CA1053362A - Cardioscan probe - Google Patents

Abstract

ABSTRACT
Ultrasonic probe apparatus for real time B-mode sector scan examination of a cross section of a structure such as the human heart.
A transducer is pivotally mounted near an end of an elongated housing, and linkage means are provided in the housing for oscillating the transducer about an axis whose plane is approximately perpendicular to the longest dimension of the housing. Means are provided for causing the transducer to produce ultrasonic pulses which are reflected by interfaces of the object under examination, and the echoes from these interfaces are returned through the transducer to a B-mode display system. A B-mode sector sweep circuit is provided to produce a B-mode display of the echo pattern received from the structure being ob-served.

Description

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The invention is in the field of B-mode ultrasonic probe systems.
The present disclosure concerns an ultrasonîc system for examina-tion of interior portions of various structures. In particular, the disclosure pertains to a medical ultrasonic system for examination of the human heart and particularly to provide real ~ime B-mode examin-ation of a cross section of the heart. Presently, M-mode echo cardi-ography is extensively used for diagnosis of heart disease in most of the major medical centers of the world. The system de.scribed herein is designed to be compatible with existing M-mode echo cardiography and utilizes the same type of transducer now commonly in use with the M-mode technique, as well as the'pulsers and amplifiers, power supplies and associated components normally included in the M-mode echo car-diographic systems.
B-mode systems for viewing internal structures of the human body have been disclosed in U. S. Patent Nos. 3,403,671, 3J480~002 and 3,605,724, all to Flaherty; No. 3,547,101 to Rosauer; and Nos. 3,779,234 and 3,817,089 to Eggleton et alO These patents have shown ultrasonic B-mode techniques wherein a transducer is rotated or oscillated about an axis parallel to the primary axis of the probeO This orientation limits the freedom of movement and angle of approach to a structure, such as the human heart, which would be available from a transducer oscillating about an axis in a plane perpendicular to the main axis of the probeO In this latter arrangement, the'transducer is located at an end of the probe and the operator can choose'the direction of approach to the structure to be viewed reely.
The patents cited above disclose sweep display systems dependent upon either-a sine-cosine potentiometer of rotor coils in the probe to develop signals having amplitudes which are'sine and cosine functions of the angular position of the shaft on which the'transducer rotates or oscillates. So far as applicant is aware,' the'sweep circuitry

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disclosed herein has not been utilized in the past for B-mode display.
The B-mode system of the presen~ application is designed as a rectrofit package compatible with existing M-mode systems. In order to accomplish an adequate diagnostic procedure, a physician must be free to direct the acoustic beam toward the structures of interest in the heart, and at the proper angle o approach, in order to make use of specular reflections from the suraces of the structures. The determination of the an~les of approach is done using a ree-hand searching technique which involves optimizing the fieId of view provided by the B-mode scanning syst~mO The physician or technologist operating the device requires a freedom of motion of the transducer, which can only be achieved by a light-weight hand-held scanning unit in which the axis of rotation of the transducer lies in a plane perpendicular to the axis of the probe housingO With the transducer thus mounted for oscillatory sector scan motion at the end of the probe housing, the assembly can be directed at essentially any angle required for optimum viewing of the patient's heart or other internal structure.
Examinations by the physician or technologist in a busy medical center may be conducted over extended periods of time) and therefor~
the scanning unit must be sufficiently light weight that it does not become tiresome for the Examiner nor uncomfortable to the patient. In order to meaningfully examine dynamic aspects of the heart, it is also necessary to optimize the data acquisition rateO This rate is es-sentially limited by the speed of sound in ~issue, approximately 1.5 millimeters per microsecondO The pulse emitted by the transducer must propagate through the tissue and reflect from targets and return to the transducer before the next pulse is emitted, and there must be a choice of perameters which optimize the data acquisition rate for selected examinationO Whereas it has been customary to limit the .

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pulse repetition frequency (PRF) of ultrasonic systems to the range of 250 pulses per second ~o 1,000 pulses per second, ~he present system provides a selectabIe PRF of, for example, 5,000 cy~les per second.
In order to accomplish`this, it is necessary to utilize special sweep circuitry with extremeIy fast fly back capabilitiesO With a 5,000 PRF, it is possible to examine tissue in the area of the human heart to a depth of 15 centimeters, and obtain 50 frames per second with 100 lines per frameO By limiting the sector to 30, it is possible to achieve line density of 3O3 lines per degree on a oscilloscope screen~
Flicker fusion oc~urs for the human visual system at about 40 frames per second, depending upon the intensity, color of the light, and the mark space ratio of the light flashesO To achieve detail concerning valvular motion of the heart, it is necessary to utilize the highest possible scan rate consistent with the depth of examina-tion and the acoustic perameters~ Thus, it is desirable that the physician be provided with a means of controlling the scanning rate.
Frame rates in the order from 5 to 20 frames per second are not particularly useful, and may be disquieting to the physician and patient because t'he normal alpha rhythm of human beings is in this frequency range, and looking at a flicker of this frequency may drive the alpha waves within the brain and, in some instances, trigger a con w lsive reaction if the person viewing the screen is subjected to prolonged periods of this excitationO
There are presently ultrasonic systems in existence'whose frame rates are in the vicinity of 10 to 20 frames per second~ These are limited in their usefulness for the reasons stated above,' and an attempt to reduce the apparent flicker by using longer persistence screens only serves to further reduce the'resolution of the image of a moving target by smearing this image on the oscilloscope'screen~ Even at 60 frames per second, the valvular motion of the heart distorts the ~ 6~
linearity of the image on the screen since the peak velocities of the heart valve lea1ets may be as high as 120 millimeters per second.
The normal range is in the vicini~y of 60 to 80 millimeters per second, and stenotic valves may move 5 to 10 millimeters per second.
At this high velocity, the valve leaflet would move 1.66 millimeters per frame, whereas at a frame rate of 15, the valve would move 6.66 millimeters per frame, which can seriously distort the valve image, if indeed it can be seen at all under these circumstances.
The optimum frequency for the transducer or examining the adult human heart is approximateIy 2.25 megahertzO This considers the acoustic absorption as a function of depth and thé beam shape. A
focused transducer offers some advantages over nonfocused systems, and inasmuch as the valvular struc~ures of the heart lie approximately 10 centimeters below the skin surface, a 10 centimeter focal length is selected for most adult patients. A frequency of 3O5 ~MZ is considered the best choice for pediatric examinations, with a 5 centimeter focal length. A 0.5 (12.7mm) inch diameter transducer can be utilized for examining the heart through the intercostal spaces. The wave length of sound at 2~25 MHZ is 0O66 millimeters, and thus the transducer is approximateIy 19 wave leng~hs in diamter. This is sufficient for weak focusing capability at depths of 10 centimeters, thus a beam width of 4 millimeters at the half power point can be achieved, and lateral resolution of 2 millimeters can be achieved for strong echoes. The range resolution is a function of pulse length. A pulse of 1 and 1/2 acoustic cycles can readily be achieved by state of the art techniques;
therefore, 1 millimeter longitudinal resolution is attainable with this device.
The presently disclosed apparatus permits the use of either B-mode or M-mode, or simultaneous B-mode and M-mode operation. The o~ 3~f~
information from the sector scan of the B-mode may be used by the physician to modulate the M-mode data. This combined M-mode and B-mode display contains more information than the standard M-mode, and it is possible for the physician to learn to interpret the new in-formation and format contained in the combined display. It has been the custom of many cardiologists to angularly sweep the transducer gradually over the heart from base to apex during an M-mode examina-tion of the heart, directing the transducer to the various features of the heart of interest during the course of the scan in order to visualize the valves and structures important to the diagnosis; thus, the surface described by the sweep in a nonplanar complex surface and requires knowledge and skill by the operator.
It is easier to include the various valves and other s~ructures in the scan when the simultaneous B-mode and M-mode sweep (from base to apex) is used, with a B-mode sweep at right angles to the slow manual sweep. With the B-mode shut off, the physician has the same equipment which he customarily used for M-mode operation, and there-fore there is no compromise to the quality of the operator's M-mode examination. The operator may also use the B-mode without the M-mode display in operation, and diagnostic criteria will be established for B-mode alone. The most promising technique, however, appears to be combined M-mode and B-mode capability. There are'features of combined mode'of operation which'cannot readily be duplicated by the single mode operation, and thi's combined system has been designed to provide both modes with'no compromise'in design features for either the M-or B-mode'of operation.
Thé B-mode operation is used to best advantage'if the operator can record the dynamic pictures appearing on the'osci'llosco'pe'screen.
Both motion picture film and TV recording techniques can be adapted to the present systemO It is not only important t~ be'a~Le'to- replay the real time display, but also to examine single'fr'ames in detail. Both ~ Os 33 ~ ~
the movie and TV approaches permit ~his freedom~ Par~icularly with stop frame examination, it is important to know what part of the cardiac cycle is represented in the frame. It has been customary to display the ECG data for this purpose; however, in the present system, a digital clock is utilized to show seconds, tenths of seconds and hundreths of seconds, and the clock is reset to O following each R-wave. The digital readout is placed adjacent ~o the B-mode display, thus perml~ting the'physician to accura~eIy determine the stage o the cardiac cycle being viewed in stop rame operation, Other alpha numeric data can also be recorded, by placing the readout within the fieId of view of the camera, such as patient number, record number, date, e~c.
The present ultrasonic probe apparatus shall now be described in detail in conjunction with the accompanying figures in which:
Figure 1 is a partially diagrammatic, partially cross-sectional, side view of an ultrasonic probe according to an embodiment of the present invention.
Figure 2 is a perspective view of the transducer end portion of the probe'of Figure lo Figure'3 is a perspective view similar to Figure 2 showing a light source~and optical wedge apparatus instead of the resistance pad of Figure 2.
Figure 4 is a diagrammatic view of an ultrasonic scan system according to an embodiment of the present invention.
Figure 5 is a schematic view of a portion of the sw~ep circuitry according to an embbdiment of the present invention.
Figure'6 is a schematic view of a sweep generatar circuit for the embodiment of Figure'5.
Referring in particular to Figure 1, there'is shown an ultrasonic probe 10 having a casing 11 and motor 12 mounted therein. Housing ll ,, ... ., . . . .. - . . ,: - .

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is a plastic shell in order to minimize shoc~ hazards to a patient and the operatorO The sheIl is in the form of a tapered cylinder and provides a compartment for motor 12, which operates at a low voltage, also to minimize shock hazard. In order to obtain good torque charac-teristics, the motor operates at high speeds and is geared down to usable outpu~ shaft speeds with spur gear sequence. Motur 12 drives shaft 13 which terminated in gear 14. Gear 14 engages gear 15, which includes eccentric pin 17 attached rigidly to its upper surace. Gear 16 is mounted on output shat-15; shaft 15 is ro~atably mounted on a plate 20 attached to housing 11, and gear 16 held in position between the plate 20 and arm 19.
As gear 16 rota~es, eccentric pin 17 drives arm 19, rigidly attached to shaft 22, and ar~ 23, which is also rigidly attached to shaft 22, through an angle of 30, sweeping through this arc twice per revolution of the output shaft 15. When arm 23 is driven through the arc of 30, lever 24, rigidly attached to the'transducer housing 26 at a first end, engages arm 23 in a ball-and-socket arrangement at its second end and rotates transducer 27 through'a 30:arcO . The bottom'of lever 24 freeIy pivots in the socket in the upper end portion of arm 23 as shown in Figure lo Transducer face 27 is there~y oscillated about an axis which'lies in a plane perpendicular to the'long dimen-sion of probe 10.
As shown most clearly in Figure 2, an electrical wiper.contact 28 is attached to arm 230 Wiper contact 28 engages position-siensing pot 29, and an electrical lead 31 (Figure l) from the'wiper cont'act passes along the'top of the arm past the'axis of rotation and terminates on a binding post 320 The looped configuration of thi's wire is important from the point of view of minimizing breakage due'to flexing. The eIectrical connections between the'oscillating transducer 26 and ~he' stationary binding post 33'and 34 must also be'properly designed in order to minimize failure due'to flexing. Transducer wires.36 and 37 ~ 1 6~i336~
are attached between transducer 26 and binding post 33 and 34, re-spectively.
The factors included in the electrical connection design include the use of tensile conductors wrapped around a cotton core and covered with a flexible plastic sheath, such as polyurethane insulation~
Flexing per unit length of wire is minimized by using a loop of wire in the plane of flex, and to avoid a concentration of stress at the terminals a tapered silastic covering is applied over the wires to give a gradual transition in stiffness from ~he rigid binding posts to the very flexible lead wiresO The wires are carefully positioned so that they will not contact other objects in the course o~ their rotation or other movemen~O
An electrical switch may be provided on the housing to enable the operator to start and stop motor 12. If the operator wishes to stop the transducer so that it is aimed along the axis of probe 10, the speed control 39 for motor 12 is turned ~o a very low speed operation, and when the transducer has the proper orientation, the power switch is turned off. This may be done if the equipment is to be used in the M-mode only. As shown in Figure 1, power supply 38, operating through speed con~rol 39, is supplied to energize motar 120 The operator- -controlled on-off switch may be easily loca~ed at the tapered portion near the head of housing 11 for easy control by extending power supply wires 40 into the housing to run past thè'switch'location.
As shown in Figure 3, the probe may be modified to include source light 41 and light receiver 42 rigidly attached to housing 11 beneath moving arm 23. Optical wedge 43 is then mounted to moving arm 23 and passes between light source 41 and light receiver 42~ With wedge'43 attached to arm 23 moving through the arc scanned and the'photo receiver and source opposite one another on either side'o the wedge, the light passing from the photo source ot the pho~o receiver is modulated by the variabIe density filter, the op~ical wedge, moving _g_

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past it. The resultant electrical signal is taken from the optical receiver and amplified, and used an in input for X sweep generating circuits of the viewer.
The resistance system of Figure 2 includes a wiper mounted on the arm that is moving through the scanned arc and a special resistance pad rigidly attached to housing 11. The pad must be of a very hard and smooth material with a low coefficient of friction, long life, and low noise properties such as a plastic element. A voltage is applied across the resistance strip and the wiper takes off a voltage from it that is a function of the angle at which the arm is pasitioned. The position-sensing element can be of other varieties besides resistive and optical such as magnetic or inductive.
In normal operation, for examination of the heart, the transducer 26 is placed in contact with the skin with a suitabIe coupling material.
Most adults tolerate the oscillatory motion of the'transducer and experience no discomfort. In using the device or pediatrics, scanning your children and infants, the'vibration produced by the'transducer may be alarming in a few cases to the subject. To avoid this problem, a small water capsule 2 inches in diameter and 112 inch'~hick is placed on the child's chest using a suitable'coupling agent, and the transducer is then placed over the'capsuleO The vibration of the transducer is completely shieIded by this methbd and avoids any squirming response'of the patientO
Wires 46 and 47 are connected from opposite'ends of resistance pad 29 (Figure 1), and these wires together with wires 31, 36 and 37 are gathered together mechanically within housing 11 and coupled to cable 48 by suitable connector means. As shown in Figure'4, the wires in cable 48 are coupled through'a ~ connector to a modified M-mode display unit 49, such as an Ekoline 20 manufactured by the'Smith Kline Instrument Company of Palo Alto, California. CabIe 48 is also coupled to Y-axis generator circuit 51. The display system uses a medium ,. -1~-.:

~33t~2 persistance oscilloscope to display the real time acoustic image. The display raster is an arc sector 52 generated by a vertical sweep sawtaoth signal of the same period as the PRF clock in unit 49, and a variable slope horizontal sawtooth wave form of the same period as the PRF clockO Conventional CRT display units ar~ provided with rect-angular coordinate display format which must be transformed to polar coordinates to display a sector raster. Due to the small angles involved, X-axis correc'tion is not necessary. The vertical Y sweep for the B-mode display is modulated by the cosine of the angle that the transducer is rotated through, and the horizontal X sweep should theoretically be modulated by the sine of ~he angle~ For the 30 scan angle utilized, it has been found that X~axis correction is not necessary due to the small error introduced. This produces a resul-tant vector that is essentially geometrically correctO These func-tions are derived from the position-sensing elements on the ultrasonic probe. The position sensing eIement may be optical, resistive and so on as discussed above in regard to Figures 2 and 3.
Display unit 49, such as an Ekoline 20, is modified in the present system as to the various necessary internal time constants to permit operation at'a 5,000 PRF rather than 1,000, for which the unit is designed. The additional sweep circuitry of unit 51 is provided to drive'CRT 53 and a sweep circuit modification similar to the circuitry in unit 51 is provided for the Ekoline 20 unit 49, as described below in more detail.
As shown in Figure 4, the various wires from thé'transducer, potentiometer and motor and travel within cabl'e'4~ to point 54 w~ere coaxial cable 56 couples the transducer wires to unit 49 a~d the remaining wires are'coupled by cable 57 to module'S10 CabLe'58 couples a PRF pulse'from unit 49 to module 51, and cable'59 couples the Z, or intensity, signal from unit 49 to osci'lloscope 53. Cables 61 and 62 couple the horizontal and vertical sweep outputs from module l Q ~

51 to oscilloscope 53. In B-mode operation of probe 10, a B-mode display is ob~ained on the screen of oscilloscope 53 through the coordination of M-mode unit 49 and B-mode module 51. For M-mode display only, the transducer in probe 10 is maintained in a nonos-cillatory condition and only the M-mode display is produced by the coupling of the transducer through cables 48 and 56 to the M-mode unit 49. The "ice pick" M-mode display appears on screen 60 of M-mode unit 49, and module 51 is turned o~f as is oscilloscope 53. The M-mode display unit 49, preferably an Ekoline 20 unit, is premarily modified simply as to its time constants to process the transducer signal at a PRF of 5,000 rather than 1,000, at which frequency the Ekoline 20 is normally operated.
Turning now to Figure 5, there is shown circuitry for X-axis sweep generation for B-mode display and cosine correction generation and a block diagram indication of the motor speed control contained in sweep generator unit 51, Motor speed control 71 provides an on-of switch and variable voltage speed control for the motor in probe 10 (Figure 4). The two motor wires from cables 48 and 57 are coupled~
through connector 72 in the~face of module 51 and coupled to the motor speed control through leads 73 and 74.
The left end of the resistive eIement in probe 10 is coupled through connector 72, lead 76 and resistar Rl to a negative supply voltage. The right side of the resistive element in the probe is coupled through connector 72, lead 77 and variable resistor R2 to a positive DC supply. This establishes a voltage divider from the B~
through R2, the resistive element in the probe, and Rl to B-. The wiper arm from the probe is coupled through the co~nector and lead 78 and resistor R3 to operational amplifier Al. Amplifier Al and ~he other amplifiers in the circuit have the usual plus and minus 15 volt connections, etc. The wiper arm input voltage to Al is a function of the position of the transducer as i~ oscillates on its axis. This ~ 6~533t~
signal is similar to a sinusodal wave form and is a function of the angular position of the transducer.
The amplified signal from the output of Al is coupled to cosine generator circuit section 79 through conductor 81. The wiper arm of potentiometer R4 picks off a portion of the signal from the output of Al, and a full wave rectifying circuit including A3, Dl and D2 gen-erates the absolute value of the signal. This full wave rPctified signal is fed into function generator 82, eOg. a Burr Brown Sin Cos Function Generator 4118/25, which produces at its output 83 a signal which is the cosine of the input voltage. This signal is now a function of the cosine of the angular position of the transducer in probe lO. The output cosine signal from function generator 82 is amplified by amplifier A4 and fed to potentiometer RSq The output 84 of the cosine generator circuit section 79 is supplied to the Y sweep generator circuitry in unit 51 for B-mode display and modulates the Y-axis sweep signal, as shall be explained in further detail herein-after.
The X-axis sweep is modulated, as described above, by the cosine of the nagle that the transducer is-sweep through'to produce the 2Q correct vectorial vertIcal component of deflection on the oscilloscope screen or B-mode scanning. The cosine function is derived from the position sensing signal, as described above,' and since'the position sensing signal goes above'and below ground potential as the transducer swings from right through center to left, a full wave-rectifier is used to make the signal positive'in both'quadrants, since the cosine is positive for these'quadran~s. The output of the'sine'cosine module is then a voltage proportional to the cosine of the angle of the transducer, which is a voltage proportional to the'position signal from the wiper arm of the potentiometer in the probe 10.
The transducer angle-dependent wave form at thé'output of Al is also coupled for X-axis swe'ep generation through'lead 86 to potentio-meter R6, the wiper arm of'which'picks off a portion of the''amplitude ~ C~533~2 of the wave form. Coupled to the wiper arm of R6 is a wiper arm of potentiometer R7 which determines ~he bias of the wave form, serving as a voltage divider between B+ and B-. The amplified position-sensing signal from the probe transducer is then input to a compli-mentary current source comprising transistors Q7 and Q8. The signal appears as a variable voltage on the collectors of Q7 and Q8, and capacitor Cl then charges up to this voltage. The slope of the voltage ramp that is created on capacitor Cl is a function of the instantaneous input signal amplitude on the collectors of Q7 and Q8.
The ramp voltage thus produced on Cl would continue to rise up to the supply voltage if retrace did not occur.
Retrace is accomplished by diodes D3, D4, DS and D6 and transistors Q5 and Q6. The initiation of the retrace period occurs in the cir-cuitry at the right-hand side of Figure 5 with a pulse input through lead 58 (Figure 4) from unit 49 to module 51 at the point labeIed 87 in Figure 5. The PRF pulse coupled from unit 49 is positive pulse of about 15 microsecond duration and 2 volts in height and is dPrived from the PRF clock in Ekoline 20, unit 49. An amplifier s~age com-prising transistor Ql inverts and amplifies the input pulse and feeds i~ to one shot multivibrator comprising Q2 and ~3. The narrow pulse from the one shot multivibrator is fed to the base of transistor Q4, which uses the pulse to turn on ~5 and Q6. As current in Q5 and Q6 increases, diodes D3, D4, D5 and D6 conduct and capacitor Cl is discharged, thus returning the ramp voltage on Cl to 0. Therefore, a variable slope ramp signal is produced at a PRF repetition rate with Cl charging toward the instantaneous voltage at the collectars of Q7 and Q8.
The variable slope ramp generator signal from capacitor Cl is then preamplified by amplifier A2 and input into the'differential output amplifier section 88. The'differential 'ampliier comprises transistors Q9 and Q10 and constant current source'Q13'w~ich provides 1~-53;~Z

linearity and high requency ~esponse at the gains necessary to deflect the plates of the CRT 53O Emitter follower transistors Qll and Q12 provide a low impedance driver for the'plates of the CRT. The output to the horizontal deflection plates of CRT 53 are shown at 89 and 91.
Referring now to Figure 6, there is shown a Y-axis sweep gen-era~or circuit, also included in module 51, whose output is coupled to sweep amplifier 92, which is of the same coniguration as sweep amplifier circuit section 88 in Figure 5. This sweep amplifier cir-cuitry 92 is contained in module 51 and provides the Y-axis sweep to oscilloscope 53. Negative pulses at the PRF rate are provided from the inverter circuit in the Y-axis, or fast axis, sweep section of the M-mode display unit 49, the Ekoline 20. The sweep circuitry shown is essentially the same as that used in the M-mode display unit 49, with C6 producing effectiveIy a sawtooth wave'which is amplified by sweep amplifier 92 to provide'the'Y-axis or vertical deflection for oscillo-scope 53. Transistor Q14 is inserted in series with the usual range control for the sweep circuit and has an input at its base from the output 84 of the cosine generator section 79 of the circuit of Figure 2Q 5. This cosine generator output 84 being applied to the base of Q14 provides a mod~lation of the vertical deflection sawtooth slope so that the'correct amour,t of vertical deflection is provided in accordance with the angle of the sweep in the B-mode'display.
As shown in Figure 6, the cosine wave generated in subcircuit 79 is fed to the base of transistor Q14 and modulates the slope of the sawtaoth produced at C6 in the'sweep generator circuit. The effect of this additional modulation is to produce a Y-axis sweep sawtooth whose slope'varies slightly according to the cosine of th~'angular position of the transducer and of the scanned lineO As indicated above, this sawtaoth is fed to the sweep amplifier which'then couples the ampli-fied sawtccth to the'pla~es' of o~cilloscope 53'for vertical deflection.
A sweep amplifier section such as 92 or 88 is also substituted for the original sweep amplifier section for the fast scan, or ~, axis of the l(~S;3;~Z
M-mode display unit 49 in order to facilitate operation at PR~ of 5,000~
The remaining scanning functicn of the M-mcde display unit 49 is not affected by the mod}fica~ions described above. This X-axis scan of the M-mode display is of slow speed and not correlated to the PRF.
Therefore, modifications to the sweep circuitry or the slow scan de1ection of the M-mode display is not necessary. It can be seen that a B-mode ultrasonic scan display sys~em has been described which may readily be retrofit wit~ an existing M-mode system and which provide fast-scan real-time viewing of the interior of structure such as the human heart.
While there have been described above the principles of this invention in conncction with specific apparatus, it is to be clearly undexstood that this description is made only by way of example and not as a limit~tion in the scope of the invention.

Claims (9)

Having thus described the invention, what is desired to be claimed and secured by Letters Patent is:

1. Ultrasonic probe apparatus comprising:
an elongated probe housing having a longest dimension;
a transducer pivotally mounted near an end of the housing and having a face adjacent the surface of the housing, the transducer being pivoted about an axis in a plane approximately perpendicular to the longest dimension of the housing;
linkage means in the housing for pivotally oscillating the transducer about its axis when the linkage means is activated;
motor means coupled to the linkage means for activating the linkage means; and means coupled to the transducer for causing the transducer to produce ultrasonic pulses.

2. The apparatus of claim 1 which further comprises indicator means mounted within the housing for indicating the angular position of the transducer as it is pivotally oscillated by the linkage means.

3. The apparatus of claim 2 in which the linkage means includes a first wheel having an eccentric pin extending from its first surface, a slotted lever positioned with the eccentric pin within the slot in the slotted lever, and an arm rigidly attached to the transducer at a first end and having a second end pivotally coupled to the slotted lever, whereby rotation of the wheel and consequent oscillation of the slotted lever is translated into oscillatory motion of the arm and transducer.

4. The apparatus of claim 3 in which the linkage further comprises a first shaft rigidly attached at the end of the slotted lever further from the slot and positioned essentially parallel to the pin, a second lever rigidly attached to the first shaft and essen-tially parallel to the slotted shaft in spaced apart relationship from the slotted shaft, the second lever including a socket pivotally receiving the arm of the transducer.

5. The apparatus of claim 4 in which the motor is mounted within the housing and includes a motor shaft and a toothed gear rigidly attached to the end of the shaft and the first wheel includes teeth engaged and driven by the teeth in the gear attached to the motor shaft.

6. The apparatus of claim 5 in which the transducer is pivot-ally mounted to the housing adjacent the face of the transducer.

7. The apparatus of claim 6 in which the indicator means includes a resistance pad coupled to the housing and the second lever includes a contact wiper which moves along the resistance pad as the second lever and transducer are oscillated.

8. The apparatus of claim 1 which further comprises means coupled from the transducer for receiving and for displaying echoes of said ultrasonic pulses.

9. The apparatus of claim 1 in which the motor means includes a variable speed control for varying the speed of the motor and con-sequently varying the frequency of oscillation of the transducer.