlos, California will be produced. Each plate 38 is 50mm by 10mm by 0.85mm and is between each pair of adjacent tungsten plates 20 fitted. At the radiation source opposite frame 18 such that the column 36 is most favorable for receiving of radiation from the source, each slot has one to the source nearest opening for receiving the radiation and a base on the opposite one End of the slot, and the edges of the plate 38 which are furthest from the radiation source are removed, are aligned with the edges of the tungsten plates 20, the are also furthest away from the radiation source (Figures 4 and 5).

To the rear face of each scintillating plate 38 is means transparent epoxy resin, a ribbon 50 made of optical fibers (schematically in fig Figures 4 and 5) attached, which have the same dimensions in cross-sectional area has like the rear end face of the plate 38 (50 mm by 0.85 mm). Every band 50 consists of approximately eight layers of fibers 0.1 in diameter mm, with about 500 fibers arranged per layer, all by conventional Fiber optic processes are made. The fibers extend away vertically from / to the plate 38. All fifty tapes 50, one for each plate 38, are cast together in transparent epoxy resin, whereby they form a block 42 extending 25 mm outward from the rear face of the Plates 38 extend. The frame sides 22 also extend 25 mm below the rear end faces of the plate 38 to form a frame for the block 42 of potted To form fibers. Conventional clamping devices (not shown) can be used to assist the frame page 22 in gripping the block 42, the extends along sides 22. When the fibers forming each strip 50 extend outside of block 42, they are independently flexible and become gradually contracted into a circular bundle, which in this arrangement be held by an iron fitting 52. The ends of each circular bundle of fibers are glued to the detection surface of a photo amplifier 54, which the light signals converted into electrical signals for transmission to a preamplifier 56 (Figure 7). The optical fiber connection between the detector array 14 and each photo amplifier 54 is flexible enough to allow a plate 60 to rotate 180 degrees.

The collimator 12, the detector 14, the slivers 50, the photo amplifiers 54 and the preamplifiers 56 are all mounted in the housing 16. The housing 16 the circular steel mounting plate 60 comprises steel tubing 62, a plate drive 64 and support arms 66. The frame 18 is in a square, in the mounting plate 60 centrally located hole fitted with clamps 68 holding the frame 18 hold in place in plate 60. The plate 60 is in the front opening of the tube 62 and it is rotatable with respect to the tube 62, a conventional one Bearing arrangement (not shown) allows rotation. The disk drive 64, which comprises a reversible electric switch motor and clock, the disk rotates 60, the outer edge of which is toothed to produce a (not shown) Gear drive with the drive 64. The frame 18, the collimator 12 and the detector field 14 all rotate with the plate 60, which is discontinuous by the drive is driven.

The tube 62 is in turn pivotably attached to the support arms 66 such that the tube 62 can be tilted towards a particular radioactive source. A lock button 44 is set to hold the tube 62 in the selected position Position.

The support arms 66 are attached to a base (not shown), which has roles in a suitable manner, so that the camera 1o as a whole in different Positions can be moved.

FIG. 7 shows conventional switching devices in a block diagram for processing the electrical signals from the photo amplifiers 54. The signals of the photo amplifiers 54 are in the form of electrical pulses, each Impulse of absorption of a gamma ray by the corresponding scintillating Plate 38 corresponds. These electrical pulses are sent to the preamplifier 56 given by fifty lines 70 from the fifty photo amplifiers 54. The preamplifiers 56 are arranged in the rear section of the tube 62, immediately in front of a (not shown) circular steel back plate that covers the rear opening of the Covered tube 62. Drilling through the center of the pipe back plate allows that fifty leads 72 which are passed through a flexible sheath 74 of the preamplifiers 56 can emerge from the tube 62. The preamplifiers 56 amplify all of the impulses coming from the photo amplifiers 54 and are in the pipe 62 arranged so that they are shielded from interference. The rest of the switchgear 7 is suitably encapsulated in the mobile base. The reinforced Pulses travel through lines 72 to fifty pulse amplifiers 76 one for each line, where the impulses are further amplified. The impulses then of the fifty pulse amplifiers 76 become fifty pulse height discriminators 7B transferred, which reject pulses that fall below a predetermined amplitude Have amplitude (such as pulses, which are the Compton effect photons be brought about), and the discriminators 78 enable the remainder the impulses pass through.

Finally, the pulses are counted in a pulse memory 80 and their number is included in this. The pulse memory is a 50 times So register and is synchronously coupled with the disk drive 64 so that those of the fifty Pulse height discriminators 78 incoming pulses for each separate angular position of the collimator 12 and the detector 14 are counted.

These data formed by the number of pulses are stored in the memory 80 and upon completion of all counts the data will become known Computer techniques follow on from one to be explained in greater detail below Reduced shape, which identifies the two-dimensional arrangement of the radiation sources, which impinge on the collimator 12 and the detector 14.

During operation, the camera 10 is arranged such that the The front of the collimator 12 is at the radiation source as long as possible. The source itself consists of technetium 99, a radioisotope that emits gamma rays emits with a characteristic energy of 140 Kev, or the source exists from some other radioisotopes which are useful for clinical or other services are suitable. If the source is inside a patient, the Collimator 12 is preferably placed in contact with the patient in proximity to the source. The source, in turn, can serve the purpose analyzing the data as a three-dimensional array of point sources which are randomly distributed Emit gamma photons. The camera 10 actually takes a picture of the two-dimensional Field, which is from the orthogonal projection of this three-dimensional source field on the detector 14 results.

The collimator plates 20 and collimator slits 36 are initially oriented vertically, and the axis of tube 62 is then directed directly to the source volume (usually to the part of the patient's body to which the isotope migrated) directed.

The locking button 44 maintains the pipe orientation.

The photo amplifiers 54 are energized and ready to respond to light signals to be addressed by the detector 14, and the signal processing circuit according to FIG. 7 gets excited. The collimator 12 remains in the vertical position for a period of time on the order of 10 sec, during which gamma photons from the source to the Wander collimator 12 and enter the most conveniently located column 36. The platform drive 64 then rotates the collimator 12 by 3.60, followed by a pause from 10 seconds followed by another 3.6 ° step, and so on to fifty such steps of 3.60, which gives a total of 180 °.

The number of turns for each 18o0 turn (here fifty) is chosen such that it corresponds to the number of gaps 36 in the collimator 12. During every 10 second interval, the tungsten plates 20 absorb anything Impact of zones on the plates. The photons that come from a particular Point source pass through a special gap, the solid angle of which the surface the impact face of a scintillating plate 38 includes step in this scintillating plate, and most of it is absorbed in it, thereby visible photons are excited in the plate. These are visible photons through the plate 38 and illuminate the optical fibers in the Volume 50, which attached to this particular scintillation plate is. All surfaces of the scintillation plate 38 except that which is adhered to the tape 50 are coated with a substance that reflects visible light so that any visible light pulses excited within plate 38, if any in the direction of the rear face of the plate 38 and the belt 50 , albeit with a higher attenuation of impulses which occur before the Tape 50 are subjected to one or more reflections. The attenuation of the visible light signals also takes place within the band 50, and about 1% of the visible light photons generated in the plate 38 reaches the photo amplifiers 54. However, the signals reaching the photo amplifiers are sufficient to create a basis for an accurate determination of the arrangement of the radiation sources.

The scintillating PlatX 38 emits an output variable which the Energy of the impinging gamma photons, thus photons can with a lower energy than the primary gamma photons resulting from Compton scattering adult and in places remote from the primary radiation sources arise in which Pulse height discriminator will be rejected. During the 10 second interval, before the collimator 12 takes its first 3.60 step, and during each the subsequent forty-nine lo-second intervals between the subsequent ones 3.60 steps, each scintillation plate collects 38 gamma photons from all radioactive point sources, which are located in the plate-shaped spaces, generated by projecting the pair of tungsten plates 20 which form the Delimit plate 38 against the sources. During this Irtervalla collects at the same time each plate 38 has all the stri development obtained from each point source within of the solid angle is sent, which is the area of the front face of the plate 38 with respect to this point source. The output size åeder Scintillation plate in each rotational position is thus a number of visible Pulses of light, which are a number of photon absorptions within the plate where the photons come from different point sources.

The method of processing those stored in memory 8o Data to generate an image of the distribution of the radioisotope source is based provisionally on the assumption that the distribution to be mapped in the plane is perpendicular to the first direction as a two-dimensional array of fifty by fifty source elements appears. This poses the problem of creating an image at fifty times fifty elements of resolution, that is, solving fifty times fifty that means 2500 unknowns. The isotope is placed wherever the value of the source element is non-null, and does not exist if the value of the source element Is zero.

Basically, when there are fifty by fifty unknowns, always possible to solve these unknowns with a system of fifty by fifty equilateral linear equations, The steps of setting up the equations in matrix form and solving by the methods of matrix algebra form a well-known one direct approximation when finding these unknowns.

The memory 80 provides the data, of which fifty (Column) times fifty (angle) that means 2500 equations are set up can. Mathematical methods performed by means of a computer are presently present able to have an expedited resolution of this number of simultaneous Be able to perform equations. The following publications, which hereby are made the subject of the disclosure of the present application Procedures for such accelerated solutions: Ramachandran and Lakshminarayanan, "their Dimensional Reconstruction From Radiographs and electron Micrographs: Applications of Convolutions Instead of Fourier Transforms, "Proceedings of the National Academy of Sciences of the United States, 1968, pp. 2236-2240; Gordon and Herman, "their Dimensional Reconstruction from Projections: A Review of Algorithms, t1 International Review of Cytology, Vol.

38 (1974); DeRosier and Klug, "Reconstruction of Three Dimensional Structures from Electron Micrographs, "217 Nature 130 (1968); and M.M. Woolfson, An Introduction to X Ray Crystallography, Chapter 4, "Ourier Transforms" (Cambridge Univ. Press 1970).

It is clear that the emitted from the edge areas of the source surface Radiation into the camera with a slightly lower likelihood of exposure the detector field enters than is the case with radiation, which of areas is emitted near the axis of rotation of the collimator. For this reason it is necessary to "weigh down" the data processing method in such a way that this bias compensates will. In the cited publications it is shown how this compensation is achieved can be.

As the resulting image created by this computer method is a two-dimensional image, although the radioisotope itself is actually occupies three-dimensional space, becomes the field of radiation therapy well-known further technique applied, after which additional images of takes different spatial positions of the collimator and combines these images to generate a three-dimensional image. In the case when the radioisotope turns located in the brain would be the easiest way to perform this technique is to take an image with the axis of the collimator between the Eyes of the patient is directed, as well as take a second image, the Collimator axis is pivoted by 9o ° so that it passes through the patient's ears directed is.

A comparison of the camera 10 with a conventional collimator-detector system with static channel shows that camera sensitivity improves 1o and thus the exposure time is reduced without any impairment of the resolution.

Furthermore, the integration of the detector 14 with the collimator improves 12 the total spatial resolution of the image in two respects. To the one when the detector 14 and the collimator 12 are constructed as separately constructed devices can be viewed without attempting to register between individual columns 36 and detector elements 38, as is the case with existing channel collimation devices usually the case, then the effective resolving power of the whole Systems commonly accepted as the square root of the sum of the squares of the minimum Resolution distances of the two devices (the collimator and the detector) taken separately.

If the spatial resolution of the two bodies is similar therefore the integration of the detector with the collimator leads to an overall improvement of resolving power by a factor of the square root of two. To the second, and more importantly, eliminates the integration of the detector 14 with the Collimator 12 essentially eliminates the loss of resolving power caused by Scattering of the radiation either within the collimator or within the detector field is self-induced.

Figures 8 to 10 show a second embodiment of the invention, which uses the same collimator 12 but a different detector 46 will. The detector 46 is composed of fifty detector elements 88, which strips of photo conductors are 9o, five of which by insulating spacers 91 made of polyethylene terephthalate are spaced to form each strip. Each cadmium tellurite photoconductor 9o is a right-angled crystal disc with measuring 10 mm by 5 mm by 0.75 mm, and each strip 88 of disks is thus approximately 50 mm long. On the two largest areas of each photoconductor 9o a pair of electrodes 92 is deposited. Each electrode 92 in turn comprises a thin layer of platinum deposited directly on the cadmium tellurite body is, thereby forming an electrode-cadmium tellurite-electrode layer structure is. The deposited layers 92 each have a thickness on the order of magnitude of 1 micron. A ground connection device 98 is aligned against one side of the strip 88 and extends parallel to the strip. The ground connection device 98 is a strip made of polyethylene terephthalate, which by the company duPont under called Mylar is manufactured and sold, on which a thin aluminum coating has been knocked down. The thickness of this Mylar aluminum strip is approximately fifty microns with the mylar taking up most of the thickness. A Aluminum mylar ground finger 100 extends downwardly from strip 98 in direction on an end to this. The aluminum surface of the ground connector 98 is on one side of the strip 88.

The Mylar gives strength to the aluminum connector while it at the same time as an insulator between an adjacent tungsten plate 20 and the Aluminum connecting device is used.

A similar connector 102 is at the other far of strip 88, but the aluminum coating was replaced by previous Removal of narrow vertical aluminum strips in five electrically isolated ones Areas 104 divided, which are the five forming the strip 88 Photoconductors correspond to 9o. Each of the five aluminum areas 104 has an aluminum mylar finger 106 extending downward from the area. The entire connector-electrode-photoconductor-electrode-connector-layer structure, which results when all these elements are brought together is between each pair of adjacent tungsten plates 20 of collimator 12 as well as between a frame side 22 and an adjacent tungsten plate 20 arranged. This layered construction has the dimensions of 50 mm by 5 mm by 0.85 mm and takes the place of the scintillation plate 38 in gap 36. A strip 88 of photo ladders 9o takes up most of the thickness the connector-electrode-photoconductor layer construction in each gap 36, so that only a small fraction of the gamma photons hit the gap 36 is lost by entering the connection devices 98, 102 or the Electrodes 92. The photoconductor strips 88 and conductors 98, and 102 are through a printed circuit board 1o8 supported. The circuit board 108 is at suitable Slotted locations to accommodate the ground finger loo and fingers 106.

The fingers go through to the underside of the circuit board, where a printed ground conductor (not shown) the ground fingers 100 for all ground connection devices of the detector array connects and where separate printed conductors (not shown) individually are connected to each of the fingers 106. The photoconductor strips 88 are longitudinal their lower end faces on the circuit board 108. The tungsten plates 20 are also grounded by connection to the ground conductor of the circuit board 108 (the connections are not shown). The strips 88 are with the help of to the Mylar spacers inserted into the strip ends and the aluminum areas of the connectors 98 and 102 have been removed from the end up also insulated by spacers 34 made of lead, which as before between the Plates 20 are fitted and form two boundaries for the detector field. The circuit board 108 is in turn fastened to the frame sides 22 by means of 7 brackets (not shown).

A voltage source 110 (50 volts) (Figure 9) is connected through to the circuit board 108 and the connectors 93 and 102 so that their Voltage through each pair of electrodes 92 across each photoconductor 9o (there are five times fifty that means 250 photoconductors 9o) is impressed. The output signal from each photoconductor 9o is carried out through the connectors 98 and 102 to printed conductors in circuit board 108 and from there through flexible conductors 112 to a preamplifier 56a. There are 25o preamps in total, and one at that for each photoconductor 9o. The output signals from five preamplifiers 56a, which each corresponding to the five photoconductors 9o in a strip 83 are combined and introduced into a pulse amplifier 76. As with the embodiment which Using a detector array 14 and photo amplifiers 54, there are fifty pulse amplifiers 76, fifty pulse height discriminators 78 and a pulse memory 80. Each preamplifier 56a is an operational amplifier with a single-open field effect transistor input Gain of 105 and an input current sensitivity of 10 11 amps.

If an impinging gamma photon has a charge of 1o14Coulomb im Photoconductor crystal generated and when the entire charge is collected on the pair of Ea $ trode 92 in one microsecond increases the current output »- = 1o 8 amperes, which can be recognized and strengthened in the preamplifier 65? Because the mylar insulation at the connection devices 98 and 102 in such a way kept thin becomes that the content of the exposed surface of the photoconductor 9o can be maximized, a large capacity becomes, (in relation to the capacity across over the photoconductor 9o) over the mylar between each tungsten plate and the aluminum overlay the connection devices 98 and 102 generated. This capacity could ordinarily the voltage swing of each signal coming from electrodes 92 is below of limits detectable by preamplifier 56, however segmenting the detector strips 88 into five separate photoconductors 9o results in one Total capacity for each photoconductor 9o which is one fifth of the total capacity of strip 88, which is acceptable as far as retrieval is concerned viewed from signals from photoconductor 9o. In terms of dæ sensitivity is at a preamplifier 56a which is capable of inputting signals down to to track down 1 -11 amps, an accurate measure of the size of the expected signal on the order of 10 8 amperes possible. Thus it is possible to use the Compton photons lower energy downstream in the pulse height discriminators 78. the Total background interference is roughly equivalent to a 1o Kev signal, so a Distinction between real source photons and a disturbance is possible, if sources of radiation greater than about 20 kev are used.

The thin strip builds up on the photo conductor 9o when the electrodes are arranged 92 parallel to the collimator plates 20, although it presents a capacity problem As just described, it also has the advantages of a short interelectrode distance and a long photon absorption distance. Using a relatively short one Distance between opposing electrodes 92 (about 0.75 mm) is the current carrier (Electron or defective electron) collection performance of the electrodes improved with resulting improvement in achieving uniformity of response Photon excitations, and the carrier collection time is reduced with resultant Improvement in temporal resolution. By using a relatively deep one Photoconductor crystal (5 mm) will be most of the incoming photons of a 140 Kev or less strong isotope source absorbed by the crystal, creating a better camera sensitivity is created. In general, when using The signal losses from photoconductors are far lower than from scintillation plates and optical fibers, and the energy resolving power is greatly improved. There more of the signal actually reaches preamplifier 56a results in a more accurate mapping.

The methods of processing the data received in memory 80 correspond to that described above, and the improvement in sensitivity one of the channel collimators is also as described above.

With regard to modifications in the method and in the device the collimator 12 can be rotated continuously instead of intermittently, or it can even be operated by having its axis curved along another or other shape is moved or without rotation. The symmetry around the axis is preferred but is not essential. Appropriate modifications in the data reduction process are then of course required. When harder radiation sources than technetium 99 are used, it is necessary that the scintillation plates 7) 5 and the photoconductor 9o are deeper from the top to the bottom (i.e. a longer photon absorption distance to have).

For example, if the source is on the order of Mev'E, then can it may be necessary for the photoconductor 9o to have a depth of 40 or 50 mm instead of just 5 mm. If greater resolution is desired, the number of Columns in the collimator 12 are correspondingly enlarged to at least one Total number of 250 columns; the assembly of such a collimator would be understandable be slightly more complicated than in the case of the fifty-slit collimator. Instead of Tungsten can be used for the 20 tantalum plates. Instead of polyvinyl toluene can be used for the scintillation plates 38 polystyrene. Finally kanbei the photoconductor detector 46 instead of aluminum for the connecting devices 98 and 102 copper can be used, electrodes 92 can be made thicker for better response uniformity (albeit possibly with disclosure of effective photoconductor area), the electrodes 92 can be a thin layer of a Have conductor, such as indium, deposited on the platinum is to improve the contact between the platinum and the metallic coating of the connectors 98 and 102, and the photoconductor strips 88 can be continuous instead of being formed in segments if the excited signals are strong enough, to deal with the capacity problem. In addition, instead of the photoconductor detector 46 a detector can be used, which consists of a continuous planar plate Photoconductor material comprises having electrodes formed in strips and deposited up and down opposite other sides, as in the case of the detector 46. Manufacture is made easier, but such a detector does not the combined advantage of a high phton collection rate and an improved one Charge carrier collection performance of detector 46.

Other embodiments of the invention will be readily apparent to those skilled in the art can be specified.

In the above, for the sake of simplicity, a 50 mm by 50 mm The device illustrated and described is the most preferred embodiment the inventor a 250 mm times 25o mm device in which each Gap the same width as in the illustrated and described embodiment has, but is five times as long, and where 250 columns are provided versus fifty are. The most preferred detector is the aforementioned semiconductor device. After progressing an? OO step by step, the camera preferably returns over a Return to its starting position. In preferred embodiments, the gap length at least ten times as much as the gap width; in the most preferred embodiments of the inventors, it is at least fifty times as large like the gap width.

While like most of the people to whom this erSiShng is due could think that the increased flow available in every position in the case of gaps instead of holes would be an advantage, which by the enlarged Number of required positions is neutralized, this turned out to be surprising as incorrect thanks to the improved signal / interference ratios, which one enable greater speed as well as increased resolution.

Claims (24)

CLAIMS Device for obtaining information about a by their location determined source, with a slit collimator, which a variety of Contains columns for receiving bundle components that extend in a straight line from a Move the source out, with each gap having an open end to point towards the source and walls extending inwardly from the open end defining the gap which extend in the same longitudinal direction and a material from the The type and thickness include such that it absorbs the bundle component hitting the walls and wherein the gaps extend further in a transverse direction than in the other transverse direction; a detector for the separate detection of bundle components, which pass through the column and for generating trace data output signals, wherein the detector is fixedly mounted relative to the collimator and a plurality of having detector elements corresponding in their arrangement to columns, of which each is arranged so that it faces the end of an associated gap closes each of the open ends; as well as a positioning device which links is connected to the collimator or the source in such a way that they simultaneously complete the arrangement which changes the column and detector elements in the transverse direction relative to the source, thereby marked- that each detector element (36, 88) within its associated Gap (36) is arranged between the walls (20) defining the gap (36). 2. Apparatus according to claim 1, characterized in that the field Detector element (88) is a photoconductor element (90). 3. Device for obtaining information about a through their location certain source, with a slit collimator, which has a plurality of slits for Contains uptake of bundle components that extend in a straight line from a source move, with each crevice having an open end for pointing towards the source and the crevice defining walls inwardly extending from the open end, the extend in the same longitudinal direction and a material of the type and thickness include that the bundle components impinging on the walls are absorbed and wherein the gaps extend further in one transverse direction than the other Transverse direction; a detector for the separate detection of bundle components, which pass through the column and generate trace data outputs, wherein the detector is fixedly mounted relative to the collimator and a plurality of having detector elements corresponding in their arrangement to the columns, of which field is arranged such that it faces the end of an associated gap closes each of the open ends; and a positioning device that links is connected to the collimator or the source in such a way that they simultaneously complete the arrangement which changes the column and detector elements in the transverse direction relative to the source, thereby characterized in that each detector element (88) is a photoconductor element (9o). 4. Device according to one of claims 1 to 3, characterized in that that each gap (36) extends at least ten times as far in one transverse direction as in the other transverse direction. 5. Apparatus according to claim 4, characterized in that each Gap (36) extends fifty times as far in one transverse direction as in that other transverse direction. 6. Device according to one of claims 1 to 3, characterized in that that the walls (20) comprise a gamma ray absorbing material. 7. Device according to one of claims 1 to 3, characterized by processing circuitry including an amplifier (56, 56a, 76) for Amplifying the tracking data output signals and an amplitude discriminator (78) for further conveying the bundle components with at least a minimal amplitude and excreting the remainder, excreting components that are derived from a Radiation below a predetermined energy threshold result. 8. Apparatus according to claim 7, characterized in that the processing circuitry means (80) for collecting the output signals generated by the Amplifier (56, 56a, 76) amplified and further conveyed by the discriminator (78) will. 9. Device according to one of claims 1 to 3, characterized in that that the positioning device (16, 60, 62, 64) is designed such that it rotates the column (36) and the detector elements (38, 88). 10. Apparatus according to claim 9, characterized in that the positioning device a housing (16) for the collimator (12), the housing (16) being a tube (62), a plate (60) rotatably mounted within it, and a device (64) for rotating the plate (60). 11. The device according to claim 10, characterized in that the Rotating device is a switching motor (64) which is used to rotate the plate (60) in separate angular steps is formed. 12. Device according to one of claims 1 to 3, characterized in that that the walls (20) of the collimator (12) made of tungsten foil exist. 13. Device according to one of claims 1 to 3, characterized in that that the collimator (12) fifty to 250 columns (36) and the detector (14, 46) one has the same number of detector elements (38, 88). 14. The device according to claim 1, characterized in that the field Detector element (38) one scintillation plate and one on the scintillation plate (38) connected photo amplifier (54) for generating an electrical output value having. 15. The device according to claim 14, characterized in that aede Scintillation plate (38) by means of a plurality of optical fibers (50) to the Photo amplifier (54) is connected. 16. The device according to claim 13, characterized in that the Collimator (12) fifty column (36) and the detector (14, 46) fifty detector elements (38, 88). 17. Device according to one of claims 1 to 3, characterized in that that each of the detector elements (38, 88) at the base of the gap (36) opposite the open end is arranged. 18. Apparatus according to claim 2 or 3, characterized in that the photoconductor element (88) consists of cadmium tellurite. 19. Apparatus according to claim 2 or 3, characterized in that the photoconductor element (88) has a pair of electrodes (92), the planes of which are parallel to the walls (20) of the collimator (12), and the route through the photoconductor (9o) in the depth direction of the gap (36) is large with respect to the distance between the pair of electrodes (92). 20. The device according to claim 19, characterized in that the No less route through the photoconductor (9o) in the depth direction of the gap (36) is than 5 mm and the distance between the pair of electrodes (92) is not is larger than 0.75 mm. 21. Device according to one of claims 1 to 3, characterized in that that the collimator (12) has a frame (18) which is rectangular and consists of two opposite side parts (22) which are supported by a rod (24) are connected at each end with the walls defining the gaps (36) are formed by plates (20), the ends of which have bores (32) for receiving of the rods (24). 22. Device according to one of claims 1 to 3 or 19, characterized in that that each detector element (88) is a strip. 23. The device according to claim 22, characterized in that each Strips (88) through a plurality of glued together detector crystals (9o) is formed. 24. The device according to claim 23, characterized in that the A plurality of detector crystals (9o) are electrically isolated with respect to one another.