JPH0880302A - Ultrasonic probe and ultrasonic diagnostic device using the same - Google Patents

Abstract

PURPOSE: To differentiate the tissues in the deep parts in a living body without executing enucleation even in the case of deep part from surface by forming a structure to diffuse part of the elastic wave energy to propagate the elastic waves generated in an electroacoustic converter into the examinee on the surface of a pricking needle. CONSTITUTION: A piezoelectric thin-film layer 10, comb-shaped electrodes 12 to 15 and a protective layer 16 are formed on the base part 11 of a needle-shaped probe 1. The elastic waves are generated in the piezoelectric thin-film layer 10 to propagate the elastic energy in the longitudinal direction of the needle when an ultrasonic pulse signal voltage having a prescribed central frequency is supplied to the set of pairs 12 and 13 of the comb-shaped electrodes. The elastic energy dissipates gradually to the tissues via the protective film 16 when the biotissues exist on the propagation route. This energy changes dependently upon the wavelengths of the elastic waves at which the energy dissipation quantity is generated when the average periodic structure of the biotissues varies. The frequency dependency of the insertion loss is, thereupon, detected when the frequency of the electric field to be impressed is changed. This characteristic reflects the periodic structure of the biotissues. The tissue differentiation is thus executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe for obtaining tissue information of a living body using ultrasonic waves and an ultrasonic diagnostic apparatus using the ultrasonic probe, and particularly to the vicinity of a region of interest by puncturing a needle. The present invention relates to an ultrasonic probe suitable for performing the tissue discrimination, and an ultrasonic diagnostic apparatus using the ultrasonic probe.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic wave is transmitted from a body surface of a subject to the inside of the subject, a reflected wave from the body is received, and ultrasonic image diagnosis is performed based on the received signal. Diagnostic devices have become widely known. In the current technology, the resolution of these ultrasonic diagnostic apparatuses is about several mm in the deep part of the living body, and when an abnormality is suspected in the tomographic image, a biopsy called biopsy is performed. In this test, the biopsy needle is punctured into the subject under observation of a tomographic image,
The cell lesion at the site is estimated by actually collecting and inspecting the cells at the site where the lesion is suspected. This method is advantageous in that it is less invasive to the subject and the burden can be reduced as compared with the case of removing by open surgery. However, for example, the diagnostic criterion is not a small amount of cells, but in many cases it is necessary to inspect its properties over a predetermined size (a few mm), and if the site suspected of abnormality is deep from the body surface, etc., After all, there is no definite method other than the removal by open surgery. In view of such problems,
For example, as disclosed in Japanese Unexamined Patent Publication No. 2-206449, a method in which a transducer for transmitting and receiving ultrasonic waves is provided at the tip of a needle that punctures the inside of a subject, and information such as attenuation of a region of interest in the subject is obtained. Is proposed. These conventional techniques form a transducer for transmitting and receiving ultrasonic waves on the surface of the needle, emit ultrasonic waves into the subject to receive reflection from a living body, or arrange the transducers to face each other. Ultrasonic waves were transmitted and received while sandwiching a part.

[0003]

Generally, in order to perform the measurement capable of distinguishing the characteristics of cell tissues of a living body, an ultrasonic wave of a very high frequency having a wavelength similar to the average size of cells is used. There is a need. For example, when an ultrasonic pulse having a center frequency of about 10 microns is transmitted / received at a suspected lesion, it is 150 MHz.
It is necessary to transmit and receive high frequency ultrasonic pulses.
However, it has been extremely difficult to transmit such an ultrasonic pulse having a high frequency because a significant attenuation occurs in the living body. Also, when ultrasonic waves are radiated from the oscillator into the subject and reflections from the living body are received, it is difficult to temporally separate the reverberation component of the oscillator from the reflected wave reception signal during transmission. When the transmission attenuation between the transducers arranged facing each other is not obtained, it is difficult to measure unless the distance between the opposing transducers is very small due to the significant attenuation in the living body. there were. Therefore, as described above, in order to obtain information over a range of an outer diameter of about several mm at a suspected lesion, a sufficient received signal strength cannot be obtained,
There is a problem that the reliability of measurement is reduced. The present invention has been made in view of the above circumstances, and an object thereof is to solve the problems as described above in the related art, and even when the site suspected of being abnormal is deep from the body surface, An object of the present invention is to provide an ultrasonic probe capable of performing tissue discrimination without extracting it and an ultrasonic diagnostic apparatus using the same.

[0004]

The above objects of the present invention are as follows:
A needle-shaped ultrasonic probe provided with an electroacoustic transducer that converts an electric signal into an elastic wave, in which an elastic wave generated by the electroacoustic transducer is propagated and a part of the propagating elastic wave energy is transferred. A structure that gradually dissipates into the contacting subject,
An ultrasonic probe formed on the surface of a needle-shaped ultrasonic probe, the ultrasonic probe, and a processing means for processing a signal from the ultrasonic probe. Is achieved by an ultrasonic diagnostic apparatus. More specifically,
The surface of the needle-shaped ultrasonic probe is provided with a piezoelectric layer and a comb-shaped electrode group, and an elastic wave is generated on the surface of the needle by applying an electric field between the comb-shaped electrodes, or is transmitted and received on the surface of the needle. An ultrasonic probe provided with a means, and a means for measuring the insertion loss of the signal by changing the frequency of the electric signal applied to the electrodes of the ultrasonic probe, and the frequency dependence of the insertion loss. It is achieved by an ultrasonic diagnostic apparatus adapted to perform tissue discrimination.

[0005]

In the ultrasonic probe according to the present invention, an elastic wave is generated from the piezoelectric layer formed of a thin film by applying an electric field between the comb electrodes. This elastic wave is composed of a surface acoustic wave (SAW) or an elastic wave propagating in an acoustic waveguide formed by the shape of a thin film. These elastic waves propagate on the surface of the needle and are again converted into electric signals by the piezoelectric property. When the biological tissue is in contact with the propagation path of the elastic wave or indirectly through another layer, the energy of the elastic wave is dissipated into the biological tissue, and the amount of the dissipation is the electrical energy of the entire element. Change the insertion loss (hereinafter also simply referred to as "insertion loss"). If the average periodic structure of the living tissue in contact (for example, the average diameter of cells that are close to spherical) is different, the amount of energy dissipated into the living tissue changes depending on the wavelength of the elastic wave that is generated. To do. The frequency dependence of the insertion loss can be detected by changing the frequency of the electric field applied between the comb-shaped electrodes or by configuring the comb-shaped electrodes with different intervals, and the average cell diameter of the living tissue with which the characteristics are in contact can be detected. Since it reflects the periodic structure such as, tissue discrimination can be performed. In the ultrasonic probe according to the present invention, since the comb electrode configuration is provided on the surface of the needle to be punctured, the contact section length with the biological tissue can be configured to be relatively long compared to the wavelength. Highly accurate evaluation is possible.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, a specific measurement procedure using the ultrasonic probe according to the embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a cross-sectional view for explaining how to perform a puncture while capturing a tomographic image. In the figure, 1 is a needle-shaped probe having an outer diameter of about 1 to 2 mm, and the needle-shaped probe 1 is a jig attached to a linear probe 81 for observing a puncture site. It is configured to slide along. Although a means for transmitting / receiving and analyzing a signal is connected to the end of the needle probe 1, the illustration is omitted in FIG. In addition, the linear probe 81 is in contact with the body surface 82 of the subject, and captures a region of interest 83, which is considered to be a diseased part in the organ 85, in the real-time scanning visual field 84. Under such tomographic image observation, the needle probe 1
Is punctured from the body surface 82 to the site of interest 83. Here, the needle probe 1 has a sliding structure capable of translation and rotation. Accordingly, the inspector can bring the detection portion of the needle probe 1 into contact with the attention site 83 and evaluate the acoustic characteristics of the cell.

Next, FIG. 1 shows a detailed structure of a detection portion near the tip of the needle probe 1. As shown in FIG. 1, the needle-shaped probe 1 has a structure in which different layers are laminated on a chamfered side surface of a cylinder. The base 11 that holds the whole as a needle is made of metal, hard resin, silicon, or the like. The piezoelectric thin film layer 10 is formed on the base portion 11. The piezoelectric thin film layer 10 is made of zinc oxide or lead titanate formed by sputtering or the like. Further, layers of comb-shaped electrodes 12 to 15 are formed on the piezoelectric thin film layer 10,
Further, a protective film 16 that covers these two layers is formed. When an ultrasonic pulse signal voltage having a center frequency of about 150 MHz is supplied to the pair of comb-shaped electrodes 12 and 13 from a transmission circuit (not shown), elastic waves are generated in the piezoelectric thin film layer 10. This elastic wave is a surface acoustic wave or a bulk wave having the piezoelectric thin film layer 10 itself as a waveguide, and propagates elastic energy in the longitudinal direction of the needle. At this time, since the piezoelectric thin film layer 10 and the base portion 11 have different acoustic impedances, the piezoelectric thin film layer 10 itself serves as an acoustic waveguide.

The amplitude directions of these elastic waves include both the longitudinal direction of the needle and the thickness direction of the piezoelectric thin film layer 10. The energy of the propagated elastic waves reaches the pair of comb-shaped electrode pairs 14 and 15 which are present in the longitudinal direction, and a part thereof is converted into electric energy again to become a reception signal. Here, if a living tissue exists on the propagation path,
The elastic wave energy is gradually dissipated into the tissue through the very thin protective film 16 described above. Here, if the average periodic structure of the living tissue with which the needle probe 1 is in contact with the protective film 16 is different (for example, the average diameter of cells having a nearly spherical shape), the energy into the living tissue is changed. The amount of dissipation changes depending on the wavelength of the generated elastic wave. The frequency dependence of the insertion loss can be detected by changing the frequency of the electric field applied between the comb-shaped electrodes or by providing the comb-shaped electrodes with different intervals. Since the periodic structure is reflected, tissue discrimination can be performed. In particular, the ultrasonic probe according to the present embodiment has a comb-shaped electrode configuration on the surface of the needle to be punctured, so that the contact section length with the biological tissue can be configured to be relatively longer than the wavelength, Highly accurate evaluation is possible.

FIG. 4 shows an example of the configuration of an apparatus for detecting the frequency dependence of insertion loss based on this principle. The extension of the comb-shaped electrodes 12 to 15 in the detection portion of the needle probe 1 is
The root portion of the needle is connected to the transmitting amplifier 41 and the receiving amplifier 42. The output of the wave transmission circuit 43 is output to the needle probe 1 via the wave transmission amplifier 41. The signal waveform generated by the transmission circuit can be designed in various ways such as a frequency-swept chirp signal or pulse signal. The output of the wave receiving amplifier 42 becomes the input of the wave receiving circuit 44. The output of the wave receiving circuit 44 becomes the input of the frequency analyzer 45, and the frequency dependence of attenuation is measured. The frequency analyzer 45 includes a measurement circuit for general frequency analysis such as frequency-shifting the received signal to a low frequency and performing bandpass filtering. The measurement result is shown to the inspector by the display 46,
For example, the ratio of the attenuation in the living body to the attenuation when the needle probe 1 is placed in water is obtained, and the frequency characteristic is displayed. The series of operations are defined by the control means 47.

FIG. 2 shows another structural example of the needle probe 1 according to the present invention. In the layered structure of the needle probe 1, the layers of the comb-shaped electrodes 12 to 15 and the piezoelectric thin film layer 10 may be formed in the reverse order. The sectional view of FIG. 2A has the same configuration as that of FIG. The piezoelectric thin film layer 10 is first formed on the base portion 11. In this configuration, by using the crystalline material for the base portion 11, the piezoelectric thin film layer 10 can be epitaxially grown, and there is an advantage in manufacturing that an alignment film having a large electromechanical coupling coefficient can be formed by sputtering or the like. On the contrary, as shown in the sectional view of FIG. 2B, the layers of the comb-shaped electrodes 12 to 15 may be first formed on the base portion 11. In this case, since the subject side surface of the piezoelectric thin film layer 10 can be formed relatively flat, it does not exist between the biological tissue in contact with the electrode and the piezoelectric thin film layer 10. It is possible to obtain an ideal configuration in which unnecessary load of is reduced. FIG. 6 shows still another configuration example of the needle probe 1 according to the present invention. In the configuration example shown in FIG. 6, the layered configuration shown in FIG. 2 has a structure in which unevenness is provided in a portion to be contacted with a living body for detection. This structure is modified so as to increase the area of the contact surface when the needle is inserted into the living tissue.

In the configuration shown in FIG. 7, the tip of the needle probe 1 has a conical shape. The probe of the present invention has a problem that it does not give a correct measurement result when the property of the inner surface of the cavity generated in the living body by penetrating the needle significantly impairs the periodic structure of cells. For this reason, it is necessary to make the tip shape of the needle as sharp as possible and not unnecessarily disturb the structure of cells on the inner surface of the cavity during the process of inserting the needle. From such a situation, it is very suitable that the tip has a conical shape. Some examples of the pattern shapes of the comb-shaped electrodes provided in contact with the piezoelectric thin film layer 10 will be shown in FIG. 3 as the next embodiment. In the figure, reference numerals 12 to 15 are for allowing the simple comb-shaped electrode pairs shown in FIG. 1 to face each other and transmitting from one side and receiving from the other side. Further, 31 and 32 use a single comb-shaped electrode pair and have two terminals.

In this case, the measuring circuit has the configuration shown in FIG. In the configuration of FIG. 4 and the configuration of FIG.
Is provided in place of the wave transmission circuit 43 and the wave reception circuit 44, and a frequency analysis circuit 45 for measuring the electrical impedance between the terminals 31 and 32 from the needle probe 1 is provided. The pattern of the comb-shaped electrode pair can be freely designed as shown in 33 to 38 of FIG. In 33 and 34, the pitch between the electrodes is sequentially changed, so that the wavelength of the generated elastic wave can be expanded. In the cases of 35 and 36, it is possible to perform spatial weighting on the envelope shape of the generated wave. Similarly, in the cases of 37 and 38, the wavelength of the generated elastic wave can be expanded. By designing such electrodes, the frequency characteristics of the elastic wave to be measured can be designed. It is needless to say that each of the above embodiments is an example of the present invention and the present invention should not be limited to this.

[0013]

As described above in detail, according to the present invention, even when a site suspected of being abnormal is deep from the body surface, it is possible to perform tissue discrimination in the deep part of a living body without removing it. This has the remarkable effect of realizing an ultrasonic probe and an ultrasonic diagnostic apparatus using the same. In detail, without incising and extracting living tissue existing in the deep region of the living body, tissue discrimination using ultrasonic attenuation characteristics at a very high frequency reflecting its average periodic structure is performed with low invasiveness. It can be carried out. In particular, since the contact section length with the biological tissue can be configured to be relatively long compared to the conventional technology,
The effect is that highly accurate evaluation is possible.

[Brief description of drawings]

FIG. 1 is a perspective perspective view for explaining a structure of a needle probe detection unit according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the structure of the needle probe detection unit shown in FIG.

FIG. 3 is a diagram illustrating another configuration example of the comb electrode shape of the needle probe according to the embodiment.

FIG. 4 is a diagram (No. 1) for explaining an example of the measurement system in the case where the needle-shaped probe according to the example has two pairs of comb-shaped electrodes.

FIG. 5 is a diagram (No. 2) for explaining an example of the measurement system in the case where the needle probe according to the example has a two-terminal comb-shaped electrode.

FIG. 6 is a cross-sectional view illustrating another embodiment of the needle probe detection unit.

FIG. 7 is a perspective perspective view for explaining another embodiment of the tip shape of the needle probe.

FIG. 8 is a diagram illustrating a state in which a needle probe according to the present invention is punctured while capturing an ultrasonic tomographic image.

[Explanation of symbols]

 1 Needle probe 10 Piezoelectric thin film layer 11 Base part 12-15, 31-38 Comb-shaped electrode 16 Protective film 41 Transmission amplifier 42 Receiving amplifier 43 Transmission circuit 44 Receiving circuit 45 Frequency analyzer 46 Indicator 47 Control Means 81 Linear probe 82 Body surface 83 Attention site 85 Organ

Claims (6)

[Claims] 1. A needle-shaped ultrasonic probe having an electroacoustic transducer for converting an electric signal into an elastic wave, wherein the elastic wave generated by the electroacoustic transducer is propagated and propagated. An ultrasonic probe having a structure in which a part of energy is dissipated in a contacted object on a surface of a puncture needle. 2. The ultrasonic probe according to claim 1, wherein the electroacoustic transducer is composed of a piezoelectric thin film and an electrode formed on the piezoelectric thin film. 3. The ultrasonic probe according to claim 2, wherein the electrodes are comb-shaped or interdigital electrodes, and the elastic waves are mainly surface waves. 4. An ultrasonic diagnostic apparatus comprising the ultrasonic probe according to claim 1 and a processing unit for processing a signal from the ultrasonic probe. 5. The ultrasonic diagnostic apparatus according to claim 4, further comprising frequency analysis means for measuring electrical insertion loss or frequency dependency of impedance of the ultrasonic probe. 6. A means for puncturing the ultrasonic probe into a living body and capturing a signal from the ultrasonic probe punctured in the living body with a real-time image. 5. The ultrasonic diagnostic apparatus according to item 5.