JP2009261608A - Ultrasonic tomographic imaging method and ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clearly project the lesion by microcalcification in an ultrasonic diagnostic apparatus for mamma. <P>SOLUTION: A plurality of predetermined two-dimensional tomographic (slice) images Pa, Pb, and Pc, etc., separated by a predetermined distance by tomographic surfaces parallel to each other for a microcalcificated lesion 31 are obtained, and they are added to prepare one two-dimensional tomographic image. That is, in the relation of X-ray imaging for obtaining compressed images transmitted through an imaging object and ultrasonic tomographic imaging for obtaining the two-dimensional tomographic (slice) images, the compressed two-dimensional tomographic (slice) images of a fine section are obtained. Thus, a minute structure such as a minute (about 100 to 200 μm) calcificated lesion or the like in a precancer stage, which blurs (S/N is low) and is not clear in three-dimensional image comprising the tomographic image of the large section such as CT and is buried in other internal organs or the like and is not clear in X-ray imaging that compresses the entire body, is clearly (excellent S/N, high contrast) projected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tomographic method referred to as so-called ultrasonic echo and an ultrasonic diagnostic apparatus using the same, in which ultrasonic waves are incident on an imaging target and a two-dimensional tomographic image of the imaging target is captured from a reflected wave. In particular, the present invention relates to an apparatus capable of displaying a tomographic image at an arbitrary position of the breast.

  An ultrasonic diagnostic apparatus is a medical imaging device that non-invasively obtains a tomographic image of soft tissue in a living body from a body surface by an ultrasonic pulse reflection method or the like. Compared to other medical imaging devices, this ultrasonic diagnostic device is small, inexpensive, and has high safety without exposure to X-rays. Therefore, the circulatory system (heart coronary artery), digestive system (gastrointestinal), internal medicine Widely used in systems (liver, pancreas, spleen), urology (kidney, bladder), and obstetrics and gynecology. In particular, in recent years, in breast diagnosis, ultrasonic diagnosis has become possible to highly diagnose tumors and tumors, and has greatly contributed to the discovery of breast cancer, and its importance has been increasingly recognized.

  In breast tissue, it is known that microcalcification often occurs as a sign of breast cancer. One or several microcalcification lesions are locally scattered. Since lime is harder than living tissue, it is expected to reflect ultrasonic waves well and to have high brightness on the image. However, when actually observing from the image, it is said that it is difficult to extract even if the size is about several hundred microns.

  More specifically, first, interference fringes called speckle patterns due to random ultrasonic interference may occur on the ultrasonic image. This speckle pattern appears remarkably in an organ with a smooth surface. For this reason, in the case of a liver that has such a smooth surface, for example, in the case of a liver, a doctor who has a certain degree of experience can use the speckle pattern that he / she knows to come out by himself While canceling, it is possible to make use of the speckle pattern for diagnosis, for example, by diagnosing a liver cirrhosis portion that is not smooth. That is, in the organ having a smooth surface, the speckle pattern, which is noise, can be used for diagnosis.

  On the other hand, in the case of breast cancer screening, the initial microcalcified lesion is buried in the speckle pattern appearing in the grain of rice (similarly) and is easily overlooked. Therefore, in breast cancer diagnosis, there is a need to remove the speckle pattern, and examples of techniques for that include spatial synthesis, CFAR processing, and speckle reduction filter.

The spatial synthesis is to superimpose transmission / reception signals from different frequencies and different directions to smooth speckles (for example, Patent Document 1). The CFAR process is a process of subtracting the target pixel by the average luminance of surroundings and using this to extract a high luminance part (see, for example, Patent Document 1). The speckle reduction filter removes speckles by performing density averaging using a moving average method or a selective local averaging method. In addition to these speckle pattern removal methods, although not in the field of ultrasonic diagnosis, various attempts to automatically recognize microcalcifications have been reported mainly as applications of X-ray diagnostic images (for example, patents). Reference 2).
JP-A 61-189476 Japanese Patent No. 3596922

  However, the mammary gland to be diagnosed in the breast cancer diagnosis has a complicated structure such as a mammary gland extending in a tree shape, and is not originally a homogeneous organ. For this reason, when the conventional filter processing is performed, a lesion portion that has been microcalcified is detected, and at the same time, the mammary gland structure is also extracted (as a structure), and there is a problem that the two cannot be clearly distinguished. In this respect, the mammary gland is a structure that is clearly larger than the microcalcified lesion. Therefore, even if it remains after filtering, it is expected to be discriminated visually. The inventors often experience in research that this is difficult. In particular, when only a part of the mammary gland structure remains, the image after the filter processing may look like a dot, and may be an image similar to a microcalcified lesion.

  An object of the present invention is to provide an ultrasonic tomography method and an ultrasonic diagnostic apparatus capable of accurately distinguishing between a continuous structure such as a mammary gland and a minute structure such as a microcalcification lesion and extracting the microstructure. It is to be.

  The ultrasonic tomography method of the present invention is a method for making a two-dimensional tomographic image of a subject to be photographed from a reflected wave by making an ultrasonic wave incident on the subject to be photographed. A step of photographing a plurality of predetermined two-dimensional images separated by a predetermined distance on a tomographic plane parallel to the step, and a step of creating one two-dimensional tomographic image by adding the obtained two-dimensional tomographic images It is characterized by including.

  In the ultrasonic diagnostic apparatus of the present invention, in an ultrasonic diagnostic apparatus that inputs an ultrasonic wave into an imaging target and captures a two-dimensional tomographic image of the imaging target from a reflected wave, there are two elements that transmit and receive the ultrasonic wave. Dimensionally arranged probe, and imaging control for sequentially transmitting and receiving ultrasonic waves to a plurality of predetermined elements of the probe and imaging tomographic planes substantially parallel to each other at intervals of the elements And an image compositing unit that adds a plurality of two-dimensional tomographic images photographed by the elements in each row to create a single two-dimensional tomographic image.

  According to the above configuration, a method for imaging a two-dimensional tomographic (slice) image of the imaging target from a reflected wave received by the probe by entering ultrasonic waves into the imaging target from the probe, and In the present invention, a two-dimensional tomographic image that is normally captured by a single image in the apparatus is separated from the probe by a predetermined distance (to the left and right) by a tomographic plane that is substantially parallel to the probe. Thus, a plurality of predetermined images are taken, and the image composition unit adds the plurality of two-dimensional tomographic images to create one two-dimensional tomographic image. That is, in the present invention, a compressed two-dimensional tomographic (slice) image of a minute section is used in relation to X-ray imaging that obtains a compressed image that has passed through the imaging target and ultrasonic tomography that obtains a two-dimensional tomographic (slice) image. Will get.

  Therefore, in a three-dimensional image composed of a tomographic image of a large section such as CT, it is not clear because it is blurred (S / N is low), and in X-ray imaging that compresses the whole body, it is applied to other organs and organs. Microstructures such as minute (about 100 to 200 μm) calcified lesions in the pre-cancerous stage, which are buried and are not clear, can be clearly displayed (good S / N, high contrast).

  Furthermore, in the ultrasonic tomography method of the present invention, the predetermined distance and the number of the plurality of sheets are selected such that a distance corresponding to the result is about 2 to 3 times the diameter of the microcalcified lesion. And

  According to the above configuration, when determining the number of two-dimensional tomographic images to be added to create one two-dimensional tomographic image, the distance obtained from the result of the above-described slice interval and the number of sheets is very small. It is set to be about 2 to 3 times the diameter of the calcified lesion, and a number of two-dimensional tomographic images suitable for the slice interval are synthesized.

  Therefore, almost all the particles of the microcalcification lesion are included in the distance, and the synthesized two-dimensional tomographic image can project the microcalcification lesion more clearly.

  Furthermore, in the ultrasonic tomography method of the present invention, in each of the two-dimensional tomographic imaging steps, the ultrasonic beam is deflected in the forward direction (front-rear) to perform transmission / reception (scanning) and the sub-direction (left-right). The method includes a step of transmitting (transmitting) and transmitting / receiving in three or more directions, and a step of spatially synthesizing the transmitted / received results.

  According to the above configuration, each of the two-dimensional tomographic images added before and after is also transmitted and received (scanned) by deflecting the ultrasonic beam in the forward direction (front and back) and deflected in the sub direction (left and right). Thus, transmission / reception (scanning) is performed in three or more directions, and the obtained results are obtained by spatial synthesis.

  Therefore, a spatially synthesized image generally has low noise and speckle (for example, in a synthesized image scanned in the n direction (having a structural unit screen), it decreases at the square root of n. Therefore, the microcalcification lesion can be projected more clearly. Further, since the deflection in the sub-direction (left and right) can cover a wider range than the distance (slice interval) between the respective two-dimensional tomographic (slice) images, the imaging range can be expanded.

  The ultrasonic tomography method of the present invention is characterized in that different frequencies are used for the deflection (scanning) in the sub-direction (left and right).

  According to said structure, the speckle in a tomographic image reduces further, and it can project the micro calcification lesion hidden in the speckle more clearly. It should be noted that the scanned image may be spatially synthesized by changing the frequency for scanning in the forward direction (front and back).

  As described above, the ultrasonic tomography method and the ultrasonic diagnostic apparatus according to the present invention make ultrasonic waves incident on the imaging object from the probe, and 2 of the imaging object from the reflected wave received by the probe. In a method for photographing a two-dimensional tomographic (slice) image, normally, a two-dimensional tomographic image that is usually photographed by a single image is obtained in advance by the photographing control unit on the probe in a plane parallel to each other. A plurality of predetermined images are taken at a predetermined distance (left and right), and the image composition unit adds the two two-dimensional tomographic images to create one two-dimensional tomographic image.

  Therefore, it is not clear in a three-dimensional image composed of a tomographic image of a large section such as CT, and is not clear (S / N is low), and other organs and organs in X-ray imaging that compresses the whole body It is possible to project a fine structure (good S / N, high contrast) such as a minute (about 100 to 200 μm) calcified lesion in the precancerous stage, which is not clear due to being buried.

[Embodiment 1]
FIG. 1 is a block diagram showing an electrical configuration of an ultrasonic diagnostic apparatus 1 that uses an ultrasonic tomography method according to an embodiment of the present invention. The ultrasonic diagnostic apparatus 1 includes a probe 2 that receives ultrasonic waves into a living body that is a subject to be imaged and receives reflected waves from the living body, and transmission / reception that causes the probe 2 to transmit and receive ultrasonic waves. A circuit (T / R) 3, an analog / digital converter (ADC) 4 that performs analog / digital conversion of a received signal while converting a transmitted signal to digital / analog, and a transmission signal are created, and the received signal is phased A digital signal processor (DSP) 5 that creates a two-dimensional tomographic image, a central processing unit (CPU) 6 that controls each unit, an input operation unit 7 that is operated by a laboratory technician or a doctor, and the digital A video processing unit (VDP) 8 that sequentially converts a two-dimensional tomographic image obtained by the signal processor 5 into a television signal form, and a video signal generated by the video processing unit 8 Constituted by a Shimesuru television monitor (TV) 9.

  As shown in FIG. 2, the DSP 5 includes a filter (FIL) 11 that digitally processes a received signal, a detection circuit 12 that detects a specific component from the filtered signal, and an amplification circuit 13 that amplifies the detected signal. And a beam forming machine (BF) 14 for forming a beam from the amplified signal, and a filter 15 for outputting the formed beam.

  FIG. 3 is a block diagram of the beam former 14. In the beam former 14, a rate pulse for forming a transmission ultrasonic wave is repeatedly generated at a predetermined rate frequency in the pulsar circuit 21, and the transmission deflection unit 22 performs delay control as will be described later to perform deflection control. Is generated and applied to the probe 2 via the analog / digital converter 4 and the transmission / reception circuit 3. Further, the reception signal is input from the transmission / reception circuit 3 to the analog / digital converter 4, and the obtained signal is subjected to delay control in the reception deflection unit 23 to perform deflection control.

  In the deflection control in the transmission deflection unit 22 and the reception deflection unit 23, the delay time is stored in the phase control unit 24, and the frequency of the ultrasonic wave that is switched in conjunction with switching of each deflection direction is the frequency control unit 25. The switching of the two-dimensional tomographic (slice) plane according to the present invention, which will be described later, is stored in the slice control unit 26, which is sequentially selected by the selector 27 and given to the pulsar circuit 21, Also provided to the adder 28. The adder 28 adds a predetermined number of obtained two-dimensional tomographic (slice) images back and forth to create a new two-dimensional tomographic (slice) image. The created images are sequentially stored in the storage unit 29, and noise generated at the time of frequency modulation is removed by the filter 15 including a band pass filter and a low pass filter, and is appropriately read out to the video processing unit 8.

  FIG. 4 is a plan view schematically showing the element structure of the probe 2. In the example of FIG. 4, the probe 2 includes 128 elements in the x (front-rear) direction and 9 elements in the y (left-right) direction, elements a1 to a128; b1 to b128; I1 to i128 (generally referred to as reference signs a to i hereinafter) arranged in an electronic scanning type ultrasonic probe. Note that the arrangement of the elements can be arbitrarily set in accordance with the application and resolution requirements. The elements a to i are shifted one by one in the x direction, and scanning (electronic scanning) is performed by delay control by the transmission deflection unit 22 and the reception deflection unit 23, for example, in units of 16.

  FIG. 5 is a diagram for explaining the scanning method. Here, elements a1 to a16 are used. In the example of FIG. 5, the focal point F is formed by focusing the ultrasonic wave on the center line L1 of the elements a1 to a16. For this purpose, according to the delay curve indicated by the reference symbol L2, the transmission ultrasonic pulse is transmitted to each of the elements a1 to a16 with a delay time as large as the central elements a8 and a9 and with a delay time as small as the end elements a1 and a16. It is only necessary to process the received ultrasonic waves by the elements a1 to a16. By performing such delay time control, a substantially fan-shaped scan as shown in FIG. 6 can be performed. The beam divergence angle θa + θb is, for example, 120 to 160 °.

  The delay time is stored in the phase control unit 24. Further, on the basis of θ = 0 °, when scanning at each of the spread angles (deflection angles) θa and θb, ultrasonic waves having different frequencies are used, and the frequencies are stored in the frequency control unit 25. Yes.

  It should be noted that in the present invention, as shown in FIG. 6, the CPU 6 that is the imaging control unit is connected to the elements a to i in each column by a predetermined distance on a tomographic plane substantially parallel to each other. Are photographed two-dimensional tomographic (slice) images Pa, Pb, Pc,... Separated before and after (in the left-right direction of the probe 2), and the images are successively added by an adder 28 serving as an image composition unit. A predetermined two (adjacent) images are added to create one two-dimensional tomographic (slice) image. FIG. 6 shows an example in which three two-dimensional tomographic (slice) images Pa, Pb, and Pc are added. The elements a to i are, for example, 100 μm square, and thus a compressed image is synthesized in the y direction in the range of 300 μm.

  FIG. 7 is a diagram showing the relationship of the two-dimensional tomographic (slice) images Pa, Pb, Pc,... With respect to the microcalcification lesion 31, (a) is a plan view, and (b) is a perspective view. It is. By the two-dimensional tomographic (slice) images Pa, Pb, Pc,..., The microcalcification lesion 31 is cut into a circle and its cross section is photographed. Here, the microcalcification lesion 31 in the precancerous stage has a spherical body, a spindle body, or an ellipsoid, and its diameter is about 100 to 200 μm. Therefore, from the pitch of the elements a to i, which is a predetermined distance (slice interval) between the images Pa, Pb, Pc,... = 100 μm, the number of composites is about 2 to 3 times the diameter, for example, 5 ( = 400 μm), the particles of the microcalcification lesion 31 are almost entirely included in the range of the composite image.

  Then, as shown in FIG. 8, the actual scanning is performed in two dimensions using the elements a1 to a16, b1 to b16, c1 to c16, d1 to d16, and e1 to e16 in the case of combining the five sheets on the left and right. The tomographic (slice) image V1, and then the elements b1 to b16, c1 to c16, d1 to d16, e1 to e16, and f1 to f16 are used to convert the two-dimensional tomographic (slice) image V2 to c1 to c16, d1. Using d16, e1 to e16, f1 to f16, and g1 to g16, a two-dimensional tomographic (slice) image V3 is used, and elements d1 to d16, e1 to e16, f1 to f16, g1 to g16, and h1 to h16 are used. Then, a two-dimensional tomographic (slice) image V4 is obtained by using e1 to e16, f1 to f16, g1 to g16, h1 to h16, and i1 to i16, and shown in FIG. First lap The scanning in H1 is terminated, and then one element is shifted in the x direction, and the same scanning in the second period H2 is performed from the elements a2 to a17, b2 to b17, c2 to c17, d2 to d17, and e2 to e17. I do.

  With this configuration, a three-dimensional image composed of a tomographic image of a large section such as a CT is not clear due to blur (S / N is low), and other than X-ray imaging that compresses the entire body. Microstructures such as microcalcification lesions 31 in the precancerous stage, which are not clear due to being buried in the organs or organs, can be clearly displayed (good S / N, high contrast). For example, when 10 sheets are combined, the S / N is increased by 20 dB, and a significantly clearer image can be obtained as compared with the conventional case.

[Embodiment 2]
FIG. 9 is a diagram for schematically explaining an ultrasonic tomography method according to another embodiment of the present invention. It should be noted that in this embodiment, scanning (deflection) in the y (left-right) direction is performed in addition to the normal scanning (deflection) in the x (front-rear) direction (array direction) shown in FIGS. In other words, the received signals are spatially synthesized to create the two-dimensional tomographic (slice) images Pa, Pb, Pc,. The scanning (deflection) method is the same as that shown in FIG. FIG. 9 shows the state of scanning (deflection) only for the image Pc. In addition to the central scanning indicated by the reference symbol Pc, the left and right scannings indicated by the reference symbols Pc ′ and Pc ″ are performed. Therefore, in combination with the scanning in the x (front and back) direction (array direction), one array has 5 directions (front, front, back, left, right) or 9 directions ((front, front, back) x (front, The scanning of left, right)) is performed. As described above, the two-dimensional tomographic (slice) images Pa, Pb, Pc,... Including the scanning (deflection) in the y (left-right) direction are substantially parallel to each other. (Slice) There may be an inclination of several degrees between the images Pa, Pb, Pc,.

  Here, if the steering angles θc, θd in the y direction and the steering angles θa, θb in the x direction are brought close to each other, too much image information before and after the tomographic plane (y direction) is taken in, resulting in noise. Therefore, by calculating the size of the lesion by steering in the x direction and determining the steering angles θc and θd in the y direction based on the size, the detection accuracy of the lesion can be improved. However, it may be determined in anticipation. In this case, in the range where the size of the lesion is 1 mm to 2 or 3 cm, the tangents θc and θd are in the range of 1/50 to 30/50 when the distance in the beam direction is about 5 cm. When the penetration distance to the living body is 20 cm, the range is 1/200 to 30/200. For this reason, the steering angle θc + θd is, for example, 12 to 16 °, and is preferably about 1/10 of the aforementioned θa + θb.

  With this configuration, each of the two-dimensional tomographic (slice) images Pa, Pb, Pc,... Added before and after the tomographic plane (in the horizontal direction of the probe 2) is also an ultrasonic beam. Was transmitted in the positive direction (x (front-rear) direction) to perform transmission / reception (scanning), and deflected in the sub-direction (y (left-right) direction) to perform transmission / reception (scanning) in three or more directions. Since the result is created by spatial synthesis, the microcalcification lesion 31 can be projected more clearly. Here, a spatially synthesized image generally has low noise and speckle (for example, in a synthesized image scanned in the n direction (having a structural unit screen), it decreases at the square root of n. To do). Further, since the deflection in the sub-direction (y (left and right) direction) can cover a wider range than the distance (slice interval) between the two-dimensional tomographic (slice) images Pa, Pb, Pc,. The shooting range can be expanded.

  Here, general spatial synthesis is an imaging technique for obtaining ultrasonic image unit screens of a large number of objects from a plurality of viewpoints and viewing angles. By combining data obtained from portions corresponding to the image unit screens, the image unit screens are combined to form a spatially synthesized image such as a three-dimensional image. In such spatial synthesis, as described in, for example, US Pat. No. 6,129,599, electron beam scanning is performed from substantially independent spatial directions, and signal images of partially overlapping constituent image unit screens are captured. Thereafter, processing such as combining the obtained structural unit screens by integration or addition to form a composite image is performed instantly (typically larger than 20 image unit screens / second). The signal capture and composite image formation is performed at a signal capture unit screen speed, i.e., a speed determined with a minimum unit of time to scan one unit of the entire screen over the amplitude and transmission distance selected for the image. Iterates and is imaged.

  On the other hand, in the present invention, a predetermined number of two-dimensional tomographic (slice) images Pa, Pb, Pc,... Are synthesized before and after, which is completely different from the conventional spatial synthesis.

1 is a block diagram showing an electrical configuration of an ultrasonic diagnostic apparatus using an ultrasonic tomography method according to an embodiment of the present invention. It is a block diagram which shows the structure of DSP in the said ultrasonic diagnostic apparatus. It is a block diagram of the beam former in the DSP. It is a top view which shows roughly the element structure of a probe. It is a figure for demonstrating the scanning method by the said probe. It is a figure for demonstrating typically the ultrasonic tomography method which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the said scan and a microcalcification lesion. It is a figure for demonstrating typically the actual scanning which repeats the scanning shown in the said FIG. It is a figure for demonstrating typically the ultrasonic tomography method which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus 2 Probe 3 Transmission / reception circuit 4 Analog / digital converter 5 Digital signal processor 6 Central processing part 7 Input operation part 8 Video processing part 9 Television monitor 11 Filter 12 Detection circuit 13 Amplification circuit 14 Beam formation Machine 15 Filter 21 Pulser circuit 22 Transmission deflection unit 23 Reception deflection unit 24 Phase control unit 25 Frequency control unit 26 Slice control unit 27 Selector 28 Adder 29 Storage unit 31 Microcalcification lesion

Claims (5)

In a method for imaging a two-dimensional tomographic image of a subject to be photographed from a reflected wave by making an ultrasonic wave enter the subject
Photographing the two-dimensional tomographic images at a predetermined distance apart from each other by a predetermined distance between substantially parallel tomographic planes;
And a step of adding the obtained two-dimensional tomographic images to create one two-dimensional tomographic image.   2. The ultrasonic tomography method according to claim 1, wherein the predetermined distance and the number of the plurality of sheets are selected such that a distance corresponding to a result value thereof is about 2 to 3 times a diameter of the microcalcified lesion. In the photographing process of each two-dimensional tomographic image,
Deflecting the ultrasonic beam in the positive direction to transmit and receive, and deflecting in the sub direction to transmit and receive in three or more directions;
The ultrasonic tomography method according to claim 1, further comprising a step of spatially synthesizing the transmitted and received results.   The ultrasonic tomography method according to claim 3, wherein different frequencies are used for the deflection in the sub direction. In an ultrasonic diagnostic apparatus for injecting ultrasonic waves into an imaging target and capturing a two-dimensional tomographic image of the imaging target from reflected waves,
A probe formed by two-dimensionally arranging the elements that transmit and receive the ultrasonic waves;
An imaging control unit that sequentially transmits and receives ultrasonic waves to a plurality of predetermined elements of the probe and performs imaging of tomographic planes substantially parallel to each other at an interval of the elements;
An ultrasonic diagnostic apparatus comprising: an image synthesis unit that adds a plurality of two-dimensional tomographic images photographed by the elements in each row to create one two-dimensional tomographic image.

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