EP0285482A1 - Multifrequency acoustic transducer, particularly for medical imaging - Google Patents

Multifrequency acoustic transducer, particularly for medical imaging Download PDF

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Publication number
EP0285482A1
EP0285482A1 EP88400583A EP88400583A EP0285482A1 EP 0285482 A1 EP0285482 A1 EP 0285482A1 EP 88400583 A EP88400583 A EP 88400583A EP 88400583 A EP88400583 A EP 88400583A EP 0285482 A1 EP0285482 A1 EP 0285482A1
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Prior art keywords
frequency
transducer
blade
transducer according
medical imaging
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German (de)
French (fr)
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EP0285482B1 (en
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Charles Maerfeld
Jean-François Gelly
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Thales SA
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Thomson CSF SA
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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
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

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  • the present invention relates to multifrequency acoustic transducers used in particular in medicine to form images of the human body by ultrasound.
  • FIG. 1 It is known to use in medical ultrasound probes, a cross section of which is shown in FIG. 1.
  • This probe is formed from aligned transducer elements such as 101 whose thickness is adapted to the operating frequency. The two faces of these elements are covered with electrodes 102 making it possible to apply the electrical voltages which make them vibrate.
  • the vibration frequency chosen is most often the resonance frequency f r which corresponds to the fundamental mode of vibration depending on the thickness of the transducer.
  • a thickness of 1 mm is commonly used for medical probes and the frequency used is therefore most often 2.85 MHz.
  • the overvoltage factor Q of the transducers is approximately equal to the ratio between the impedance of the piezoelectric material constituting this transducer and the impedance of the external medium where the vibration will propagate. If ⁇ and ⁇ o are respectively the specific masses of the piezoelectric material and the external medium, and c and c o the velocities of sound in this material and in this medium, Q is then equal to In the case of a piezoelectric ceramic such as PZT, this ratio is close to 17.
  • the vibrations are emitted in the form of short duration pulses in order to have sufficient distance resolution. This widens the frequency band of the transmitted signal and therefore requires having a relatively large probe bandwidth. To obtain this, it is known to place in front of the transducers a blade 103 whose thickness is a quarter of the wavelength at the frequency fundamental. The impedance of this quarter wave plate is chosen to be of the order of ⁇ c ⁇ o c o .
  • the transducers are fixed to the body of the probe by means of a reflector 104, known by the Anglo-Saxon backing name, which is advantageously of the soft type, that is to say having a neighboring acoustic impedance from 0.
  • the invention proposes to modify the traditional probes by adding additional adaptation blades in order to be able to operate these probes. simultaneously on several frequencies and therefore simultaneously perform mode B imaging and DFM imaging with a single probe.
  • the probe according to the invention comprises a transducer 201 provided with two electrodes 202 and a quarter-wave plate 203. According to the invention, this transducer is fixed to the soft reflector 204 by means of a half-wave plate 205.
  • this probe operates for two passbands centered one around a high frequency f o , and the other around a low frequency f1 equal to These frequencies are for example equal to those mentioned above, ie 5 MHz and 2.5 MHz.
  • half-wave and quarter-wave used respectively for the transducer 201 and the blade 205 on the one hand and for the blade 203 on the other hand correspond to the high frequency.
  • the materials used not being dispersive, at the low frequency the transducer 201 and the blade 205 are quarter wave, while the blade 203 is at 1 / 8th of the wavelength.
  • the transducer would obviously not resonate at the frequency f1 and the acoustic signal possibly emitted would be extremely weak.
  • the presence of the blade 205 does not change anything at the frequency f o since, being half-wave at this frequency, it is transparent to the acoustic waves and it brings back to the level of the transducer the same impedance than that of reflector 204.
  • this blade being quarter wave at this frequency, everything happens as if the transducer were extended by a quarter wavelength and that the transducer assembly 201-blade 205 is equivalent to a half wave. Under these conditions, the excitation brought back by the electrodes 202 allows this assembly to vibrate at resonance on the frequency f1.
  • FIG. 3 represents the amplitude A of the vibrational speed along the transducer 201 and the blade 205.
  • Such a line would be short-circuited at the end on the side of the reflector where there would therefore always be a maximum vibrational speed, known as the belly, whatever the frequency, in particular at the frequencies f o and f1.
  • this blade 203 it is always quarter wave at the frequency f o and therefore plays its role of bandwidth expander.
  • this blade only has a length equivalent to 1 / 8th of a wavelength and the adaptation to this frequency is therefore very different from that obtained at the frequency f1, so that the band of frequencies obtained around f o is narrower than that around f1.
  • this frequency f o is used for DFM imaging, such a narrowing of the bandwidth is not a problem.
  • the electronic equipment associated with the probe includes circuits which make it possible to use the two frequencies f o and f1 both on transmission and on reception.
  • FIG. 4 shows a longitudinal section of a probe according to the invention operating at 5 MHz and at 2.5 MHz. It can be seen that this probe comprises a set of transducers 201 coated with metallizations 202. These transducers are obtained by sections of a block of ceramic previously metallized on its two faces to form the electrodes. This set of transducers is bonded to the blade 205 which is itself bonded to the reflector 204. The blade 203 itself covers the transducers on which it is also bonded. Note that only the transducer block is formed of individual elements, while both the blades 203 and 205 as the reflector 204 are continuous. In this example shown the bar is linear, but the invention also applies to bars having another shape and in particular to curved bars.
  • the invention is not limited to the case of probes operating on two frequencies, one of which is half the other. It also extends to probes and in general to acoustic transducers operating on a set of distinct frequencies forming the center frequencies of separate frequency bands. For this, the number of additional adaptation blades is multiplied so as to create the number of degrees of freedom sufficient in the transfer function to determine these bandwidths.

Abstract

Disclosed is a probe for medical echography wherein, between the piezoelectric transducers and the backing, there is inserted a half-wave strip at the natural resonance frequency of these transducers, thus enabling the use of the probe in two distinct frequencies, one of which is substantially equal to half the other, and thus providing for ordinary mode B imaging and DFM Doppler imaging with one and the same probe.

Description

La présente invention se rapporte aux transducteurs acoustiques multifréquences utilisés notamment en médecine pour former des images du corps humain par échographie.The present invention relates to multifrequency acoustic transducers used in particular in medicine to form images of the human body by ultrasound.

Il est connu d'utiliser en échographie médicale des sondes dont une coupe transversale est représentée sur la figure 1. Cette sonde est formée d'éléments transducteurs alignés tel que 101 dont l'épaisseur est adaptée à la fréquence de fonctionnement. Les deux faces de ces éléments sont recouverts d'électrodes 102 permettant d'appliquer les tensions électriques qui les font vibrer. La fréquence de vibration choisie est le plus souvent la fréquence de résonance fr qui correspond au mode fondamental de vibration selon l'épaisseur du transducteur. Pour les matériaux piézoélectriques généralement utilisés dans ces sondes la relation entre fr exprimée en kilohertz et l'épaisseur h exprimée en millimètres du transducteur est donnée par fr =

Figure imgb0001
. On utilise couramment pour les sondes médicales une épaisseur de 1 mm et la fréquence utilisée est donc alors le plus souvent de 2,85 MHz.It is known to use in medical ultrasound probes, a cross section of which is shown in FIG. 1. This probe is formed from aligned transducer elements such as 101 whose thickness is adapted to the operating frequency. The two faces of these elements are covered with electrodes 102 making it possible to apply the electrical voltages which make them vibrate. The vibration frequency chosen is most often the resonance frequency f r which corresponds to the fundamental mode of vibration depending on the thickness of the transducer. For the piezoelectric materials generally used in these probes the relation between f r expressed in kilohertz and the thickness h expressed in millimeters of the transducer is given by f r =
Figure imgb0001
. A thickness of 1 mm is commonly used for medical probes and the frequency used is therefore most often 2.85 MHz.

Le facteur de surtension Q des transducteurs est approximativement égal au rapport entre l'impédance du matériau piézoélectrique constituant ce transducteur et l'impédance du milieu extérieur où va se propager la vibration. Si ρ et ρo sont respectivement les masses spécifiques du matériau piézoélectrique et du milieu extérieur, et c et co les vitesses du son dans ce matériau et dans ce milieu, Q est donc alors égal à

Figure imgb0002
Dans le cas d'une céramique piézoélectrique telle que le PZT, ce rapport est voisin de 17.The overvoltage factor Q of the transducers is approximately equal to the ratio between the impedance of the piezoelectric material constituting this transducer and the impedance of the external medium where the vibration will propagate. If ρ and ρ o are respectively the specific masses of the piezoelectric material and the external medium, and c and c o the velocities of sound in this material and in this medium, Q is then equal to
Figure imgb0002
 In the case of a piezoelectric ceramic such as PZT, this ratio is close to 17.

Les vibrations sont émises sous forme d'impulsions de faible durée afin d'avoir une résolution en distance suffisante. Ceci élargit la bande de fréquences du signal émis et nécessite donc d'avoir une largeur de bande de la sonde relativement importante. Pour obtenir cela, il est connu de placer devant les transducteurs une lame 103 dont l'épaisseur est le quart de la longueur d'onde à la fréquence fondamentale. L'impédance de cette lame quart d'onde est choisie pour être de l'ordre de √ρcρoco.The vibrations are emitted in the form of short duration pulses in order to have sufficient distance resolution. This widens the frequency band of the transmitted signal and therefore requires having a relatively large probe bandwidth. To obtain this, it is known to place in front of the transducers a blade 103 whose thickness is a quarter of the wavelength at the frequency fundamental. The impedance of this quarter wave plate is chosen to be of the order of √ρcρ o c o .

La fixation des transducteurs sur le corps de la sonde se fait par l'intermédiaire d'un réflecteur 104, connu sous le nom anglo-saxon de backing, qui est avantageusement de type mou c'est-à-dire présentant une impédance acoustique voisine de 0.The transducers are fixed to the body of the probe by means of a reflector 104, known by the Anglo-Saxon backing name, which is advantageously of the soft type, that is to say having a neighboring acoustic impedance from 0.

En imagerie médicale on utilise couramment deux types de fonctionnement :
- une imagerie classique, dite en mode B, dans laquelle on représente sectoriellement les échos en fonction de l'angle de tir et de la distance, l'amplitude de ces échos modulant la brillance de l'image ;
- une imagerie codée en couleurs, dite DFM, abréviation de l'expression anglo-saxonne "Doppler Flow Mapping", dans laquelle le décalage Doppler dû à la circulation sanguine est représenté par des variations de couleurs en surcroît des variations de brillance dues à l'amplitude des échos.In medical imaging, two types of functioning are commonly used:
- conventional imagery, known as B mode, in which the echoes are represented sectorally as a function of the firing angle and the distance, the amplitude of these echoes modulating the brightness of the image;
- color coded imaging, called DFM, short for the English expression "Doppler Flow Mapping", in which the Doppler shift due to blood circulation is represented by variations in color in addition to variations in brightness due to the amplitude of the echoes.

Pour l'imagerie en mode B, il faut une bonne résolution latérale et en distance. Ceci nécessite une fréquence centrale relativement élevée, par exemple de l'ordre de 5 MHz.For B-mode imaging, good lateral and distance resolution are required. This requires a relatively high central frequency, for example of the order of 5 MHz.

Pour l'imagerie DFM, il n'y a pas besoin d'une résolution aussi grande que pour l'imagerie en mode B, mais on a besoin d'un rapport signal à bruit aussi grand que possible pour pouvoir mesurer des écarts Doppler faibles, correspondant eux-mêmes à des vitesses sanguines faibles. Le rapport signal à bruit est d'autant plus grand que la fréquence de fonctionnement est plus basse. Une valeur typique de la fréquence utilisée sera par exemple de 2,5 MHz.For DFM imaging, there is no need for as high a resolution as for B-mode imaging, but you need as large a signal-to-noise ratio as possible to measure small Doppler deviations , corresponding themselves to low blood speeds. The lower the signal-to-noise ratio, the higher the operating frequency. A typical value of the frequency used will be for example 2.5 MHz.

Selon l'art antérieur on utilise deux sondes branchées sur un même appareil, mais ceci augmente bien entendu les coûts de l'appareillage et complique son utilisation. Une autre solution, beaucoup moins satisfaisante, consiste à utiliser une seule sonde fonctionnant sur une fréquence intermédiaire, par exemple 3,5 MHz.According to the prior art, two probes connected to the same device are used, but this naturally increases the costs of the apparatus and complicates its use. Another solution, much less satisfactory, consists in using a single probe operating on an intermediate frequency, for example 3.5 MHz.

Pour pallier ces inconvénients l'invention propose de modifier les sondes traditionnelles en rajoutant des lames supplémentaires d'adaptation afin de pouvoir faire fonctionner ces sondes simultanément sur plusieurs fréquences et d'effectuer donc simultanément une imagerie en mode B et une imagerie DFM avec une sonde unique.To overcome these drawbacks, the invention proposes to modify the traditional probes by adding additional adaptation blades in order to be able to operate these probes. simultaneously on several frequencies and therefore simultaneously perform mode B imaging and DFM imaging with a single probe.

D'autres particularités et avantages de l'invention apparaîtront clairement dans la description suivante présentée à titre d'exemple non limitatif en regard des figures annexées qui représentent :

  • - la figure 1, une coupe transversale d'une sonde connue ;
  • - la figure 2, une coupe transversale d'une sonde selon l'invention ;
  • - la figure 3, un diagramme de fonctionnement ; et
  • - la figure 4, une coupe longitudinale d'une sonde selon l'invention.
Other features and advantages of the invention will appear clearly in the following description presented by way of nonlimiting example with reference to the appended figures which represent:
  • - Figure 1, a cross section of a known probe;
  • - Figure 2, a cross section of a probe according to the invention;
  • - Figure 3, an operating diagram; and
  • - Figure 4, a longitudinal section of a probe according to the invention.

Dans le mode de réalisation bi-fréquence représenté sur la figure 2, selon la même coupe que sur la figure 1, la sonde selon l'invention comporte un transducteur 201 muni de deux électrodes 202 et d'une lame quart d'onde 203. Selon l'invention ce transducteur est fixé sur le réflecteur mou 204 par l'intermédiaire d'une lame demi-­onde 205.In the dual-frequency embodiment represented in FIG. 2, according to the same section as in FIG. 1, the probe according to the invention comprises a transducer 201 provided with two electrodes 202 and a quarter-wave plate 203. According to the invention, this transducer is fixed to the soft reflector 204 by means of a half-wave plate 205.

Selon l'invention cette sonde fonctionne pour deux bandes passantes centrées l'une autour d'une fréquence haute fo, et l'autre autour d'une fréquence basse f₁ égale à

Figure imgb0003
Ces fréquences sont par exemple égales à celles mentionnées plus haut, soit 5 MHz et 2,5 MHz.According to the invention, this probe operates for two passbands centered one around a high frequency f o , and the other around a low frequency f₁ equal to
Figure imgb0003
 These frequencies are for example equal to those mentioned above, ie 5 MHz and 2.5 MHz.

Les termes de demi-onde et de quart d'onde utilisés respectivement pour le transducteur 201 et la lame 205 d'une part et pour la lame 203 d'autre part, correspondent à la fréquence haute. Dans ces conditions, les matériaux utilisés n'étant pas dispersifs, à la fréquence basse le transducteur 201 et la lame 205 sont quart d'onde, tandis que la lame 203 est au 1/8e de la longueur d'onde.The terms of half-wave and quarter-wave used respectively for the transducer 201 and the blade 205 on the one hand and for the blade 203 on the other hand, correspond to the high frequency. Under these conditions, the materials used not being dispersive, at the low frequency the transducer 201 and the blade 205 are quarter wave, while the blade 203 is at 1 / 8th of the wavelength.

Si le transducteur était tout seul, comme dans la figure 1, il ne résonerait bien évidemment pas à la fréquence f₁ et le signal acoustique éventuellement émis serait extrêmement faible.If the transducer were all alone, as in FIG. 1, it would obviously not resonate at the frequency f₁ and the acoustic signal possibly emitted would be extremely weak.

La présence de la lame 205 ne change rien à la fréquence fo puisque, étant demi-onde à cette fréquence, elle est transparente aux ondes acoustiques et elle ramène au niveau du transducteur la même impédance que celle du réflecteur 204.The presence of the blade 205 does not change anything at the frequency f o since, being half-wave at this frequency, it is transparent to the acoustic waves and it brings back to the level of the transducer the same impedance than that of reflector 204.

Par contre à la fréquence f₁ cette lame, étant quart d'onde à cette fréquence, tout se passe comme si le transducteur était prolongé d'un quart de longueur d'onde et que l'ensemble transducteur 201-lame 205 soit équivalent à une demi-onde. Dans ces conditions l'excitation ramenée par les électrodes 202 permet à cet ensemble de vibrer à la résonance sur la fréquence f₁ .On the other hand at the frequency f₁ this blade, being quarter wave at this frequency, everything happens as if the transducer were extended by a quarter wavelength and that the transducer assembly 201-blade 205 is equivalent to a half wave. Under these conditions, the excitation brought back by the electrodes 202 allows this assembly to vibrate at resonance on the frequency f₁.

Pour mieux expliquer les phénomènes, on peut faire en première approximation une comparaison avec l'électromagnétisme et considérer la lame 205 comme une ligne quart d'onde ou demi-onde selon le cas. Cette comparaison est explicitée par la figure 3 qui représente l'amplitude A de la vitesse vibratoire le long du transducteur 201 et de la lame 205.To better explain the phenomena, we can make a comparison with electromagnetism as a first approximation and consider the blade 205 as a quarter-wave or half-wave line as appropriate. This comparison is explained by FIG. 3 which represents the amplitude A of the vibrational speed along the transducer 201 and the blade 205.

Une telle ligne serait court-circuitée en extrémité du côté du réflecteur où il y aurait donc toujours un maximum de vitesse vibratoire, connue sous le nom de ventre, quelle que soit la fréquence, en particulier aux fréquences fo et f₁.Such a line would be short-circuited at the end on the side of the reflector where there would therefore always be a maximum vibrational speed, known as the belly, whatever the frequency, in particular at the frequencies f o and f₁.

A la fréquence fo, comme la ligne est demi-onde elle ramène à son autre extrémité, c'est-à-dire au niveau du transducteur, une impédance égale à celle du réflecteur c'est-à-dire en l'occurrence 0. Il y a donc ainsi dans ce cas un ventre de vibrations à la jonction transducteur-ligne.At the frequency f o , since the line is half-wave it brings back to its other end, that is to say at the level of the transducer, an impedance equal to that of the reflector, that is to say in this case 0. There is thus in this case a belly of vibrations at the transducer-line junction.

A la fréquence f₁, comme la ligne est quart d'onde, elle ramène sur cette même interface une impédance infinie, qui correspond donc à un minimum de vitesse vibratoire, appelé noeud.At the frequency f₁, as the line is quarter-wave, it brings back to this same interface an infinite impedance, which therefore corresponds to a minimum of vibrational speed, called a node.

En ce qui concerne la lame 203, celle-ci est toujours quart d'onde à la fréquence fo et joue donc son rôle d'élargisseur de bande passante. A la fréquence f₁ par contre cette lame n'a plus qu'une longueur équivalente à 1/8e de longueur d'onde et l'adaptation à cette fréquence est donc bien différente de celle obtenue à la fréquence f₁, de sorte que la bande de fréquences obtenues autour de fo est plus étroite que celle autour de f₁. Cependant comme cette fréquence fo est utilisée pour l'imagerie DFM, un tel rétrécissement de la bande passante n'est pas gênant.Regarding the blade 203, it is always quarter wave at the frequency f o and therefore plays its role of bandwidth expander. On the other hand, at the frequency f₁, this blade only has a length equivalent to 1 / 8th of a wavelength and the adaptation to this frequency is therefore very different from that obtained at the frequency f₁, so that the band of frequencies obtained around f o is narrower than that around f₁. However, since this frequency f o is used for DFM imaging, such a narrowing of the bandwidth is not a problem.

En ce qui concerne l'impédance à choisir pour la lame 205, comme celle-ci est transparente pour la fréquence fo, il y a lieu de choisir cette impédance essentiellement compte-tenu des caractéristiques souhaitées pour la bande passante autour de f₁. On a déterminé que la fourchette la meilleure était comprise entre 3.10⁶ et 20.10⁶ ohms acoustiques.Regarding the impedance to choose for the blade 205, as this is transparent for the frequency f o , it is necessary to choose this impedance essentially taking into account the characteristics desired for the passband around f₁. It has been determined that the best range is between 3.10⁶ and 20.10⁶ acoustic ohms.

Bien entendu l'appareillage électronique associé à la sonde comprend des circuits qui permettent d'exploiter les deux fréquences fo et f₁ aussi bien à l'émission qu'à la réception.Of course, the electronic equipment associated with the probe includes circuits which make it possible to use the two frequencies f o and f₁ both on transmission and on reception.

On a représenté sur la figure 4 une coupe longitudinale d'une sonde selon l'invention fonctionnant à 5 MHz et à 2,5 MHz. On constate que cette sonde comporte un ensemble de transducteurs 201 revêtus de métallisations 202. Ces transducteurs sont obtenus par des coupes d'un bloc de céramique préalablement métallisé sur ses deux faces pour former les électrodes. Cet ensemble de transducteurs est collé sur la lame 205 qui est elle-même collée sur le réflecteur 204. La lame 203 vient elle-même recouvrir les transducteurs sur lesquels elle est également collée. On remarque que seul le bloc de transducteurs est formé d'éléments individuels, alors qu'aussi bien les lames 203 et 205 que le réflecteur 204 sont continus. Dans cet exemple représenté la barrette est linéaire, mais l'invention s'applique également aux barrettes présentant une autre forme et en particulier aux barrettes courbes.FIG. 4 shows a longitudinal section of a probe according to the invention operating at 5 MHz and at 2.5 MHz. It can be seen that this probe comprises a set of transducers 201 coated with metallizations 202. These transducers are obtained by sections of a block of ceramic previously metallized on its two faces to form the electrodes. This set of transducers is bonded to the blade 205 which is itself bonded to the reflector 204. The blade 203 itself covers the transducers on which it is also bonded. Note that only the transducer block is formed of individual elements, while both the blades 203 and 205 as the reflector 204 are continuous. In this example shown the bar is linear, but the invention also applies to bars having another shape and in particular to curved bars.

L'invention n'est pas limitée au cas des sondes fonctionnant sur deux fréquences dont l'une est la moitié de l'autre. Elle s'étend également aux sondes et de manière générale aux transducteurs acoustiques fonctionnant sur un ensemble de fréquences distinctes formant les fréquences centrales de bandes de fréquences séparées. Pour cela on multiplie le nombre de lames d'adaptation supplémentaires de façon à créer le nombre de degrés de liberté suffisant dans la fonction de transfert pour déterminer ces bandes passantes.The invention is not limited to the case of probes operating on two frequencies, one of which is half the other. It also extends to probes and in general to acoustic transducers operating on a set of distinct frequencies forming the center frequencies of separate frequency bands. For this, the number of additional adaptation blades is multiplied so as to create the number of degrees of freedom sufficient in the transfer function to determine these bandwidths.

Claims (8)

1. Transducteur acoustique multifréquences, notamment pour imagerie médicale, du type comportant au moins un transducteur piézoélectrique (101) destiné à être excité pour émettre des vibrations acoustiques, caractérisé en ce qu'il comprend au moins une lame d'adaptation (205) placée sur au moins l'une des faces de ce transducteur piézoélectrique pour permettre à l'ensemble de résonner sur au moins deux fréquences distinctes.1. Multifrequency acoustic transducer, in particular for medical imaging, of the type comprising at least one piezoelectric transducer (101) intended to be excited to emit acoustic vibrations, characterized in that it comprises at least one adaptation blade (205) placed on at least one of the faces of this piezoelectric transducer to allow the assembly to resonate on at least two distinct frequencies. 2. Transducteur selon la revendication 1, caractérisé en ce qu'il comporte en outre un réflecteur (204) servant de support au transducteur piézoélectrique (201), et que la lame d'adaptation (205) est située entre ce transducteur piézoélectrique et le réflecteur.2. Transducer according to claim 1, characterized in that it further comprises a reflector (204) serving as a support for the piezoelectric transducer (201), and that the adapter blade (205) is located between this piezoelectric transducer and the reflector. 3. Transducteur selon la revendication 2, caractérisé en ce que le réflecteur (204) présente une impédance sensiblement nulle, que les épaisseurs du transducteur piézoélectrique (201) et de la lame d'adaptation (205) sont demi-ondes à une première fréquence de résonance (fo) et sont donc quart d'onde à une deuxième fréquence de résonance (f₁) égale à la moitié de la première fréquence.3. Transducer according to claim 2, characterized in that the reflector (204) has a substantially zero impedance, that the thicknesses of the piezoelectric transducer (201) and of the adapter plate (205) are half-wave at a first frequency resonance (f o ) and are therefore quarter wave at a second resonance frequency (f₁) equal to half of the first frequency. 4. Transducteur selon la revendication 3, caractérisé en ce qu'il comprend en outre une autre lame d'adaptation (203) située sur l'autre face du transducteur piézoélectrique (201) par rapport à la première lame (205), dont l'épaisseur est quart d'onde à la première fréquence de résonance (fo) et dont l'impédance acoustique permet d'obtenir une largeur de bande déterminée autour de cette première fréquence.4. Transducer according to claim 3, characterized in that it further comprises another adapter blade (203) located on the other face of the piezoelectric transducer (201) relative to the first blade (205), the l thickness is quarter wave at the first resonant frequency (f o ) and whose acoustic impedance makes it possible to obtain a determined bandwidth around this first frequency. 5. Transducteur selon la revendication 4, caractérisé en ce que la première fréquence (fo) permet de l'utiliser en imagerie médicale en mode B, et que la deuxième fréquence (f₁) permet de l'utiliser en imagerie médicale DFM.5. Transducer according to claim 4, characterized in that the first frequency (f o ) allows to use it in medical imaging in mode B, and that the second frequency (f₁) allows to use it in medical imaging DFM. 6. Transducteur selon la revendication 5, caractérisé en ce que les première et deuxième fréquence (fo, f₁) sont sensiblement égales à 5 et 2,5 MHz.6. Transducer according to claim 5, characterized in that the first and second frequencies (f o , f₁) are substantially equal to 5 and 2.5 MHz. 7. Transducteur selon l'une quelconque des revendications 1 à 6, caractérisé en ce que l'impédance acoustique de la lame d'adaptation (205) est située entre 3.10⁶ et 20.10⁶ ohms acoustiques.7. A transducer according to any one of claims 1 to 6, characterized in that the acoustic impedance of the adaptation blade (205) is located between 3.10⁶ and 20.10⁶ acoustic ohms. 8. Transducteur selon l'une quelconque des revendications 1 à 7, caractérisé en ce qu'il comprend un ensemble de lames d'adaptation (205) permettant de le faire fonctionner sur un ensemble de fréquences distinctes.8. Transducer according to any one of claims 1 to 7, characterized in that it comprises a set of adaptation blades (205) allowing it to operate on a set of distinct frequencies.
EP88400583A 1987-03-19 1988-03-11 Multifrequency acoustic transducer, particularly for medical imaging Expired - Lifetime EP0285482B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88400583T ATE72609T1 (en) 1987-03-19 1988-03-11 MULTI-FREQUENCY ACOUSTIC TRANSDUCER, PARTICULARLY FOR MEDICAL IMAGE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8703839 1987-03-19
FR8703839A FR2612722B1 (en) 1987-03-19 1987-03-19 MULTI-FREQUENCY ACOUSTIC TRANSDUCER, ESPECIALLY FOR MEDICAL IMAGING

Publications (2)

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EP0285482A1 true EP0285482A1 (en) 1988-10-05
EP0285482B1 EP0285482B1 (en) 1992-02-12

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EP88400583A Expired - Lifetime EP0285482B1 (en) 1987-03-19 1988-03-11 Multifrequency acoustic transducer, particularly for medical imaging

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US (1) US4870972A (en)
EP (1) EP0285482B1 (en)
JP (1) JPS63255044A (en)
AT (1) ATE72609T1 (en)
DE (1) DE3868337D1 (en)
FR (1) FR2612722B1 (en)
NO (1) NO881125L (en)

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EP0550193A1 (en) * 1991-12-30 1993-07-07 Xerox Corporation Method for ejecting ink droplets in an acoustic ink printer and a piezoelectric transducer for an ink printer
DE4313229A1 (en) * 1993-04-22 1994-10-27 Siemens Ag Ultrasonic transducer arrangement with an attenuating body
EP0641606A2 (en) * 1993-09-07 1995-03-08 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof
FR2722358A1 (en) * 1994-07-08 1996-01-12 Thomson Csf BROADBAND MULTI-FREQUENCY ACOUSTIC TRANSDUCER
US5582177A (en) * 1993-09-07 1996-12-10 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof
US5743855A (en) * 1995-03-03 1998-04-28 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof

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US5400788A (en) * 1989-05-16 1995-03-28 Hewlett-Packard Apparatus that generates acoustic signals at discrete multiple frequencies and that couples acoustic signals into a cladded-core acoustic waveguide
US5212671A (en) * 1989-06-22 1993-05-18 Terumo Kabushiki Kaisha Ultrasonic probe having backing material layer of uneven thickness
GB2268806B (en) * 1992-07-14 1997-02-26 Intravascular Res Ltd Methods and apparatus for the examination and treatment of internal organs
US5351546A (en) * 1992-10-22 1994-10-04 General Electric Company Monochromatic ultrasonic transducer
GB2293240B (en) * 1994-09-15 1998-05-20 Intravascular Res Ltd Ultrasonic visualisation method and apparatus
WO1996016600A1 (en) * 1994-11-30 1996-06-06 Boston Scientific Corporation Acoustic imaging and doppler catheters and guidewires
US5558623A (en) * 1995-03-29 1996-09-24 Rich-Mar Corporation Therapeutic ultrasonic device
US6254542B1 (en) 1995-07-17 2001-07-03 Intravascular Research Limited Ultrasonic visualization method and apparatus
US5825117A (en) * 1996-03-26 1998-10-20 Hewlett-Packard Company Second harmonic imaging transducers
JP3573567B2 (en) * 1996-04-12 2004-10-06 株式会社日立メディコ Ultrasonic probe and ultrasonic inspection apparatus using the same
DE29708338U1 (en) * 1997-05-12 1998-09-17 Dwl Elektron Systeme Gmbh Multifrequency ultrasound probe
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FR2815723B1 (en) * 2000-10-24 2004-04-30 Thomson Csf SYSTEM METHOD AND PROBE FOR OBTAINING IMAGES VIA A BROADCAST EMITTED BY AN ANTENNA AFTER REFLECTION OF THESE WAVES AT A TARGET ASSEMBLY
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0550193A1 (en) * 1991-12-30 1993-07-07 Xerox Corporation Method for ejecting ink droplets in an acoustic ink printer and a piezoelectric transducer for an ink printer
DE4313229A1 (en) * 1993-04-22 1994-10-27 Siemens Ag Ultrasonic transducer arrangement with an attenuating body
EP0641606A2 (en) * 1993-09-07 1995-03-08 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof
EP0641606A3 (en) * 1993-09-07 1996-06-12 Acuson Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof.
US5582177A (en) * 1993-09-07 1996-12-10 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof
US5976090A (en) * 1993-09-07 1999-11-02 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof
FR2722358A1 (en) * 1994-07-08 1996-01-12 Thomson Csf BROADBAND MULTI-FREQUENCY ACOUSTIC TRANSDUCER
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US5743855A (en) * 1995-03-03 1998-04-28 Acuson Corporation Broadband phased array transducer design with frequency controlled two dimension capability and methods for manufacture thereof

Also Published As

Publication number Publication date
JPS63255044A (en) 1988-10-21
NO881125L (en) 1988-09-20
US4870972A (en) 1989-10-03
FR2612722B1 (en) 1989-05-26
EP0285482B1 (en) 1992-02-12
ATE72609T1 (en) 1992-02-15
DE3868337D1 (en) 1992-03-26
NO881125D0 (en) 1988-03-14
FR2612722A1 (en) 1988-09-23

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