CA1087292A - Method and apparatus for ultrasonic examination - Google Patents
Method and apparatus for ultrasonic examinationInfo
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- CA1087292A CA1087292A CA330,610A CA330610A CA1087292A CA 1087292 A CA1087292 A CA 1087292A CA 330610 A CA330610 A CA 330610A CA 1087292 A CA1087292 A CA 1087292A
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Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus for ultrasonic examination of an object use pulses of ultrasonic energy directed along a plurality of beams into the object from positions spaced rela-tive to each other, the beams being steered to a plurality of angular directions in a single plane. The pulses are directed sequentially along each of the beams in each of the angular positions at a rate sufficiently fast, compared to the rate of movement of the transducer beams, that each transducer beam moves only a small distance between successive activations thereof, the sequential activation along the transducer beams comprising sequential activation along non-adjacent beams.
A method and apparatus for ultrasonic examination of an object use pulses of ultrasonic energy directed along a plurality of beams into the object from positions spaced rela-tive to each other, the beams being steered to a plurality of angular directions in a single plane. The pulses are directed sequentially along each of the beams in each of the angular positions at a rate sufficiently fast, compared to the rate of movement of the transducer beams, that each transducer beam moves only a small distance between successive activations thereof, the sequential activation along the transducer beams comprising sequential activation along non-adjacent beams.
Description
~087Z9Z
This is a division of Canadian Patent Application 251,297 filed April 2~, 1976.
This invention relates to the technique of ultrasonic echoscopy of objects and in particular to decreasing the time required for examination of an object using the pulse-echo ultrasonic technique and for improving the clarity and hence the utility of the examination results. It is particularly, but not solely, directed to the use of this technique in medical diagnostic examination.
Ultrasonic echoscopy provides information about an examined object which may be displayed in the form of an ultra-sonic echogram. Such an echogram consists of a display of acoustic impedance discontinuities or reflecting surfaces in the object. It is obtained by directing a short pulse of ultrasonic energy, typically in the 1-30 MHz frequency range, into the examined object where any acoustic impedance discontinuities in the object reflect and return some of the energy in the form of an echo. This echo is received, converted into an electric signal and displayed as an echogram on a cathode ray oscillo-scope, a film, a chart or the like.
The echogram may constitute either a one dimensional or a two dimensional representation and in both cases the infor-mation is contained in the position and magnitude of the echo displayed. In a one dimensional display, the position along a base line is used to indicate the distance to the reflecting surface whilst the magnitude of the echo is displayed for example as a deflection of the base line "A mode" or as an intensity ` change "B ~ode". In a two dimensional display, the position : along a base line is used to indicate the distance to the re-flecting surface as in a one dimensional display, and the r ~ , ~
direction of the base line is used to represent the direction of propagation of the acoustic energy. The two dimensional display is obtained by changing this direction of propagation of the acoustic energy and by instituting a similar but not necessarily identical movementof the base line of the display. The magni-tude of the echo is displayed as for a one dimensional display, for example, as a deflection of the base line or as an intensity change.
The technique of ultrasonic echoscopy is used in medical diagnosis to obtain information about the anatomy of patients. The application of this technique is now widely in-vestigated and is described, for example, by D. E. Robinson in Proceedings of the Institution of Radio and Electronics Engineers Australia, Vol. 31, No. 11, pages 385 - 392, November 1970:
"The Application of Ultrasound in Medical Diagnosis". As pointed out in this article, ultrasonic echoscopy may be used to produce displays resembling anatomical cross-sections which have proved clinically useful when the desired information concerns physical dimensions, shapes of organs or structures or the like. Ultra-sonic echography has proved of particular value as a diagnosticaid in the abdomen and pregnant uterus, eye, breast, brain, lung, kidney, liver and heart, these being areas of soft tissue ~ with little bone and air. In general, the technique is con-; sidered to complement other techniques to provide a more complete picture of the patients' condition, however, particularly in pregnancies, ultrasonic echoscopy may be useful in place of X-rays where the latter may not give sufficient information or may be dangerous. In medical use, a pulse of ultrasonic energy is transmitted into a patient in a known direction and echoes are received from reflecting surfaces within the body. The time , ~087Z92 delay between a transmitted pulse and the received echo depends on the distance from the transmitter to the reflecting surface and the distance information so obtained may be displayed in a suitable way for interpretation and clinical use as a one dimensional range reading or as a two dimensional cross-section as previously described.
In one presently known form of ultrasonic diagnostic examination, a single transducer is used and it is physically moved to various positions around the patient. At each of these 10 positions the beam is swept with an oscillatory motion while constrained to remain within a single plane by mechanical oscil-lation of the transducer, to obtain the required scan pattern.
By the use of suitable deflection circuits, for example, in a cathode ray display tube, a line is caused to follow the motions of the beam axis and echoes within the part examined are thus displayed in their correct geometrical positions. By way of example, for transverse sections, the transducer may be moved horizontally in a 150 arc around a patient who is substantially erect while undergoing + 15 oscillations and for longitudinal ; 0 sections the transducer may be moved vertically while undergoing + 30 oscillations.
It has, however, been found that in such systems where the transducer is physically moved around the patient this move-ment leads to a limitation on the examination time of between ten and twenty seconds for each cross-sectional visualization due to c mechanical inertia and, in the case where the transducer is coupled to the patient via a coupling medium such as water, the generation of turbulence by the transducer when it moves quickly in the coupling medium.
Several alternative forms of ultrasonic examination ' _ 3 _ .
equipment have been devised which will avoid the limitations discussed above and thus enable a speeding up of the time re-quired for each cross-sectional visualization. It will be ap-parent that a reduction in examination time of a patient will lead to a technical improvement in the resultant echograms as the effects of movement of the part under examination will be reduced. In addition, a reduction in examination time of a patient will have the economic advantage that more cross-sectional visualizations and hence more examinations will be able to be performed in a given time.
In the currently used two dimensional B mode svstems of ultrasonic examination, a single transducer is either mechani-cally driven or manually operated to obtain an echogram. To enable examination of region of interest, for example of a patient, the plane of scan is adjusted as required, an echogram obtained in that plane, and then the plana of scan moved, and so on, usually in such a way as to examine parallel sections of the region of interest. As each cross-section visualization using the known systems requires from ten to twenty seconds, the entire examination may take up to half an hour or so. Such a long examination time is undesirable for a number of reasons.
Firstly, there can be considerable movement during the examina-tion period, particularly of the fetus in a pregnant uterus, blurring individual echograms and causing difficulty in inter-preting a full set of cross-sectional visualizations over a region of interest. Furthermore, a prolonged examination is often not possible or is at least most undesirable when the technique is used in the examination of sick patients. Of course, a lengthy examination time precludes the use of the technique as a screening test, and the reduced throughput of 10~37Z~Z
patients has an obviously deleterious effect on the economics of the technique.
It is therefore an object of the present invention to provide a methodof ultrasonicexamination ofan objectby thepulse-echo technique whichis capable of performinga complete ultrasonic examination in a time considerably less than that possible at present. As will be appreciated from the above, any reduction of the time necessary for the examination will have the further benefit that the quality of the echograms which are obtained will be improved since the effects of patient movement will be reduced.
According to the present inventionthere is provided a method of ultrasonic examination of an object which comprises directing pulses of ultrasonic energy from a plurality of trans-ducers along a plurality of beam axes through a liquid coupling bath and into the object, each beam axis being associated with one of the plurality of transducers, and receiving echoes of the pulses reflected along the beam axes by acoustic impedance dis-continuities in the object, the directing step including direct-ing the beams into the object from the plurality of transducers at spaced positions relative to each other and to the object;
steering the beam axes to a plurality of angular directions in a single plane; and directing the pulses sequentially along each of the beam axes in each of the angular positions at a rate suffi-ciently fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance between successive activations of each respective transducer; the sequential activation along the transducer beam axes comprising sequential activation along a non-adjacent beam axis substanti-ally simultaneously with the receiptof echoesof aprevious pulse.
The invention further provides apparatus for the ultra-sonic examination of an object comprising a liquid coupling bath;
~' .
a plurality of transducer for directing pulses of ultrasonic energy along a beam axis through the liquid coupling bath and in-to the object and receiving echoes of the pulses reflected along the beam axis by acoustic impedance discontinuities in the object, the transducers being spatially positioned relative to each other and to the said object; means for steering the beam axis of each of the transducers to a plurality of angular directions in a single plane; and means for sequentially activating each of the transducers to direct a pulse of ultrasonic energy along a beam axis into the object and to receive echoes reflected along the beam axis in each of the angular directions at a rate sufficient-ly fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance bet-ween successive activations of each respective transducer, the means for sequentially activating each of the transducers compris-ing means for activating non-adjacent transducers to direct a pulse of ultrasonic energy along a beam axis into the object sub-stantially simultaneously with the receipt of echoes resulting from activation of the previously activated transducer.
20 . The plurality of transducers may be mounted in a single arm, the arm being mounted within a housing by a support-ing mechanism, forming the steering means, for movement thereof with respect to the object to be examined to facilitate examina-tion thereof in any desired plane. Preferably, this supporting mechanism provides movement in the "x", "y" and "z" directions ,.
with respect to the object and also provides for rotation and tilting of the arm with re~pect to the object, thereby allowing : 30 10~7Z9~
focusing of the transducers of the arm on the desired region of the object and scanning in any desired plane. Preferably also, the arm supporting the transducers is curved thereby enabling a degree of mechanical focusing of the transducers at a point within the object to be examined. The curve of the arm may be circular. However, linear arms or other non-linear arms may be used if desired.
The use of a plurality of transducers has been found to enable a speeding up of the time required for each cross-sectional visualization. In a typical operation the transducers are spatially positioned in the aforementioned single plane relative to each other and to the object under examination as by mounting ; in the arm described above and the beam from each transducer is steered to a plurality of angular directions in thls plane, for example by oscillation of the transducers in the plane of the arm.
The transducers may then be energized sequentially, the time of energizing each of the transducers being set so that the whole set of transducers is energized before the appropriate beam from each transducer has moved a significant distance. In this way an entire scanned cross-section may be formed in one cycle of the transducers.
Oscillatory motion of the beam axes from the plurality of transducers in order to build up a complete cross-sectional visualization may be provided by two alternative means. The first means of obtaining oscillatory motion of the beam axes is by mechanically scanning all of the plurality of transducers either independently or simultaneously. In this case, although mechanical movement of the transducers does introduce a limita-~ tion on the scanning rate, the effect of this limitation may be ;~ ~ 30 minimized by providing suitable switching means which require ~ .
the transducers to scan only once while obtaining a complete cross-sectional visualization. Thus, each transducer is activa-ted in turn to direct a pulse of ultrasonic energy along the beam axis, the rate at which the transducers are activated being sufficiently fast, compared with the rate of mechanical oscilla-tion of the transducers, that each transducer oscillates only a small distance between successive activations thereof. The final result achieved by this method of operation is that at the end of a single mechanical scan, each of the transducers has been activated whilst its beam was directed in all required directions.
It will be apparent that monitoring of the direction of the beam axes will be necessary in order to build up the complete visualization.
The alternative means of obtaining oscillatory motion of the beam axes is by use of transducer arrays at each trans-ducer position, the arrays being appropriately designed as to be capable of being steered electronically. In such a system there are no moving parts and the scanning rate obtainable with this system is limited only by considerations of electronic switching speeds and the rate of acquisition of ultrasonic information by the transducer after each transmitted pulse. Since such an array may be electronically steered to direct its beam in all required directions at a rate much faster than that possible when mechanical oscillation of the transducer is required, it is possible to operate this system by steering the beam from each ; transducer array to each of the required directions to measure the reflected echoes before activating the next transducer array and steering the beam from it to each of the required directions, and so on. It will, however, be appreciated that this plurality of transducer arrays capable of being electronically steered may , ~ , also be operated in a manner similar to the operation of the mechanically oscillated transducers previously described.
In a further important embodiment of the present in-vention, however, the individual transducers of an array which is being mechanically scanned may be energized in a "scattered"
operation rather than in a sequence of energizing adjacent trans-ducers. Thus, instead of energizing transducer No. 2 after transducer No. 1, and then transducer No. 3, transducer No. 4 and so on, in accordance with this invention transducer No. 5 in 10 the array may be energized after transducer No. 1, then trans- 7 ducer No. 2 followed by transducer No. 6 and so on. It has been found that such "scattered" operation of a plurality of trans-ducers enables even further speeding up of the visualization since it enables one transducer to be energized without having ~ to wait for multiple reflections arising from energization of ; the previous transducer to die down, this being possible since the transducer is to transmit its pulse and receive reflections along a beam which is spaced substantially from the beam of the previous transducer. Since the "wait period" which can be 20 avoided by such "scattered" operation may be of the order of 500 ~ sec, a significant speeding up of the examination is thereby achieved.
In yet another mode of operation of apparatus emobody-ing the present invention the individual transducers of an array may be energized in such a manner that the time of display of echoes approximates the total available time. In the "scattered"
operation described above in which the circuit conventionally includes a single deflection generator circuit for the display means, the time of display of echoes is approximately half of 30 the total available time, the other half of thé available time . . .
:,: _ g _ ., , being taken up by time for transmission of the pulses through the coupling mediurn In the present alternative mode of operation, however, it has been found that the use of two deflection genera-tor circuits enables one pulse to be transmitted through the coupling medium during the period of display of echoes from the preceding pulse so that the display of echoes from the one pulse may commence almost immediately after conclusion of the display of echoes from the preceding pulse.
Where the plurality of transducers are mounted in a single arm for oscillation in the plane of the arm, it is pre-ferred that the transducers be mechanically linked for simul-taneous oscillation. Thus a single motor may be utilized for oscillation of all of the transducers, and, if desired, a single monitoring device may be utilized to monitor the oscillation of all transducers since their respective beams will be fixed rela-tive to one another. The single arm may be mounted on a support-ing mechanism which provides for both rotation and tilting of the arm with respect to the object under examination. Rotation of the arm of course enables different cross-sectional visualiza-; 20 tions to be obtained without repositioning of the object while tilting of the arm enables the transducers to be directed to a single point from different angles, thereby enabling inclined sections to be obtained. Appropriate drive means may be provided to perform this rotation and tilting, and monitoring means pro~ -vided to measure the position of the transducers. Similarly, drive means and monitoring means are provided to move the arm in the "x", "y" and "z" directions and to monitor this movement.
Embodiments of the present invention are illustrated ; in the accompanying drawings in which:
r 30 Figures 1 to 3 illustrate schematically apparatus em-.
bodying the present invention;
Figure 4 illustrates in more detail the mechanism for oscillation of the transducers of the apparatus of Figures 1 to 3;
Figure 5 shows a basic block diagram of one form of ;~
the electronics for ultrasonic examination apparatus in accor-dance with the present invention;
Figure 6 shows a transmitter and receiver switching block diagram for the circuit of Figure 5;
Figure 7 shows a block diagram of an angle and origin switching network for the circuit of Figure 5;
Figure 8 graphically depicts a "scattered" mode of operation of the apparatus utilizing the circuit of Figure 5;
Figure 9 shows a modification of the circuit of Figure 5; and Figure 10 graphically depicts an alternative mode of operation of the apparatus utilizing the modified circuit of Figure 9.
As shown in Figures 1 to 3 of the drawings, the appara-tus comprises a housing 19 in the form of a couch upon which apatient 17 can be positioned. The patient 17 is positioned with the region to be examined placed in contact with a flexible , coupling membrane 18 which seals an aperture in the top of the housing. Housing 19 is filled with a coupling medium such as , ,:
~, water and is provided with a header tank as at 24 to maintain , proper contact between the patient and the membrane.
! ~. Located within the housing 19 and immersed in the ' `- coupling medium is a plurality of transducers 2 spatially mounted in a main supporting arm 1 so as to be capable of oscillating in the plane of the arm, thereby directing the respective pulses of .~,'; ~
, :
ultrasonic energy along beams which are steerable in said plane.
Eight transducers are shown in the Figures by way of example, however it will be appreciated that this number may be increased or decreased as desired. As shown in greater detail in Figure 4, each transducer 2 is arranged to oscillate about pivot centre 3 by action of oscillator arm 4. The respective oscillator arms 4 of each of the transducers 2 are coupled by links 5 which are provided with adjusters 6 to enable accurate positioning of the transducers 2 with respect to each other and the arm 1. One of the oscillator arms 4 is provided with a sector gear 7 which meshes with a geared output 8 of motor 9, attached to arm 1. It will be apparent that rotation of the shaft 8 of the motor 9 will result in simultaneous pivoting of each of the transducers 2 about its pivot centre 3. The position or angle of each trans-ducer is monitored by means of monitoring potentiometers 10.
Referrlng again to Figure 1, main arm 1 is mounted on a main frame which is slidable towards and away from the patient 17 to enable positioning of the transducers mounted on arm 1 relative to the patient. The main frame is slidable on pillars 11 and movement along these pillars is controlled by motor 12, for example, by means of a rack and pinion drive. The main frame is also mounted on a carriage 25 which slides along a track 15 controlled by motor 22 (Figure 3), again by means of a rack and ; pinion drive or the like. As depicted, the apparatus enables movement of carriage 25 along track 15 transverse to the patient 17 in the position depicted. Longitudinal movement of the arm 1 with respect to the patient is effected by movement along track 16 provided by motor 23 (Figure 3) again, for example, by means of a rack and pinion drive.
As best seen in Figure 2, arm 1 is mounted on a frame , f: ~
~0~7Z9Z
20 which is supported by bearings or the like on carriage 25 for tilting motion with respect to the patient. Thus frame 20 is provided with an arcuate track section which engages the shaft of motor 13, for example in a rack and pinion type drive, for tilting of the arm. Frame 20 is in turn mounted on turntable 21 which provides rotary motion of the arm 1 relative to the ~ -carriage 25, this rotary motion being controlled by motor 14.
It will thus be apparent that by provision of appropriate mechanisms supporting arm l, this arm can be positioned trans-versely, longitudinally, or toward or away from the patient.
;Further, the arm may be tilted or rotated relative to the patient to enable any desired plane of scan of the transducers
This is a division of Canadian Patent Application 251,297 filed April 2~, 1976.
This invention relates to the technique of ultrasonic echoscopy of objects and in particular to decreasing the time required for examination of an object using the pulse-echo ultrasonic technique and for improving the clarity and hence the utility of the examination results. It is particularly, but not solely, directed to the use of this technique in medical diagnostic examination.
Ultrasonic echoscopy provides information about an examined object which may be displayed in the form of an ultra-sonic echogram. Such an echogram consists of a display of acoustic impedance discontinuities or reflecting surfaces in the object. It is obtained by directing a short pulse of ultrasonic energy, typically in the 1-30 MHz frequency range, into the examined object where any acoustic impedance discontinuities in the object reflect and return some of the energy in the form of an echo. This echo is received, converted into an electric signal and displayed as an echogram on a cathode ray oscillo-scope, a film, a chart or the like.
The echogram may constitute either a one dimensional or a two dimensional representation and in both cases the infor-mation is contained in the position and magnitude of the echo displayed. In a one dimensional display, the position along a base line is used to indicate the distance to the reflecting surface whilst the magnitude of the echo is displayed for example as a deflection of the base line "A mode" or as an intensity ` change "B ~ode". In a two dimensional display, the position : along a base line is used to indicate the distance to the re-flecting surface as in a one dimensional display, and the r ~ , ~
direction of the base line is used to represent the direction of propagation of the acoustic energy. The two dimensional display is obtained by changing this direction of propagation of the acoustic energy and by instituting a similar but not necessarily identical movementof the base line of the display. The magni-tude of the echo is displayed as for a one dimensional display, for example, as a deflection of the base line or as an intensity change.
The technique of ultrasonic echoscopy is used in medical diagnosis to obtain information about the anatomy of patients. The application of this technique is now widely in-vestigated and is described, for example, by D. E. Robinson in Proceedings of the Institution of Radio and Electronics Engineers Australia, Vol. 31, No. 11, pages 385 - 392, November 1970:
"The Application of Ultrasound in Medical Diagnosis". As pointed out in this article, ultrasonic echoscopy may be used to produce displays resembling anatomical cross-sections which have proved clinically useful when the desired information concerns physical dimensions, shapes of organs or structures or the like. Ultra-sonic echography has proved of particular value as a diagnosticaid in the abdomen and pregnant uterus, eye, breast, brain, lung, kidney, liver and heart, these being areas of soft tissue ~ with little bone and air. In general, the technique is con-; sidered to complement other techniques to provide a more complete picture of the patients' condition, however, particularly in pregnancies, ultrasonic echoscopy may be useful in place of X-rays where the latter may not give sufficient information or may be dangerous. In medical use, a pulse of ultrasonic energy is transmitted into a patient in a known direction and echoes are received from reflecting surfaces within the body. The time , ~087Z92 delay between a transmitted pulse and the received echo depends on the distance from the transmitter to the reflecting surface and the distance information so obtained may be displayed in a suitable way for interpretation and clinical use as a one dimensional range reading or as a two dimensional cross-section as previously described.
In one presently known form of ultrasonic diagnostic examination, a single transducer is used and it is physically moved to various positions around the patient. At each of these 10 positions the beam is swept with an oscillatory motion while constrained to remain within a single plane by mechanical oscil-lation of the transducer, to obtain the required scan pattern.
By the use of suitable deflection circuits, for example, in a cathode ray display tube, a line is caused to follow the motions of the beam axis and echoes within the part examined are thus displayed in their correct geometrical positions. By way of example, for transverse sections, the transducer may be moved horizontally in a 150 arc around a patient who is substantially erect while undergoing + 15 oscillations and for longitudinal ; 0 sections the transducer may be moved vertically while undergoing + 30 oscillations.
It has, however, been found that in such systems where the transducer is physically moved around the patient this move-ment leads to a limitation on the examination time of between ten and twenty seconds for each cross-sectional visualization due to c mechanical inertia and, in the case where the transducer is coupled to the patient via a coupling medium such as water, the generation of turbulence by the transducer when it moves quickly in the coupling medium.
Several alternative forms of ultrasonic examination ' _ 3 _ .
equipment have been devised which will avoid the limitations discussed above and thus enable a speeding up of the time re-quired for each cross-sectional visualization. It will be ap-parent that a reduction in examination time of a patient will lead to a technical improvement in the resultant echograms as the effects of movement of the part under examination will be reduced. In addition, a reduction in examination time of a patient will have the economic advantage that more cross-sectional visualizations and hence more examinations will be able to be performed in a given time.
In the currently used two dimensional B mode svstems of ultrasonic examination, a single transducer is either mechani-cally driven or manually operated to obtain an echogram. To enable examination of region of interest, for example of a patient, the plane of scan is adjusted as required, an echogram obtained in that plane, and then the plana of scan moved, and so on, usually in such a way as to examine parallel sections of the region of interest. As each cross-section visualization using the known systems requires from ten to twenty seconds, the entire examination may take up to half an hour or so. Such a long examination time is undesirable for a number of reasons.
Firstly, there can be considerable movement during the examina-tion period, particularly of the fetus in a pregnant uterus, blurring individual echograms and causing difficulty in inter-preting a full set of cross-sectional visualizations over a region of interest. Furthermore, a prolonged examination is often not possible or is at least most undesirable when the technique is used in the examination of sick patients. Of course, a lengthy examination time precludes the use of the technique as a screening test, and the reduced throughput of 10~37Z~Z
patients has an obviously deleterious effect on the economics of the technique.
It is therefore an object of the present invention to provide a methodof ultrasonicexamination ofan objectby thepulse-echo technique whichis capable of performinga complete ultrasonic examination in a time considerably less than that possible at present. As will be appreciated from the above, any reduction of the time necessary for the examination will have the further benefit that the quality of the echograms which are obtained will be improved since the effects of patient movement will be reduced.
According to the present inventionthere is provided a method of ultrasonic examination of an object which comprises directing pulses of ultrasonic energy from a plurality of trans-ducers along a plurality of beam axes through a liquid coupling bath and into the object, each beam axis being associated with one of the plurality of transducers, and receiving echoes of the pulses reflected along the beam axes by acoustic impedance dis-continuities in the object, the directing step including direct-ing the beams into the object from the plurality of transducers at spaced positions relative to each other and to the object;
steering the beam axes to a plurality of angular directions in a single plane; and directing the pulses sequentially along each of the beam axes in each of the angular positions at a rate suffi-ciently fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance between successive activations of each respective transducer; the sequential activation along the transducer beam axes comprising sequential activation along a non-adjacent beam axis substanti-ally simultaneously with the receiptof echoesof aprevious pulse.
The invention further provides apparatus for the ultra-sonic examination of an object comprising a liquid coupling bath;
~' .
a plurality of transducer for directing pulses of ultrasonic energy along a beam axis through the liquid coupling bath and in-to the object and receiving echoes of the pulses reflected along the beam axis by acoustic impedance discontinuities in the object, the transducers being spatially positioned relative to each other and to the said object; means for steering the beam axis of each of the transducers to a plurality of angular directions in a single plane; and means for sequentially activating each of the transducers to direct a pulse of ultrasonic energy along a beam axis into the object and to receive echoes reflected along the beam axis in each of the angular directions at a rate sufficient-ly fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance bet-ween successive activations of each respective transducer, the means for sequentially activating each of the transducers compris-ing means for activating non-adjacent transducers to direct a pulse of ultrasonic energy along a beam axis into the object sub-stantially simultaneously with the receipt of echoes resulting from activation of the previously activated transducer.
20 . The plurality of transducers may be mounted in a single arm, the arm being mounted within a housing by a support-ing mechanism, forming the steering means, for movement thereof with respect to the object to be examined to facilitate examina-tion thereof in any desired plane. Preferably, this supporting mechanism provides movement in the "x", "y" and "z" directions ,.
with respect to the object and also provides for rotation and tilting of the arm with re~pect to the object, thereby allowing : 30 10~7Z9~
focusing of the transducers of the arm on the desired region of the object and scanning in any desired plane. Preferably also, the arm supporting the transducers is curved thereby enabling a degree of mechanical focusing of the transducers at a point within the object to be examined. The curve of the arm may be circular. However, linear arms or other non-linear arms may be used if desired.
The use of a plurality of transducers has been found to enable a speeding up of the time required for each cross-sectional visualization. In a typical operation the transducers are spatially positioned in the aforementioned single plane relative to each other and to the object under examination as by mounting ; in the arm described above and the beam from each transducer is steered to a plurality of angular directions in thls plane, for example by oscillation of the transducers in the plane of the arm.
The transducers may then be energized sequentially, the time of energizing each of the transducers being set so that the whole set of transducers is energized before the appropriate beam from each transducer has moved a significant distance. In this way an entire scanned cross-section may be formed in one cycle of the transducers.
Oscillatory motion of the beam axes from the plurality of transducers in order to build up a complete cross-sectional visualization may be provided by two alternative means. The first means of obtaining oscillatory motion of the beam axes is by mechanically scanning all of the plurality of transducers either independently or simultaneously. In this case, although mechanical movement of the transducers does introduce a limita-~ tion on the scanning rate, the effect of this limitation may be ;~ ~ 30 minimized by providing suitable switching means which require ~ .
the transducers to scan only once while obtaining a complete cross-sectional visualization. Thus, each transducer is activa-ted in turn to direct a pulse of ultrasonic energy along the beam axis, the rate at which the transducers are activated being sufficiently fast, compared with the rate of mechanical oscilla-tion of the transducers, that each transducer oscillates only a small distance between successive activations thereof. The final result achieved by this method of operation is that at the end of a single mechanical scan, each of the transducers has been activated whilst its beam was directed in all required directions.
It will be apparent that monitoring of the direction of the beam axes will be necessary in order to build up the complete visualization.
The alternative means of obtaining oscillatory motion of the beam axes is by use of transducer arrays at each trans-ducer position, the arrays being appropriately designed as to be capable of being steered electronically. In such a system there are no moving parts and the scanning rate obtainable with this system is limited only by considerations of electronic switching speeds and the rate of acquisition of ultrasonic information by the transducer after each transmitted pulse. Since such an array may be electronically steered to direct its beam in all required directions at a rate much faster than that possible when mechanical oscillation of the transducer is required, it is possible to operate this system by steering the beam from each ; transducer array to each of the required directions to measure the reflected echoes before activating the next transducer array and steering the beam from it to each of the required directions, and so on. It will, however, be appreciated that this plurality of transducer arrays capable of being electronically steered may , ~ , also be operated in a manner similar to the operation of the mechanically oscillated transducers previously described.
In a further important embodiment of the present in-vention, however, the individual transducers of an array which is being mechanically scanned may be energized in a "scattered"
operation rather than in a sequence of energizing adjacent trans-ducers. Thus, instead of energizing transducer No. 2 after transducer No. 1, and then transducer No. 3, transducer No. 4 and so on, in accordance with this invention transducer No. 5 in 10 the array may be energized after transducer No. 1, then trans- 7 ducer No. 2 followed by transducer No. 6 and so on. It has been found that such "scattered" operation of a plurality of trans-ducers enables even further speeding up of the visualization since it enables one transducer to be energized without having ~ to wait for multiple reflections arising from energization of ; the previous transducer to die down, this being possible since the transducer is to transmit its pulse and receive reflections along a beam which is spaced substantially from the beam of the previous transducer. Since the "wait period" which can be 20 avoided by such "scattered" operation may be of the order of 500 ~ sec, a significant speeding up of the examination is thereby achieved.
In yet another mode of operation of apparatus emobody-ing the present invention the individual transducers of an array may be energized in such a manner that the time of display of echoes approximates the total available time. In the "scattered"
operation described above in which the circuit conventionally includes a single deflection generator circuit for the display means, the time of display of echoes is approximately half of 30 the total available time, the other half of thé available time . . .
:,: _ g _ ., , being taken up by time for transmission of the pulses through the coupling mediurn In the present alternative mode of operation, however, it has been found that the use of two deflection genera-tor circuits enables one pulse to be transmitted through the coupling medium during the period of display of echoes from the preceding pulse so that the display of echoes from the one pulse may commence almost immediately after conclusion of the display of echoes from the preceding pulse.
Where the plurality of transducers are mounted in a single arm for oscillation in the plane of the arm, it is pre-ferred that the transducers be mechanically linked for simul-taneous oscillation. Thus a single motor may be utilized for oscillation of all of the transducers, and, if desired, a single monitoring device may be utilized to monitor the oscillation of all transducers since their respective beams will be fixed rela-tive to one another. The single arm may be mounted on a support-ing mechanism which provides for both rotation and tilting of the arm with respect to the object under examination. Rotation of the arm of course enables different cross-sectional visualiza-; 20 tions to be obtained without repositioning of the object while tilting of the arm enables the transducers to be directed to a single point from different angles, thereby enabling inclined sections to be obtained. Appropriate drive means may be provided to perform this rotation and tilting, and monitoring means pro~ -vided to measure the position of the transducers. Similarly, drive means and monitoring means are provided to move the arm in the "x", "y" and "z" directions and to monitor this movement.
Embodiments of the present invention are illustrated ; in the accompanying drawings in which:
r 30 Figures 1 to 3 illustrate schematically apparatus em-.
bodying the present invention;
Figure 4 illustrates in more detail the mechanism for oscillation of the transducers of the apparatus of Figures 1 to 3;
Figure 5 shows a basic block diagram of one form of ;~
the electronics for ultrasonic examination apparatus in accor-dance with the present invention;
Figure 6 shows a transmitter and receiver switching block diagram for the circuit of Figure 5;
Figure 7 shows a block diagram of an angle and origin switching network for the circuit of Figure 5;
Figure 8 graphically depicts a "scattered" mode of operation of the apparatus utilizing the circuit of Figure 5;
Figure 9 shows a modification of the circuit of Figure 5; and Figure 10 graphically depicts an alternative mode of operation of the apparatus utilizing the modified circuit of Figure 9.
As shown in Figures 1 to 3 of the drawings, the appara-tus comprises a housing 19 in the form of a couch upon which apatient 17 can be positioned. The patient 17 is positioned with the region to be examined placed in contact with a flexible , coupling membrane 18 which seals an aperture in the top of the housing. Housing 19 is filled with a coupling medium such as , ,:
~, water and is provided with a header tank as at 24 to maintain , proper contact between the patient and the membrane.
! ~. Located within the housing 19 and immersed in the ' `- coupling medium is a plurality of transducers 2 spatially mounted in a main supporting arm 1 so as to be capable of oscillating in the plane of the arm, thereby directing the respective pulses of .~,'; ~
, :
ultrasonic energy along beams which are steerable in said plane.
Eight transducers are shown in the Figures by way of example, however it will be appreciated that this number may be increased or decreased as desired. As shown in greater detail in Figure 4, each transducer 2 is arranged to oscillate about pivot centre 3 by action of oscillator arm 4. The respective oscillator arms 4 of each of the transducers 2 are coupled by links 5 which are provided with adjusters 6 to enable accurate positioning of the transducers 2 with respect to each other and the arm 1. One of the oscillator arms 4 is provided with a sector gear 7 which meshes with a geared output 8 of motor 9, attached to arm 1. It will be apparent that rotation of the shaft 8 of the motor 9 will result in simultaneous pivoting of each of the transducers 2 about its pivot centre 3. The position or angle of each trans-ducer is monitored by means of monitoring potentiometers 10.
Referrlng again to Figure 1, main arm 1 is mounted on a main frame which is slidable towards and away from the patient 17 to enable positioning of the transducers mounted on arm 1 relative to the patient. The main frame is slidable on pillars 11 and movement along these pillars is controlled by motor 12, for example, by means of a rack and pinion drive. The main frame is also mounted on a carriage 25 which slides along a track 15 controlled by motor 22 (Figure 3), again by means of a rack and ; pinion drive or the like. As depicted, the apparatus enables movement of carriage 25 along track 15 transverse to the patient 17 in the position depicted. Longitudinal movement of the arm 1 with respect to the patient is effected by movement along track 16 provided by motor 23 (Figure 3) again, for example, by means of a rack and pinion drive.
As best seen in Figure 2, arm 1 is mounted on a frame , f: ~
~0~7Z9Z
20 which is supported by bearings or the like on carriage 25 for tilting motion with respect to the patient. Thus frame 20 is provided with an arcuate track section which engages the shaft of motor 13, for example in a rack and pinion type drive, for tilting of the arm. Frame 20 is in turn mounted on turntable 21 which provides rotary motion of the arm 1 relative to the ~ -carriage 25, this rotary motion being controlled by motor 14.
It will thus be apparent that by provision of appropriate mechanisms supporting arm l, this arm can be positioned trans-versely, longitudinally, or toward or away from the patient.
;Further, the arm may be tilted or rotated relative to the patient to enable any desired plane of scan of the transducers
2. By way of example, the arm may be rotated in increments of 1 through 180 to give transverse, longitudinal or oblique echograms, and it may be tilted in increments of 1 through an angle of + 30 to give inclined section. The tilting movement of the arm is designed to pivot about the patients skin line minimizing the translational movement of the scanning plane normally obtained with tilting. The arm may also be translated in the "x", "y" and "z" directions in increments ranging from l mm to 2 cm to give automatic acquisition of a number of parallel echograms separated by the selected distance. With the water coupling method all of these sections are obtained without changing the coupling to the patient thus allowing ;reliable cross correlation of detail in echograms obtained in different planes.
- Preferably, all movement of the transducer means is powered by stepper motors. These have the advantage that their operation is controlled by the application of electrical pulses.
For oscillatory motion of the transducers the rate of applica-10~7Z92 tion is gradually built up, then kept constant during the echo-gram forming period and then gradually slowed down giving a reproduceable even motion necessary for the attainment of a consistent grey scale and reducing the vibrations set up during acceleration or deceleration of the transducers. Stepper motors are also amenable to control by computers and all of the motions of the scanner may be placed under computer control.
The rapid rate of acquisition of high quality echo-grams has obvious advantages. It reduces blurring of detail caused by movement of structures during the echogram forming period and allows quasi real time viewing of the same section.
Alternatively it allows the taking of many views from different angles making the examination somewhat similar to fluoroscopy.
The total time necessary for the total examination is also significantly reduced allowing the same instrument to handle a much greater clinical load. The instrument also has the advan-tage that it utilizes the minimum number of pulses to acquire a compound scan echogram and no tissue need be irradiated more than for example eight times. To minimize the irradiation dosage the at~enuator settings of the echoscope control the level of the transmitted energy and not the gain of the receiver. The echo-scope of this invention may also have the provision to switch off any set of transducers and also allow a simple scan to be ~, obtained from any transducer.
~' The many degrees of movement of the apparatus of this ~, invention makes it very versatile and it can be used in a variety of other modes of operation. For instance by combining a trans-lational movement in the length direction of the arm, a compound scan echogram is obtained where the origin of oscillation of the 30 transducers is moved. This mode of operation is useful in cir-~' .
y - 14 -:'. ' .
~08729Z
cumstances where it is desirable to view around some overlying shadowing structures such as ribs. This translation movement also reduces the Moires interference pattern obtained in the stationary mode of operation. The translation movement in this case need not be large, a movement corresponding to the inter transducer distance being adequate and this movement may be achieved in the same time as that taken for the single oscilla-tory movement.
In another mode of operation all of the transducers 10 may be made to function as a single transducer corresponding to the size of the arm and focusing of the type used in annular phased array transducers may be used to generate a highly focused line of sight along the axis of the arm. A linear scan may then be formed by translating the arm in the length direction.
The multiple transducer configuration of the echo-scope may be used to examine tissues in the single transmit-multi receiver mode of operation analogous to the multi-channel receiver operation used in seismology. Cross-correlation of information received by the multiple transducer may then be used 20 to reduce multiple reflection artifacts in tissue and to measure local values of velocity in the various visualized tissues.
The echo scattering cross-section of tissue may also be obtained by two methods with the echoscope. In the first method, the tilting motion of the echoscope is used, the echo : scattering cross-section being obtained from tissue at a depth , .
corresponding to the projection from the transducer to the axis of rotation of the tilting motion. For a transducer facing ver-tically up this depth is equal to the radius of curvature of the tilting motion. Alternatively by pointing the transducers to cross at the centre the echo scattering cross-section of tissue " .
, ~ . .
lying at the radius of curvature of the arm being obtained by rotating the arm. The first method gives the echo scattering cross as function of angle in a fixed plane whilst the second - method gives the value of this parameter when viewed at constant angle in variable plane. In both methods the multiple trans-ducer nature of the echoscope also allows a relatively coarse two dimensional dependence of the parameter.
One mode of operation of apparatus in accordance with the invention is depicted in Figures 5 to 7.
As shown in Figure 5, the master clock 65 provides basic time impulses to initiate multi-channel clock 64 and to drive motors 52, 54 via the motor controller 57, 58, 59.
~ The multi-channel clock 64 outputs, in turn, trigger - pulses to each channel upon receiving a pulse from the master clock 65.
The channel selector 60 counts trigger pulses and sends a binary channel address code to transmitter and receiver switch-ing network 65 and to angle and origin switching network 56.
The signal processor 62 processes echoes from trans-mitter and receiver switching network 55, which echo signals arefed together with blanking pulses to the intensity modulation input of the display unit 66.
Deflection generator 61 generates X and Y deflection voltages from signals received from angle and origin switching ; network 56.
Figure 6 shows the transmitter and receiver switching network in greater detail. As seen in Figure 6, transmit and receive decoder 73 decodes channel selector output signals from channel selector 60 to activate the correct diode switch drive 72 and transmitter drive 71. The multi-channel clock output then :;
,, ~, . . .
triggers the transmitter drive 71 to energize the transmitter 70.
Receiver diode switch 74 is energized by the decoder 73 via diode switch drive 72 which allows echo signals to pass to the preamplifier 76.
In Figure 7, the angle and origin switching network 56 of Figure 5 is more fully disclosed. As seen in Figure 7, angle -~ and origin decoder 82 decodes the channel selector output to activate the correct switch drive 81 and hence turn on the cor-rect potentiometer supply switch 80. The supply switch 80 sup-plies reference voltages to the sine cosine angle monitoring potentiometer 83 and to the origin network 84.
The X and Y origin coordinates from the origin network 84 and the sine and cosine angle output from the potentiometer 83 are fed via their respective OR gates to the deflection genera-tors 61 (see Figure 5) within the processing electronics.
Figure 8 illustrates graphically the "scattered" mode of operation which can be adopted using the circuits of Figures 5 to 7. It will be apparent from Figure 8 that by timing the pulses such that pulse 1 is followed by pulse 5, rather than directly by pulse 2, pulse 5 may be transmitted through the water acting as coupling medium after a brief lapse of time, the settling time, following completion of the display of echoes from pulse 1. As described above, in this "scattered" mode of operation, transmission of pulse 5 through the coupling medium need not be delayed until multiple reflections from pulse 1 die down as the beam of pulse 5 is substantially spaced from the beam of pulse 1. Of course, when pulse 2 is transmitted after the display of echoes from pulse 5 and a brief settling time the multiple reflections from pulse 1 will by then have died down.
Figure 8 illustrates that by use of this mode of operation a j ; - 17 -~6)87Z9;~
display time approximating half the total available time can be achieved.
Figure 9 shows a modification of the circuit of Figure 5 in which deflection generator 61 thereof is replaced by deflection generator 1, deflection generator 2 and a deflection selector. Separate angle and origin switching networks are also provided for each deflection generator. Other integers of Figure 9 which are not shown are as shown in Figure 5.
Figure 10 illustrates an alternative mode of operation of the apparatus of the present invention, utilizing the modified circuit of Figure 9. In this alternative mode of operation, the existence of a second deflection generator enables pulse 5 to be transmitted through the coupling medium at substantially the same time as the display of echoes from pulse 1 is effected using the first deflection generator. Thus, display of echoes from pulse 5 can be effected almost immediately after completion of display of echoes from pulse 1. At substantially the same time, pulse 2 can be transmitted through the coupling medium utilizing the first deflection generator. Figure 10 illustrates that by use of this mode of operation a display time approximating the total available time can be achieved.
From the foregoing description it will therefore be appreciated that the present invention enables more rapid and complete scanning of an object subject to ultrasonic examination.
While the invention has been described with reference to illus-trative embodiments, it will be generally understood by those ;- skilled in the art that various changes may be made and equiva-lents be substituted for elements thereof without departing from the true spirit and scope of the invention.
:
'
- Preferably, all movement of the transducer means is powered by stepper motors. These have the advantage that their operation is controlled by the application of electrical pulses.
For oscillatory motion of the transducers the rate of applica-10~7Z92 tion is gradually built up, then kept constant during the echo-gram forming period and then gradually slowed down giving a reproduceable even motion necessary for the attainment of a consistent grey scale and reducing the vibrations set up during acceleration or deceleration of the transducers. Stepper motors are also amenable to control by computers and all of the motions of the scanner may be placed under computer control.
The rapid rate of acquisition of high quality echo-grams has obvious advantages. It reduces blurring of detail caused by movement of structures during the echogram forming period and allows quasi real time viewing of the same section.
Alternatively it allows the taking of many views from different angles making the examination somewhat similar to fluoroscopy.
The total time necessary for the total examination is also significantly reduced allowing the same instrument to handle a much greater clinical load. The instrument also has the advan-tage that it utilizes the minimum number of pulses to acquire a compound scan echogram and no tissue need be irradiated more than for example eight times. To minimize the irradiation dosage the at~enuator settings of the echoscope control the level of the transmitted energy and not the gain of the receiver. The echo-scope of this invention may also have the provision to switch off any set of transducers and also allow a simple scan to be ~, obtained from any transducer.
~' The many degrees of movement of the apparatus of this ~, invention makes it very versatile and it can be used in a variety of other modes of operation. For instance by combining a trans-lational movement in the length direction of the arm, a compound scan echogram is obtained where the origin of oscillation of the 30 transducers is moved. This mode of operation is useful in cir-~' .
y - 14 -:'. ' .
~08729Z
cumstances where it is desirable to view around some overlying shadowing structures such as ribs. This translation movement also reduces the Moires interference pattern obtained in the stationary mode of operation. The translation movement in this case need not be large, a movement corresponding to the inter transducer distance being adequate and this movement may be achieved in the same time as that taken for the single oscilla-tory movement.
In another mode of operation all of the transducers 10 may be made to function as a single transducer corresponding to the size of the arm and focusing of the type used in annular phased array transducers may be used to generate a highly focused line of sight along the axis of the arm. A linear scan may then be formed by translating the arm in the length direction.
The multiple transducer configuration of the echo-scope may be used to examine tissues in the single transmit-multi receiver mode of operation analogous to the multi-channel receiver operation used in seismology. Cross-correlation of information received by the multiple transducer may then be used 20 to reduce multiple reflection artifacts in tissue and to measure local values of velocity in the various visualized tissues.
The echo scattering cross-section of tissue may also be obtained by two methods with the echoscope. In the first method, the tilting motion of the echoscope is used, the echo : scattering cross-section being obtained from tissue at a depth , .
corresponding to the projection from the transducer to the axis of rotation of the tilting motion. For a transducer facing ver-tically up this depth is equal to the radius of curvature of the tilting motion. Alternatively by pointing the transducers to cross at the centre the echo scattering cross-section of tissue " .
, ~ . .
lying at the radius of curvature of the arm being obtained by rotating the arm. The first method gives the echo scattering cross as function of angle in a fixed plane whilst the second - method gives the value of this parameter when viewed at constant angle in variable plane. In both methods the multiple trans-ducer nature of the echoscope also allows a relatively coarse two dimensional dependence of the parameter.
One mode of operation of apparatus in accordance with the invention is depicted in Figures 5 to 7.
As shown in Figure 5, the master clock 65 provides basic time impulses to initiate multi-channel clock 64 and to drive motors 52, 54 via the motor controller 57, 58, 59.
~ The multi-channel clock 64 outputs, in turn, trigger - pulses to each channel upon receiving a pulse from the master clock 65.
The channel selector 60 counts trigger pulses and sends a binary channel address code to transmitter and receiver switch-ing network 65 and to angle and origin switching network 56.
The signal processor 62 processes echoes from trans-mitter and receiver switching network 55, which echo signals arefed together with blanking pulses to the intensity modulation input of the display unit 66.
Deflection generator 61 generates X and Y deflection voltages from signals received from angle and origin switching ; network 56.
Figure 6 shows the transmitter and receiver switching network in greater detail. As seen in Figure 6, transmit and receive decoder 73 decodes channel selector output signals from channel selector 60 to activate the correct diode switch drive 72 and transmitter drive 71. The multi-channel clock output then :;
,, ~, . . .
triggers the transmitter drive 71 to energize the transmitter 70.
Receiver diode switch 74 is energized by the decoder 73 via diode switch drive 72 which allows echo signals to pass to the preamplifier 76.
In Figure 7, the angle and origin switching network 56 of Figure 5 is more fully disclosed. As seen in Figure 7, angle -~ and origin decoder 82 decodes the channel selector output to activate the correct switch drive 81 and hence turn on the cor-rect potentiometer supply switch 80. The supply switch 80 sup-plies reference voltages to the sine cosine angle monitoring potentiometer 83 and to the origin network 84.
The X and Y origin coordinates from the origin network 84 and the sine and cosine angle output from the potentiometer 83 are fed via their respective OR gates to the deflection genera-tors 61 (see Figure 5) within the processing electronics.
Figure 8 illustrates graphically the "scattered" mode of operation which can be adopted using the circuits of Figures 5 to 7. It will be apparent from Figure 8 that by timing the pulses such that pulse 1 is followed by pulse 5, rather than directly by pulse 2, pulse 5 may be transmitted through the water acting as coupling medium after a brief lapse of time, the settling time, following completion of the display of echoes from pulse 1. As described above, in this "scattered" mode of operation, transmission of pulse 5 through the coupling medium need not be delayed until multiple reflections from pulse 1 die down as the beam of pulse 5 is substantially spaced from the beam of pulse 1. Of course, when pulse 2 is transmitted after the display of echoes from pulse 5 and a brief settling time the multiple reflections from pulse 1 will by then have died down.
Figure 8 illustrates that by use of this mode of operation a j ; - 17 -~6)87Z9;~
display time approximating half the total available time can be achieved.
Figure 9 shows a modification of the circuit of Figure 5 in which deflection generator 61 thereof is replaced by deflection generator 1, deflection generator 2 and a deflection selector. Separate angle and origin switching networks are also provided for each deflection generator. Other integers of Figure 9 which are not shown are as shown in Figure 5.
Figure 10 illustrates an alternative mode of operation of the apparatus of the present invention, utilizing the modified circuit of Figure 9. In this alternative mode of operation, the existence of a second deflection generator enables pulse 5 to be transmitted through the coupling medium at substantially the same time as the display of echoes from pulse 1 is effected using the first deflection generator. Thus, display of echoes from pulse 5 can be effected almost immediately after completion of display of echoes from pulse 1. At substantially the same time, pulse 2 can be transmitted through the coupling medium utilizing the first deflection generator. Figure 10 illustrates that by use of this mode of operation a display time approximating the total available time can be achieved.
From the foregoing description it will therefore be appreciated that the present invention enables more rapid and complete scanning of an object subject to ultrasonic examination.
While the invention has been described with reference to illus-trative embodiments, it will be generally understood by those ;- skilled in the art that various changes may be made and equiva-lents be substituted for elements thereof without departing from the true spirit and scope of the invention.
:
'
Claims (2)
1. A method of ultrasonic examination of an object which comprises directing pulses of ultrasonic energy from a plurality of transducers along a plurality of beam axes through a liquid coupling bath and into said object, each beam axis being associated with one of said plurality of transducers, and receiving echoes of said pulses reflected along said beam axes by acoustic impedance discontinuities in said object, said directing step including :
directing said pulses into the object from said plurality of transducers at spaced positions relative to each other and to said object; steering said beam axes to a plurality of angular directions in a single plane; and directing said pulses sequentially along each of said beam axes in each of said angular positions at a rate sufficiently fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance between successive activations of each respective transducer; said sequential activation along said trans-ducer beam axes comprising sequential activation along a non-adjacent beam axis substantially simultaneously with the receipt of echoes of a previous pulse.
directing said pulses into the object from said plurality of transducers at spaced positions relative to each other and to said object; steering said beam axes to a plurality of angular directions in a single plane; and directing said pulses sequentially along each of said beam axes in each of said angular positions at a rate sufficiently fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance between successive activations of each respective transducer; said sequential activation along said trans-ducer beam axes comprising sequential activation along a non-adjacent beam axis substantially simultaneously with the receipt of echoes of a previous pulse.
2. Apparatus for the ultrasonic examination of an object comprising : a liquid coupling bath; a plurality of transducers for directing pulses of ultrasonic energy along a beam axis through said liquid coupling bath and into said object and receiving echoes of said pulses reflected along said beam axis by acoustic impedance discontinuities in said object, said transducers being spatially positioned relative to each other and to the said object; means for steering the beam axis of each of said transducers to a plurality of angular directions in a single plane; and means for sequentially activating each of said transducers to direct a pulse of ultrasonic energy along a beam axis into the object and to receive echoes reflected along said beam axis in each of said angular directions at a rate sufficiently fast, compared to the rate of movement of the transducer beams, that each transducer beam axis moves only a small distance between successive activations of each respective transducer, said means for sequentially activating each of said transducers comprising means for activating non-adjacent transducers to direct a pulse of ultrasonic energy along a beam axis into the object substantially simultaneously with the receipt of echoes resulting from activation of the previously activated transducer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA330,610A CA1087292A (en) | 1975-05-01 | 1979-06-26 | Method and apparatus for ultrasonic examination |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU144375 | 1975-05-01 | ||
| AUPC1443 | 1975-05-01 | ||
| CA251,297A CA1076244A (en) | 1975-05-01 | 1976-04-28 | Method and apparatus for ultrasonic examination |
| CA330,610A CA1087292A (en) | 1975-05-01 | 1979-06-26 | Method and apparatus for ultrasonic examination |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1087292A true CA1087292A (en) | 1980-10-07 |
Family
ID=27151389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA330,610A Expired CA1087292A (en) | 1975-05-01 | 1979-06-26 | Method and apparatus for ultrasonic examination |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1087292A (en) |
-
1979
- 1979-06-26 CA CA330,610A patent/CA1087292A/en not_active Expired
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