CA1152729A - Curved array of sequenced ultrasound transducers - Google Patents
Curved array of sequenced ultrasound transducersInfo
- Publication number
- CA1152729A CA1152729A CA000366878A CA366878A CA1152729A CA 1152729 A CA1152729 A CA 1152729A CA 000366878 A CA000366878 A CA 000366878A CA 366878 A CA366878 A CA 366878A CA 1152729 A CA1152729 A CA 1152729A
- Authority
- CA
- Canada
- Prior art keywords
- elements
- array
- transducer elements
- group
- ultrasound
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/18—Methods or devices for transmitting, conducting or directing sound
- G10K11/26—Sound-focusing or directing, e.g. scanning
- G10K11/34—Sound-focusing or directing, e.g. scanning using electrical steering of transducer arrays, e.g. beam steering
- G10K11/341—Circuits therefor
- G10K11/345—Circuits therefor using energy switching from one active element to another
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Transducers For Ultrasonic Waves (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
"Curved array of sequenced ultrasound transducers".
An array of ultrasound transducers for pulsed sector-scan operation includes a plurality of transducer elements disposed on an arc of a circle and oriented to emit and receive ultrasound radiation in the direction of the center of the arc. A group of adjacent transducers within the array is active for each ultrasound pulse.
The position of the group in the array is incrementally shifted along the arc, one transducer at a time, to effect scanning. The inherent focussing effect of a curved group of transducers is compensated with time delays or a negative lens to provide a parallel, sector-scanned radiation beam.
The array may be manufactured by cutting grooves in a solid bar of piezoelectric ceramic and bending the grooved bar around a mandrel to separate individual transducer elements from each other.
"Curved array of sequenced ultrasound transducers".
An array of ultrasound transducers for pulsed sector-scan operation includes a plurality of transducer elements disposed on an arc of a circle and oriented to emit and receive ultrasound radiation in the direction of the center of the arc. A group of adjacent transducers within the array is active for each ultrasound pulse.
The position of the group in the array is incrementally shifted along the arc, one transducer at a time, to effect scanning. The inherent focussing effect of a curved group of transducers is compensated with time delays or a negative lens to provide a parallel, sector-scanned radiation beam.
The array may be manufactured by cutting grooves in a solid bar of piezoelectric ceramic and bending the grooved bar around a mandrel to separate individual transducer elements from each other.
Description
- ~15Z729 PHA 20925 1 21-l0-1980 "Curved array of sequenced ultrasound transducers".
The invention relates to an array of ultrasound transducers which is particularly useful for medical imagi~g applications. More specifically, the invention relates to a curved, linear array of ultrasound transducer elements.
~ group of active elements are incrementally shifted along the array to sector-scan a parallel ultrasound beam.
BACKGROUND OF T~E INVENTIO~
Internal body organs may beimaged and otherwise characterized by apparatus which directs pulses of ultra-~ 10 sound energy into the body and subsequently detects echoes ; which originate when the energy is reflected from tissue interfaces or other discontinuities within the body. In typical apparatus the ultrasound energy is directed i~to the body in a relatively narrow beam. Electric signals which describe the position and direction of the beam with respect to the body, as well as the relative arrival time and amplitude of the echos, are utilized to generate a visual display and/or mapping of the~nternal body struc-tures. In many applications the direction of the ultra-sound beam is manually controlled by a technlcian (general-ly by phy~ical motion of a probe head) to build up a display pattern. While these methods are adequate for imaging stationary body structures, the time required for physical motion of a probe is generally much too long to image rapidly moving body structures (for example the valves in a heating heart) in real time. Ultrasound systems for generating real time displays of rapidly moving body organs generally utilize electromechanical or electronic means to change the position and direction of one or more beams of u trasound energy with respect to the body.
; Motion of a beam of ult~asound energy with respect to the body may be provided by sequentially activating .',~ , : - .
g lSZ729 PHA 20925 -2- 21-1 o- 1980 transducer elements in a flat linear array to effectively scan an area of the body with a sequence of substantially parallel ultrasound beams. Adevice of this type is describ-ed in U.S. Patent 3,013,170. A beam of ultrasound energy may, alternately, be scanned around a single origin point to produce a so-called "sector-scan". Sector-scan geome-tries are particularly useful since ultrasound energy may ; be directed betwecn the ribs to scan the interior of the chest cavity. Sector-scanning has been achieved in the lO prior art by rapidly rotating one or more transducers about an axis, by steering energy Prom a fixed transducer with a rotating ultrasound reflector, or by sequencing individual transducer elements in a linear curved array.
British patent 1,546,445 describes a curved transducer 15 array with individual transducers which are individually activated to produce a sector-scan.
The transverse spatial resolution which may be obtained from a sequence array of ultrasound transducers is related to dimensions of the individual transducer 20 elements in the array. Small transducer elements are desirable for obtaining fine resolution. The amount of ultrasound energy produced by an individual transducer element isj however, limited by its size. The signal-to-noise ratio of the returned ultrasound echoes necessarily 25 depends on the amount of ultrasound energy introduced into the body. Thus, the signal to noise ratio suffers if small transducer elements are individually activated to achieve ,1 a scanning action. Diffraction effects will furthermore, ;~l cause spreading of an ultrasound beam which originates 30 from a single, small ultrasound transducer element.
This problem has been solved in the prior art by simultaneously activating a group of adjacent transducers within a flat linear array. Means were provided for incrementally shifting the active group along the array to provide fine spatial resolution and high signal-to-noise - ratios. While this technique is appropriate for use with flat transducer arrays, which produce a parallel beam scanni~g geometry, the simultaneous activation of a group , 115Z7zg of adjacent transducers in a curved array inherently generates a focussed ultrasound beam. Sequenced group arrays have not, therefore, found appli-cation for the generation of high resolution sector-scans.
SUMMARY OF THE INVENTION
A concave linear array of small transducer elements is utilized to generate an ultrasound sector scan. A group of active elements is in-crementally shifted along the array to provide a steerable beam providing high resolution and a high signal to noise ratio. Defocussing means, which compensate for the inherent focussing effects in a curved group of adjacent transducers, are provided. The defocussing means may comprise a negative ultrasound lens disposed between the array and the body. Alter-nately, the defocussing means may delay electrical signals, which are transmitted to and received from each transducer element in the active ~ group, in proportion to the distance between that element and the center of ; the active group.
A curved array of small, high resolution transducer elements may be manufactured by first sawing the back surface of an electroded bar of piezoelectric ceramic to form a series of parallel grooves. A flexible matching window is cast on the front surface of the grooved bar. The bar and wlndow are then bent around a convex mandrel so that the individual elements are fractured one from the other. A foam air cell is then cast ; over the back of the elements to retain them in place.
According to a broad aspect of the invention there is provided apparatus for producing and/or receiving a scanned beam of ultrasound energy comprising: an array, including a plurality of ultrasound trans-ducer elements disposed along a curved line, each element being oriented to direct ultrasound energy toward and to receive ultrasound energy from the center of the curve; and means for transmitting electrical pulses to and for receiving electrical pulses from the transducer elements; characterized in that the apparatus further comprises- means for connecting a group of active transducer elements to the means for transmitting electrical pulses -~, and for receiving electrical pulses, the group of active elements compris-ing a preselected number of adjacent transducer elements in the array, said preselected number being greater than one and less than the total number of transducer elements in the array; means for sequentially changing the elements in the active group to incrementally shift the active group along the curve; and means for defocussing ultrasound energy produced and re-ceived by the transducer elements in the active group which means function to cause said ultrasound energy to be directed in a substantially parallel beam.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be understood with reference to the attached drawings in which:
Figures 1 and 2 show a prior art sequenced flat array of ultra-sound transducers;
Figure 3 is a curved transducer array of the present invention;
Figure 4 illustrates the principle of time delay defocussing .
for the array of Fig. 3;
Figure 5 schematically illustrates a system for operating the ;
array of Figure 3;
Figure 6 is an alternate embodiment of the invention which ~ includes a defocussing lens;
; Figure 7 illustrates a stage in the production of the array of Figure 3;
Figure 8 illustrates a completed array; and Figure 9 is a detail of Figure 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
;~ Figure 1 is a linear array of ultrasound transducers 110 which . is known in the prior art. A series of individual transducers elements :'~
-i 100 are disposed along a line 101. Separate electrodes 102 are provided ~' 30 for each transducer in the array and are connected to electronic circuits (not shown) which permit sequential activation of the elements to, in ~4~
~ ' . ... .. . . .
~52~7Z9 effect. move the source of an ultrasound beam along the line 101.
Figure 2 illustrates an application of the array 110 of Figure 1. A group of adjacent transducers 111 are simultaneously activated to produce a beam of ultrasound energy 112 which is inwardly projected into a body 113. The array 110 is disposed on the surface of a probe assembly 114 which includes switching circuits 115. The switching circuits act to incrementally shift the group of active transducers 111 along the array to generate a linear scan of the beam 112 with respect to the body. The operation of prior art imaging systems with incrementally shifted arrays is described in the articles Ultrasonic Imaging Using Arrays, Albert Nacovski and Methods and TerminologY for Diagnostic Ultrasound Imaging Systems, Ma~well G. Maginness in the Proceedings of the IEEE, Vol. 67, No. 4, April 1979 at page 484 and 641 respectively. As indicated in those articles, the incremental shifting of a group of transducers within the array improves spatial resolution and provides a higher signal to nolse ratio than could be achieved by the sequential activation of individual transducer elements.
Brleish patent Speciflcation 1,546,445 describee a , . ~
., , s -"
-~ ~ -4a-~,. , ,~ ~
. . ,,, - ~:
` ~152729 curved linear arra~ of transducers which are individually activated to generate a sector-scanned ultrasound beam. A
positive (converging) lens is utilized with the transducer array to focus the beam through the spaces; between the ribs.
Because only one transducer element is active at a time, the array of British patent 1,546,445 suffers from relative-ly low spatial resolution and signal-to-noise ratio. The performance of the array cannot, howe~er, be improved by directly applying the incrementally shifted active group 10 geometry of Figure 2 to the curved array configuration.
~ The simultaneous activation of a group of adjacent elements;~ on a curved array necessarily produces a sharply focussed beam which diverges in the far field and is unsuitable for ~, medical imaging.
Figure 3 schematically illustrates a transducer array of the present invention. A plurality of electro-! acoustic transducer elements 200 are disposed along an arc and are oriented to project and receive ultrasound energy in the direction of the center of the arc. The individual 20 eléments 200 in the array are provided with separate electrodes and are connected, via wires 202, and a ~, . .
sequencing circuit to pulse generator and receiver cir-cuits ~not shown). The array is contained in a housing 204 ;; which includes an ultrasound transmissive window 206. The 25 housing may be filled with an ultrasound transmissive i fluid 208~ for example, castor oil, which is matched to thei''ï ultrasound transmissive properties of the human body.
Alternately the housing may be filled with a solid material.
In general the filling should have an acoustic attenuation 30 between those of water and human tissue and should have an acoustic impedance which is matched to the impedance of human tissue.
A group of adjacent transducer elements (for example 220) within the array is activated for the trans-; 35 mission and reception of each ultrasound pulse. The active ,~ group of transducers is incremen-tally shifted along the ~-~ array, one transducer at a time, on a pulse to pulse basis to provide a sector scan of ultrasound energy. Defocussing , ' ... . ~ .
` ~` llSZ7;~9 means are included to compensate for the strong inherent focussing of the curved array. The curved array, with an incrementall-y shifted group of active detectors, in combi-nation with the defocussing means, produces a finer spatial 5 resolution and higher signal to noise ratio than curved sequenced arrays of the prior art.
Figure 4 illustrates a preferred embodiment of the defocussing means. At a given instant, a group 220 of adjacent transducers A-K wi~thin the array is activated by 10 sequencing switches (not shown for the sake for clarity).
The central transducer F within the zone is connected ~ directly to ultrasound pulse generator 240 and receiver s 250 circuits via a transmit-receive (TR) switch 260. The ; transducer pair E and ~ immediately adjacent the central 15 transducer is connected to the TR switch 260 via a first deIay 270. The next adjacent pair of transducers D and H are connected to the TR switch through a second delay circuit 280 which provides a longer delay than the delay , circuit 270. Each next adjacent pair of transducers within i ~ 20 the group (i.e. C and I, B and J, A and K) are connected to the 'rR switch via delay circuits (290, 30~, 310) which provide increasing delays in proportion to the distance from the center of the active group to the associated transducers. The magnitude of the delays are chosen, using techniques which are well known in the art and which are described, for example, in the above referenced Macovski article, to compensate for the physical focussing effects .! ~ .
of the curved array and thus provide a more parallel beam o~ ultrasound energy. Alternately the beam ma-y thus be focussed at a point deep within the body of a patient.
Figure 5 illustrates a system for incrementally shifting the active group along the transducer array.
; Puls~ers 400~ receiver amplifiers 410, and associated TR
isolators 420 are connected in a conventional fashion to first ends of a bank of bidirectional delay lines 430. The ~ ~ , bank of delay lines 430 includes delay lines of varying time delay which are calculated to provide the defocussing compensation for the active group as described ~bove Wit~
, , . , ~ - . .
- -` ilS27Z9 PHA 20925 -7- 21-10-lg80 respect to the Figure 4. The opposite end of each delay line in the bank 430 is connected to a row of switches in an analog switch matrix 440.Each column of switches in the switch matrix 440 is connected to a separate element 200 in the transducer array 450. A separate switch (1~hich may be a MOS transistor) is provided at each cross point (that is the intersection of each row with each column) in the switch matrix, The switching elements are individually activated by the output lines of a read-only memory (ROM) 10 460. Input lines of the read-only memory 460 are addressed by the output of a sequencer circuit which may be a sequential counter 470 driven by a clock 480. The sequencer , circuit addresses consecutive words in the~read-only! memory which establish the connection patterns between the `~ 15 individual transducer elements in the array and corres-~i ponding delay lines to effect incremental shifting of a '"t ~ defocussed~ active group along the array. As an example, , Table I illustrates the first three words of a read-only j memory which shifts an active group of nine transducer Y~ 20 elements along an array by establishing connections ~to ' I , , ~
four delay lines I through IV.
TABLE I
Delay Line 1 2 3 4 5 6 7 8 91011 12 13 ~ ~ IV 1 0 0 0 0 0 1 0 0 0 0 0 0 1, 30 I O O 0 0 1 0 0 0 0 0 O O O
';~''lt ~ ~ II O O 0 1 0 1 0 0 0 0 0 0 0 WORD 2 ~,l III O 0 1 0 0 0 1 0 0 0 0 0 0 ~, ~ III O 0 0 1 0 0 0 1 0 0 O O O
. ~::, :
PHA 20925 -8- 2l-10-1980 The bit patterns of Table I are shortened for the sake of clarity of illustration; the principles illustrated therein may be extended to active groups and arrays which include larger or smaller numbers of transducer elements.
Figure 6 is an alternate embodiment of a trans-ducer array wherein the defocussing means comprise a negative lens 500. A group of transducers is sequentially shifted across the array as in the embodiment o~ Figure 3 to produce a sector scan. All of the transducers in the group 200 may be simultaneously pulsed. Alternately, the delay line defocussing means of Figure 4 may be utilized in ¢onjunction with the lens 500. The lens may be con-structed from metal or plastic and may advantageously comprise two negative lens elements separated by a fluid-~illed cavity 510.
Figure 7 illustrates first steps in a preferredmethod for manufacturing the transducer arra~. The array is advantageously ~ormed from a single rectangular bar 600 of piezoelectric ceramic (which may cornprise Type PZT-5).
20 Copper electrodes 605 and 610 are bonded to the front 601 and rear 602 major surfaces of the bar with a silver bearing epoxy resin. A flexible matching window 615 is then cast directly on the front electrode. The matching window may be advantageously cast from a mixture of two parts of a Stycast 1264 resin binder and one part tungsten powder.
The window is cast by pouring the mixture directly onto the surface of the front electrode and allowing the tungsten powder to settle. After the resin is cured, the window~is machined to a thickness of one quarter acoustic wavelength at the operating frequency of the array. For example, a window designed for operation at 3.5 MHz is machined to approximately 0.09 mm thickness.
A series of parallel grooves 620 are then cut through the rear electrode 610 and into the upper surface of the bar to segregate individual transducer elements 630 with their associated rear electrodes. Typically the grooves are approximateIy 0.13 mm wide and penetrate to 75% of the thickness of the ceramic bar.
'- PHA 20925 -9- 21-10-1980 In a preferred embodiment of the array the ' ceramic bar is approximately 80.5 millimeters;long, 12.5 millimeters wide, and 2.0 millimeters thick. The bar is divided by 71 saw cuts to form 72 transducer elements. The rear electrodes on the endmost~transduoer elements are grounded to the front electrode so that the array comprises 70 func~tional transdueer elements.
s'~ ~ Figures 8 and -9 iIlustrate the further construction of the array.~The grooved ceramic bar 600 with attached elec-trodes 605 and 610 and window 615 i~s formed around a , semicylindrical mandrel~ 650,~the~groovés in~the bar being ,, parallel~to the axis~ of the cylinder. ~s illustrated in - detail Figure g the bar cracks under each'groove 620 to produce a curved array of separate,,electroded transducer elements 630 which are retained in place by the front électrode 605 and~window 615, ,',',',~ A supporting foam air cell 660 is then cast ,,i;~, ~' between the elements 630 and around the rear surface of the ,, ~ curved transducer array.~ The alr~celI retains the trans-, ~ ; 20 ~ducer e~lement~s in place and further provides-a low ,~ ,acoustic impedance baoking for the individual elements. The ai~r~cell~may typioally~comprise glass micro-balloons in an 'epoxy resin binder.~
In a preferred embodiment of the invention the 5~ upper elecbrodes~610 are wider than the ceramic bar and are fo'lded back along,the~edges of the air cell to provide rleot~10al oonnection~ ~o t~e _ndividual elements.
The invention relates to an array of ultrasound transducers which is particularly useful for medical imagi~g applications. More specifically, the invention relates to a curved, linear array of ultrasound transducer elements.
~ group of active elements are incrementally shifted along the array to sector-scan a parallel ultrasound beam.
BACKGROUND OF T~E INVENTIO~
Internal body organs may beimaged and otherwise characterized by apparatus which directs pulses of ultra-~ 10 sound energy into the body and subsequently detects echoes ; which originate when the energy is reflected from tissue interfaces or other discontinuities within the body. In typical apparatus the ultrasound energy is directed i~to the body in a relatively narrow beam. Electric signals which describe the position and direction of the beam with respect to the body, as well as the relative arrival time and amplitude of the echos, are utilized to generate a visual display and/or mapping of the~nternal body struc-tures. In many applications the direction of the ultra-sound beam is manually controlled by a technlcian (general-ly by phy~ical motion of a probe head) to build up a display pattern. While these methods are adequate for imaging stationary body structures, the time required for physical motion of a probe is generally much too long to image rapidly moving body structures (for example the valves in a heating heart) in real time. Ultrasound systems for generating real time displays of rapidly moving body organs generally utilize electromechanical or electronic means to change the position and direction of one or more beams of u trasound energy with respect to the body.
; Motion of a beam of ult~asound energy with respect to the body may be provided by sequentially activating .',~ , : - .
g lSZ729 PHA 20925 -2- 21-1 o- 1980 transducer elements in a flat linear array to effectively scan an area of the body with a sequence of substantially parallel ultrasound beams. Adevice of this type is describ-ed in U.S. Patent 3,013,170. A beam of ultrasound energy may, alternately, be scanned around a single origin point to produce a so-called "sector-scan". Sector-scan geome-tries are particularly useful since ultrasound energy may ; be directed betwecn the ribs to scan the interior of the chest cavity. Sector-scanning has been achieved in the lO prior art by rapidly rotating one or more transducers about an axis, by steering energy Prom a fixed transducer with a rotating ultrasound reflector, or by sequencing individual transducer elements in a linear curved array.
British patent 1,546,445 describes a curved transducer 15 array with individual transducers which are individually activated to produce a sector-scan.
The transverse spatial resolution which may be obtained from a sequence array of ultrasound transducers is related to dimensions of the individual transducer 20 elements in the array. Small transducer elements are desirable for obtaining fine resolution. The amount of ultrasound energy produced by an individual transducer element isj however, limited by its size. The signal-to-noise ratio of the returned ultrasound echoes necessarily 25 depends on the amount of ultrasound energy introduced into the body. Thus, the signal to noise ratio suffers if small transducer elements are individually activated to achieve ,1 a scanning action. Diffraction effects will furthermore, ;~l cause spreading of an ultrasound beam which originates 30 from a single, small ultrasound transducer element.
This problem has been solved in the prior art by simultaneously activating a group of adjacent transducers within a flat linear array. Means were provided for incrementally shifting the active group along the array to provide fine spatial resolution and high signal-to-noise - ratios. While this technique is appropriate for use with flat transducer arrays, which produce a parallel beam scanni~g geometry, the simultaneous activation of a group , 115Z7zg of adjacent transducers in a curved array inherently generates a focussed ultrasound beam. Sequenced group arrays have not, therefore, found appli-cation for the generation of high resolution sector-scans.
SUMMARY OF THE INVENTION
A concave linear array of small transducer elements is utilized to generate an ultrasound sector scan. A group of active elements is in-crementally shifted along the array to provide a steerable beam providing high resolution and a high signal to noise ratio. Defocussing means, which compensate for the inherent focussing effects in a curved group of adjacent transducers, are provided. The defocussing means may comprise a negative ultrasound lens disposed between the array and the body. Alter-nately, the defocussing means may delay electrical signals, which are transmitted to and received from each transducer element in the active ~ group, in proportion to the distance between that element and the center of ; the active group.
A curved array of small, high resolution transducer elements may be manufactured by first sawing the back surface of an electroded bar of piezoelectric ceramic to form a series of parallel grooves. A flexible matching window is cast on the front surface of the grooved bar. The bar and wlndow are then bent around a convex mandrel so that the individual elements are fractured one from the other. A foam air cell is then cast ; over the back of the elements to retain them in place.
According to a broad aspect of the invention there is provided apparatus for producing and/or receiving a scanned beam of ultrasound energy comprising: an array, including a plurality of ultrasound trans-ducer elements disposed along a curved line, each element being oriented to direct ultrasound energy toward and to receive ultrasound energy from the center of the curve; and means for transmitting electrical pulses to and for receiving electrical pulses from the transducer elements; characterized in that the apparatus further comprises- means for connecting a group of active transducer elements to the means for transmitting electrical pulses -~, and for receiving electrical pulses, the group of active elements compris-ing a preselected number of adjacent transducer elements in the array, said preselected number being greater than one and less than the total number of transducer elements in the array; means for sequentially changing the elements in the active group to incrementally shift the active group along the curve; and means for defocussing ultrasound energy produced and re-ceived by the transducer elements in the active group which means function to cause said ultrasound energy to be directed in a substantially parallel beam.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be understood with reference to the attached drawings in which:
Figures 1 and 2 show a prior art sequenced flat array of ultra-sound transducers;
Figure 3 is a curved transducer array of the present invention;
Figure 4 illustrates the principle of time delay defocussing .
for the array of Fig. 3;
Figure 5 schematically illustrates a system for operating the ;
array of Figure 3;
Figure 6 is an alternate embodiment of the invention which ~ includes a defocussing lens;
; Figure 7 illustrates a stage in the production of the array of Figure 3;
Figure 8 illustrates a completed array; and Figure 9 is a detail of Figure 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
;~ Figure 1 is a linear array of ultrasound transducers 110 which . is known in the prior art. A series of individual transducers elements :'~
-i 100 are disposed along a line 101. Separate electrodes 102 are provided ~' 30 for each transducer in the array and are connected to electronic circuits (not shown) which permit sequential activation of the elements to, in ~4~
~ ' . ... .. . . .
~52~7Z9 effect. move the source of an ultrasound beam along the line 101.
Figure 2 illustrates an application of the array 110 of Figure 1. A group of adjacent transducers 111 are simultaneously activated to produce a beam of ultrasound energy 112 which is inwardly projected into a body 113. The array 110 is disposed on the surface of a probe assembly 114 which includes switching circuits 115. The switching circuits act to incrementally shift the group of active transducers 111 along the array to generate a linear scan of the beam 112 with respect to the body. The operation of prior art imaging systems with incrementally shifted arrays is described in the articles Ultrasonic Imaging Using Arrays, Albert Nacovski and Methods and TerminologY for Diagnostic Ultrasound Imaging Systems, Ma~well G. Maginness in the Proceedings of the IEEE, Vol. 67, No. 4, April 1979 at page 484 and 641 respectively. As indicated in those articles, the incremental shifting of a group of transducers within the array improves spatial resolution and provides a higher signal to nolse ratio than could be achieved by the sequential activation of individual transducer elements.
Brleish patent Speciflcation 1,546,445 describee a , . ~
., , s -"
-~ ~ -4a-~,. , ,~ ~
. . ,,, - ~:
` ~152729 curved linear arra~ of transducers which are individually activated to generate a sector-scanned ultrasound beam. A
positive (converging) lens is utilized with the transducer array to focus the beam through the spaces; between the ribs.
Because only one transducer element is active at a time, the array of British patent 1,546,445 suffers from relative-ly low spatial resolution and signal-to-noise ratio. The performance of the array cannot, howe~er, be improved by directly applying the incrementally shifted active group 10 geometry of Figure 2 to the curved array configuration.
~ The simultaneous activation of a group of adjacent elements;~ on a curved array necessarily produces a sharply focussed beam which diverges in the far field and is unsuitable for ~, medical imaging.
Figure 3 schematically illustrates a transducer array of the present invention. A plurality of electro-! acoustic transducer elements 200 are disposed along an arc and are oriented to project and receive ultrasound energy in the direction of the center of the arc. The individual 20 eléments 200 in the array are provided with separate electrodes and are connected, via wires 202, and a ~, . .
sequencing circuit to pulse generator and receiver cir-cuits ~not shown). The array is contained in a housing 204 ;; which includes an ultrasound transmissive window 206. The 25 housing may be filled with an ultrasound transmissive i fluid 208~ for example, castor oil, which is matched to thei''ï ultrasound transmissive properties of the human body.
Alternately the housing may be filled with a solid material.
In general the filling should have an acoustic attenuation 30 between those of water and human tissue and should have an acoustic impedance which is matched to the impedance of human tissue.
A group of adjacent transducer elements (for example 220) within the array is activated for the trans-; 35 mission and reception of each ultrasound pulse. The active ,~ group of transducers is incremen-tally shifted along the ~-~ array, one transducer at a time, on a pulse to pulse basis to provide a sector scan of ultrasound energy. Defocussing , ' ... . ~ .
` ~` llSZ7;~9 means are included to compensate for the strong inherent focussing of the curved array. The curved array, with an incrementall-y shifted group of active detectors, in combi-nation with the defocussing means, produces a finer spatial 5 resolution and higher signal to noise ratio than curved sequenced arrays of the prior art.
Figure 4 illustrates a preferred embodiment of the defocussing means. At a given instant, a group 220 of adjacent transducers A-K wi~thin the array is activated by 10 sequencing switches (not shown for the sake for clarity).
The central transducer F within the zone is connected ~ directly to ultrasound pulse generator 240 and receiver s 250 circuits via a transmit-receive (TR) switch 260. The ; transducer pair E and ~ immediately adjacent the central 15 transducer is connected to the TR switch 260 via a first deIay 270. The next adjacent pair of transducers D and H are connected to the TR switch through a second delay circuit 280 which provides a longer delay than the delay , circuit 270. Each next adjacent pair of transducers within i ~ 20 the group (i.e. C and I, B and J, A and K) are connected to the 'rR switch via delay circuits (290, 30~, 310) which provide increasing delays in proportion to the distance from the center of the active group to the associated transducers. The magnitude of the delays are chosen, using techniques which are well known in the art and which are described, for example, in the above referenced Macovski article, to compensate for the physical focussing effects .! ~ .
of the curved array and thus provide a more parallel beam o~ ultrasound energy. Alternately the beam ma-y thus be focussed at a point deep within the body of a patient.
Figure 5 illustrates a system for incrementally shifting the active group along the transducer array.
; Puls~ers 400~ receiver amplifiers 410, and associated TR
isolators 420 are connected in a conventional fashion to first ends of a bank of bidirectional delay lines 430. The ~ ~ , bank of delay lines 430 includes delay lines of varying time delay which are calculated to provide the defocussing compensation for the active group as described ~bove Wit~
, , . , ~ - . .
- -` ilS27Z9 PHA 20925 -7- 21-10-lg80 respect to the Figure 4. The opposite end of each delay line in the bank 430 is connected to a row of switches in an analog switch matrix 440.Each column of switches in the switch matrix 440 is connected to a separate element 200 in the transducer array 450. A separate switch (1~hich may be a MOS transistor) is provided at each cross point (that is the intersection of each row with each column) in the switch matrix, The switching elements are individually activated by the output lines of a read-only memory (ROM) 10 460. Input lines of the read-only memory 460 are addressed by the output of a sequencer circuit which may be a sequential counter 470 driven by a clock 480. The sequencer , circuit addresses consecutive words in the~read-only! memory which establish the connection patterns between the `~ 15 individual transducer elements in the array and corres-~i ponding delay lines to effect incremental shifting of a '"t ~ defocussed~ active group along the array. As an example, , Table I illustrates the first three words of a read-only j memory which shifts an active group of nine transducer Y~ 20 elements along an array by establishing connections ~to ' I , , ~
four delay lines I through IV.
TABLE I
Delay Line 1 2 3 4 5 6 7 8 91011 12 13 ~ ~ IV 1 0 0 0 0 0 1 0 0 0 0 0 0 1, 30 I O O 0 0 1 0 0 0 0 0 O O O
';~''lt ~ ~ II O O 0 1 0 1 0 0 0 0 0 0 0 WORD 2 ~,l III O 0 1 0 0 0 1 0 0 0 0 0 0 ~, ~ III O 0 0 1 0 0 0 1 0 0 O O O
. ~::, :
PHA 20925 -8- 2l-10-1980 The bit patterns of Table I are shortened for the sake of clarity of illustration; the principles illustrated therein may be extended to active groups and arrays which include larger or smaller numbers of transducer elements.
Figure 6 is an alternate embodiment of a trans-ducer array wherein the defocussing means comprise a negative lens 500. A group of transducers is sequentially shifted across the array as in the embodiment o~ Figure 3 to produce a sector scan. All of the transducers in the group 200 may be simultaneously pulsed. Alternately, the delay line defocussing means of Figure 4 may be utilized in ¢onjunction with the lens 500. The lens may be con-structed from metal or plastic and may advantageously comprise two negative lens elements separated by a fluid-~illed cavity 510.
Figure 7 illustrates first steps in a preferredmethod for manufacturing the transducer arra~. The array is advantageously ~ormed from a single rectangular bar 600 of piezoelectric ceramic (which may cornprise Type PZT-5).
20 Copper electrodes 605 and 610 are bonded to the front 601 and rear 602 major surfaces of the bar with a silver bearing epoxy resin. A flexible matching window 615 is then cast directly on the front electrode. The matching window may be advantageously cast from a mixture of two parts of a Stycast 1264 resin binder and one part tungsten powder.
The window is cast by pouring the mixture directly onto the surface of the front electrode and allowing the tungsten powder to settle. After the resin is cured, the window~is machined to a thickness of one quarter acoustic wavelength at the operating frequency of the array. For example, a window designed for operation at 3.5 MHz is machined to approximately 0.09 mm thickness.
A series of parallel grooves 620 are then cut through the rear electrode 610 and into the upper surface of the bar to segregate individual transducer elements 630 with their associated rear electrodes. Typically the grooves are approximateIy 0.13 mm wide and penetrate to 75% of the thickness of the ceramic bar.
'- PHA 20925 -9- 21-10-1980 In a preferred embodiment of the array the ' ceramic bar is approximately 80.5 millimeters;long, 12.5 millimeters wide, and 2.0 millimeters thick. The bar is divided by 71 saw cuts to form 72 transducer elements. The rear electrodes on the endmost~transduoer elements are grounded to the front electrode so that the array comprises 70 func~tional transdueer elements.
s'~ ~ Figures 8 and -9 iIlustrate the further construction of the array.~The grooved ceramic bar 600 with attached elec-trodes 605 and 610 and window 615 i~s formed around a , semicylindrical mandrel~ 650,~the~groovés in~the bar being ,, parallel~to the axis~ of the cylinder. ~s illustrated in - detail Figure g the bar cracks under each'groove 620 to produce a curved array of separate,,electroded transducer elements 630 which are retained in place by the front électrode 605 and~window 615, ,',',',~ A supporting foam air cell 660 is then cast ,,i;~, ~' between the elements 630 and around the rear surface of the ,, ~ curved transducer array.~ The alr~celI retains the trans-, ~ ; 20 ~ducer e~lement~s in place and further provides-a low ,~ ,acoustic impedance baoking for the individual elements. The ai~r~cell~may typioally~comprise glass micro-balloons in an 'epoxy resin binder.~
In a preferred embodiment of the invention the 5~ upper elecbrodes~610 are wider than the ceramic bar and are fo'lded back along,the~edges of the air cell to provide rleot~10al oonnection~ ~o t~e _ndividual elements.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for producing and/or receiving a scanned beam of ultrasound energy comprising: an array, including a plurality of ultra-sound transducer elements disposed along a curved line, each element being oriented to direct ultrasound energy toward ant to receive ultra-sound energy from the center of the curve; and means for transmitting electrical pulses to and for receiving electrical pulses from the trans-ducer elements; characterized in that the apparatus further comprises:
means for connecting a group of active transducer elements to the means for transmitting electrical pulses and for receiving electrical pulses, the group of active elements comprising a preselected number of adjacent transducer elements in the array, said preselected number being greater than one and less than the total number of transducer elements in the array; means for sequentially changing the elements in the active group to incrementally shift the active group along the curve; and means for defocussing ultrasound energy produced and received by the transducer elements in the active group which means function to cause said ultrasound energy to be directed in a substantially parallel beam.
means for connecting a group of active transducer elements to the means for transmitting electrical pulses and for receiving electrical pulses, the group of active elements comprising a preselected number of adjacent transducer elements in the array, said preselected number being greater than one and less than the total number of transducer elements in the array; means for sequentially changing the elements in the active group to incrementally shift the active group along the curve; and means for defocussing ultrasound energy produced and received by the transducer elements in the active group which means function to cause said ultrasound energy to be directed in a substantially parallel beam.
2. Apparatus as claimed in claim 1 characterized in that the means for defocussing comprise means for delaying the electrical pulses which are transmitted to and received from elements in the active group, pulses from each element being delayed in proportion to the distance between that element and the center of the active group.
3. Apparatus as claimed in claim 1, characterized in that the means for connecting an active group comprises a matrix of switches, the means for sequentially changing the elements in the active group comprising a read only memory having outputs connected to actuate the switches and a sequencer circuit connected to sequentially address the read only memory.
4. Apparatus as claimed in claim 1 characterized in that the means for defocussing comprise a negative lens disposed in the path of ultra-sound energy projected from the elements of the active group.
5. Apparatus as claimed in claim 1, characterized in that each element includes a front face directed toward the center of the curve and a back face directed away from the center of the curve and further comp-rising front and back conductive electrodes disposed, respectively, on the front and back faces of the elements.
6. Apparatus as claimed in claim S, characterized in that a single continuous electrode is disposed across the front faces of all elements in the array.
7. Apparatus as claimed in claim 5, characterized in that it further comprises a matching window disposed adjacent the front surface of the transducer elements, the front electrode being disposed between the matching window and the transducer elements.
8. Apparatus as claimed in claim 5, characterized in that it further comprises an air cell disposed over the rear electrodes of the transducer elements.
9. Apparatus as claimed in claim 8, characterized in that the air cell comprises glass micro-balloons in a resin binder.
10. A method for manufacturing a curved array of ultrasound trans-ducer elements for an apparatus as claimed in claim 1, characterized in that it comprises the steps of: attaching front and rear conductive electrodes to front and rear surfaces respectively of a substantially flat bar of piezo-electric ceramic, cutting a plurality of parallel grooves through the rear electrode and partially through the thickness of the bar;
placing the front surface of the grooved bar on a semicylindrical mandrel, the grooves being parallel to the axis of the mandrel, and bending the bar around the mandrel so that portions of the bar under the grooves are fractured to separate individual transducer elements, the front electrode remaining intact during the fracturing of the bar, the individual elements being retained against the mandrel by at least the front electrodes; and filling the spaces between the individual transducer elements with a resin binder which retains the elements on an arc conforming to the surface of the mandrel.
placing the front surface of the grooved bar on a semicylindrical mandrel, the grooves being parallel to the axis of the mandrel, and bending the bar around the mandrel so that portions of the bar under the grooves are fractured to separate individual transducer elements, the front electrode remaining intact during the fracturing of the bar, the individual elements being retained against the mandrel by at least the front electrodes; and filling the spaces between the individual transducer elements with a resin binder which retains the elements on an arc conforming to the surface of the mandrel.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10451679A | 1979-12-17 | 1979-12-17 | |
| US104,516 | 1979-12-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1152729A true CA1152729A (en) | 1983-08-30 |
Family
ID=22300906
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000366878A Expired CA1152729A (en) | 1979-12-17 | 1980-12-16 | Curved array of sequenced ultrasound transducers |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0031614B2 (en) |
| JP (1) | JPS56103598A (en) |
| CA (1) | CA1152729A (en) |
| DE (1) | DE3069525D1 (en) |
| ES (1) | ES8107014A1 (en) |
Families Citing this family (35)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57113596U (en) * | 1980-12-30 | 1982-07-14 | ||
| JPS5887998A (en) * | 1981-11-20 | 1983-05-25 | Hitachi Ltd | Manufacture of ultrasonic wave probe |
| JPS5996999U (en) * | 1982-12-21 | 1984-06-30 | 横河電機株式会社 | Ultrasonic array transducer |
| DE3478357D1 (en) * | 1983-03-17 | 1989-06-29 | Matsushita Electric Ind Co Ltd | Ultrasonic transducers having improved acoustic impedance matching layers |
| JPS59202058A (en) * | 1983-05-02 | 1984-11-15 | Hitachi Medical Corp | Production of probe for ultrasonic inspection apparatus |
| DE3483174D1 (en) * | 1983-06-07 | 1990-10-18 | Matsushita Electric Ind Co Ltd | ULTRASONIC TRANSMITTER WITH AN ABSORBING CARRIER. |
| JPS60114239A (en) * | 1983-11-28 | 1985-06-20 | 株式会社日立製作所 | Ultrasonic probe |
| JPS60192500A (en) * | 1984-03-14 | 1985-09-30 | Nippon Dempa Kogyo Co Ltd | Matrix array type ultrasonic wave probe and its manufacture |
| FR2580286B1 (en) * | 1985-04-12 | 1987-05-22 | Sintra | LIGHT ANECHICAL MATERIAL |
| FR2614747B1 (en) * | 1987-04-28 | 1989-07-28 | Dory Jacques | ELASTIC PULSE GENERATOR HAVING A PREDETERMINED WAVEFORM AND ITS APPLICATION TO TREATMENT OR MEDICAL DIAGNOSIS |
| DK5392A (en) * | 1992-01-17 | 1993-07-18 | Reson System As | SONAR EQUIPMENT FOR MARITIME ENVIRONMENT |
| US5423220A (en) * | 1993-01-29 | 1995-06-13 | Parallel Design | Ultrasonic transducer array and manufacturing method thereof |
| KR0165516B1 (en) * | 1996-02-26 | 1999-05-01 | 김광호 | Vibration detecting sensor |
| US6337465B1 (en) * | 1999-03-09 | 2002-01-08 | Mide Technology Corp. | Laser machining of electroactive ceramics |
| US6618620B1 (en) | 2000-11-28 | 2003-09-09 | Txsonics Ltd. | Apparatus for controlling thermal dosing in an thermal treatment system |
| US6632179B2 (en) * | 2001-07-31 | 2003-10-14 | Koninklijke Philips Electronics N.V. | Acoustic imaging system with non-focusing lens |
| JP3856380B2 (en) * | 2002-04-26 | 2006-12-13 | テイカ株式会社 | Composite piezoelectric vibrator and manufacturing method thereof |
| US7611462B2 (en) | 2003-05-22 | 2009-11-03 | Insightec-Image Guided Treatment Ltd. | Acoustic beam forming in phased arrays including large numbers of transducer elements |
| US8409099B2 (en) | 2004-08-26 | 2013-04-02 | Insightec Ltd. | Focused ultrasound system for surrounding a body tissue mass and treatment method |
| US20070016039A1 (en) | 2005-06-21 | 2007-01-18 | Insightec-Image Guided Treatment Ltd. | Controlled, non-linear focused ultrasound treatment |
| DE102006010009A1 (en) * | 2006-03-04 | 2007-09-13 | Intelligendt Systems & Services Gmbh & Co Kg | A method of manufacturing an ultrasonic probe with an ultrasonic transducer assembly having a curved transmitting and receiving surface |
| US8235901B2 (en) | 2006-04-26 | 2012-08-07 | Insightec, Ltd. | Focused ultrasound system with far field tail suppression |
| US8661873B2 (en) | 2009-10-14 | 2014-03-04 | Insightec Ltd. | Mapping ultrasound transducers |
| US9852727B2 (en) | 2010-04-28 | 2017-12-26 | Insightec, Ltd. | Multi-segment ultrasound transducers |
| WO2011138784A1 (en) * | 2010-05-05 | 2011-11-10 | Technion Research & Development Foundation Ltd. | Method and system of operating a multi focused acoustic wave source |
| US9981148B2 (en) | 2010-10-22 | 2018-05-29 | Insightec, Ltd. | Adaptive active cooling during focused ultrasound treatment |
| WO2012141682A1 (en) | 2011-04-11 | 2012-10-18 | Halliburton Energy Services, Inc. | Piezoelectric element and method to remove extraneous vibration modes |
| WO2013059358A2 (en) | 2011-10-17 | 2013-04-25 | Butterfly Network, Inc. | Transmissive imaging and related apparatus and methods |
| US9667889B2 (en) | 2013-04-03 | 2017-05-30 | Butterfly Network, Inc. | Portable electronic devices with integrated imaging capabilities |
| DE102013211627A1 (en) * | 2013-06-20 | 2014-12-24 | Robert Bosch Gmbh | Electroacoustic transducer |
| FR3027827B1 (en) * | 2014-11-03 | 2020-01-31 | Imasonic | ULTRASONIC TRANSDUCER WITH MICROBALLOON LAYER |
| GB2557345B (en) | 2016-12-08 | 2021-10-13 | Bae Systems Plc | MIMO communication system and data link |
| GB2565159B (en) * | 2017-07-19 | 2021-12-01 | Bae Systems Plc | Electroacoustic transducer |
| CN110646802B (en) * | 2019-09-26 | 2022-08-02 | 哈尔滨工程大学 | Hydrophone mirror symmetry arc array and arrangement method thereof |
| WO2024112570A1 (en) * | 2022-11-22 | 2024-05-30 | Provisio Medical, Inc. | Multifrequency ultrasound measuring systems and methods |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52131676A (en) * | 1976-04-27 | 1977-11-04 | Tokyo Shibaura Electric Co | Probe for ultrasonic diagnostic device |
-
1980
- 1980-12-09 DE DE8080201181T patent/DE3069525D1/en not_active Expired
- 1980-12-09 EP EP19800201181 patent/EP0031614B2/en not_active Expired
- 1980-12-13 JP JP17527380A patent/JPS56103598A/en active Granted
- 1980-12-15 ES ES497752A patent/ES8107014A1/en not_active Expired
- 1980-12-16 CA CA000366878A patent/CA1152729A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ES497752A0 (en) | 1981-09-16 |
| DE3069525D1 (en) | 1984-11-29 |
| EP0031614B1 (en) | 1984-10-24 |
| EP0031614A1 (en) | 1981-07-08 |
| ES8107014A1 (en) | 1981-09-16 |
| EP0031614B2 (en) | 1990-07-18 |
| JPS56103598A (en) | 1981-08-18 |
| JPH0452040B2 (en) | 1992-08-20 |
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