EP0102179B1 - Ultraschallwandler mit einstellbarem Fokus für Tomographie - Google Patents

Ultraschallwandler mit einstellbarem Fokus für Tomographie Download PDF

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Publication number
EP0102179B1
EP0102179B1 EP83304222A EP83304222A EP0102179B1 EP 0102179 B1 EP0102179 B1 EP 0102179B1 EP 83304222 A EP83304222 A EP 83304222A EP 83304222 A EP83304222 A EP 83304222A EP 0102179 B1 EP0102179 B1 EP 0102179B1
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EP
European Patent Office
Prior art keywords
transducer
transducer assembly
piezo
conical
electric material
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
Application number
EP83304222A
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English (en)
French (fr)
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EP0102179A1 (de
Inventor
Perry Kaminski
Eugene A. Larson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Technicare Corp
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Technicare Corp
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Priority claimed from US06/400,551 external-priority patent/US4445380A/en
Application filed by Technicare Corp filed Critical Technicare Corp
Publication of EP0102179A1 publication Critical patent/EP0102179A1/de
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    • 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
    • G10K11/32—Sound-focusing or directing, e.g. scanning characterised by the shape of the source
    • 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
    • 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
    • G10K11/30—Sound-focusing or directing, e.g. scanning using refraction, e.g. acoustic lenses

Definitions

  • This invention relates to ultrasonic transducers for diagnostic imaging and, in particular, to transducers of a novel geometric design with reduced sidelobe patterns.
  • Ultrasonic transducers are used in ultrasonic diagnostic systems to transmit waves of ultrasonic energy into a patient's body. Tissue interfaces in the body reflect some of this energy back toward the transducer in the form of echoes. The echoes are received by the transducer and converted into electrical signals. These signals may be processed by associating them with their times of arrival to reconstruct an image of the tissue or make fluid flow measurements.
  • a selectable focus transducer is shown in U.S. Patent 4,138,895.
  • the transducer there shown comprises a disc divided into a center electroded region and an annular electroded region. A user can select just the center electrode for a large depth of focus, or the central and annular regions together for a smaller depth of focus.
  • An acoustic lens provides the transducer arrangement with the desired aperture with point focal characteristics.
  • Transducers like antennas, have transmissive characteristics that can be analyzed in terms of main and sidelobes. It is desirable in general to have small sidelobes for an ultrasonic transducer, since large sidelobes can result in the reception and introduction of noise in a reproduced ultrasound image.
  • an ultrasonic transducer prefferably has good geometric focal characteristics which are adjustable so as to provide good resolution over a range of tissue depths. It is further desirable to reduce the transducer sidelobe patterns so as to minimize noise in the reproduced image.
  • an ultrasonic transducer assembly having a novel geometric focal characteristic.
  • the ultrasonic transducer assembly includes a piezo- electric material, the transducer exhibiting an effective radiating surface having a center point.
  • the assembly is characterised in that said effective radiating surface has an aspheric, semi- conical configuration resembling a concave spherical surface with opposite sides, relative to the center of the surface, canted toward each other.
  • This geometric focal characteristic provides a concentration of ultrasonic energy over a particular range of interest.
  • the transducer material is divided into a center disc and an annular ring.
  • the center disc When the center disc is activated, the range of optimal focus is located a relatively short distance from the transducer.
  • the range of optimal focus is located at a relatively greater distance from the transducer.
  • sidelobes of a transducer of the present invention are reduced by apodization, wherein damping material is located at the outer periphery on the back of the transducer.
  • a proximity switch is provided in the transducer assembly to switch between the long and short focal ranges.
  • the transducer electronics including the switch contacts are surrounded by a continuous shield.
  • the proximity switch comprises a reed switch which is controlled by a magnet located external to the shield. The use of a proximity switch such as a reed switch thus permits the focal ranges to be switched without physically interrupting the shield and hence impairing the noise characteristic of the transducer assembly.
  • a conical transducer is shown in cross-section.
  • the transducer includes a conical surface 12 of piezoelectric ceramic material on a backer 10.
  • the conical transducer exhibits an idealized aperture outlined at 16, which comprises a line of geometric focal points 14 emanating from the center of the transducer.
  • Conical transducers are advantageous in that they exhibit a narrow region of sharply defined focal points. Their disadvantage is that the energy emitted by the conical surface is relatively evenly distributed over the line of focal points. It would be desirable to be able to concentrate the emitted energy in a particular region of the aperture, so as to improve the sensitivity of the transducer at a particular tissue depth of interest.
  • FIG. 2a illustrates a spherical transducer in cross-section.
  • This transducer includes a spherical surface 22 of piezoelectric material mounted on a backer 20.
  • the spherical transducer exhibits an idealized aperture outlined at 26, which contains a single geometric focal point 24.
  • the ultrasonic energy emitted from the spherical surface of the transducer 22 converges at this point, and diverges beyond it.
  • the spherical transducer is capable of producing sharply focused images of tissue in the vicinity of the geometric focal point 24 by reason of the concentrated ultrasonic energy at the point.
  • the aperture is only sharply focused at one point, with resolution degrading at regions removed from this point.
  • a transducer constructed in accordance with the present invention is shown in cross-section in Figure 3a.
  • the transducer there shown is neither conical nor spherical, but exhibits many of the advantages of these two transducer types while overcoming several of their shortcomings.
  • the novel transducer of Figure 3a includes an aspheric surface 32 of piezoelectric material mounted on a backer 30.
  • the shape of the surface 32 is difficult to visualize in three dimensions, but in two dimensional cross-section it resembles a spherical surface transducer which has been bent at the center point 38.
  • the halves of the spherical surface on either side of the center point appear to be folded toward each other.
  • the transducer exhibits the idealized aperture outlined at 36, in which most of the emitted ultrasonic energy is focused at points 34 in an elongated focal region.
  • the ultrasonic energy emitted by the novel transducer is neither focused along the entire center line of the transducer, nor is it focused at a single point. Rather, it is concentrated in an elongated region of optimal focus in which tissue of a significant depth can be imaged with good lateral resolution.
  • the elongated region in a constructed embodiment of the present invention can extend over a six to seven centimeter depth for a 19 mm, 3.5 MHz transducer.
  • an aspheric surface piezoelectric element 300 includes a central area 312 which is electrically separate from an outer annulus 314.
  • the piezo- electric material is mounted in a cylindrical mount 306.
  • the inner area 312 may be activated alone, or a switch 316 may be closed to activate both areas 312 and 314 simultaneously to focus the transducer over different depths of focus.
  • the concave front of the transducer 300 is filled in with an epoxy material to provide a flat face 302 on the transducer.
  • the piezoelectric material exhibits a conical shape, and contains an annular groove which divides the material into an inner conical region 212 and an annular outer region 214.
  • the center region 212 may be activated alone or together with the annular region 214 by closing a switch 216. When the switch 216 is open, the center region 212 will focus in the near field out to a point 218 at approximately 9 centimeters, and when the two regions are activated together, far field focusing is effected out to a point 201 at approximately 14 centimeters.
  • the acoustic lens 210 On the face of the piezoelectric material is an acoustic lens having a spherical face 210.
  • the combination of the conical piezoelectric material 212, 214 and the spherical faced lens provide the aspheric aperture characteristic of the embodiments of Figure 3a and 4.
  • the concave lens is again filled in with epoxy to provide a flat face 208 on the transducer.
  • the acoustic lens 210 was composed of a high acoustic impedance and velocity epoxy material, and the filler material at 208 was a lower acoustic impedance and velocity epoxy material.
  • the conical piezoelectric transducer 212, 214 and the spherical acoustic lens provide the desired elongated focal region aperture, and the filler 208 forms a simple plano-convex lens which extends the focal zone to point 201. It follows from the principles of this embodiment that an aspheric transducer could also be made utilizing a spherical piezoelectric disc and a conical faced lens.
  • the embodiment of Figure 5 is more easily manufactured than the other illustrated embodiments of the present invention. This is because a conical ceramic transducer can be readily manufactured and the spherical acoustic lens can be formed by a simple lapping technique.
  • the embodiment of Figure 4 with its aspheric ceramic surface, could be formed by grinding the ceramic material with a precise, numerically controlled lathe, for example.
  • the embodiment of Figure 6 is composed of a flat disc 400 of piezoelectric material, including a central disc 404 and an annular ring 406, the activation of which is controlled by a switch 416.
  • the disc 400 is fronted with an acoustic lens 402 having an aspheric surface. This combination of piezoelectric material and aspheric lens will produce the same aperture as the embodiments of Figure 4 and 5.
  • a conical transducer such as that shown in Figure 1a a will exhibit a lobe pattern as shown in Figure 1 b, with a large main lobe 40 and sizeable sidelobes 42 and 42'.
  • the large sidelobes 42 and 42' are undesirable in an ultrasonic diagnostic system.
  • the spherical transducer of Figure 2a will exhibit a more acceptable lobe pattern as shown in Figure 2b.
  • the pattern there shown includes a large main lobe 50 and small sidelobes 52, 52'.
  • the aspheric transducer of the present invention will exhibit a lobe pattern intermediate those of Figures 1b and 2b.
  • the lobe pattern of a transducer of the present invention is improved in accordance with a further aspect of the present invention by providing backing material around the outer perimeter of the transducer as shown at 304 in Figures 4 and 5.
  • This ring of backing material damps vibrations at the outer perimeter of the piezoelectric material thereby reducing the energy radiated from the perimeter of the piezo- electric material.
  • the ring of backing material may be extended to back the central region 212 or 312 to damp vibrations at the perimeter of the central region when it is operated along.
  • This damping technique causes the transducer to be a non-uniform radiator, which "smears" the small side lobes of the transducer as shown in Figure 3b, which illustrates a large main lobe 60 and side lobes 62, 62', which are approximately the same size as the side lobes 52, 52' of the spherical transducer.
  • Figure 7a illustrates the focal pattern of a simple dual aperture spherical transducer, including a central spherical region 120 and an outer annular region 122.
  • the transducer When both regions 120 and 122 of the transducer are activated simultaneously, the transducer exhibits an aperture outlined at 124, which narrows sharply at a focal region 125. Focusing is ineffective beyond the near field limit 129 of the transducer, which is approximately equal to the radius of the transducer squared, divided by the wavelength of operation.
  • the near field limit 129 is thus a linear function of the area of the transducer, which in this case is the total of both regions 120 and 122.
  • the aperture is as outlined by dotted lines 126.
  • This aperture produces a focal region 127 closer to the transducer, with a near field limit at 128 by reason of the reduced area of the transducer.
  • the aperture outlined at 126 does not narrow as sharply as the aperture outlined at 124, however, and the focal region 127 has a greater lateral dimension 1 than focal region 125. This is because the focus is changed by changing the near field limit from 129 to 128; the geometric focus remains the same, generally located slightly beyond the far focal region 125.
  • Figure 7b illustrates the focal pattern of a simple dual aperture conical transducer having an inner conical surface 130 and an outer annular surface 132.
  • the energy from surface 130 focuses along the broken line shown at 137 and bounded by dotted lines 136.
  • both regions 130 and 132 are activated, the line of focal points is extended to include the points indicated at 135 as well as those at 137, bounded by dashed lines 134. Switching from operation using both regions to operation using only the center region 130 reduces the near field limit, since the transducer area changes, and also reduces the geometric focal length to only the focal points included in aperture outline 136. A line of distributed energy focal points is produced in both cases.
  • Figure 7c illustrates the focal pattern of a dual focus aspheric transducer of the present invention.
  • a narrow focal region 145 is produced at the narrow portion of the aperture outlined by dashed lines 144.
  • the area of the full transducer provides a near field limit indicated at 129.
  • the diameter d' of the central region 140 can be made larger than the diameter d of the equivalent central region 120 of the spherical transducer of Figure 7a.
  • Several benefits result from use of a relatively larger central region. First, a larger region will transmit and receive more energy than a smaller region, thereby increasing the sensitivity of the transducer. Second, with a larger region there is less impedance change when switching from double to single region operation, which makes the tuning electronics coupled to the transducer simpler. And third, a larger central region 140 contributes to the narrowing effect on the aperture 146.
  • the ultrasonic transducer of the present invention is conveniently mounted in a probe assembly such as that shown in Figure 8.
  • the probe assembly there shown advantageously provides an electrically shielded environment which reduces the tendency to pick up stray electronic interference.
  • the probe assembly also provides a means for switching the.focus of the transducer in a manner which does not interrupt the shielded environment. As the focus of the transducer is switched, the tuning of the transducer is also changed and a signal is provided which indicates the selected focal characteristics.
  • the probe assembly of Figure 8 includes a forward plastic cylindrical section 150 with a closed acoustic window face 151.
  • the aspheric transducer 152 is located behind the window 151.
  • Leads 156 extend from the separate regions of the transducer.
  • the interior of the cylindrical section 150 is lined with a nonmagnetic shield 154 such as copper.
  • the rear portion of the cylindrical section 150 narrows to a smaller diameter as indicated by dividing ridge 157.
  • Two dimples shown at 158 are provided on the outside of the narrow portion which form a portion of the detent mechanism of the switch.
  • the end 159 of the cylindrical section 150 is open.
  • a plastic ring 160 slides over the narrow portion of the cylindrical section 150 up to the ridge 157.
  • a small ball 162 which rides between the dimples 158 and snaps into them to provide a detent mechanism for the ring.
  • a groove 168 is formed around the inner surface of the ring to hold a magnet 164 in a predetermined position relative to the ball bearing 162.
  • a small pin 166 extends from the inner surface of the ring at the bottom of the ring.
  • a rear cylindrical section 170 slides over the remainder of the narrow portion of section 150.
  • a recessed collar 176 is then located under the ring 160.
  • the collar 176 has a slot 174 in it so that pin 166 can move from one end of the slot to the other as the ring 160 is turned. The pin and slot thereby provide a stop for the ring to permit the ring to be turned only through the arc of the slot.
  • the wires 156 from the transducer are soldered to a small printed circuit board 190, mounted on an r.f. connector 180.
  • the r.f. connector 180 is inserted into the open end 159 of the section 150 up to the lip 181 of the connector.
  • Mounted on the connector at a plastic ring 183 are three reed switches 184, 186 and 188.
  • the reed switches are wired to the printed circuit board 190.
  • the r.f. connector 180 and copper shield 154 provide a completely shielded cavity for the wiring, printed circuit board, switches, and board components in the inside of the section 150.
  • the ring performs three switching functions in the probe assembly.
  • the focal characteristics of the transducer are switched between short focus using only the central disc of the transducer, and long focus by connecting the central disc and annular ring of the transducer together to be activated simultaneously.
  • the tuning of the circuitry on circuit board 190 is switched to match the respective electrical characteristics of the transducer in the two operating modes.
  • a resistance value on the circuit board is changed to produce a signal indicative of the operating mode, which signal is coupled out through the connector along with signals to and from the transducer.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Claims (11)

1. Ultraschallwandler, umfassend ein piezoelektrisches Material, wobei der Wandler eine wirksame strahlende Oberfläche (32) mit einem Mittelpunkt (38) aufweist, dadurch gekennzeichnet, daß die wirksame strahlende Oberfläche (32) eine asphärische, halbkonische Konfiguration aufweist, die einer konkaven sphärischen Oberfläche, wobei die gegenüberliegenden Seiten in bezug auf die Mitte der Oberfläche gegeneinander abgschrägt sind.
2. Ultraschallwandler nach Anspruch 1, worin das piezoelektrische Material (300) die asphärische, halbkonische Konfiguration aufweist.
3. Ultraschallwandler nach Anspruch 1, worin die wirksame strahlende Oberfläche durch Verwendung eines konischen Teils aus piezoelektrischem Material (212, 214) und einer akustischen Linse (210) vorgesehen ist, die an der konischen Oberfläche befestigt ist und eine sphärische Oberfläche entfernt von der konischen Oberfläche aufweist.
4. Ultraschallwandler nach Anspruch 1, worin die wirksame strahlende Oberfläche unter Verwendung einer flachen Scheibe aus piezoelektrischem Material (400) mit einer Vorderseite und einer akustischen Linse (402) vorgesehen ist, die an der Vorderseite angebracht ist, wobei die Linse die asphärische halbkonische Konfiguration an ihrer von der flachen Scheibe (400) entfernten Oberfläche aufweist.
5. Ultraschallwandler nach Anspruch 3 oder Anspruch 4, worin die akustische Linse (210 oder 402) aus Epoxyharz besteht, das in bezug auf menschliches Gewebe eine hohe akustische Impedanz und Geschwindigkeit aufweist.
6. Ultraschallwandler nach einem der Ansprüche 1 bis 5, worin das piezoelektrische Material ein mittleres Organ (212, 312, 404) mit einem Außendurchmesser umfaßt, der in bezug auf den Mittelpunkt symmetrisch angeordnet ist, sowie einem ringförmigen Organ (214, 314, 406), das von dem mittleren Organ elektrisch getrennt und um den Umfang des mittleren Organs symmetrisch angeordnet ist.
7. Ultraschallwandler nach Anspruch 6, worin das mittlere Organ (140) einen ersten geometrischen Mittelpunkt (147) und eine nahe Feldmittelpunktbegrenzung (128) aufweist und das mittlere Organ (140) sowie das ringförmige Organ (142) zusammen einen zweiten geometrischen Mittelpunkt (145) und eine nahe Feldmittelpunktgrenze (129) aufweisen.
8. Ultraschallwandler nach einem der Ansprüche 1 bis 7, bestehend ferner aus einem Ring (304) aus abstützendem Werkstoff, der an der Rückseite des piezoelektrischen Materials rund um dessen Umfang befestigt ist.
9. Ultraschallwandlermeßkopf, bestehend aus:
einem Gehäuse (150,160,170) mit einem elektrisch abgeschirmten Innenraum mit einem Ultraschallwandler gemäß Anspruch 6 oder irgend einem von diesem abhängigen Anspruch, der an einem Ende desselben angeordnet ist;
Mitteln (180), die in einer Wand des Gehäuses zur Herstellung einer elektrischen Verbindung zwischen dem Innenraum und dem Äußeren des Gehäuses angeordnet sind;
ein Reed-Schalter (184), der in dem abgeschirmten Innenraum angeordnet ist und mit dem genannten mittleren und ringförmigen Organ sowie den elektrischen Verbindungsmitteln (180) für die selektive Kupplung der Organe mit den Verbindungsmitteln verbunden ist; und
einem Magneten (164), der außerhalb des abgeschirmten Innenraums angeordnet sowie beweglich befestigt ist, um den Reed-Schalter (184) zur Veränderung der Kupplung der zentralen und ringförmigen Organe mit den elektrische Verbindungsmitteln (80) wahlweise zu öffnen und zu schließen.
10. Meßkopf nach Anspruch 9, worin der Reed-Schalter (184) eine erste Klemme aufweist, die an das mittlere Organ gekoppelt ist, sowie eine zweite Klemme, die mit dem ringförmigen Organ verbunden ist, und daß die elektrischen Verbindungsmittel eine r.f. Steckverbindung (180) mit einem Stecker umfassen, der mit der Klemme des ersten Reed-Schalters verbunden ist.
11. Sonde nach Anspruch 10, bestehend aus einem abgestimmten Kreis (190), der in dem abgeschirmten Innenraum angeordnet ist, sowie einem zweiten Reed-Schalter (186), der in dem abgeschirmten Innenraum in unmittelbarer Nähe zu dem äußeren Magnet (164) angeordnet und an das piezoelektrische Material sowie den abgestimmten Kreis (190) zur wahlweisen Kopplung des abgestimmten Kreises (190) an das piezoelektrische Material angeschlossen ist.
EP83304222A 1982-07-21 1983-07-20 Ultraschallwandler mit einstellbarem Fokus für Tomographie Expired EP0102179B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US40054782A 1982-07-21 1982-07-21
US400551 1982-07-21
US400547 1982-07-21
US06/400,551 US4445380A (en) 1982-07-21 1982-07-21 Selectable focus sphericone transducer and imaging apparatus

Related Child Applications (1)

Application Number Title Priority Date Filing Date
EP86200472.8 Division-Into 1986-03-21

Publications (2)

Publication Number Publication Date
EP0102179A1 EP0102179A1 (de) 1984-03-07
EP0102179B1 true EP0102179B1 (de) 1987-09-16

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EP83304222A Expired EP0102179B1 (de) 1982-07-21 1983-07-20 Ultraschallwandler mit einstellbarem Fokus für Tomographie
EP86200472A Expired - Lifetime EP0196139B1 (de) 1982-07-21 1983-07-20 Ultraschallwandler-Sondengerät mit Doppelöffnung

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP86200472A Expired - Lifetime EP0196139B1 (de) 1982-07-21 1983-07-20 Ultraschallwandler-Sondengerät mit Doppelöffnung

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EP (2) EP0102179B1 (de)
AU (1) AU572464B2 (de)
DE (2) DE3382654T2 (de)
IL (1) IL69293A0 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220373372A1 (en) * 2021-05-19 2022-11-24 Honeywell International Inc. Fluid sensor for bubble and occlusion detection

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Publication number Priority date Publication date Assignee Title
AU572464B2 (en) * 1982-07-21 1988-05-12 Technicare Corp. Selectable focus ultrasonic transducer
FR2559266B1 (fr) * 1984-02-02 1986-07-04 Comp Generale Electricite Dispositif a ondes acoustiques focalisees pour etudier la structure d'un objet
JPH02159266A (ja) * 1988-12-14 1990-06-19 Matsushita Electric Ind Co Ltd 超音波探触子
JPH02215452A (ja) * 1989-02-17 1990-08-28 Toshiba Corp 結石破砕装置
JPH03176040A (ja) * 1989-09-29 1991-07-31 Terumo Corp 超音波診断装置
EP1005693B1 (de) * 1997-08-23 2003-02-12 Valeo Schalter und Sensoren GmbH Ultraschallwandler mit in wandlerlängsrichtung angeordneter platine für eine elektrische schaltung
DE10114819A1 (de) * 2001-03-26 2002-10-10 Siemens Ag Verfahren zur Verbesserung des Signalempfangs eines Ultraschall-Näherungsschalters und Ultraschall-Näherungsschalter mit verbessertem Signalempfang

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JPS4963401A (de) * 1972-10-18 1974-06-19
US4016751A (en) * 1973-09-13 1977-04-12 The Commonwealth Of Australia Care Of The Department Of Health Ultrasonic beam forming technique
US3958559A (en) * 1974-10-16 1976-05-25 New York Institute Of Technology Ultrasonic transducer
US4138895A (en) * 1977-10-20 1979-02-13 Rca Corporation Switchable depth of focus pulse-echo ultrasonic-imaging display system
US4276779A (en) * 1979-03-29 1981-07-07 Raytheon Company Dynamically focussed array
JPS56158648A (en) * 1980-05-09 1981-12-07 Tokyo Shibaura Electric Co Ultrasonic diagnostic apparatus
US4398539A (en) * 1980-06-30 1983-08-16 Second Foundation Extended focus transducer system
US4445380A (en) * 1982-07-21 1984-05-01 Technicare Corporation Selectable focus sphericone transducer and imaging apparatus
AU572464B2 (en) * 1982-07-21 1988-05-12 Technicare Corp. Selectable focus ultrasonic transducer
US4557146A (en) * 1982-07-21 1985-12-10 Technicare Corporation Selectable focus ultrasonic transducers for diagnostic imaging

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220373372A1 (en) * 2021-05-19 2022-11-24 Honeywell International Inc. Fluid sensor for bubble and occlusion detection

Also Published As

Publication number Publication date
AU572464B2 (en) 1988-05-12
IL69293A0 (en) 1983-11-30
EP0196139A3 (en) 1990-12-05
EP0196139B1 (de) 1993-01-20
EP0196139A2 (de) 1986-10-01
EP0102179A1 (de) 1984-03-07
DE3382654T2 (de) 1993-05-13
DE3382654D1 (de) 1993-03-04
DE3373739D1 (en) 1987-10-22
AU1712483A (en) 1984-01-26

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