JP2763906B2 - Ultrasound diagnostic equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus that irradiates an object with an ultrasonic pulse and receives a reflected wave to obtain a tomographic image of the object. The present invention relates to a method of transmitting and receiving an ultrasonic pulse.

[Conventional technology]

In this type of ultrasonic diagnostic apparatus, a plurality of ultrasonic transducers (hereinafter, referred to as “elements”) are provided in an image sensor.
The ultrasonic waves transmitted from a predetermined element are arranged in a dimensional array, and are converged on a tomographic plane of the subject in an imaging positional relationship with the ultrasonic imaging element using an acoustic lens. Then, the reflected wave from the tomographic plane is received by the element again. Such an operation is sequentially shifted to adjacent elements at predetermined time intervals, and is performed for all elements arranged in a two-dimensional array. Such an operation is repeatedly performed at a predetermined cycle by the ultrasonic imaging element to obtain a tomographic image. Note that the imaging cycle of the ultrasonic imaging device is uniquely determined by the frame rate of a desired tomographic image and the time required for a reciprocating acoustic path between elements and tomographic planes. It is decided uniquely. As such an ultrasonic diagnostic apparatus for C mode, for example, “Acoustic Holography” (PRENUM PUBL)
ISHING CORPORATION), P619 to P631, USP3979711, and the like.

[Problems to be solved by the invention]

As described above, the conventional ultrasonic diagnostic apparatus transmits ultrasonic waves sequentially from adjacent elements at a uniquely determined transmission time interval and scans a tomographic plane. , The ultrasonic wave is transmitted from the adjacent element with a delay of a predetermined time. Therefore, the reflected wave from the tomographic plane at the position converged by the acoustic lens of the ultrasonic wave transmitted from an arbitrary element is converged by the acoustic lens of the ultrasonic wave transmitted from the adjacent element with a predetermined time delay. May overlap with a reflected wave from a tomographic plane remote from the tomographic plane. When such a superimposition phenomenon occurs, reflection near the tomographic plane is included in addition to the reflected wave from the target tomographic plane. When an ultrasonic tomographic image is formed using such a reflected wave, the azimuth resolution determined by the beam width of the convergence point and the distance resolution determined by the transmission pulse width deteriorate.

As a means for solving such a problem, it is sufficient to transmit the reflected waves from the convergent tomographic plane to all the elements at a transmission time that allows simultaneous reception of the reflected waves. In this case, the transmission timing is generally simultaneous transmission because the acoustic path of each element is almost equal. However, in order to realize simultaneous transmission and reception, it is necessary to provide a transmission / reception amplifier for each element, and the circuit scale becomes enormous.

Further, when the reflected wave is converged on the ultrasonic imaging element using an acoustic lens, the image plane may be curved on the image plane unless the imaging position is set large. In order to obtain a plane tomographic image from such an image, the ultrasonic imaging element must be formed into a spherical shape that matches the curvature of the curved surface, which is technically difficult.

Therefore, an object of the present invention is to provide an ultrasonic diagnostic apparatus capable of extracting a reflected wave only from a convergent tomographic plane and improving azimuth resolution and distance resolution.

Another object of the present invention is to provide an ultrasonic diagnostic apparatus capable of obtaining a planar tomographic image without being affected by field curvature caused by an ultrasonic lens without forming an ultrasonic imaging element in a spherical shape. Is to provide.

[Means for solving the problem]

The present invention has taken the following measures in order to solve the above-mentioned problems and achieve the object. That is, an ultrasonic imaging device that transmits and receives an ultrasonic pulse, which includes a plurality of elements divided and arranged in a matrix, and a predetermined depth of an object to detect the ultrasonic pulse transmitted from the ultrasonic imaging device An ultrasonic lens installed so as to converge a position on an imaging plane and converge a reflected wave from the tomographic plane to the ultrasonic imaging element; An element capable of arbitrarily selecting a plurality of elements having a positional relationship in which a reflected wave at an intersection cross section where an acoustic path of an ultrasonic pulse to be intersected intersects is sufficiently smaller than a reflected wave at the imaging plane. Selecting means, and the transmission / reception time interval of the ultrasonic pulse transmitted and received from the plurality of elements selected by the element selection means, the sound between the cross section and the imaging plane. And a configuration in which a transducing time setting means for setting the following round trip time of the path.

In addition, based on surface shape measuring means for measuring the shape of the surface of the subject, which is the incident surface of the ultrasonic pulse transmitted from the ultrasonic imaging device, and position information of the subject surface detected by the surface shape measuring means. The time until the reflected wave on the imaging surface and the reflected wave on the subject surface reach the ultrasonic imaging device is calculated, and the transmission / reception time interval of the ultrasonic pulse is controlled based on the calculation result. It is preferable to include a transmission / reception time setting unit.

Further, in order to achieve the other object, an ultrasonic lens that forms a planar imaging surface on the object side and forms a spherical imaging surface on the ultrasonic imaging element side, Delay time is applied to a plurality of elements selected by the element selecting means so that reflected waves from an imaging surface formed on the subject side converge on a spherical imaging surface formed by an ultrasonic lens. In addition to transmitting the signal, the signal is received with the delay time.

[Operation] By taking the above means, the reflected wave at the cross section where the acoustic path of the ultrasonic pulse transmitted successively from the plurality of elements of the ultrasonic imaging element intersects is reflected at the convergent tomographic plane. A plurality of elements having a positional relationship sufficiently smaller than the wave are selected by the element selecting means. Then, from the selected elements, the time interval set by the transmission / reception time setting means, that is, the time required for the reciprocation of the acoustic path between the cross-section where the acoustic paths of different ultrasonic pulses intersect and the convergent tomographic plane, is not more than Ultrasonic pulses are transmitted at set time intervals. Then, the ultrasonic pulse is reflected by the imaging surface, and a reflected wave on which the reflected wave other than the imaging surface is not superimposed is received by the element selected by the element selecting means at a predetermined reception timing, and the received signal is received. Is converted to In this way, it is possible to obtain a tomographic image using the reflected wave reflected only from the imaging plane.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to an embodiment. In the figure, A is the probe, B is the device body, C
Is the subject.

A bellows-shaped container 2 is mounted on one end of the case 1 forming the outer shape of the probe A and facing the subject C so as to cover the opening of the one end. The bellows-shaped container 2 allows the probe A to stably contact the surface of the subject C by the expansion and contraction action of the bellows, and the positional relationship between the ultrasonic lens 5 described later and the convergent tomographic plane 4 in the subject C ( The separation distance is adjusted so that tomographic images at different positions can be detected. A sound absorbing material is mounted on the inner wall of the bellows type container 2 for the purpose of preventing irregular reflection of ultrasonic waves. An acoustic medium 3 is sealed in the bellows-type container 2. As the acoustic medium 3, for example, water is used. When water is used, it is necessary to provide a temperature control mechanism and a defoaming mechanism for removing bubbles in order to prevent a change in sound speed due to a temperature change.

The ultrasonic lens 5 having the above-described large aperture is attached inside one end of the probe A to which the bellows-type container 2 is mounted. The ultrasonic lens 5 converges the ultrasonic pulse transmitted from each element 7 of the ultrasonic imaging element 6 and irradiates the convergent tomographic plane 4 at a desired depth position in the subject C with the ultrasonic pulse. The reflected wave from the convergent tomographic plane 4 is converged, and a tomographic image is formed on the wave receiving surface of the ultrasonic imaging device 6 installed in the probe A. An acoustic medium 3 is sealed in a space formed by the ultrasonic lens 5, the ultrasonic imaging element 6, and the case 1. In addition, a temperature control mechanism and a defoaming mechanism are additionally provided as needed. The ultrasonic lens 5 is formed of a substance whose acoustic impedance is close to that of the acoustic medium 3 and whose sound speed is different from that of the acoustic medium 3. As such a substance, for example, the acoustic medium 3
If is water, plastic materials such as acrylic resin and polystyrene resin can be considered. A plastic material has an advantage that an aspheric lens can be easily formed by molding. The ultrasonic lens 5 may be a single lens or a combination lens. That is,
The lens may be a combination lens for removing aberrations, or may be provided with a zoom mechanism and a focus adjustment mechanism for enlarging and reducing a tomographic image. It is necessary to enclose an acoustic medium such as water between the lenses of the combination lens.

The position where the convergent tomographic plane 4 is set is uniquely determined by the focal length of the ultrasonic lens 5. Therefore, the time from transmission of the ultrasonic pulse until the ultrasonic pulse is reflected by the convergent tomographic plane 4 and received is also
The distance is determined from the distance between the ultrasonic imaging element 6 and the ultrasonic lens 5 and the distance (lens focal length) between the ultrasonic lens 5 and the convergent tomographic plane 4. Here, when the set position of the convergent tomographic plane 4 is changed, the distance between the ultrasonic lens 5 and the subject C is changed by expanding and contracting the bellows type container 2.

As described above, the time until the reflected wave returns can be obtained from the probe A, so that the transmission and reception timing of the ultrasonic pulse may be controlled in accordance with the time. Further, by changing the time until the reflected wave returns, the position of the convergent tomographic plane 4 can be changed. However, in this case, the resolution is reduced, so that it is preferable to provide a configuration including a diaphragm mechanism and the like.

The ultrasonic imaging element 6 has a function of transmitting an ultrasonic pulse to the convergent tomographic plane 4 in a time series and a function of transmitting a sound pressure distribution of an ultrasonic wave received by an ultrasonic wave receiving plane in a time-series electric signal (video signal). ).

FIG. 2 shows a specific configuration of the ultrasonic imaging device 6. The ultrasonic imaging element 6 has a structure in which a signal electrode 62, an electroacoustic exchange element 63, a ground electrode 64, and an acoustic matching layer 65 are stacked and fixed on an element mounting table 61 also serving as acoustic damping. Note that the signal electrode 62 and the ground electrode 64 are each divided into a plurality of parts in different directions. Electro-acoustic element 63 is PVDF, as PVF _2, the use of the lateral acoustic coupling is less material is advantageous because it is only divided electrodes. When an electroacoustic conversion material such as PZT is used, it is necessary to perform mechanical cutting.

Further, in the case 1 of the probe A, in addition to the ultrasonic lens 5 and the ultrasonic imaging element 6, multiplexers 11 and 12 for switching each element 7 of the ultrasonic imaging element 6, and the ultrasonic imaging element 6 And a preamplifier 13 for amplifying a video signal to be output to the device main body B.

The apparatus main body B controls a tomographic image processing system for performing processing for obtaining a tomographic image from a video signal obtained by the ultrasonic imaging element 6 and the timing of transmission and reception of each element 7 of the ultrasonic imaging element 6. And a control signal generation system.

The tomographic image processing system includes a two-dimensional gain correction signal generation circuit 14,
A signal processing circuit including an adding circuit 15, a logarithmic amplifier 16, a detecting circuit 17, an adding circuit 18, a black flip circuit 19, an integrating circuit 20, a comparing circuit 21, a switching circuit 22, a multiplier 23, and a frame memory 24.
25, and a display device 26 for converting a video signal into an image.

On the other hand, the control signal generation system includes an address selection circuit 27, a transmission timing generation circuit 28, a reception timing generation circuit 29, and a controller 30 for controlling these components.

The transmission / reception controller 30 has an address of each element having a positional relationship capable of extracting a reflected wave only from the convergent tomographic plane 4 which is a focal plane of the ultrasonic lens 5 and a transmission time which is a transmission time interval from each element 7. Is programmed. At the time of transmission, the multiplexers 11 and 12 are switched via the address selection circuit 27 in accordance with the program, and an arbitrary transmission element 7 is selected. Then, in accordance with the above-mentioned program, a transmission signal is transmitted from the transmission circuit 10 via the transmission timing circuit 28, and transmitted from the selected element. Note that the timing for selecting the transmission element 7 and the timing for transmitting a transmission signal to the element are synchronized.

On the other hand, at the time of receiving a wave, the ultrasonic pulse transmitted from the selected element 7 is delayed by the time required for a reciprocating acoustic path that is reflected by the convergent tomographic plane 4 and returns to the same element 7, and is the same as the transmission timing. The receiving element is selected by the pattern and received. Receive timing is controller
In accordance with the program stored in 30, a command signal is output to the detection circuit 17 via the reception timing generation circuit 29, and the reflected signal from the convergent tomographic plane 4 is selected from the video signals sent to the signal processing circuit 25. Select and extract signal components.

Here, a description will be given of a method of obtaining each element having a positional relationship capable of extracting a reflected wave only from the convergent tomographic plane 4 programmed by the controller 30 and a method of obtaining a transmission time interval from each element 7.

First, a phenomenon in which a reflected wave from another tomographic plane is superimposed on a reflected wave from the converging tomographic plane 4 will be described in detail with reference to FIGS. 3 and 4. FIG.

FIG. 3 shows an element 7 in an arbitrary row of the ultrasonic imaging element 6.
FIG. 2 is a diagram schematically showing an acoustic path created by the system configuration shown in FIG. The ultrasonic pulse transmitted from the element P1 shown in FIG. 2 is focused by the acoustic lens 5 on a point P11 on the imaging plane f which is the convergent tomographic plane 4. Similarly, the ultrasonic wave transmitted from the element Pi focuses on a point Pii on the imaging plane. However, i = 1, 2,... N.

Four reflection surfaces l, m, n, o are placed in the subject C with the imaging plane f interposed therebetween.
Is assumed. Then, consider the reflected waves from the respective reflecting surfaces.

When the elements P1, P2, P3,..., PN are sequentially transmitted at a predetermined interval ΔT, for example, the time when the ultrasonic wave transmitted from the element P1 is reflected at the imaging point P11 and reaches the reflecting surface l is determined. There is a case where the time when the ultrasonic wave transmitted from another element Pi reaches the reflection surface 1 and is reflected after the elapse of the predetermined time after the transmission. Under such conditions, the reception wave observed by the element P1 is a reflection wave of the reflection surface l superimposed on the reflection wave of the imaging surface f. Similarly, the reflected wave of the ultrasonic wave transmitted from the element P1 reflected on the reflecting surface o and the reflected wave of the ultrasonic wave transmitted from the element P2 reflected on the imaging surface f may be superimposed. When such a superimposition phenomenon occurs, as described above, it is impossible to extract only the reflected wave from the imaging plane f in a temporally separated manner.

When the ultrasonic wave transmitted from each element P is reflected by the reflection surface m or n existing in the region Ff-f-Fr separated as an acoustic path, even if the superimposition phenomenon occurs, Due to the image formation relationship by the lens, no wave is received except for the corresponding element. That is, even if the time at which the wave is transmitted from the element P1 and reflected at the imaging surface f and reaches the reflecting surface m coincides with the time at which the wave is transmitted from the element P2 and reflected at the reflecting surface m, both reflected waves are It will be spatially separated.

FIG. 4 is a diagram showing a temporal relationship between ultrasonic waves sequentially transmitted from the elements P1 to PN at a predetermined transmission interval. Also, in the figure, the ultrasonic wave transmitted from the element Pi (i = 1, 2,... N) is reflected on the reflection surface j (j = 1, m, f, n, o) in the subject C.
The reflected wave reflected by is indicated by W (Pi-j). In addition,
f is the imaging plane 4. As shown in the figure, when the adjacent elements are sequentially transmitted at a fixed time interval ΔT,
For example, the reflected wave W (P2-m) of the ultrasonic wave transmitted from the element P2 to the reflected wave W (P1-f) of the imaging point P11 corresponding to P1.
Overlap. The reflected wave W (P1-f) cannot be separated and extracted from such a superimposed wave.

Therefore, in the present embodiment, the following conditions are programmed and stored in the controller 30 shown in FIG.

Select an element that has a positional relationship where the reflected wave at the cross section where the acoustic paths of the ultrasonic waves transmitted before and after intersecting is sufficiently smaller than the reflected wave from the imaging plane (-40 dB or less). Let it wave.

Further, the transmission time interval from each element selected under the above conditions is set to be equal to or less than the time required for reciprocation of the acoustic path from the cross section where the acoustic paths of the ultrasonic waves transmitted before and after intersecting to the imaging plane intersect. .

The element selection control of the ultrasonic diagnostic apparatus set under the above conditions will be described with reference to FIG. 5 and FIG. FIG. 5 is a diagram schematically showing an acoustic path of each ultrasonic wave when every fourth element is selected and transmitted. Based on the above selection conditions, the elements of the arbitrary row of the ultrasonic imaging element 6 are set to P (4i + 0) -P (4i + 1) -P (4i + 2)-
Waves are transmitted in the order of P (4i + 3). Note that i = 0, 1, 2,... N / 4. The transmission time interval at this time is set to be equal to or less than the time required for reciprocation of the acoustic path between the boundary plane Ff (or Fr) at which the acoustic path can be separated and the imaging plane f. Note that the boundary surface Ff (or Fr) from which the acoustic path can be separated refers to a cross section where the transmitted acoustic paths of the elements that are continuously transmitted as described above intersect. The reflected wave from the imaging surface f of the ultrasonic wave transmitted in this way is received by an element selected according to the time until the reflected wave.

FIG. 6 is a diagram showing a waveform of a received signal received by each element. As shown in the figure, the reflected wave obtained by controlling the element under the above conditions does not have the reflected wave from other than the imaging plane f superimposed.

Therefore, by performing the element control as described above, the reflected wave from the imaging surface f is received at the same time as the reflected wave from the reflecting surface existing outside the regions Ff and Fr separated in the acoustic path. Is not affected by reflected waves from other than the imaging surface f,
, It is possible to obtain an ultrasonic tomographic image of a desired imaging plane.

Next, a second embodiment of the present invention will be described. In this embodiment, the probe A shown in FIG. 1 is provided with a surface shape measuring means 70 for the object C, and the position information of the surface of the object C measured by the surface shape measuring means 70 is used to send each element. The timing of wave and wave reception is controlled.

FIG. 7 is a diagram showing the configuration of the surface shape measuring means. The surface shape measuring means 70 uses the space inside the bellows-shaped container 2 as a first space 71,
A closed space formed by forming a thin layer with a thin film between itself and the surface of the second space 72 is defined as a second space 72, and the second space 72 is connected to solenoid valves 75 and 76 via tubes 73 and 74. , And also a container 79 filled with air and a container filled with an acoustic medium such as water.
Connected to 80. In addition, the second space 72 and each solenoid valve 76,7
7 and pumps 77 and 78 are provided, and the second space
The configuration is such that air or an acoustic medium can flow in or out of the containers 79, 80 in the 72. Further, the probe A can move in parallel along the center axis of the lens, and its movement amount Z ₀
Is detected by the displacement meter.

In such a configuration, the probe A is moved in the direction of the center axis of the lens, and is fixed at a position where the image plane of the ultrasonic lens 5 coincides with the surface of the subject C. In this state, the electromagnetic valve 75 or 76 is opened, and the acoustic medium 3 sealed in the first space 71 is opened.
Medium having a large difference in acoustic impedance
The air on the 79 side is sent in, and when the second space 72 is sufficiently filled, the solenoid valve 75 is closed.

Next, the elements P1, P2,... PN of the ultrasonic imaging element 6 in an arbitrary row shown in FIG. 3 are sequentially transmitted, and reflected waves from the surface of the subject C near the imaging plane are reflected by the same elements. Receive the wave. Such an operation is performed in all the rows of the ultrasonic imaging element 6. The reflected waves received in this manner are different from each other in the first space 71 and the second space 71 where the difference in acoustic impedance is significantly different.
The reflected wave reflected at the boundary with 72 becomes extremely large,
Other reflected waves, for example, reflected waves on the lens surface and reflected waves from the lens support member and the side surface of the container 2 are reduced.

FIG. 8 is a diagram showing a waveform of a reflected wave received by each element when a signal is sequentially and continuously transmitted from each element at a time interval ΔT. The principle of measuring the surface shape of the subject C will be described with reference to FIG. For example, let t1 be the propagation time until the ultrasonic wave transmitted from the element P1 is reflected from the boundary surface between the first space 71 and the second section 72 and returns to the same element. The propagation time of the reflected wave from the boundary surface on an axis perpendicular to the wave receiving surface of the ultrasonic imaging element 6 and passing through the center of the wave receiving surface and passing through the lens center is defined as tc.

Here, for example, if the surface shape of the subject C is as shown in FIG. 9, the position vector of the reflection point P11 on the boundary surface of the ultrasonic wave transmitted from the element P1
Is Can be represented by Here, O is the center position of the receiving surface, L is the center position of the acoustic lens 5, and O 'is the first space 71 and the second space 72.
The position where the central axis intersects the boundary surface between and Vω indicates the speed of sound in the medium.

The propagation time from transmission to reception of each element can be calculated by the above equation (1), and the shape of the boundary surface between the first space 71 and the second space 72 is measured by using the calculation result. be able to. Since the shape of the boundary surface can be regarded as the surface shape of the subject C, as a result, the surface shape of the subject C can be measured.

When the shape of the surface of the subject C is measured, the electromagnetic valve 75 is opened to return the medium in the second space 72 to the container 79, and the electromagnetic valve 76 is opened to be sealed in the first space 71. The same medium as the sound medium, for example, the sound medium contained in the container 80 is used as the second medium.
Into the space 72. When a wave is transmitted from each element in such a state, since the medium sealed in the first space 71 and the second space 72 has the same acoustic impedance, the reflected wave reflected from the boundary surface is extremely small. , And can be received without being affected by the reflected wave from the boundary surface.

Next, the probe A is moved in a direction approaching the subject C, and the image plane formed by the ultrasonic lens 5 is set to a desired depth in the subject C. Then, the transmission time and the reception time of each element are controlled by means to be described later while controlling so that the reflected wave from the imaging plane and the reflected wave from the surface of the subject C do not overlap with each other to obtain a tomographic image. .

That is, based on the surface shape of the subject C measured by the surface shape measuring means 70 and the positional information on the surface, the reflected wave from the imaging surface 4 of the ultrasonic wave transmitted from the element and the reflected wave from the surface of the subject C are determined. Predicts the time until the light reaches the wave receiving surface of the image sensor 6 again and its wave receiving element. And
Based on the prediction result, a transmission time and a reception time at which both reflected waves from the imaging surface 4 and the surface of the subject C do not overlap are determined. For example, in the case of transmitting waves, the transmission is performed in the order of adjacent elements, and the transmission time interval at that time is not controlled at a constant interval, but is changed as needed and controlled to an optimum interval.

As a result, the reflected wave from the surface of the subject C can be temporally separated, and only the reflection from the imaging plane can be extracted.

Next, a third embodiment of the present invention will be described. This embodiment is an example in which means for eliminating the curvature of field formed by the ultrasonic lens 5 is added to the first and second embodiments.

By the way, when an acoustic lens such as the ultrasonic lens 5 is used to form an acoustic wave, unless the imaging position is set large, the surface that forms an image with the lens interposed therebetween becomes a curved surface instead of a flat surface. As described above.

Therefore, in the present embodiment, an acoustic lens is used in which one of the two imaging planes having an imaging relationship with the lens interposed therebetween is a plane and the other is a spherical surface due to field curvature. A predetermined delay time is given to an arbitrary element to transmit and receive.

FIG. 10 is a diagram schematically showing an acoustic path when the imaging surface in the subject C is made flat and the imaging surface on the ultrasonic imaging element side is made spherical using the above acoustic lens. FIG. 11 is an enlarged view of a portion M shown in FIG. 10 shown in Fig. 10
Numeral 0 denotes the acoustic lens, which forms image points A1, A2,... AN in a matrix at regular intervals on an image plane 101 in the subject C, and forms an image on a virtual spherical surface 102 on the image sensor side. Points Q1, Q2 ... QN
To form Note that each imaging point (A1, Q1), (A2, Q2) ...
(AN, QN) are in an imaging relationship.

In such an acoustic path, a plurality of adjacent elements are transmitted as one block, and each block is transmitted with an appropriate delay time and converged to Q1, Q2,.

For example, when transmitting from the elements P1, P2,... P7 of the block A1 and forming a convergent sound field in Q1, Pi and P (i + 1)
Are sequentially transmitted as Δti (i + 1) = (P (i + 1) Q1-PiQ1) / Vω (2). However, i = 1, 2,...

In the above equation (2), when Δti (i + 1) takes a negative value, it means that the transmission time of the element of P (i + 1) is delayed by | Δti (i + 1) | with respect to Pi. .

The selection of a plurality of elements in one block is performed so that the acoustic path 104 once converged at Q1, Q2,... QN falls within the aperture plane of the acoustic lens 100. If the vertex QC of the spherical imaging surface 102 generated by the curvature of field coincides with the center axis PC of the ultrasonic imaging device 6, the number of elements in the block decreases as the transmission block approaches the center. , At the center can be one element PC. Moreover, in the element in the transmission block,
Since there are no plurality of elements to be transmitted at the same time, each element can be selected and transmitted in a time-division manner.

In the case of receiving a wave, the element is selected in the opposite manner to the time of the transmission, and the wave is received at the reception time opposite to the time of the transmission. That is, the reflected wave at the imaging point A11 is the block A
1 is received, and the elements to be received at this time are selected in the order of P7, P6,... P1. According to the equation (2), the reception time interval between P (i + 1) and Pi is |
The signal is received with a delay of Δti (i + 1) |. And the second
As shown in FIG. 12, the received signal received is temporarily stored in a buffer memory, and added in a state where the times are aligned, and the added signal is used as a received signal corresponding to the reflected wave at the imaging point A11.

The timing of outputting the transmission signal to be given to each element at the time of transmission and the selection of the transmission element are determined by the address selection circuit 27, the transmission timing generation circuit 28, and the transmission timing generation circuit 28 shown in FIG.
This is performed by the reception timing generation circuit 29 and the transmission / reception controller 30.

Therefore, according to the present embodiment, a planar imaging surface 101 is formed on the subject C side by the acoustic lens 100, and a spherical imaging surface 102 is formed on the ultrasonic imaging element side, and the block-formed element is formed. Is given a delay time | Δti (i + 1) | in which the reflected wave forms an image once on the spherical imaging surface 102, and the element is selected at the time of receiving the signal in the reverse of the time of the transmitting. Since the reception time interval is delayed by | Δti (i + 1) |, the influence of the field curvature of the acoustic lens can be removed. As a result, a flat ultrasonic tomographic image can be obtained in a flat state without making the ultrasonic imaging element 105 spherical.

Further, in the peripheral portion of the ultrasonic imaging element 105, the signal is received by a plurality of elements, so that the sensitivity can be prevented from deteriorating.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to extract a reflected wave from a desired tomographic plane in a subject without overlapping with a reflected wave from a reflective layer near the tomographic plane. Thus, a tomographic image having excellent azimuth resolution and distance resolution can be obtained.

Further, it is possible to extract the reflected wave from the surface of the subject without superimposing the reflected wave from the image forming surface, and to faithfully reproduce the tomographic image in the subject, which is the image forming surface.

Furthermore, a reflected wave from the image plane can be obtained without being affected by the curvature of field caused by the ultrasonic lens.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of an ultrasonic diagnostic apparatus which is the apparatus of the present invention, FIG. 2 is a structural view of an ultrasonic imaging device, and FIGS. 4 and 6 are waveform diagrams of a received signal received by each element, FIG. 7 is a diagram showing a configuration of a surface shape measuring means, and FIG. 8 is a surface shape. 9 is a waveform diagram for explaining the measurement principle of FIG. 9, FIG. 9 is a diagram showing the surface shape of the object, FIG. 10 is an acoustic path diagram for explaining means for eliminating field curvature, and FIG. FIG. 12 is an enlarged view of a portion M shown in FIG. 12, and FIG. 12 is a diagram showing a process of adding received signals. 4 ... convergent tomographic plane, 5 ... ultrasonic lens, 6 ... ultrasonic imaging element, 7 ... element, 27 ... address selection circuit, 28 ... transmission timing generation circuit, 29 ... reception timing generation circuit, 30 ... Controller.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Eiji Ikuta 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (56) References JP-A-63-203143 (JP, A) JP-A-51-113601 (JP, A) JP-A-58-143265 (JP, A) JP-A-56-20438 (JP, A) JP-A-57-75640 (JP, A) JP-A-56-75146 (JP, A) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) A61B 8/00 G01N 29/00

Claims (3)

(57) [Claims] An ultrasonic imaging device comprising a plurality of elements divided and arranged in a matrix to transmit and receive an ultrasonic pulse, and an object to be detected which detects the ultrasonic pulse transmitted from the ultrasonic imaging device. An ultrasonic lens installed so as to converge on an imaging plane at a predetermined depth position and to converge a reflected wave from the imaging plane to the ultrasonic imaging element; and a plurality of elements of the ultrasonic imaging element. Arbitrarily selecting a plurality of elements in a positional relationship in which the reflected wave at the cross section where the acoustic paths of the ultrasonic pulses transmitted before and after intersect intersects sufficiently smaller than the reflected wave at the imaging plane Possible element selection means, the transmission and reception time interval of the ultrasonic pulse transmitted and received by the plurality of elements selected by the element selection means, between the cross-section and the imaging plane Ultrasonic diagnostic apparatus characterized by comprising a transducing time setting means for setting the following round trip time of the sound path. 2. A surface shape measuring means for measuring a shape of a surface of an object to be an incident surface of an ultrasonic pulse transmitted from the ultrasonic imaging device, and positional information on the surface of the object detected by the surface shape measuring means. The time for the reflected wave on the imaging surface and the reflected wave on the subject surface to reach the ultrasonic imaging element is calculated based on the time interval between transmission and reception of the ultrasonic pulse based on the calculation result. 2. The ultrasonic diagnostic apparatus according to claim 1, further comprising a transmission / reception time setting means for controlling the transmission / reception time. 3. An ultrasonic lens which forms a planar imaging surface on the object side and forms a spherical imaging surface on the ultrasonic imaging element side, and is formed by the ultrasonic lens. A plurality of elements selected by the element selecting means are provided with a delay time so as to converge reflected waves from an imaging surface formed on the subject side on a spherical imaging surface, and the waves are transmitted. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic diagnostic apparatus is configured to receive a wave with a delay time.