JPH0530464B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION A. Technical Field The present invention relates to an ultrasonic tomography apparatus, and particularly to an ultrasonic tomography apparatus for superficial tissues of a living body.

B. Prior art and its problems Ultrasonic tomography devices are linear electronic scanners,
Various ultrasonic scanner systems such as sector electronic scanners and contact compound scanners are used for various parts of objects to be examined, such as living bodies. For example, it is used clinically in a wide range of areas including the abdomen, including the liver, pancreas, and kidneys, obstetrics and gynecology, including the fetus, and the heart, and provides diagnostically useful information.

It is applicable not only to such deep parts of living tissues but also to superficial tissues. At the current state of the art, the focus is on the thyroid, mammary glands, and neck (carotid artery).

Ordinary ultrasonic tomography devices are designed to take tomographic images of relatively deep parts of living bodies, and such devices are designed to take images relatively close to the body surface (several centimeters or less).
Even when used for diagnosing an area, the resolution usually tends to be lower than that used to visualize deep parts. This uses 3.5MHz, which has low absorption of ultrasound in the living body, for deep observation, and uses a large ultrasound transmission aperture to ensure good directivity even deep inside the living body. by. For this reason,
Distance resolution and azimuth resolution in shallow parts of the body are sacrificed.

Referring to FIG. 1, consider an approximate sound field of a planar circular vibrator 10 with a transmitting aperture D vibrating at a frequency f.
If the sound speed of an ultrasonic wave propagating in a living body is c, its wavelength λ is c/f. As shown in the figure, the region from the vibrator 10 to a distance D ² /2λ is called a Fresnel region FN, and the beam diameter is equal to the aperture D. In other words, y=D. This creates a near-field sound field. Beyond this distance, the beam diameter is at an angle λ/D
This is the Fraunhofer region FH, which extends in the region. That is, y=2(λ/D)·x.

As can be seen from this, if the aperture D is constant, the higher the frequency f, the better the directivity. Furthermore, if the frequency is constant, the larger the aperture D, the better the directivity, but naturally the beam diameter also becomes larger.

Recently, ultrasonic tomography devices for superficial tissues that use frequency bands of 5 MHz, 7.5 MHz, and 10 MHz have been actively developed and commercialized. This improves distance resolution by using high frequencies, and improves azimuth resolution by making the transmission aperture smaller.

Electronic scanning is an excellent method for obtaining real-time tomographic images. Mechanical or manual scanners for superficial tissue have already been commercialized, but they lack real-time performance, so there is a desire to develop a real-time dedicated ultrasonic tomography apparatus.

There are several technical and manufacturing issues in constructing high frequency probes for electronic scanners.
That is, the first problem is the material of the electroacoustic conversion transducer, and the second problem is the manufacturing technology.

For example, as shown in Fig. 2, in the case of a rectangular parallelepiped transducer array 12 in which ultrasonic waves propagate in the direction of arrow A, the thickness vibration of the transducer is utilized, so in order to use high frequencies, it is necessary to Thickness t
must be made thinner. Furthermore, in order to approximate a piston sound source, the ratio of its width W to thickness t must be kept away from 1. By using highly anisotropic lead titanate instead of the conventionally widely used PZT (piezoelectric ceramic material based on titanate and lead zirconate), the width W can be made larger than the thickness T. However, the latter has a problem in that the conversion efficiency is lower than the former.

When transmitting, multiple elements on array 12 are
When driving as a set, in order to suppress the grating globe, it is necessary to make the pitch P of each element smaller than the wavelength λ of the ultrasonic wave.

In summary, as the frequency increases, the thickness of the vibrating body becomes thinner, and the width must be made narrower accordingly in order to bring it closer to the piston sound source, but configuring such vibrating bodies in an array is , there are difficulties in manufacturing technology. It also improves azimuth resolution,
Furthermore, in order to increase the scanning line density, one acoustic aperture can be constructed from multiple vibrating bodies, but in order to suppress the crater globe that occurs at this time, the element spacing of the vibrating body should be set to be less than the wavelength of the ultrasonic wave. However, there are also difficulties in terms of manufacturing technology. Electron focusing to further improve lateral resolution inherently produces quantization sidelobes.

Thus, in order to realize a high-frequency superficial tissue scanner, it is necessary to appropriately select the electroacoustic transducer material and solve problems in microfabrication technology.

Purpose of the invention The present invention overcomes the drawbacks of the prior art,
An object of the present invention is to provide an ultrasonic tomography apparatus for superficial tissues that can obtain high-resolution tomographic images.

According to the present invention, there is provided an electroacoustic transducer that performs mutual conversion between an electrical signal and an ultrasound, and an electroacoustic transducer that drives the electroacoustic transducer to transmit ultrasound, which is reflected from a subject and detected by the electroacoustic transducer. a transmitting/receiving circuit that receives an electrical signal corresponding to the sound wave; a video output means that visually displays an image corresponding to the received electrical signal;
In an ultrasonic tomography apparatus that includes an electroacoustic transducer, a transmitting/receiving circuit, and a control circuit that controls an image outputting means to perform ultrasonic tomography of a subject, the electroacoustic converting means converts a plurality of vibrations to transmit and receive ultrasound. Each of the plurality of vibrating bodies has an approximately flat rectangular parallelepiped shape as a whole, and the rectangular parallelepiped has two sides perpendicular to the direction in which the ultrasound is transmitted and received. The lengths of the sides in two directions are approximately equal, the plurality of vibrating bodies output relatively high frequency ultrasonic waves, and the control circuit sequentially controls the plurality of vibrating bodies one by one. By driving, linear scanning of ultrasonic wave transmission and reception is performed.

According to one feature of the present invention, the frequency of the ultrasonic wave is set such that when the ultrasonic wave is output from the surface of a living body as an object into the body by an electroacoustic transducer, The frequency is set high enough to form a distance sound field.

According to one feature of the present invention, the vibrator array includes two arrays in which vibrating bodies are linearly arranged, and the vibrating bodies in the two arrays are mutually arranged between the arrays in each column. The vibrating body array pitch is shifted by a length substantially equal to half of the vibrating body array pitch.

According to one feature of the present invention, each of the plurality of vibrating bodies is provided with an acoustic lens for converging ultrasonic waves in front of the vibrating body.

According to one feature of the invention, the two rows of arrays are arranged such that the directivity centers of the two rows of arrays in the slice direction intersect each other within the near field.

According to one feature of the present invention, the video output means displays the video in real time at a predetermined frame rate, and the control circuit displays the electroacoustic conversion means at the frame rate.
The transmitting/receiving circuit and the video output means are controlled, and the vibrating body is sequentially scanned at a speed such that the ultrasonic waves reflected from the superficial tissues of the living body are detected by the electroacoustic transducer. Performs signal processing.

According to one feature of the invention, the signal processing includes processing to increase the S/N ratio of the video.

According to one feature of the invention, the signal processing includes processing to increase the number of scan lines of the video.

According to one feature of the present invention, the transducer array includes a plurality of arrays arranged to slice the subject and obtain a plurality of slice tomographic images in the azimuth direction.

DETAILED DESCRIPTION AND OPERATIONS OF THE INVENTION Next, embodiments of the ultrasonic tomography apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 3, in an embodiment of an ultrasonic tomography apparatus according to the present invention, a high frequency probe 100 for superficial tissue includes an array 104 of 16 transducers 102 of electroacoustic transducer material and a corresponding A switch 106 is provided.

The switch circuit 106 is connected to a transmitting/receiving circuit 110 that transmits ultrasonic waves of a predetermined frequency and receives echoes reflected from the subject. This transmitting/receiving circuit 110 has the function of one channel in this embodiment. The signal received by the transmitting/receiving circuit 110 undergoes necessary signal processing in the received signal processing circuit 112, and is converted into a video signal by the video circuit 114. This video signal is displayed as a visible image on a video display device such as a cathode ray tube (CRT), ie, a monitor 116. The operation of each of these circuits is controlled by control circuit 118.

The entire operation of this apparatus is based on so-called B-mode tomography using normal ultrasound pulses. In order to obtain tomographic images in relatively deep parts of the living body, the transducer usually has an acoustic aperture of 10 to 15 mm to improve the directivity of the transmitted and received ultrasound waves. However, in the shallow parts of the body,
That is, such a large aperture is not necessary to obtain an ultrasonic tomographic image of superficial tissues. For example, even if the target diagnostic depth is limited to areas such as the thyroid gland or carotid artery, it is sufficient to be able to image to a depth of about 3 cm from the surface of the human body, and it is thought that the target tissue exists approximately 1 to 2 cm deep from the epidermis. It will be done. Further, it is considered that a scanning width of about 3 to 5 cm is sufficient.

As mentioned above, in the case of a circular ultrasonic transducer, the distance from the vibrating body, which is approximately the near field, is D ² /2λ
In the range up to this point, the diameter of the ultrasonic beam is approximately equal to the acoustic aperture D. Therefore, the wavelength λ of the ultrasonic wave, that is, the frequency f, and the diameter D of the aperture may be selected so that this is about 2 to 3 cm.

The relationship between D ² /2λ and D is as shown in Figure 4 (D ² /2λ = fD ² /2C = fD ² /3, where f is MHz)
Therefore, depending on the frequency f, for example, curve 2
0, 22, 24 are plotted. From now on, for example, to set D ² /2λ to 20 mm, the frequency f must be
At 15MHz (curve 22), the aperture diameter D is 2mm, 20MHz
(Curve 24), it should be 1.7 mm. In this way, the optimal f according to the aforementioned diagnostic depth D ² /2λ
and D can be selected. Note that the curve 20 is for the case where the frequency f is 10 MHz.

Since the azimuth resolution depends on the beam diameter due to the nature of the near-field sound field, the smaller the aperture diameter D, the better it becomes. Further, the distance resolution becomes better as the frequency f becomes higher. Therefore, if D is made smaller and f is made higher, both resolutions will improve.

However, the near field or diagnostic depth is D
The smaller the value and the higher the value of f, the shorter it becomes.
From this point of view, there are limits to the values of D and f. Furthermore, at high frequencies, the attenuation of ultrasound waves in the living body increases, and the depth of diagnosis is also limited by the dynamic range of the electronic circuits connected thereto.

For example, as shown in Figure 5, if the attenuation in biological soft tissue is approximately 1 dB/cm・MHz, the higher the frequency f, the greater the amount of attenuation inside the biological body.If the dynamic range is 100 dB, then the ultrasonic frequency f
is approximately 16 MHz at a diagnostic depth of 3 cm, and approximately 16 MHz at a diagnostic depth of 2 cm.
25MHz is the limit. Conversely, at 20MHz, diagnosis can be made to a depth of approximately 2.5cm.

For example, when f is 15 MHz and the aperture diameter D is 2 mm, the beam diameter is 2 mm up to a depth of 2 cm, and even at a depth of 3 cm, the beam diameter is only 3 mm. The half width is 1.4 mm for a circular aperture and 1.2 mm for a rectangular aperture. For example, if 16 such transducers are arranged in an array, an array with a total length of 32 mm can be constructed, which is about 3
A scanning width of about cm can be achieved.

Returning to FIG. 3, the control circuit 118 sequentially energizes the switches 106 at the timing shown in FIG. 6, turning on each switch S1 to S16 in sequence. This results in 16 oscillators 1 in Figure 3.
02 is sequentially scanned from left to right, and at each timing, ultrasonic waves are transmitted and their echoes reflected inside the living body are received.

In conventional linear scanning, transducers for a plurality of channels, for example, eight channels, are driven at the same time, and the driving is shifted one channel at a time to perform scanning. Only one vibrator 102 is driven, and the channels are sequentially shifted one by one. Once it has been driven up to 16 channels, it can be driven from channel 1 again and scanning can be repeated. For example, scan depth 30
mm, scanning width 32 mm with 16 channels, in-vivo sound velocity c
Assuming that the speed is 1500 m/sec, the time required to scan one frame is 640 microseconds. Generally, real-time display of tomographic images is performed at a rate of about 60 frames per second, so the time required to scan one frame is about 16.7 milliseconds. Therefore, in this embodiment, scanning is completed in about 1/26th of the required time.

The remaining time in this one frame period can be used for various signal processing in the signal processing circuit 112. This will be detailed later. The received signal image-processed by the signal processing circuit 112 is converted into a video signal in the video circuit 114, and is displayed as a visible image in so-called B mode by modulating the brightness in the display device 116. . Furthermore, since this embodiment does not provide an electronic focus function, one of the features is that there is no need for a delay circuit to provide a phase delay to the transmitted and received signals, which was required in the conventional linear electronic scanning method. be.

Various signal processing may be performed at times other than scanning in the one frame period described above. For example, the S/N ratio can be improved by averaging the received signals for a plurality of frames. For example, in the above example, within one frame period
If the averaging operation is performed 26 times, the S/N ratio can be improved by about 5 times. Further, even if the scanning interpolation method described later is performed in parallel during the averaging operation, the averaging operation can be performed 13 times within one frame period.

In the surplus time of scanning at a high frame rate, real-time scanning of a plurality of cross sections may be performed. This includes a probe 20 including a plurality of transducer arrays A1, A2 and A3 as shown in FIG.
This is realized by 0. This probe 200 has a switching circuit 202, from which energizing signals are sequentially supplied to signal lines S01, S02, and S03 under the control of a control circuit 110, as shown in the timing diagram of FIG. Therefore, switches S1 to S16 of array A1 and switches S1 to S1 of array A2
The switches 106 are energized in order such as S16 and switches S1 to S16 of array A3, and the corresponding vibrators 102 are sequentially driven. In this example, 3
Although arrays of columns A1-A3 are shown, this is by way of example only and does not limit the invention; it is clear that more or fewer arrays may be arranged. .

The arrays A1 to A3 are arranged in the azimuth direction indicated by arrow B, that is, in the direction perpendicular to the slice direction, as shown in FIG. Therefore, when sequentially driven as described above, tomography can be performed for three scanning slices 210, 212, and 214 as shown in the figure. In the example above,
The time required for this is 1920 microseconds. Therefore, the averaging operation can be performed eight times in one frame period. Furthermore, even if you perform a scanning line interpolation operation that interpolates the scanning line every two slices, the
Since it is completed in microseconds, the averaging can be performed six times.

By applying this method, it is basically possible to display multiple cross sections simultaneously in real time. In addition, so-called C-mode display is also possible, and by combining these, it is also possible to display a tomographic image three-dimensionally.As shown in Figure 10, such signal processing Temporary storage digital memory 3
00 may be provided on the output side of the video circuit. This may realize a freeze function that temporarily freezes the scanned image.

FIG. 11 shows an array 10 of 16 transducers 102.
4, an example of a probe 400 having no switch circuit is shown. In the case of this embodiment, each vibrator 102 is connected to a transmitting/receiving circuit 402 via multiple wires, and the transmitting/receiving circuit 402 has a transmitting function for 16 channels and a receiving function for one channel. This allows a scan similar to that described for the embodiment of FIG. 3 to be performed.

As described above, since the ultrasonic tomography apparatus according to the present invention does not use electronic focus, the circuit configuration is simple and no side lobes occur due to this. In other words, it basically has the same effect as a normal B-mode scanner using a single probe.

In order to further improve resolution in such ultrasonic tomography equipment, increasing the number of scanning lines,
It is advantageous to focus the ultrasound beam.

Unless the number of scan lines is increased, the number of scan lines is generally equal to the number of transducers and their spacing is equal to the transducer spacing P (FIG. 2). For example, when the acoustic aperture diameter is 2 mm, the scanning line density is 5 lines/cm. For comparison, conventional linear electronic scanners have a scanning rate of about 12 lines/cm.

Such sparse scanning line density may be interpolated using a data interpolation method. This is the signal processing circuit 11
By the signal processing operation in step 2, pixel data between two adjacent scanning lines is interpolated by, for example, linear interpolation. According to this, as shown in FIG. 12, the kth scanning line (solid line 50
0)), then the data Nk' of the interpolated scanning line k' (indicated by dotted line 502) between the k-th scanning line and the k+1-th scanning line is (Nk+Nk+1)/2. It can be obtained with

Further, scanning lines may be increased by the following scanning interpolation method. According to this, scanning can be performed at intervals that are half the transducer pitch P.
Referring to FIGS. 13 and 14, the array
Both arrays A1 and A2 are arranged at relative positions shifted by P/2 from each other in the array direction, that is, in a direction perpendicular to arrow B, and are supported by a support 504. In other words, the scanning line 506 output from the array A1 and the scanning line 510 output from the array A2 are arranged shifted by P/2 in the array direction. Furthermore, Figures 15 and 16
As shown in the figure, both arrays A1 and A2 are given directivity such that the centers of the ultrasound beams intersect each other in the slice direction, for example, at a position approximately half of the diagnostic depth. Therefore, as can be seen from FIG. 16, the diameter of the beam is equal to the aperture diameter D at position F. In this way, the resolution in the slice direction is made comparable to that in the azimuth direction B. This position F can be arbitrarily set by adjusting the orientations of arrays A1 and A2.

In addition, as shown in FIG. 17, array A1 and
An acoustic lens 600 may be provided at A2 to further improve the resolution. The beam width in the slice direction is focused by this lens 600 as shown in FIG. 18, and the region where the slice width is equal to or less than the aperture diameter D is expanded as shown by L1 in the same figure. If this scanning interpolation method is combined with the scanning line increasing method described above, the scanning line density will be further doubled. Overall, therefore, the scanning line density can be increased by a factor of 2 to 4. Note that in these figures, the acoustic matching layer in the vibrator array is not directly related to the understanding of the present invention, and is therefore omitted to avoid complicating the figures.

A beam focusing method using such an acoustic lens is advantageously applied to focus the ultrasonic beam.
As shown in FIG. 19, the ultrasonic probe includes a vibrator 102 supported on a support 504, and an acoustic matching layer 700 formed thereon. In this embodiment, the vibrator 102 has a rectangular parallelepiped shape with an aperture D and a slice width L, as shown in FIG. 20A. The slice width L may be equal to the aperture D as shown in FIG. In this way, the ultrasonic tomography apparatus according to the present invention can have the same resolution in the slice direction and in the azimuth direction.

In conventional linear electronic scanners, due to the scanning method,
Although an acoustic lens can be applied only in the slice direction, in the ultrasonic tomography apparatus according to the present invention, an acoustic lens can be provided for each single transducer. Therefore, the focused sound field is inherently superior compared to electronic focus methods.

The acoustic lens 600 shown in FIG. 21 is a convex type, and the acoustic lens 610 shown in FIG. 22 is a concave type. These have a circular planar shape as shown in B of these figures, but may also be rectangular in the azimuth direction B and semicylindrical shape as shown in FIG. Of course, this may also be concave.

The radii of curvature of the convex surface 620 and concave surface 622 are as shown in FIG. 24 for those corresponding to FIG. 21 or 23, and as shown in FIG. 25 for those corresponding to FIG. 22, respectively. r1 and
r2, the sound velocity in the lens material is v1 and v2, respectively
Then, r1=F.(1-n) =F.(1-c/v1) r2=F.(1-n) =F.(1-c/v2). However, c is the speed of sound in the living body 710. Further, in a concave type, r is positive when n<1 (v>c), and in a convex type, r is negative when n>1 (v<c). For example, if c is approximately 1500 m/s,
If F is 10 mm and silicone rubber with v1 of 1100 m/s is used as the convex lens material, n =
1.36, r=3.6mm, and v2 is the concave lens material.
Using polycarbonate at 1800 m/s, n=0.83 and r1.7 mm.

An acoustic lens having such a shape can be easily manufactured by molding or the like, and it is advantageous to manufacture a lens that is integrally molded with the number of elements required for the vibrator array.

Specific Effects of the Invention The ultrasonic tomography apparatus according to the present invention can obtain tomographic images of superficial tissues with high resolution without using electronic focus.

More specifically, since no electronic focus is used, there are no sidelobes due to quantization, a concave transducer or acoustic lens forms a focused sound field, and the transducer material has a width greater than its thickness. By doing this, it is possible to approximately configure a piston sound source. Therefore, excellent ultrasonic sound field characteristics can be formed.

In particular, since ultrasonic waves can be transmitted and received with good directivity in a high frequency region of about 10 MHz or higher, it can be particularly effectively applied to tomography of superficial tissues.
In addition, compared to conventional linear electronic scanners, there is no need to cut each vibrator material into small pieces, which means that the width of the vibrator is wider and fewer in number, making it easier to process probes and wire electrodes. The advantages are also significant. Furthermore, there is no need for a circuit to form an electronic focus, and the number of transmission and reception channels is small, so the circuit configuration is simple and the number of cable connections between the device and the probe is small. The device configuration is simplified.

Furthermore, because of the high scanning rate, there is a considerable margin in the scanning period of one frame, so various signal processing such as averaging pixel signals over multiple frames and simultaneous scanning of multiple cross sections can be performed in real time. I can do it.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams for explaining the basic principle of the ultrasonic tomography apparatus according to the present invention, FIG. 3 is a block diagram showing an embodiment of the ultrasonic tomography apparatus according to the present invention, and FIG. 4 5 is a graph for explaining the ultrasonic propagation characteristics of the ultrasonic probe used in the embodiment shown in FIG. 3, FIG. 6 is a timing diagram showing the operation of the embodiment shown in FIG. 3, and FIG. 8 are block diagrams and timing diagrams showing other embodiments of the present invention, respectively, and FIG.
FIG. 10 and FIG. 11 are block diagrams showing other embodiments of the present invention, and FIG. 12 is a perspective view showing an example of a probe used in the embodiment shown in FIG. Explanatory diagram for explaining the increase in scanning lines due to the applied data interpolation method, 13th
25 through 25 are explanatory diagrams for explaining the configurations of various probes applied to the ultrasonic tomography apparatus according to the present invention. Explanation of symbols of main parts, 100... Ultrasonic probe, 102... Vibrator, 104... Transducer array, 110... Transmission/reception circuit, 112... Reception signal processing circuit, 116... Video monitor, 118... Control circuit, 600...acoustic lens.

Claims (1)

[Scope of Claims] 1. An electroacoustic transducer for mutually converting an electrical signal and an ultrasonic wave, and an electroacoustic transducer that drives the electroacoustic transducer to transmit an ultrasonic wave that is reflected from a subject and transmitted by the electroacoustic transducer. a transmitting/receiving circuit that receives an electrical signal according to the detected ultrasound; a video output means that visually displays an image according to the received electrical signal; and a video output means that controls the electroacoustic converting means, the transmitting/receiving circuit, and the video output means. an ultrasonic tomography apparatus including a control circuit for performing ultrasonic tomography of a subject, wherein the electroacoustic transducer includes a transducer array made up of a plurality of vibrating bodies that transmit and receive ultrasonic waves; Each of the bodies has the shape of a generally flat rectangular parallelepiped as a whole, and the length of the side of the rectangular parallelepiped in the direction of transmitting and receiving ultrasound waves is shorter than the length of the sides in two directions perpendicular to this, and The plurality of vibrating bodies output ultrasonic waves of a relatively high frequency, and the control circuit sequentially drives the plurality of vibrating bodies one by one to generate ultrasonic waves. An ultrasonic tomography apparatus characterized by performing linear scanning of transmitting and receiving sound waves. 2 The frequency of the ultrasound is such that when the ultrasound is output from the surface of a living body as a subject into it by the electroacoustic transducer, a far-field sound field is formed beyond the superficial tissues of the living body. The ultrasonic tomography apparatus according to claim 1, wherein the ultrasonic tomography apparatus is set to a reasonably high frequency. 3. The vibrator array includes two arrays in which vibrating bodies are linearly arranged, and the vibrating bodies in the two arrays are substantially spaced apart from each other between the arrays in each column of the vibrating body array pitch in each array. 3. The ultrasonic tomography apparatus according to claim 2, wherein the ultrasonic tomography apparatus is arranged so as to be shifted by a length equal to half of . 4. The ultrasonic tomography according to claim 2 or 3, wherein each of the plurality of vibrating bodies is formed with an acoustic lens for converging ultrasonic waves in front of the vibrating body. Photography equipment. 5. Claim 3, wherein the two rows of arrays are arranged such that the directivity centers of the two rows of arrays in the slice direction intersect with each other within the range of the near sound field. Ultrasonic tomography device described in Section 1. 6. The video output means displays the video in real time at a predetermined frame rate, and the control circuit controls the electroacoustic conversion means, the transmitting/receiving circuit, and the video output means at the frame rate, and displays the video on the superficial tissues of the living body. Claims characterized in that the vibrating body is sequentially scanned at a speed such that reflected ultrasonic waves are detected by the electroacoustic transducer, and the image output means performs signal processing on the image. The ultrasonic tomography apparatus according to item 2. 7. The ultrasonic tomography apparatus according to claim 6, wherein the signal processing includes processing to increase the S/N ratio of the image. 8. The ultrasonic tomography apparatus according to claim 6, wherein the signal processing includes processing to increase the number of scanning lines of the image. 9. The ultrasonic wave according to claim 6, wherein the transducer array includes a plurality of arrays arranged to slice the subject and obtain a plurality of slice tomographic images in the azimuth direction. Tomography device.