JP3860862B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus that analyzes an ultrasonic response signal generated by applying a pulse voltage to an ultrasonic transducer and detects an acoustic structure over a surface and a deep portion of a test object.
[0002]
[Prior art]
In general, an ultrasonic diagnostic apparatus that detects an acoustic structure of a test object by analyzing an ultrasonic response signal generated by applying a pulse voltage to an ultrasonic transducer is practical in the medical field and the nondestructive inspection field. It has become.
[0003]
Various structures and driving methods have been developed for these ultrasonic transducers. For example, in the medical field, there is a rapid increase in demand for an ultrasonic endoscope that can diagnose an abnormality of a living tissue without inserting an ultrasonic transducer into a body cavity and being obstructed by subcutaneous fat or ribs. Furthermore, an ultrasonic diagnostic apparatus has been proposed in which an ultrasonic transducer catheter is inserted into a blood vessel to diagnose the presence or absence of a thrombus deposited in the blood vessel and the hardening of the blood vessel. On the other hand, an ultrasonic diagnostic apparatus for diagnosing the viscoelastic characteristics of the surface of a living tissue is also called a tactile sensor apparatus, and research and development are being promoted.
[0004]
For example, USP 5,454,373 discloses an ultrasound transducer catheter. This ultrasonic transducer catheter has a structure as shown in FIGS. 13A and 13B, that is, rotates a transducer assembly 103 that is rotatably arranged via a bearing 102 at the tip of a flexible tubular structure 101. By rotating with the rotation of the drive shaft 104, the ultrasonic beam is mechanically scanned to obtain an ultrasonic tomographic image.
[0005]
The ultrasonic transducer 105 used in this apparatus has a structure as shown in FIG. 13, that is, an ultrasonic transmission lens 108 on the ultrasonic transmission / reception side surface of a piezoelectric element 107 of about 0.2 mmφ, and a backing material on the back side. 109 is joined. With such a structure, the shape of the thrombus 112 attached to the blood vessel wall 111 in the vicinity of the blood vessel bifurcation 100 can be drawn, and the ultrasonic wave is detected from the detection time of the ultrasonic echo signal and the amplitude of the ultrasonic echo signal. It is a composition of images.
[0006]
On the other hand, the applicant of the present invention has proposed a tactile sensor for detecting viscoelasticity of blood vessels in Japanese Patent Laid-Open No. 6-273396. This tactile sensor extracts vibration response parameters when an impulse voltage is applied to an ultrasonic transducer as shown in FIG. 14 (piezoelectric body 107a shown in FIG. 15), and processes and calculates these parameters. Is a tactile sensor device that provides a tactile sensation corresponding to the viscoelasticity of both the surface and the deep part of the object and is capable of deep diagnosis. Here, since tactile sensing is to detect the hardness of the surface of the object, the proposal of this tactile sensor is an ultra-thin sensor that detects the acoustic structure over the surface and depth of the object to be examined. It can be rephrased as an ultrasonic diagnostic apparatus.
[0007]
[Problems to be solved by the invention]
As described above, Japanese Patent Laid-Open No. 6-273396 proposes an ultrasonic diagnostic apparatus that detects an acoustic structure over the surface and depth of an object to be examined. However, the following problems can be improved. Thus, a more preferable ultrasonic diagnostic apparatus can be provided.
[0008]
First, when detecting information on the acoustic structure over the surface and deep part from the vibration response waveform when the impulse voltage is applied, the surface information, that is, the tactile information is included in the ultrasonic response signal immediately after the impulse voltage is applied. The deep information is included in an ultrasonic response signal, that is, an echo signal subsequent to the ultrasonic response signal immediately after.
[0009]
These ultrasonic response signals are converted into high-frequency pulse signals by the piezoelectric effect of the piezoelectric vibrator, but an impulse voltage signal is superimposed on the high-frequency pulse signal converted from the ultrasonic response signal immediately after that, and is observed. For this reason, it is difficult to detect a change in the ultrasonic response signal immediately after the object contact from the superimposed signal. That is, it is difficult to detect surface information, that is, tactile information with high sensitivity.
[0010]
Accordingly, there is a problem that it is necessary to separately detect and analyze a high-frequency pulse signal corresponding only to the ultrasonic response signal immediately after applying the impulse voltage from the high-frequency pulse signal on which the impulse voltage signal is superimposed.
Then, this invention aims at providing the ultrasonic diagnosing device which can detect an acoustic structure over the surface and deep part of a test subject.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, the present inventionAn ultrasonic transducer comprising a piezoelectric vibrator, a pulser / receiver for applying a pulse voltage to the ultrasonic transducer and receiving an ultrasonic response signal generated in the ultrasonic transducer by the application of the pulse voltage, and an output signal of the pulser / receiver In the ultrasonic diagnostic apparatus that detects the acoustic structure of the test object by analyzing the output signal, the ultrasonic response signal immediately after the pulse voltage is applied is separated by analyzing the output signal. Has a means to detect and analyzeAn ultrasound diagnostic apparatus is provided.
[0013]
  The ultrasonic diagnostic apparatus configured as described aboveA pulse voltage is applied to the ultrasonic transducer, and only the ultrasonic response signal immediately after the pulse voltage is applied is separated, detected, and analyzed to detect the acoustic structure of the test object.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A first embodiment of an ultrasonic diagnostic apparatus according to the present invention will be described with reference to FIGS. Here, FIG. 1 is a diagram showing a configuration example of the ultrasonic diagnostic apparatus of the first embodiment, FIG. 2 is a diagram schematically showing an ultrasonic response waveform, and FIG. 3 is an internal view of a trapezoidal pulse generator. FIG. 4 is a diagram illustrating a configuration example, FIG. 4 is a diagram for explaining the principle of dynamic damping, and FIG. 5 is a method used for a normal ultrasonic diagnostic apparatus for explaining the present embodiment. It is a figure which shows the ultrasonic response waveform obtained.
[0018]
In this ultrasonic diagnostic apparatus, for example, the maximum voltage is 10 V or less, the rise time t_r Is 20 ns or less, voltage holding time t_w Is variable from 20 to 100ns, fall time t_f Trapezoidal pulse generator 1 that repeatedly generates a trapezoidal pulse that can be varied in a period of 20 to 200 ns, and an output signal 16 of this trapezoidal pulse generator 1 is branched into two, and two equivalent signals 17a and 17b A high-frequency amplifier 3 for amplifying the signal 17a to 50 to 100 V, an ultrasonic transducer 4 to which the amplified signal 18 amplified by the high-frequency amplifier 3 is directly applied, and an ultrasonic transducer Among the high-frequency pulse voltage signals 19a and 19b described later outputted by 4, the attenuator 5 for attenuating the voltage of the high-frequency pulse voltage signal 19 a to a low voltage, the gate circuit 59 for removing the response signal immediately after the pulse voltage signal 19 b, The delay circuit 7 for delaying the signal 17b and the difference between the signal 21 from the delay circuit 7 and the signal 20 from the attenuator 5 The differential amplifier 6, the FFT circuit 9 for combining the output signal of the differential amplifier 6 and the output signal of the high frequency amplifier 8 for waveform analysis, and the gate timing of one output signal 23 from the differential amplifier 6. Based on the signal from the unit 10, the gate circuit 11 that passes for a predetermined time and the maximum value of the signal 25 that passes through the gate circuit 11 are detected, and the output signal 26 is related to the falling time of the trapezoidal pulse. The maximum value detector 12 that is automatically input to the trapezoidal pulse waveform control unit 15 of the next stage as the n value and a plurality of n values related to the falling time of the trapezoidal pulse are stored in advance, and a manual used for optimizing the trapezoidal waveform A setting circuit 13; a change-over switch 14 for selecting either the signal 26 of the maximum value detector 12 or the n-value from the manual setting circuit 13; A trapezoidal pulse waveform control unit 15 that controls the trapezoidal pulse generator 1 based on the signal is configured.
[0019]
The high-frequency pulse voltage signals 19a and 19b are superimposed signals of the applied voltage signal 18 and the high-frequency pulse voltage signal obtained by piezoelectrically converting the ultrasonic response signal, and are generated immediately after the applied voltage signal 18 is applied. The immediately following high frequency pulse voltage signal is a superposition of the immediately following high frequency pulse voltage signal (waveform 29 shown in FIG. 2) obtained by piezoelectric conversion of the immediately following ultrasonic response signal and the applied voltage signal 18 (same as the waveform 30 shown in FIG. 2). It is a signal and has a fairly complex waveform (not shown). In FIG. 1, a portion surrounded by a dotted line with the attenuator 5, the differential amplifier 6, and the delay circuit 7 indicates a circuit block unit for separating the immediately after ultrasonic response from the applied voltage signal 18.
[0020]
Next, FIG. 3 shows a specific circuit configuration example of the trapezoidal pulse generator 1 and will be described. This circuit is a specific circuit example for realizing dynamic damping described later, and has a circuit configuration that is not used in a conventional ultrasonic diagnostic apparatus.
[0021]
In the trapezoidal pulse generator 1, the output portion of the rectangular wave generator 37 is connected to an emitter follower circuit composed of a transistor 38 and an emitter resistor 46, and its output is the rise time of a trapezoidal pulse composed of a diode 39 and a resistor 40. The setting unit 35 is connected to a parallel circuit including a trapezoidal pulse falling time setting unit 36 including a diode 41, a resistor 42, and an FET 43.
[0022]
Further, these outputs are connected to an emitter follower circuit comprising a transistor 45 and an emitter resistor 47 via an integrating capacitor 44, the other of which is grounded, and led to the trapezoidal pulse generator output section. The gate of the FET is connected so that a control signal 28 from the trapezoidal pulse waveform control circuit 15 is input. This control signal 28 is converted into a duty setting signal 48 in the trapezoidal pulse waveform control unit 15 by a signal from the m value setting unit 10 that determines the pulse width of the trapezoidal pulse, and then input to the duty setting unit 49. Then, the generated rectangular wave duty ratio setting signal is sent to the rectangular wave generator 37.
[0023]
The operation of the ultrasonic diagnostic apparatus of the first embodiment configured as described above will be described. This embodiment has the following features.
As a first feature, the ultrasonic response signal immediately after the trapezoidal pulse is applied to the ultrasonic transducer is separated and detected. The second characteristic is that the ultrasonic response signal immediately after the above has an area where no mechanical damping is performed and the ultrasonic pulse has a short pulse width. As a third feature, the signal immediately after the ultrasonic response signal is incident on the object, reflected by the boundary surface with the abnormal tissue in the object, and returned as an echo signal to the ultrasonic transducer is also received. And the echo signal or the relationship between the echo signals can be analyzed through FFT.
[0024]
According to this embodiment, as a method for realizing the first feature, the ultrasonic response signal separation is performed immediately after electrical signal processing. Hereinafter, the operation will be described in detail with reference to FIGS.
[0025]
First, the pulse width t is determined by the control signal 28 from the trapezoidal pulse waveform controller 15._w And fall time t_f The trapezoidal pulse signal 16 that is optimally controlled is branched by the branch circuit 2 into two equivalent branch signals 17a and 17b. Among these branch signals, the branch signal 17 a is amplified to 50 to 100 V by the high frequency amplifier 3, and the amplified signal 18 is applied to the ultrasonic transducer 4. As shown in FIGS. 6 (a) and 6 (b), the ultrasonic transducer 4 made of a piezoelectric vibrator has no back surface load material, so that ultrasonic vibration is generated near the resonance frequency of the piezoelectric vibrator. .
[0026]
This ultrasonic vibration is generated at the boundary surface between the ultrasonic response signal 29 generated immediately after the trapezoidal pulse voltage is applied and the superimposed signal having a large amplitude between the applied voltage signal 30 and the target object, and is attenuated. The ultrasonic signals 31, 32, 33, and 34 that are reflected and observed as echo signals become signals 19a and 19b synthesized on the time axis. This signal 19a is input to one input terminal of the differential amplifier 6 as an attenuated signal 20 that has been attenuated by the attenuator 5 to a voltage of the same level as the signal 17a.
[0027]
On the other hand, the other output signal 17 b in the branch circuit 2 is input to the other input terminal of the differential amplifier 6 through the delay circuit 7 in order to correct the phase delay caused by the high frequency amplifier 3 and the attenuator 5. The differential amplifier 6 outputs a signal 23 from which the applied voltage signal has been removed.
[0028]
As for the signal 19b, only the echo signal from which the response signal is removed immediately after by the gate circuit 59 is detected. The echo signal and the signal 22 are combined to be a signal in the same time domain to form a combined signal 24, which is analyzed by the FFT circuit 9. In the first operation, the ultrasonic transducer 4 is in a no-load state, the echo signal is not detected at all, only the immediate response signal 22 is detected, and the n value is set so that the immediate ultrasonic response waveform has an optimum shape. Set manually. At the same time, the FFT analysis result in that state, that is, the center frequency f of the ultrasonic response signal immediately after₀ , Maximum amplitude A₀ , Specific bandwidth α₀ Etc. are stored.
[0029]
Next, an object load is applied. When the object is a viscoelastic body, it is known that it is equivalently represented by a series connection of an inductance L and a DC resistance R, and this is inserted in series into a series resonance circuit of an equivalent circuit of a piezoelectric vibrator. As a result, the resonance resistance increases and the resonance frequency decreases. This is immediately after the maximum amplitude A of the ultrasonic response signal.₀ Decreases and the center frequency f₀ On the contrary, it can be detected from the state of this change how much viscoelastic load is applied.
[0030]
This detection sensitivity is the maximum amplitude A in the no-load state.₀ Is preferably not damped at all. In order to realize this, a method called dynamic damping (DD) is used.
[0031]
This DD method is usually used to brake mechanical vibrations by applying other mechanical vibrations, but a conventional back load material is formed on an ultrasonic transducer to form mechanical, static, In contrast to a method that is used for a normal ultrasonic diagnostic apparatus that is structurally damped, in the present embodiment, in the sense that only a wave having a predetermined wave number or more is electrically damped electrically in a drive waveform. This is called dynamic damping. What is important is that the dynamic damping region (DD region) 57 shown in FIG. 4 is greatly damped, and as a result, the pulse width of the entire pulse is shortened. However, in the immediately preceding non-damping region 56, it is completely damped. Therefore, surface information sensing (tactile sensing) can be realized with high sensitivity by using the ultrasonic response signal immediately after that. An ultrasonic response waveform obtained by a method used in a normal ultrasonic diagnostic apparatus in which a back load material is formed on an ultrasonic transducer and mechanically, statically, or structurally is damped is a signal 59a shown in FIG. In this way, the pulse width is shortened by damping, but at the same time, the entire ultrasonic pulse is damped, and the maximum amplitude is already damped greatly, which causes a highly sensitive change in the maximum amplitude and the center frequency. I can't.
[0032]
Here, the principle of the DD method will be described in detail with reference to FIG.
When the step-up voltage 50 is applied to the piezoelectric vibrator in which the back load material is not formed, the ultrasonic vibration 51 having the maximum amplitude ampA is excited from the step-up time T1. Further, when the step-down voltage 52 is applied, the ultrasonic vibration 53 having the maximum amplitude ampB and the phase inverted from the step-down time T2 is excited. This is based on the premise that the frequency component of the sudden change part of the applied voltage at time T2 is equal to or higher than the resonance frequency of the piezoelectric vibrator._f ), And the maximum amplitude is attenuated to amp B.
[0033]
Voltage holding time t obtained by synthesizing the above two step-like applied voltages_w It can be seen that an ultrasonic pulse 55 having a non-damping region 56 and a damping region 57 can be obtained by applying a trapezoidal pulse 54 with
[0034]
In order to obtain an ultrasonic pulse with a short pulse width having such a non-damping region, the rise time of the trapezoidal pulse is set to t_r , The voltage holding time is t_w , T_f , The inverse of the resonance frequency of the piezoelectric vibrator is t_p Then,
t_r <T_p <T_f
t_w = N × t_p (N = 1-5)
t_f = M × t_p (M = 1-10)
Is a preferable condition. When n> 5, the pulse width becomes too long, and the resolution in the depth direction decreases. However, when m> 10, the frequency component of the sudden change portion of the applied voltage at the time T2 described above does not become higher than the resonance frequency of the piezoelectric vibrator, and the DD effect is greatly reduced.
[0035]
Next, the operation of the trapezoidal pulse signal generator for generating the optimum trapezoidal pulse signal will be described in detail with reference to FIG.
According to the control signal from the duty setting device 49, the pulse width t_w The rectangular wave generator 37 generates a rectangular wave having a repetition frequency of 1 k to 10 kHz. This generated signal is transmitted through an emitter follower circuit composed of a transistor 38 and an emitter resistor 46, and is formed by a series connection of a forward diode 39 and a resistor 40._r T consisting of a series connection of a setting unit, a diode 41, a resistor 42 and a variable resistance FET 43 in the reverse direction_f Input to the parallel connection branch of the setting unit 36.
[0036]
Rise time t_r Is determined by the resistor 40 and the capacitor 44. Fall time t_f Is determined by the resistor 42, the resistance between the source and drain of the FET 43, and the capacitor 44. The source-drain resistance is controlled by the gate voltage signal 28 (control signal 28) of the FET 43. The gate voltage signal 28 is converted from the signal 27 by the trapezoidal pulse waveform control circuit 15 and the m-value setting circuit. The signal 27 is a feedback signal for minimizing the maximum voltage in the DD region, and is used manually from the n value setting circuit 13 or directly from the output 26 of the maximum value detection circuit 12.
[0037]
Next, detection of information on the deep part, that is, detection of the internal viscoelastic property of the object by detecting the echo signal will be described with reference to FIG.
The branch signal 19b of the ultrasonic response signal of the piezoelectric vibrator of the ultrasonic transducer 4 is controlled so as to pass only the echo signal having a small amplitude through the gate circuit 59, and is input to the high frequency amplifier 8 and amplified. The output signal is immediately combined with the ultrasonic response signal 22 to obtain a combined signal 24, and the signal is analyzed by the FFT circuit 9.
[0038]
As shown in FIG. 2, the synthesized signal 24 includes an ultrasonic response signal 29, an echo signal 31 (foreign object surface reflection), a signal 32 (foreign object rear surface reflection), and a signal 33 (multiplex between the foreign object surface and the object surface). Reflection), signal 34 (back reflection of object), time t₁ To the sound speed of the object is time t₂ To the sound velocity of the foreign matter in the object, and the amplitude ratio A between the ultrasonic response signal 29 and the echo signal 31 immediately thereafter.₁ / A₀ The attenuation rate α of the object₁ Is the amplitude ratio A between the echo signal 31 and the echo signal 32.₂ / A₁ From the relationship, the attenuation rate α of the foreign matter present in the object₂ Are calculated based on the following equations.
[0039]
Speed of sound V₁ = 2d₁ / t₁ , V₂ = 2d₂ / t₂
Attenuation α₁ = 20log (A₁ / A₀ ) / D₁
α₂ = 20log (A₂ / A₁ ) / D₂
However, in the above equation, the distance d from the surface to the foreign object₁ , Layer thickness d of foreign matter₂ Can be expressed by absolute values of sound velocity and attenuation rate, but in the case of an object such as an actual living tissue, d₁ , D₂ Is never known. However, the speed of sound V of the foreign material formed inside the object₂ Is V₁ Can be approximated as close to₁ / d₂ T₁ / t₂ It can be approximated by.
[0040]
Therefore, since the damping rate ratio corresponds to the viscosity rate ratio, the relative viscosity rate ratio of the foreign matter inside the object can be known. Usually, the sound speed of the living body is 1570 m / s for the liver with relatively fast sound speed and 1476 m / s for fat with relatively slow sound speed, and the difference is 6.5%.₁ Is the speed of sound V₂ Even if it is approximated to be equal to, the dimensional error due to this approximation is 6.5%, which is in the range where there is no problem in actual diagnosis, and is not considered as a problem even in normal ultrasonic diagnosis.
[0041]
In addition, since there is a method by the FFT analysis shown below as the method of calculating | requiring a sound speed and attenuation | damage, either may be used.
The FFT of each of the ultrasonic response signals 29, 31, 32, 33, and 34 shown in FIG.₀ , F₁ , F₂ , F_Three , F_Four And at frequency f. F₀ And F₁ The phase difference of_Ten, F₁ And F₂ The phase difference of_{twenty one}Then,
V₁ = 4πd₁ / (Φ_Ten/ f), V₂ = 4πd₂ / (Φ_{twenty one}/ f)
Attenuation α₁ = 20log (| F₁ / F₀ |) / 2 d₁
α₂ = 20log (| F₂ / F₁ |) / 2 d₂
It becomes. Since the subsequent processing is the same as the method described above, description thereof is omitted here.
[0042]
Next, FIG. 6 shows and describes the configuration of an ultrasonic transducer used in the ultrasonic diagnostic apparatus of the present invention.
The piezoelectric vibrator 4a of the ultrasonic transducer 4 has an extraction electrode 60ac folded back from the partial electrode 60a, and the partial electrode 60b also has an extraction electrode 60bc. The holding part 61 has conducting wires 67 and 68 insulated from each other, and ends thereof are connected to portions shown in the drawing of the holding part 61 as electrode pads 61a, 61b, 61c and 61d.
[0043]
Further, in order to be detachable from the tubular structure 77, an internal thread portion (not shown) of the tubular structure 77 as shown in FIG. The lead electrode 61ac is bonded to the holding electrode pad 61a and 61bc is bonded to the electrode pad 61b to integrate the piezoelectric vibrator 59 and the holding portion.
[0044]
As an example of the bonding method at this time, a conductive paste is applied to the electrode pads 61a and 61b, an anaerobic adhesive is applied around the electrode pads 61a and 61b, and then the piezoelectric vibrator 4a is dropped onto the holding unit 61 while confirming the position. Washing is performed after pressurizing for a certain time.
[0045]
By using an anaerobic adhesive, the adhesive at the site that has been in contact with air does not cure and can be easily removed. Thereafter, the pressure receiving part is applied.
When a material to be an adhesive such as an epoxy resin is used for the pressure receiving portion material, the process as described above is not performed, and the pressure receiving portion application, the bonding between the piezoelectric vibrator and the holding portion, and the pressure receiving portion formation are performed in one process. Can be done.
[0046]
The assembled holding portion 61 is screwed into the tubular structure 77. The tubular structure 77 has an O-ring 69 and spring portions 66a and 66b serving as electric terminals connected to signal lines in the tubular structure 77. . The ring 69 ensures airtightness, and the spring portion ensures conduction with the holding portion. Here, the two spring portions correspond to the upper electrode 60a and the lower electrode 60b, respectively, and the signal line connected to the spring portions 66a and 66b shows the change in the impedance characteristic of the piezoelectric vibrator 4a. Will be communicated as.
[0047]
Since the material of the holding portion may be in direct contact with the living body, high density polyethylene is desirable in consideration of biocompatibility and adhesiveness with the piezoelectric vibrator. However, if priority is given to biocompatibility, Teflon or polyurethane may be used. Further, when the attachment / detachment is not considered, the screw portion 62 may be omitted and simply bonded.
[0048]
FIG. 7 shows a modification of the holding unit 61.
In the rivet shape of the holding portion, electrode terminals 61c and 61d connected to the respective electrodes of the piezoelectric vibrator 4a are exposed in the recesses of the rivet. On the other hand, the tubular structure 77 shown in FIG. 8 is provided with a female part (not shown) of a rivet, and terminals 66ta and 66tb electrically connected to the signal line are provided at the tip thereof.
[0049]
When the holding portion 61 and the tubular structure 77 are fitted, the respective terminals come into contact and become electrically conductive. After confirming the conduction, the holding portion and the tubular structure are bonded and fixed using an adhesive (epoxy system). To do.
[0050]
In the state where the pressure receiving part 63 is not in contact with the object 65, there is a large difference in acoustic impedance between the acoustic coupling layer / pressure receiving part 63 and the air, so that the ultrasonic wave hardly radiates on any surface. Then, it vibrates freely at the resonance frequency of the ultrasonic vibrator comprising the piezoelectric vibrator 4a and the acoustic coupling layer / pressure receiving portion 63.
[0051]
Since this free vibration has no back load material formed on the back side, that is, on the electrode 60b side, free vibration with a large amplitude can be realized. Another reason why such a large amplitude free vibration can be realized is that the electrodes 60a and 60b are partial electrodes and mounted on the mount structure 61 so that no vibration occurs at the edge of the piezoelectric vibrator. It is that.
[0052]
When the object 65 comes into contact with the free vibration with such a large amplitude, the resonance frequency and the resonance resistance of the free vibration with the large amplitude change according to the load state of the object. Accordingly, since the center frequency and vibration amplitude of the ultrasonic vibration also change, it is possible to grasp the mechanical characteristics of the object 65, for example, the viscoelastic characteristics, by detecting the amount of change. As described above, according to the present embodiment, the response signal immediately after the ultrasonic wave immediately after the application of the trapezoidal pulse can be detected separately, and the echo signal can also be detected. The response signal immediately after the ultrasonic wave can be obtained as a response signal immediately after the ultrasonic wave having a short pulse width that is hardly subjected to damping by using a characteristic technique called dynamic damping.
[0053]
Since this signal is hardly damped, its center frequency and amplitude are changed with high sensitivity according to the object load. This means that detection of surface information (surface viscoelasticity) of an object can be performed with high sensitivity, and if the viscoelastic object is considered to be a biological tissue, a favorable effect that a highly accurate biological tissue diagnosis can be performed. It means to be tied to.
[0054]
-On the other hand, the echo signal obtained when the response signal immediately after the ultrasonic wave with a short pulse width enters the object also changes the amplitude and the center frequency according to the viscoelastic characteristics of the propagation path. By analyzing the relationship between the signal and the echo signal and the relationship between the echo signals, for example, changes in amplitude and center frequency, it is possible to detect the depth information (viscoelasticity in the depth direction) of the object with high sensitivity. This means that if the viscoelastic object is considered to be a living tissue, it leads to a preferable effect that a deep diagnosis of the living tissue can be performed with high accuracy.
[0055]
From the above, this embodiment can provide an ultrasonic diagnostic apparatus capable of detecting surface information, which was impossible with a conventional ultrasonic diagnostic apparatus. On the other hand, since the detection of the surface information can be regarded as tactile sensing, it is possible to provide a tactile sensor device capable of detecting deep information, which was impossible with a conventional tactile sensor device.
[0056]
Next, FIGS. 8A to 8D show and explain the configuration of an ultrasonic transducer used in the ultrasonic diagnostic apparatus of the present invention as a second embodiment.
FIG. 8A shows the appearance of an ultrasonic transducer catheter 77 having an acoustic coupling layer / pressure receiving portion 78 provided at the tip, and FIG. 8B shows the ultrasonic transducer catheter 77 viewed from the A direction. A cross section near the tip is shown.
[0057]
The ultrasonic transducer catheter 77 has a two-body structure as shown in FIG. 8C and is a fitted structure as shown in FIG.
One of the two-body structures has a structure in which a plurality of piezoelectric vibrators 82a to 82h are joined to a plurality of portions of a holding structure 80 provided with a fitting portion 80a and a fitting stopper 83.
[0058]
First, a cylindrical material made of fused silica or the like is cut or ground to form an inset portion 80a, and surfaces 89a to 89h for mounting the piezoelectric vibrators 82a to 82h are formed.
[0059]
Next, as a common ground electrode 99, using a means such as sputtering or vacuum deposition, a two-layer metal layer such as gold, platinum, or gold / titanium, platinum / titanium, etc., including piezoelectric vibrator bonding surfaces 89a to 89h It is formed so as to be continuous with the surface and the surface of the fitting portion 80a. Further, the piezoelectric vibrators 82a to 82h are joined to the piezoelectric vibrator joining surfaces 89a to 89h by bonding or the like. Then, a silicone resin or a urethane resin is thinly coated on the piezoelectric vibrators 82a to 82h to form the pressure receiving portion 78.
[0060]
The stopper ring 83 is fixed to the cylindrical fitting portion 80a with an adhesive, and the ultrasonic transducer head 92 is completed. FIG. 8D shows the ultrasonic transducer head 92 viewed from the direction B in FIG.
[0061]
From these piezoelectric vibrators 82a to 82h, lead wires 93a to 93h are led to the central shaft tubular hole 98 and connected to the terminals 93a "to 93h" via the internal wirings 93a "to 93h".
[0062]
On the other hand, a metal film 94 is formed on the inner wall of the central shaft tubular hole 98 ′ of the tubular structure 79, and a coaxial multicore cable 96 that transmits and receives electrical signals to each of the piezoelectric vibrators 82 a to 82 h is disposed. The shielded wire (not shown) of the coaxial multicore cable 96 is connected to a metal film 94 formed on the inner wall of the central shaft tubular hole 98 ′ in the vicinity of the hand operating portion of the tubular structure 79.
[0063]
The front end of the ultrasonic transducer head 92 is finally joined and sealed with the front plugging material 97.
The operation of the ultrasonic transducer head configured as described above will be described. A trapezoidal pulse voltage is sequentially applied to each of the piezoelectric vibrators 82a to 82h via the coaxial multicore cable 96 and the surface ground electrodes 94 and 99. As a result of this application, the ultrasonic pulses generated in the piezoelectric vibrators 82a to 82h act on the object, are modulated according to the viscoelastic characteristics of the object, and are immediately observed as an ultrasonic response signal. This transmission / reception is sequentially operated using means such as an electronic switch for each of the piezoelectric vibrators 82a to 82h.
[0064]
Since the piezoelectric vibrator in which no echo signal is observed is not in contact with the object, the orientation of the ultrasonic transducer head 92 can be known if the position of the piezoelectric vibrator is known. Further, the response signal from the piezoelectric vibrator not in contact with the object is subjected to FFT analysis, and the center frequency f₀ Maximum value A₀ , Parameters such as specific bandwidth are extracted, and these are used as reference values, and the center frequency f of the reflected ultrasound 29 from the object contact surface₀ Maximum value A₀ The viscoelastic characteristics of the object can be determined by comparing with the specific bandwidth α. The signal processing method for each of the plurality of ultrasonic transducers is the same as that in the first embodiment described above, and a description thereof is omitted here.
[0065]
Further, when the piezoelectric vibrator comes into contact with the object and the echo signals can be detected from the respective objects, an annular scanning tomographic image is obtained by sequentially scanning electronically. The signal processing method in this case is exactly the same as that of the linear electronic scan ultrasonic diagnostic apparatus, and description thereof is omitted here.
[0066]
Such an annular scanning tomographic image is effective for diagnosing a state around a 360-degree lumen wall such as a blood vessel.
As described above, when in contact with the object, the ultrasonic response signal reflected on the object surface is analyzed to evaluate the viscoelastic characteristics of the object, and tomographic information can be obtained from the echo signal. By arranging piezoelectric vibrators in an annular shape and sequentially scanning them, an annular scanning tomographic image is obtained, and a state around 360 ° around a lumen wall such as a blood vessel is diagnosed together with the surface information and tomographic information of the object. I can do it.
[0067]
Next, with reference to FIGS. 9A to 9D, an ultrasonic transducer used in the ultrasonic diagnostic apparatus of the present invention will be described as a third embodiment.
Here, differences from the configuration of the second embodiment described above will be described. From the viewpoint of the structure, from the comparison between FIG. 8 and FIG. 9, in the configuration of the ultrasonic transducer catheter, it is the same that a plurality of piezoelectric vibrators are formed. The ultrasonic delay medium 80 is provided on the front surface of 82h, and the acoustic coupling layer / pressure receiving portion is not directly formed on the piezoelectric vibrator, but is formed on the contact surface of the ultrasonic delay medium 80 with the object. The point is different.
[0068]
Moreover, the structural example of the ultrasonic diagnosing device for implementing this embodiment is shown in FIG. In this configuration, parts equivalent to those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. This ultrasonic diagnostic apparatus has a simple configuration in which the branch circuit 2, the attenuator 5, the delay circuit 7, and the differential amplifier 6 are omitted from the configuration of the first embodiment described above.
[0069]
In FIG. 10, the trapezoidal pulse signal 16 from the trapezoidal pulse generator 1 is amplified to a signal 18 of 50 to 100 V by the high frequency amplifier 3 and applied to the ultrasonic transducer 66.
[0070]
In the ultrasonic transducer, as shown in FIG. 9D, a plurality of piezoelectric vibrators 82 a to 82 h are attached to a single ultrasonic delay medium 80. The ultrasonic vibration generated in the piezoelectric vibrators 82a to 82h passes through the ultrasonic delay medium 80._d / 2 propagates and the surface t of the object 75_d / 2 and undergoes changes in the center frequency and amplitude depending on the viscoelastic properties of the surface of the object.
[0071]
The ultrasonic response signal after being affected by this is the ultrasonic signal 29 shown in FIG. 11, and the trapezoidal pulse 30 is applied in a state where the object 75 is not in contact with the center frequency and amplitude of the ultrasonic signal 29. T_d By comparing the center frequency and amplitude of the response signal generated after the time, the surface viscoelastic property of the object can be detected. As shown in FIG. 11, the ultrasonic response waveform at the time of contact with the target object is observed as echo signals 31, 32, 33, 34, etc., following the ultrasonic response signal 29 including the first surface information. By applying FFT processing to each of these signals, extracting the parameters of the center frequency, amplitude, and phase from each of these signals and comparing them, the viscoelastic characteristic ratio between the target object and the abnormal tissue present therein can be known. The above is sequentially switched for each ultrasonic transducer.
[0072]
According to the present embodiment, the response signal immediately after the ultrasonic wave reaches the surface of the object can be detected separately from the applied trapezoidal pulse waveform, and the target signal can be detected by comparing with the response signal when the object is not in contact. The viscoelastic property of the surface of the object can be detected. In addition, the depth direction viscoelasticity characteristic of the object can be detected from the echo signal observed immediately after the response signal. In addition, since the ultrasonic transducer does not directly contact an object such as a living body, the ultrasonic transducer not only has no fear of current leakage to the living body, but also does not have to worry about damage due to cleaning or disinfection of the ultrasonic transducer.
[0073]
Next, FIG. 12 illustrates a modification of the above-described third embodiment.
This modified example is different from the third embodiment only in the structure of the piezoelectric vibrator. That is, partial electrodes 86a to 86h corresponding to the number of elements (eight in the example of FIG. 12) and full-surface electrodes (not shown) are provided on the back surface of the circular annular piezoelectric ceramics 85. After the electrodes are formed, they are all polarized at the same potential, and bonded by a method such as adhesion so that the entire electrode side contacts the ultrasonic delay medium.
[0074]
Then, lead wires 87a to 87h are attached to each partial electrode, and a trapezoidal pulse voltage is applied between the lead wire and the surface ground electrode 99 formed on the surface of the fitting portion 80a of the ultrasonic delay medium.
[0075]
In this modification, it is not necessary to join the piezoelectric vibrators one by one as in the third embodiment, and it is not necessary to pay attention to variations in characteristics between the piezoelectric vibrators due to assembly. Furthermore, since each piezoelectric vibrator part becomes a curved surface and ultrasonic waves are emitted from the concave side of the curved surface, the ultrasonic beam is narrowed down, and the stray of the ultrasonic beam is less likely to occur. As a result, it is possible to detect the ultrasonic response and echo signal with high accuracy. In this embodiment, the piezoelectric vibrator is disposed on the side that does not contact the object with respect to the delay medium. However, the position of the piezoelectric vibrator is the same as in the second embodiment described above. Needless to say, the configuration arranged on the side in contact with the object is also within the scope of the present invention.
[0076]
In addition, the ultrasonic diagnostic apparatus of the present invention is not limited to the conventional ultrasonic diagnostic apparatus, and what is conventionally referred to as a tactile sensor or a pressure sensor is also considered as long as ultrasonic vibration is used for detection. .
[0077]
Although the above embodiment was demonstrated, this specification also includes the invention which solves the following subjects.
As a problem, the first problem can be achieved if a high-frequency pulse signal corresponding only to the ultrasonic response signal immediately after the above can be separated, but this alone can be applied to the surface and the deep part of the test object. Therefore, the acoustic structure cannot be detected with high sensitivity and high resolution. In particular, when detecting deep part information, the pulse width of the echo signal greatly affects.
[0078]
In general, the pulse width of the echo signal is almost determined by the pulse width of the ultrasonic response signal immediately after. In the prior art, as shown in FIG. 14, the ultrasonic vibration is damped by the structure of the ultrasonic transducer in which the back surface load material 109 is formed on the back surface of the piezoelectric element 107, and the pulse width is shortened. Yes.
[0079]
As with conventional ultrasonic diagnostic equipment, this is sufficient when only echo information is processed for the purpose of deep information detection. However, not only deep information but also surface information, that is, tactile information, is detected with high sensitivity. If the immediately following ultrasonic response signal is damped from the beginning, there is a problem that the desired detection sensitivity cannot be obtained. Therefore, in order to detect surface information, that is, tactile information with high sensitivity, the ultrasonic response signal immediately after is not damped from the beginning, and the pulse width of the ultrasonic pulse must be shortened in order to increase the resolution of deep diagnosis. .
[0080]
When the immediately following ultrasonic response signal becomes available by solving the technical problems as described above, it is meaningful to derive the relationship between this signal and the subsequent signal. In the past, the acoustic discontinuity was simply drawn from which position and what kind of acoustic discontinuity was depicted simply from the relationship between the time when the echo signal was detected and the magnitude of the echo amplitude. It does not depict viscoelastic properties of living tissue existing at positions up to the continuous part or viscoelastic properties of living abnormal tissue. However, a more desirable ultrasonic diagnosis is that it is possible to diagnose what kind of abnormal tissue is located at which position of normal living tissue and how much abnormality is present compared to normal living tissue. .
[0081]
Therefore, there is a problem that it is necessary to express what and how much abnormal tissue is present at which position of normal living tissue by an absolute value or a relative value.
Furthermore, when performing ultrasonic diagnosis of a living tissue, a certain degree of diagnosis can be performed without scanning the ultrasonic beam, but if surface information is obtained by scanning the ultrasonic beam, the accuracy of the diagnosis is further improved. In order to obtain such surface information, there is a method in which a single ultrasonic transducer is rotated and an ultrasonic beam is scanned, as in the prior art. In order to detect an acoustic structure over the surface and depth of an object, the ultrasonic transmission / reception surface of the ultrasonic transducer needs to be in contact with the surface of the object to be examined. However, there is a problem that it is necessary to make an electronic scanning ultrasonic transducer, and it must be an electronic scanning ultrasonic transducer.
[0082]
(1) An ultrasonic transducer comprising a piezoelectric vibrator, a pulser / receiver that applies a pulse voltage to the ultrasonic transducer and receives an ultrasonic response signal generated in the ultrasonic transducer by the application of the pulse voltage, and the pulser / receiver An ultrasonic response immediately after applying the pulse voltage in an ultrasonic diagnostic apparatus that detects the acoustic structure of the test object by analyzing the output signal. An ultrasonic diagnostic apparatus comprising means for separately detecting and analyzing a signal.
[0083]
However, the ultrasonic response signal immediately after the above is an ultrasonic signal that first acts on the object. A pulsar / receiver is a commonly used integrated device. The pulsar includes a pulse generator, a pulse width, a pulse generation period setting unit, a time constant setting device, etc. It is a device composed of a circuit and the like. When a pulse voltage is applied from the pulsar to an ultrasonic transducer composed of a piezoelectric vibrator, the ultrasonic transducer generates an ultrasonic response signal having a frequency component equal to the inherent resonance frequency of the piezoelectric vibrator.
[0084]
This signal is converted into a high-frequency pulse voltage signal by the piezoelectric effect of the piezoelectric vibrator. Among these voltage signals, a voltage signal generated immediately after application of the pulse voltage includes a high-frequency pulse voltage signal obtained by piezoelectrically converting the applied pulse voltage signal and the immediately following ultrasonic response signal. Among these, the immediately following ultrasonic response signal includes a tactile signal corresponding to the surface state of the object. Therefore, if it has a means for separating and detecting the ultrasonic response signal immediately after applying the pulse voltage and analyzing it, the effect of diagnosing the surface state of the object can be obtained.
[0085]
(2) In the ultrasonic diagnostic apparatus described in (1) above, the means for separating and detecting only the ultrasonic response signal immediately after the above is one of the means for branching the output of the pulse generator (pulsa) and one of the branch signals Means for inputting a response signal immediately after the amplified signal is applied to the ultrasonic transducer, attenuating means for reducing the amplitude of the immediately following signal, and means for delaying the other signal of the branch signal An ultrasonic diagnostic apparatus comprising means for taking a difference between the delayed output and the attenuated output.
[0086]
The first embodiment is applicable.
The ultrasonic diagnostic apparatus described in the item (1) has means for branching the output of the pulse generator (pulser), the pulse output is branched, one as a reference signal and the other as amplification means. After being amplified by the above, it is used as an ultrasonic excitation signal for applying a pulse voltage to the ultrasonic transducer. By applying this ultrasonic excitation signal, an ultrasonic response signal is immediately excited in the ultrasonic transducer, but there is almost no time difference between the applied pulse voltage signal and the high-frequency pulse voltage signal obtained by piezoelectrically converting the ultrasonic response signal. Therefore, it is observed as a superimposed signal of both. Since this superimposed signal has a high voltage, it is attenuated to an appropriate amplitude by the attenuation means. On the other hand, the reference signal gives a time delay equal to the total time delay due to the amplifying means, the attenuating means and the wiring existing in the other signal transmission path. Then, both signals are input to a means for taking a difference to obtain a differential output. By using these means, only the ultrasonic response signal immediately after can be separated and detected, and the surface state of the object can be diagnosed.
[0087]
(3) In the ultrasonic diagnostic apparatus described in the item (1), the means for separating and detecting only the ultrasonic response signal immediately after the ultrasonic diagnosis includes a low-loss ultrasonic delay medium and a gate means. apparatus.
[0088]
The second embodiment is applicable.
However, in the second embodiment, the low-loss ultrasonic delay medium is exemplified by fused quartz. However, other materials are also lossy with respect to, for example, silicon, lithium niobate, crystallized glass, or vibration. For example, a material with a small amount of attenuation, specifically, an attenuation factor α <0.1 dB / cm may be used. In addition, when it is known that only an object with a small ultrasonic loss is originally measured, it is not always necessary to have an ultrasonic loss as high as that of fused silica, and it is sufficient if α <5 dB / cm.
[0089]
Therefore, the item (3) applies the ultrasonic wave generated in the piezoelectric vibrator to the object through the low-loss ultrasonic delay medium, and the response signal at this time passes through the low-loss ultrasonic delay medium to the piezoelectric vibrator. In other words, the high frequency pulse voltage signal is converted by the piezoelectric effect of the piezoelectric vibrator. The high-frequency pulse voltage signal in this case is delayed from the pulse voltage application timing by the time that the ultrasonic wave generated in the piezoelectric vibrator reciprocates through the low-loss ultrasonic delay medium, so that only the signal after this time has passed is transmitted. Pass through. The signal passing through the gate means does not include the voltage waveform applied to the piezoelectric vibrator.
[0090]
With the above means, only the ultrasonic response signal immediately after the object can be separated and detected, and the surface state of the object can be diagnosed.
(4) In the ultrasonic diagnostic apparatus described in (1) above, the means for applying the pulse voltage includes an ultrasonically-damped time region and an undamped time region. An ultrasonic diagnostic apparatus comprising means for generating pulse vibration.
[0091]
All the embodiments are applicable.
Therefore, in the above item (4), the ultrasonic pulse vibration generated in the piezoelectric vibrator immediately after applying the pulse voltage has almost no vibration amplitude in the time region where the vibration is electrically damped and is damped. In the non-time region, the piezoelectric vibrator vibrates completely unaffected and has a large vibration amplitude. Therefore, when an object load is applied, the ultrasonic pulse vibration in a time region in which damping is not performed changes greatly when the object load is applied. Further, as described above, since the tailing portion originally possessed by the ultrasonic pulse is electrically damped, the pulse width of the ultrasonic pulse can be shortened. By the above means, it becomes possible to detect the surface information of the object with high sensitivity.
[0092]
(5) In the ultrasonic diagnostic apparatus described in the above item (4), the means for applying the pulse voltage described above is configured such that the voltage rise time t_r , Voltage holding time t_w , Voltage fall time t_f And the inverse of the resonance frequency of the piezoelectric vibrator constituting the ultrasonic transducer is t_p Then,
t_r <T_p <T_f
t_w = nxt_p   (N = 1-5)
t_f = m × t_p   (M = 1-10)
An ultrasonic diagnostic apparatus comprising: means for generating a trapezoidal pulse having the following relationship; and means for amplifying the trapezoidal pulse.
[0093]
All the embodiments are applicable.
However, m and n do not necessarily have to be integers and represent real numbers. In addition, since the piezoelectric vibrator is a differential element, it causes a vibration whose phase is reversed when the applied voltage increases and decreases.
[0094]
Therefore, the term (5) is the reciprocal t of the resonance frequency of the piezoelectric vibrator._p Shorter time t_r When the step-up voltage of the rising edge is given, the piezoelectric vibrator freely vibrates at the resonance frequency, whereas the reciprocal t_p Longer time t_f When the step-down voltage at the falling edge is applied, the piezoelectric vibrator oscillates at the resonance frequency corresponding to the time tf. Therefore, the appropriate t_w And t_r , T_p , T_f By applying the trapezoidal pulse of the relationship, it is possible to generate ultrasonic pulse vibrations consisting of an electrically damped time region and an undamped time region.
[0095]
By the above means, it becomes possible to detect the surface information of the object with high sensitivity, and an ultrasonic response signal having a short pulse width can be used.
(6) In the ultrasonic diagnostic apparatus described in (5) above, the means for generating the trapezoidal pulse has variable signal input means for changing the values of m and n. A characteristic ultrasonic diagnostic apparatus.
[0096]
All the embodiments are applicable.
Therefore, the item (6) has variable signal input means for changing the values of m and n, so that the variable signal is inputted and the optimum trapezoidal pulse signal that can obtain the optimum ultrasonic response signal is generated. It becomes possible to do. However, the value of m determines the wave number of the ultrasonic response waveform. As the wave number increases, the pulse width becomes longer and adversely affects the resolution, but the ultrasonic energy of the ultrasonic pulse increases as the wave number increases, contributing to an increase in the dynamic range. Therefore, the trapezoidal pulse t_w , T_f If there is a function to adjust the surface, it is possible to detect the surface information of the object with a large sensitivity and a large dynamic range, and an ultrasonic response signal having a short pulse width can be used.
[0097]
(7) In the ultrasonic diagnostic apparatus described in (6) above, the value of n is set to the value of m, and then the electrically damped time region described in (5) above An ultrasonic diagnostic apparatus comprising means for automatically setting so that the maximum amplitude is minimized.
[0098]
All the embodiments are applicable.
Therefore, in the item (7), if the value of m can be automatically set, an optimum ultrasonic response waveform can be obtained even if the ultrasonic transducer to be used is replaced.
[0099]
(8) In the ultrasonic diagnostic apparatus described in the item (1), the means for detecting and analyzing the ultrasonic response signal immediately after the application of the pulse voltage has a center frequency f from the immediate ultrasonic response signal.₀ And maximum amplitude A₀ An ultrasonic diagnostic apparatus comprising means for extracting parameters.
[0100]
All the embodiments are applicable.
However, the center frequency f₀ And maximum amplitude A₀ In the embodiment, the parameter extracting means performs parameter extraction after subjecting the ultrasonic response signal to the time axis to FFT processing.
[0101]
Therefore, the term (8) indicates that the center frequency and amplitude of the immediately after ultrasonic response signal change depending on the presence or absence of the object load and the magnitude of the object load.₀ And maximum amplitude A₀ By knowing these changes by means of parameter extraction, it is possible to know the presence or absence of the object load and the magnitude of the object load.
[0102]
(9) The ultrasonic diagnostic apparatus described in (1) above, further comprising means for detecting and analyzing an ultrasonic response signal following the ultrasonic response signal. .
[0103]
However, the subsequent ultrasonic response signal means an ultrasonic echo signal.
All the embodiments are applicable.
Therefore, the item (9) is the ultrasonic response signal S immediately after₀ It is possible to detect the surface information of the object. Subsequent ultrasonic response signals are reflected at the boundary when an ultrasonic pulse that has propagated deep from the surface of the object encounters tissue with an acoustic impedance different from that of the propagation medium. The echo signal Se1 is then returned to the ultrasonic transducer. The ultrasonic pulse transmitted through the boundary surface passes through the next boundary surface and returns to the first boundary surface, where a part of the ultrasonic pulse passes through the boundary surface and becomes an echo signal Se2. Return to the ultrasonic transducer.
[0104]
These echo signals S₀ And the echo signal Se1 indicate the sound velocity of the propagation medium, and the amplitude ratio indicates the attenuation of the propagation medium. Further, the sound speed of the tissue having the different acoustic impedance can be found from the relationship between Se1 and Se2, and the attenuation of the tissue having the different acoustic impedance can be found from the amplitude ratio.
[0105]
In addition, since the sound velocity and attenuation are related to the elasticity and viscosity of the viscoelastic characteristics, respectively, an ultrasonic response signal that immediately follows the ultrasonic response signal is detected and analyzed, so that not only the surface but also the deep portion. Diagnosis of viscoelastic properties of
[0106]
(10) In the ultrasonic diagnostic apparatus described in (9) above, means for measuring a time interval between the immediately following ultrasonic response signal and the subsequent ultrasonic response signal, and a plurality of subsequent ultrasonic responses An ultrasonic diagnostic apparatus comprising means for measuring a time interval between signals.
[0107]
All the embodiments are applicable.
Accordingly, the item (10) provides the same effect as the item (9).
(11) In the ultrasonic diagnostic apparatus described in (9) above, means for measuring the maximum amplitude ratio between the immediately following ultrasonic response signal and the subsequent ultrasonic response signal, and a plurality of subsequent ultrasonic waves An ultrasonic diagnostic apparatus comprising means for measuring a time interval between response signals.
[0108]
All the embodiments are applicable.
Accordingly, the item (11) can obtain the same effect as the item (9).
(12) In the ultrasonic diagnostic apparatus described in the item (9), the ultrasonic diagnostic apparatus includes means for measuring a relationship between a phase of the immediately following ultrasonic response signal and a phase of the subsequent ultrasonic response signal. Ultrasonic diagnostic equipment.
[0109]
All the embodiments are applicable.
Therefore, the same effect as the item (9) can be obtained in the item (12).
(13) In the ultrasonic diagnostic apparatus described in the item (4), a stress load against ultrasonic vibration is applied to the ultrasonic transducer on a surface opposite to the ultrasonic transmission / reception side of the ultrasonic transducer. An ultrasonic diagnostic apparatus characterized by having no structure.
[0110]
All the embodiments are applicable.
Therefore, the item (13) has a structure in which the ultrasonic transducer does not join the back load material at all, so that it is not damped with the time domain electrically damped as described in the item (4). Ultrasonic pulse vibration consisting of a time domain can be generated. Therefore, changes in the center frequency and amplitude of the ultrasonic pulse vibration when the object comes into contact can be detected with high sensitivity and high dynamic range.
[0111]
(14) In the ultrasonic diagnostic apparatus described in (13), the transducer includes a piezoelectric vibrator, an acoustic coupling layer bonded to the surface on the ultrasonic wave output side, and a pressure receiving unit bonded to the acoustic coupling layer. An ultrasonic diagnostic apparatus comprising:
[0112]
All the embodiments are applicable.
Therefore, in the above item (14), the ultrasonic wave excited by the piezoelectric vibrator passes through the acoustic coupling layer, and a part of the ultrasonic wave penetrates efficiently through the pressure receiving portion in the depth direction of the object. It is used for detecting surface information as a sound wave response signal. When acoustically coupled optimally, large ultrasonic energy enters the object, and even a highly attenuated object reaches the acoustic boundary, where the reflected ultrasonic echo signal can be detected and the highly attenuated object can be detected. Elastic modulus and viscosity can be evaluated.
[0113]
(15) In the ultrasonic diagnostic apparatus described in (13) above, the ultrasonic transducer joins the low-loss ultrasonic delay medium described in (4) to the ultrasonic transmission / reception side surface of the piezoelectric vibrator. An ultrasonic diagnostic apparatus having a structure in which an acoustic matching layer serving also as a pressure receiving portion is formed on a surface of the low loss ultrasonic delay medium that is in contact with an object.
[0114]
The second embodiment is applicable.
Therefore, in the above item (15), the structure of the ultrasonic transducer is bonded with a low-loss ultrasonic delay medium, and a back load material is formed on the back so as to be a load of ultrasonic vibration of the piezoelectric vibrator. It has no structure.
[0115]
The ultrasonic vibration excited by the piezoelectric vibrator propagates through the low-loss ultrasonic delay medium, reaches the object, and is divided into a component that reflects at the interface and a component that enters the object. The former component is used as an immediate ultrasonic response signal, the surface information of the object is detected from this signal, the latter component is used to generate an echo signal, and the depth information is detected from this echo signal. Since an acoustic matching layer is formed between the low-loss ultrasonic delay medium and the object, multiple reflections in the low-loss ultrasonic delay medium are reduced, and surface information and depth information can be detected appropriately. . Furthermore, since the piezoelectric vibrator does not come into direct contact with the target object, when the target object is a living body, it is possible to obtain an effect of completely wiping out safety concerns. In addition, the problem of chemical resistance at the time of cleaning and disinfection of the ultrasonic transducer is completely eliminated.
[0116]
(16) In the ultrasonic diagnostic apparatus described in (15), the ultrasonic transducer joins a plurality of piezoelectric vibrators to one low-loss ultrasonic delay medium, An ultrasonic diagnostic apparatus having a structure in which a pressure receiving portion for transmitting and receiving ultrasonic waves to an object is formed on a surface of a low-loss ultrasonic delay medium on a diagonal side across a loss ultrasonic delay medium .
[0117]
The second embodiment is applicable.
Therefore, in the item (16), in addition to the function and effect of the item (15), since a plurality of piezoelectric vibrators are bonded to one low-loss ultrasonic delay medium, the posture of the ultrasonic transducer is not changed. However, the object can be diagnosed using a piezoelectric vibrator that is in contact with the object via a low-loss ultrasonic delay medium. In addition, with reference to the signal from the piezoelectric vibrator that is not in contact with the object via the low-loss ultrasonic delay medium as a reference signal, the temperature characteristics of the signal from the piezoelectric vibrator that is in contact with the low-loss ultrasonic delay medium It is also possible to correct unnecessary characteristics such as common.
[0118]
(17) In the ultrasonic diagnostic apparatus described in the above (16), the plurality of piezoelectric vibrators are arranged in a ring shape, and the ultrasonic transmission / reception surface of the low-loss ultrasonic delay medium is also formed in a diagonal ring shape. An ultrasonic diagnostic apparatus characterized by being configured.
[0119]
The second and third embodiments are applicable.
Therefore, in the embodiment described in (16) above, the number of piezoelectric vibrators arranged in the form (17) is eight, but this number is not necessarily the best, and it depends on the application. The number may be larger or smaller and may be designed according to the application. In addition, it is assumed that a plurality of discrete piezoelectric elements are joined. For example, a piezoelectric thick film or a piezoelectric thin film is formed on an ultrasonic delay medium having high heat resistance and good film form via a lower electrode, A structure in which an upper electrode is formed and wired may be used.
[0120]
Therefore, the ultrasonic beam can be scanned in an annular shape by arranging a plurality of piezoelectric vibrators in an annular shape and sequentially performing drive scanning along the annular shape. This eliminates the need for mechanically rotating the ultrasonic transducer like the prior art, greatly reducing mechanical structural components and greatly improving the reliability of the apparatus.
[0121]
(18) In the ultrasonic diagnostic apparatus described in the item (17), the plurality of annularly arranged piezoelectric vibrators have a structure in which a divided electrode is formed on an annular piezoelectric element. Diagnostic device.
The second and third embodiments are applicable.
Therefore, the item (18) can obtain the same effect as the item (17).
[0122]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide an ultrasonic diagnostic apparatus capable of detecting an acoustic structure over the surface and deep part of a test object.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of an ultrasonic diagnostic apparatus according to a first embodiment.
2 is a diagram schematically showing an ultrasonic response waveform in the ultrasonic diagnostic apparatus shown in FIG. 1. FIG.
3 is a diagram showing an example of the internal configuration of a trapezoidal pulse generator in the ultrasonic diagnostic apparatus shown in FIG.
FIG. 4 is a diagram for explaining the principle of dynamic damping in the ultrasonic diagnostic apparatus according to the first embodiment.
FIG. 5 is a diagram showing an ultrasonic response waveform obtained by a method conventionally used in a normal ultrasonic diagnostic apparatus.
FIG. 6 is a diagram illustrating a configuration example of an ultrasonic transducer used in the ultrasonic diagnostic apparatus according to the first embodiment.
7 is a view showing a modification of the ultrasonic transducer shown in FIG. 6. FIG.
FIG. 8 is a diagram showing a configuration of an ultrasonic transducer used in an ultrasonic diagnostic apparatus of the present invention as a second embodiment.
FIG. 9 is a diagram showing a configuration of an ultrasonic transducer used in an ultrasonic diagnostic apparatus of the present invention as a third embodiment.
FIG. 10 is a diagram illustrating a configuration example of an ultrasonic diagnostic apparatus for carrying out a third embodiment.
11 is a diagram schematically showing an ultrasonic response waveform in FIG.
FIG. 12 is a diagram showing a modification of the ultrasonic transducer used in the ultrasonic diagnostic apparatus according to the third embodiment.
FIG. 13 is a diagram showing a configuration of a conventional ultrasonic transducer catheter.
FIG. 14 is a diagram showing a configuration of a conventional ultrasonic transducer.
FIG. 15 is a diagram illustrating a configuration example of a conventional ultrasonic diagnostic apparatus.
[Explanation of symbols]
1 ... Trapezoidal pulse generator
2 ... Branch circuit
3. High frequency amplifier
4 ... Ultrasonic transducer
5 ... Attenuator
6 ... Differential amplifier
7. Delay circuit
8 ... High frequency amplifier
9 ... FFT circuit
10: Gate timing setting section
11, 59... Gate circuit
12 ... Maximum value detector
13 ... n value setting circuit
14 ... changeover switch
15 ... Trapezoidal pulse waveform controller
16-28 ... Signal

Claims (11)

An ultrasonic transducer comprising a piezoelectric vibrator, a pulser / receiver for applying a pulse voltage to the ultrasonic transducer and receiving an ultrasonic response signal generated in the ultrasonic transducer by the application of the pulse voltage, and an output signal of the pulser / receiver In the ultrasonic diagnostic apparatus for detecting the acoustic structure of the test object by analyzing the output signal,
An ultrasonic diagnostic apparatus comprising means for separately detecting and analyzing an ultrasonic response signal immediately after applying the pulse voltage. In the ultrasonic diagnostic apparatus,
Means for separating and detecting only the ultrasonic response signal immediately after the above
Means for branching the output of the pulse generator (pulsa);
Means for amplifying one of the branch signals;
Attenuating means for inputting a response signal immediately after a voltage is applied to the ultrasonic transducer and applying a voltage to the ultrasonic transducer to reduce the amplitude of the signal.
Means for delaying the other signal of the branch signal;
Means for taking the difference between the delayed output and the attenuated output;
The ultrasonic diagnostic apparatus according to claim 1, further comprising: In the ultrasonic diagnostic apparatus,
The ultrasonic diagnostic apparatus according to claim 1, wherein the means for separating and detecting only the ultrasonic response signal immediately after is provided with a low-loss ultrasonic delay medium and a gate means. In the ultrasonic diagnostic apparatus,
The means for applying the pulse voltage includes means for generating an ultrasonic pulse vibration consisting of an electrically damped time region and an undamped time region. An ultrasonic diagnostic apparatus according to 1. In the ultrasonic diagnostic apparatus,
Means for applying a pulse voltage the is has a voltage rise time t _r, the voltage holding time t _w, the voltage fall time t _f, the inverse of the resonance frequency of the piezoelectric vibrator constituting the ultrasonic transducer and t _p Then
_{t r} <t p <t _f
t _w = n × t _p (n = 1 to 5)
_{t f = m × t p (} m = 1~10)
The ultrasonic diagnostic apparatus according to claim 4, further comprising: means for generating a trapezoidal pulse having the following relationship; and means for amplifying the trapezoidal pulse. In the ultrasonic diagnostic apparatus,
6. The ultrasonic diagnostic apparatus according to claim 5, wherein the means for generating the trapezoidal pulse has variable signal input means for changing the values of m and n. In the ultrasonic diagnostic apparatus,
Claim 1, wherein the pulse voltage to detect the ultrasonic response signal immediately after the application of the means for analyzing is characterized in that it comprises means for parameter extraction the center frequency f ₀ and a maximum amplitude A ₀ from the ultrasonic response signal immediately An ultrasonic diagnostic apparatus according to 1. In the ultrasonic diagnostic apparatus,
5. The ultrasonic wave according to claim 4, wherein the ultrasonic transducer has a structure in which a stress load against ultrasonic vibration is not applied to a surface opposite to the ultrasonic wave transmission / reception side of the ultrasonic transducer. Diagnostic device. In the ultrasonic diagnostic apparatus,
The transducer is a piezoelectric vibrator;
An acoustic coupling layer joined to the surface on the ultrasonic emission side, and a pressure receiving part joined on the acoustic coupling layer;
The ultrasonic diagnostic apparatus according to claim 8, comprising: In the ultrasonic diagnostic apparatus,
The ultrasonic transducer is bonded to the ultrasonic transmission / reception side surface of the piezoelectric vibrator with a low-loss ultrasonic delay medium having a function of separating and detecting only the ultrasonic response signal, and is attached to an object of the low-loss ultrasonic delay medium. The ultrasonic diagnostic apparatus according to claim 8, wherein an acoustic matching layer that also serves as a pressure receiving portion is formed on a surface on the contact side. In the ultrasonic diagnostic apparatus,
The ultrasonic transducer includes a plurality of piezoelectric vibrators bonded to one low-loss ultrasonic delay medium, and a low-loss ultrasonic delay medium on a diagonal side sandwiching the low-loss ultrasonic delay media of the plurality of piezoelectric vibrators. The ultrasonic diagnostic apparatus according to claim 10, wherein the ultrasonic diagnostic apparatus has a structure in which a pressure receiving portion for transmitting and receiving ultrasonic waves to an object is formed on a surface.

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