JP2009082450A - Medical imaging apparatus and medical imaging method - Google Patents

Abstract

In a medical imaging apparatus and a medical imaging method for imaging a mammary gland and a breast using radiation and ultrasound together, a multiple reflection image of a compression plate superimposed on an ultrasound diagnostic image is removed.
The medical imaging apparatus includes a compression plate having a first surface that compresses a subject and a second surface opposite to the first surface, and moves along the second surface of the compression plate. Ultrasonic transducers that transmit and receive ultrasonic waves, and a plurality of ultrasonic waves when the compression plate or the ultrasonic probe is at a plurality of different positions based on a reception signal output from the ultrasonic probe Image data generating means for generating image data representing an image and multiplexing for generating image data representing a multiple reflection image by extracting a multiple reflection image of a compression plate based on image data representing at least one ultrasonic image A reflection image extraction unit; and a subtraction unit that generates image data representing an image obtained by subtracting the multiple reflection image from the image of the subject including the multiple reflection image.
[Selection] Figure 1

Description

  The present invention relates to a medical imaging apparatus and a medical imaging method for imaging breasts and breasts by transmitting and receiving ultrasound while compressing a breast with a compression plate in order to diagnose breast cancer and the like.

  In a medical imaging apparatus that performs imaging of a subject by transmitting and receiving ultrasonic waves, an ultrasonic probe (probe) is usually used to combine the ultrasonic waves formed by combining a plurality of ultrasonic waves. By scanning the specimen and receiving the ultrasonic echo reflected inside the specimen, image information relating to the tissue of the specimen can be obtained based on the intensity of the ultrasonic echo.

  According to ultrasonic imaging, since a living body is acoustically measured using ultrasonic waves, tissue characteristics of an organ in the living body can be diagnosed noninvasively. For example, early diagnosis of breast cancer can be performed by diagnosing the mammary gland and breast tissue characteristics by ultrasonic imaging. That is, since a characteristic occurs in the intensity pattern of the ultrasound echo in the captured ultrasound image of the mammary gland and breast, the progress of the breast cancer symptom can be visually confirmed.

  Furthermore, in order to diagnose breast cancer, it is considered to make a diagnosis based on both an ultrasound image and a radiographic image. X-ray imaging (X-ray mammography) of the mammary glands and breasts used to diagnose breast cancer is suitable for imaging calcification, which is one of the early symptoms of cancer, and enables high-resolution and high-sensitivity detection. It is. In particular, in the case of fat (so-called “fat breast”) in which mammary gland tissue begins to atrophy and is replaced with fat like a postmenopausal woman, more information is obtained by X-ray mammography. However, X-ray imaging has the disadvantage that the ability to detect tissue specificity (tissue properties) is low.

  In addition, in the X-ray image, since the mammary gland exhibits a uniform soft tissue concentration, in the case of a mammary gland in which the mammary gland has developed (so-called “dense breast”) like adolescent to premenopausal women Detecting a tumor becomes difficult. Furthermore, in X-ray mammography, only a two-dimensional image obtained by projecting a three-dimensional subject onto a plane can be obtained. Therefore, even if a tumor is found, information such as the position and size of the tumor in the depth direction is available. It is difficult to grasp.

  On the other hand, ultrasonic imaging can detect tissue specificity (for example, the difference between a cyst and a solid substance) and can also detect lobular cancer. It is also possible to observe an image in real time and generate a three-dimensional image. However, the accuracy of the ultrasonic imaging inspection often depends on the technique of an operator such as a doctor, and the reproducibility is low. In addition, it is difficult to observe minute calcification in an ultrasonic image.

  As described above, since the X-ray mammography examination and the ultrasonic imaging examination have advantages and disadvantages, it is desirable to perform both examinations in order to detect breast cancer with certainty. Since the X-ray mammography examination is performed in a state where the subject (breast) is compressed by the compression plate, in order to make a diagnosis based on the X-ray image and the ultrasonic image of the subject in the same state, ultrasonic imaging is performed. The examination must be performed in the same state as when the X-ray mammography examination is performed, that is, in a state where the subject (breast) is compressed by the compression plate. Furthermore, a medical imaging apparatus that performs imaging of the mammary gland and breast using radiation and ultrasound in combination has been studied.

  A medical imaging apparatus that performs ultrasonic imaging while compressing a breast compresses a subject (breast) with a compression plate, and is a surface (second surface) opposite to the compression surface (first surface) of the compression plate. A plurality of ultrasonic images are acquired for the subject while moving the ultrasonic probe along the line and scanning the subject. In that case, the acoustic connection (coupling | bonding) between an ultrasonic probe and a compression board is maintained by using an echo jelly etc. as an ultrasonic coupling material.

  However, resin is often used as the material for the compression plate, and since there is a difference in acoustic impedance between the compression plate made of resin and the subject (breast), the ultrasonic wave transmitted from the ultrasonic probe is Many reflections are made at the interface (first surface) between the compression plate and the subject. A portion of the reflected wave passes through the second surface of the compression plate and enters the ultrasonic probe, and the remaining reflected wave is reflected by the second surface of the compression plate and is reflected by the first surface of the compression plate. Head to the face. By repeating this, a multiple reflection image corresponding to the thickness of the compression plate is formed. This multiple reflection image overlaps the image of the subject, making diagnosis difficult.

  As a related technique, in Patent Document 1, an ultrasonic reception signal including a multiple reflection image is branched by a distributor, one signal is delayed by one cycle of multiple reflection, and the attenuation of the reflection signal is adjusted. Thus, an ultrasonic inspection method is disclosed in which multiple reflected signals are removed by subtracting from the other signal.

  Patent Document 2 discloses a compression plate suitable for reducing reflection and attenuation of ultrasonic waves by a compression plate in an apparatus that generates an image of a breast by transmitting ultrasonic waves through an X-ray mammography compression plate. In addition to these materials and frequencies, it has been proposed to use a gel pad and apply a linking agent.

However, Patent Literature 1 and Patent Literature 2 do not propose removing an ultrasonic multiple reflection image by a compression plate by image processing.
JP-A-6-308105 Japanese Patent No. 3461509

  Therefore, in view of the above points, the present invention is superimposed on an ultrasound diagnostic image in a medical imaging apparatus and a medical imaging method for imaging breasts and breasts by transmitting and receiving ultrasound while compressing a breast with a compression plate. An object of the present invention is to remove a multiple reflection image of a compression plate using image processing.

  In order to solve the above problem, a medical imaging apparatus according to one aspect of the present invention has a first surface that compresses a subject and a second surface that faces the first surface, and transmits ultrasound. And a compression plate moving mechanism for moving the compression plate in a direction substantially perpendicular to the first surface of the compression plate, while moving along the second surface of the compression plate, An ultrasonic probe that transmits a sound wave, receives an ultrasonic echo, and outputs a reception signal; and a plurality of compression plates or ultrasonic probes based on the reception signal output from the ultrasonic probe. Based on image data generating means for generating image data representing a plurality of ultrasonic images at different positions, and image data representing at least one ultrasonic image generated by the image data generating means, the first of the compression plates By reflection of ultrasonic waves on one surface and / or second surface Multiple reflection image extraction means for generating image data representing the multiple reflection image by extracting the generated multiple reflection image, and image data representing an image obtained by subtracting the multiple reflection image from the image of the subject including the multiple reflection image are generated. Subtraction means.

  According to another aspect of the present invention, there is provided a medical imaging method along a second surface of a compression plate having a first surface that compresses a subject and a second surface that opposes the first surface. Step (a) of generating image data representing a plurality of ultrasound images when the compression plate or the ultrasound probe is at a plurality of different positions based on a reception signal output from the moving ultrasound probe And extracting a multiple reflection image generated by reflection of the ultrasonic wave on the first surface and / or the second surface of the compression plate based on the image data representing at least one ultrasonic image generated in step (a). (B) generating image data representing the multiple reflection image, and (c) generating image data representing an image obtained by subtracting the multiple reflection image from the image of the subject including the multiple reflection image. To do.

  According to the present invention, the multiple reflection image of the compression plate is extracted from the ultrasonic image in advance, and the multiple reflection image is removed by subtracting the multiple reflection image from the ultrasonic image of the subject. A good image can be obtained even at.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a block diagram showing a configuration of a medical imaging apparatus according to an embodiment of the present invention. The present invention can be applied to all medical imaging apparatuses that perform imaging of breasts and breasts by transmitting and receiving ultrasonic waves while compressing the breasts with a compression plate. The function of a radiation mammography device that generates a radiographic image by detecting the radiation to be transmitted, and an ultrasonic diagnosis that generates an ultrasonic image by transmitting ultrasonic waves to the breast and receiving ultrasonic echoes reflected inside the breast A medical imaging apparatus having both functions of the apparatus will be described. In addition to X-rays, α rays, β rays, γ rays, electron beams, ultraviolet rays, and the like can be used as radiation.

  As shown in FIG. 1, the medical imaging apparatus includes an X-ray tube 10, a filter 11, an X-ray detection unit 12 that detects X-rays generated by the X-ray tube 10 and transmitted through the subject 1, and the subject 1. A compression plate 13 for pressing the breast, a compression plate moving mechanism 14 for moving the compression plate 13, a pressure sensor 15 for detecting the pressure applied to the compression plate 13, and a plurality of ultrasonic waves for transmitting and receiving ultrasonic waves. An imaging unit including an ultrasonic probe 16 including an acoustic transducer, a probe moving mechanism 17 that moves the ultrasonic probe 16, and a position sensor 18 that detects the position of the ultrasonic probe 16. Have in.

  Furthermore, the medical imaging apparatus includes a movement control unit 20 that controls the compression plate moving mechanism 14 and the probe moving mechanism 17, an X-ray imaging control unit 30, an ultrasonic imaging control unit 40, and an image processing unit 60. , Display units 71 and 72, console 80, control unit 90, and storage unit 100.

  FIG. 2 is a side view showing the appearance of the imaging unit of the medical imaging apparatus shown in FIG. As shown in FIG. 2, the imaging unit of the medical imaging apparatus includes an arm unit 2, a base 3 that holds the arm unit 2 movably in the vertical direction (Z-axis direction), and the arm unit 2 on the base 3. It has the axial part 4 to connect. The arm unit 2 includes an X-ray tube 10, a filter 11, a radiation detection unit 12, an imaging table 19 disposed between the X-ray tube 10 and the radiation detection unit 12, and the imaging table 19. A compression plate 13 that compresses the subject 1, a compression plate moving mechanism 14 that moves the compression plate 13 in a vertical direction (Z-axis direction) substantially perpendicular to the compression surface, an ultrasonic probe 16, and an ultrasonic probe A probe moving mechanism 17 for moving the child 16 in the X-axis, Y-axis, and Z-axis directions is provided.

  The X-ray tube 10 and the filter 11 constitute a radiation generation unit. The X-ray tube 10 generates X-rays when a tube voltage is applied. The filter 11 is made of a material such as molybdenum (Mo) or rhodium (Rh), and selectively transmits a desired wavelength component from among a plurality of wavelength components included in the X-ray generated by the X-ray tube 10. To do. The X-ray detector 12 is a flat panel detector (FPD) that captures an X-ray image by detecting X-rays that have passed through the subject 1 at a plurality of detection points in a two-dimensional region. By irradiating each detection point with X-rays emitted from the X-ray tube 10 and transmitted through the subject 1, a detection signal having a magnitude corresponding to the intensity of the X-rays is output from the X-ray detection unit 12. This detection signal is input to the X-ray imaging control unit 30 (FIG. 1) via a cable.

  The compression plate 13 is installed in parallel with the imaging table 19, and the compression plate moving mechanism 14 moves the compression plate 13 in the Z-axis direction. The pressure sensor 15 detects the pressure applied to the compression plate 13, and the movement control unit 20 (FIG. 1) controls the compression plate moving mechanism 14 based on the detection result. When the subject (breast) 1 is sandwiched between the compression plate 13 and the imaging table 19, X-ray imaging is performed with the breast thickness uniform.

  Here, the compression plate 13 needs to be optically transparent in order to perform alignment and confirmation of the compression state when compressing the breast, and transmits X-rays emitted from the X-ray tube 10. At the same time, it is desirable to be formed of a material that easily propagates the ultrasonic wave transmitted from the ultrasonic probe 16. As the material of the compression plate 13, for example, a resin such as acrylic or polymethylpentene having a suitable value in the acoustic impedance that affects the reflectance of the ultrasonic wave and the attenuation coefficient that affects the attenuation of the ultrasonic wave can be used. .

  The ultrasonic probe 16 includes a plurality of ultrasonic transducers arranged one-dimensionally or two-dimensionally. Each ultrasonic transducer transmits an ultrasonic wave based on an applied drive signal and outputs a reception signal by receiving an ultrasonic echo.

  Each ultrasonic transducer is, for example, a piezoelectric ceramic represented by PZT (Pb (lead) zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene difluoride), or the like. It is comprised by the vibrator | oscillator which formed the electrode at the both ends of the material (piezoelectric body) which has the piezoelectricity. When a voltage is applied to the electrodes of such a vibrator by sending a pulsed or continuous wave electric signal, the piezoelectric body expands and contracts. By this expansion and contraction, pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and an ultrasonic beam is formed by synthesizing those ultrasonic waves. Each vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. These electrical signals are output as ultrasonic reception signals and input to the ultrasonic imaging control unit 40 (FIG. 1) via a cable.

  The ultrasonic probe 16 may be moved while being in close contact with the compression plate 13 or moved away from the compression plate 13 by inserting an ultrasonic transmission medium such as echo jelly between the compression plate 13 and the ultrasonic probe 16. You may let them. More preferably, an ultrasonic transmission medium such as echo jelly is applied to the compression plate 13 and moved while the ultrasonic probe 16 is in contact with the compression plate 13. Further, the operator may move the ultrasonic probe 16, or the probe moving mechanism 17 may move the ultrasonic probe 16. In the following, the latter case will be described.

  Referring again to FIG. 1, the X-ray imaging control unit 30 includes a tube voltage / tube current control unit 31, a high voltage generation unit 32, an A / D converter 33, and a radiation image data generation unit 34. Yes. In the X-ray tube 10, the X-ray transmission is determined by the tube voltage applied between the cathode and the anode, and the amount of X-rays generated is determined by the time integral value of the tube current flowing between the cathode and the anode. The The tube voltage / tube current control unit 31 adjusts imaging conditions such as tube voltage and tube current according to the target value. The target values of the tube voltage and tube current can be manually adjusted by the operator using the console 80. The high voltage generator 32 generates a high voltage applied to the X-ray tube 10 under the control of the tube voltage / tube current controller 31. The A / D converter 33 converts the analog radiation detection signal output from the X-ray detection unit 12 into a digital signal (radiation detection data), and the radiation image data generation unit 34 performs a radiation image based on the radiation detection data. Generate data.

  The ultrasonic imaging control unit 40 includes a scanning control unit 41, a transmission circuit 42, a reception circuit 43, an A / D converter 44, a signal processing unit 45, a B-mode image data generation unit 46, and a multiple reflection image. An extraction unit 47, a subtraction unit 48, and an image data storage unit 49 are included.

  The scanning control unit 41 sets the frequency and voltage of the drive signal applied to each ultrasonic transducer of the ultrasonic probe 16 from the transmission circuit 42 under the control of the movement control unit 20 and transmits the ultrasonic signal. Adjust the sound frequency and sound pressure. In addition, the scanning control unit 41 sequentially sets the transmission direction of the ultrasonic beam and sequentially sets and sets the transmission control function for selecting the transmission delay pattern according to the set transmission direction and the reception direction of the ultrasonic echo. And a reception control function for selecting a reception delay pattern according to the received reception direction.

  Here, the transmission delay pattern is applied to a plurality of drive signals in order to form an ultrasonic beam in a desired direction by ultrasonic waves transmitted from a plurality of ultrasonic transducers included in the ultrasonic probe 16. The reception delay pattern is a pattern of delay times given to a plurality of reception signals in order to extract ultrasonic echoes from a desired direction by ultrasonic waves received by a plurality of ultrasonic transducers. It is. The plurality of transmission delay patterns and the plurality of reception delay patterns are stored in a memory or the like.

  The transmission circuit 42 generates a plurality of drive signals respectively applied to the plurality of ultrasonic transducers. At that time, the transmission circuit 42 delays a plurality of drive signals based on the transmission delay pattern selected by the scanning control unit 41 so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers form an ultrasonic beam. The amount may be adjusted and supplied to the ultrasonic probe 16, or a plurality of drive signals may be ultrasonically transmitted so that ultrasonic waves transmitted from a plurality of ultrasonic transducers reach the entire imaging region of the subject. You may supply to the probe 16.

  The reception circuit 43 amplifies a plurality of ultrasonic reception signals respectively output from the plurality of ultrasonic transducers, and the A / D converter 44 converts the analog ultrasonic reception signal amplified by the reception circuit 43 into a digital ultrasonic signal. Convert to sound wave reception signal. Based on the reception delay pattern selected by the scanning control unit 41, the signal processing unit 45 gives respective delay times to the plurality of ultrasonic reception signals, and adds the ultrasonic reception signals, thereby receiving focus processing. I do. By this reception focus processing, sound ray data in which the focus of the ultrasonic echo is narrowed down is formed.

  Further, the signal processing unit 45 corrects the attenuation by the distance according to the depth of the reflection position of the ultrasonic wave by STC (Sensitivity Time gain Control) for the sound ray data. Then, envelope data is generated by performing envelope detection processing with a low-pass filter or the like.

  The B-mode image data generation unit 46 performs processing such as logarithmic compression and gain adjustment on the envelope data to generate image data, and the image data is converted into image data according to a normal television signal scanning method. B-mode image data is generated by performing conversion (raster conversion).

  The position of the ultrasonic probe 16 is detected by a position sensor 18 built in the ultrasonic probe 16. The movement control unit 20 grasps the position of the ultrasonic probe 16 based on the output signal of the position sensor 18 and controls the probe moving mechanism 17. While the probe moving mechanism 17 moves the ultrasonic probe 16, ultrasonic imaging is performed by the ultrasonic probe 16 transmitting and receiving ultrasonic waves.

  In the compression plate 13, a compression surface (the lower surface in FIG. 2) that compresses the subject 1 is a first surface, and a surface opposite to the compression surface (an upper surface in FIG. 2) is a second surface. The ultrasonic wave transmitted from the ultrasonic probe 16 is largely reflected at the interface (first surface) between the compression plate 13 and the subject 1 (or the air layer). A part of the reflected wave passes through the second surface of the compression plate 13 and enters the ultrasonic probe 16, and the remaining reflected wave is reflected by the second surface of the compression plate 13 to be compressed. Head to the 13th first side. By repeating this, a multiple reflection image corresponding to the thickness of the compression plate 13 is formed.

  In the present embodiment, the movement control unit 20 controls the probe movement mechanism 17 and the scanning control unit 41 so that the subject 1 does not exist between the compression plate 13 and the imaging table 19, 1 is present between the compression plate 13 and the imaging table 19 but is not compressed, and / or ultrasonic imaging is performed in a plurality of states such as a state in which the subject 1 is compressed. By performing subtraction processing based on the sound wave image, the multiple reflection image is removed from the ultrasonic image of the subject 1.

  The B-mode image data generation unit 46 generates B-mode image data representing B-mode images in a plurality of states based on reception signals output from the ultrasound probe 16 in a plurality of states. The multiple reflection image extraction unit 47 generates B mode image data representing a multiple reflection image by extracting multiple reflection images of the compression plate 13 based on B mode image data representing at least one ultrasonic image. The image data is stored in an image data storage unit 49 constituted by a memory or a hard disk. The subtraction unit 48 performs subtraction processing that takes a difference between the B-mode image data of the subject 1 including the multiple reflection image and the B-mode image data of the multiple reflection image, thereby performing the subtraction processing from the image of the subject 1 including the multiple reflection image. B-mode image data representing an image obtained by subtracting multiple reflection images is generated.

  Below, the 1st-3rd Example of a multiple reflection image extraction part is demonstrated. In the first embodiment, the subject 1 does not exist between the compression plate 13 and the imaging table 19, or the subject 1 exists between the compression plate 13 and the imaging table 19 but is compressed. By performing ultrasonic imaging in the absence, the multiple reflection image extraction unit 47a shown in FIG. 3 extracts the multiple reflection image. In such a state, since the first surface of the compression plate 13 is in contact with the air layer having an acoustic impedance that is significantly different from the acoustic impedance of the compression plate 13, the ultrasonic wave is reflected by almost 100%, and multiple reflections are performed. Is likely to occur.

  When resin is used as the material of the compression plate 13, the acoustic impedance of the compression plate 13 is about 1.5 MRayl to 5 MRayl and the acoustic impedance of air is 0.0004 MRayl. It becomes 0.00027 times or less of the acoustic impedance. In addition to the air layer, a substance having a difference in acoustic impedance may be in contact with the first surface of the compression plate 13.

  As shown in FIG. 3, the multiple reflection image extraction unit 47a according to the first embodiment is in a state where the subject does not exist between the compression plate and the imaging table, or the subject is between the compression plate and the imaging table. A first image data acquisition unit 51 that acquires, from the B-mode image data generation unit 46, B-mode image data representing an ultrasonic image obtained by performing ultrasonic imaging in a state that exists between them but is not compressed; By performing luminance correction processing on the B-mode image data acquired by the first image data acquisition unit 51 based on the difference in reflectance caused by the difference between the acoustic impedance of the subject and the acoustic impedance of air, And a luminance correction calculation unit 52 that generates B-mode image data representing a multiple reflection image. B-mode image data representing the multiple reflection image generated by the brightness correction calculation unit 52 is stored in the image data storage unit 49.

  In the second embodiment, when a plurality of B-mode image data is acquired while changing the position of the compression plate 13 with the compression plate 13 compressing the subject 1, the multiple reflection image extraction unit shown in FIG. 47b is based on the difference in variation between the ultrasonic image of the subject tissue that varies with the change in the position (compression state) of the compression plate 13 and the multiple reflection image that is not affected by the change in the position of the compression plate 13. A multiple reflection image is extracted from a plurality of different images.

  As shown in FIG. 4, the multiple reflection image extraction unit 47b according to the second embodiment represents a plurality of ultrasonic images generated while changing the position of the compression plate in a state where the compression plate compresses the subject. A second image data acquisition unit 54 that acquires B-mode image data from the B-mode image data generation unit 46 via the image data storage unit 49, and a value of B-mode image data representing a plurality of ultrasound images with different compression states Based on the difference between the ultrasonic image of the subject that changes with the change in the position of the compression plate and the multiple reflection image that is not affected by the change in the position of the compression plate, the multiple reflection image is obtained. And an arithmetic mean computing unit 55 for generating B-mode image data representing.

  In the third embodiment, the ultrasonic probe 16 is moved along the second surface of the compression plate 13 while the compression plate 13 is compressing the subject 1 with the first surface. When the plurality of ultrasonic images are acquired, the multiple reflection image extraction unit 47c shown in FIG. 5 determines the ultrasonic image of the subject tissue that differs depending on the position of the ultrasonic probe 16, and the ultrasonic probe 16. A multiple reflection image is extracted from a plurality of different images using the difference from the multiple reflection image that is not influenced by the position.

  As shown in FIG. 5, the multiple reflection image extraction unit 47c according to the third embodiment uses a plurality of ultrasonic waves generated while changing the position of the ultrasonic probe while the compression plate presses the subject. A third image data acquisition unit 57 that acquires B-mode image data representing an image from the B-mode image data generation unit 46 via the image data storage unit 49, and B that represents a plurality of ultrasonic images captured at different positions. Based on the difference between the ultrasonic image of the subject that differs depending on the position of the ultrasonic probe and the multiple reflection image that is not affected by the position of the ultrasonic probe, by calculating the arithmetic average of the values of the mode image data And an arithmetic mean calculator 58 for generating B-mode image data representing a multiple reflection image.

  Referring again to FIG. 1, the image processing unit 60 performs gradation processing on the radiation image data output from the X-ray imaging control unit 30 and the ultrasound image data output from the ultrasound imaging control unit 40. The necessary image processing is performed to generate display image data. Thereby, the radiation image and the ultrasonic image are displayed on the display units 71 and 72, respectively.

  The console 80 is used by an operator to operate the medical imaging apparatus. The control unit 90 controls each unit based on the operation of the operator. In the above, the movement control unit 20, the radiation image data generation unit 34, the scanning control unit 41, the signal processing unit 45 to the subtraction unit 48, the image processing unit 60, and the control unit 90 are a central processing unit (CPU) and a CPU. Are configured with software (programs) for performing various processes, but may be configured with digital circuits or analog circuits. This software (program) is stored in a storage unit 100 configured by a hard disk or a memory. Further, the storage unit 100 may store the transmission delay pattern and the reception delay pattern selected by the scanning control unit 41.

  Next, the medical imaging method according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3, 6, and 7. In the medical imaging method according to the first embodiment, the multiple reflection image extraction unit according to the first example is used.

FIG. 6 is a flowchart showing a medical imaging method according to the first embodiment of the present invention.
In step S11, the movement control unit 20 controls the compression plate moving mechanism 14 to place the compression plate 13 at a position where the subject (breast) is not compressed. As shown in FIG. 7A, an ultrasound image is acquired without pressing the subject with the compression plate 13. In a state in which the subject is not compressed by the compression plate 13, the first surface 131 of the compression plate 13 is in contact with the air layer, so that the ultrasonic wave transmitted from the ultrasonic probe 16 is transmitted through the first plate 131 of the compression plate 13. 1 surface 131 reflects almost 100%. In step S12, the B-mode image data generation unit 46 generates B-mode image data representing an ultrasonic image in a non-compressed state. In step S13, the first image data acquisition unit 51 of the multiple reflection image extraction unit 47a acquires the generated B-mode image data and stores it in the image data storage unit 49.

  In step S <b> 14, as shown in FIG. 7B, the subject (breast) 1 is compressed with the compression plate 13, and ultrasonic imaging of the subject 1 is performed. In step S15, the B-mode image data generation unit 46 generates B-mode image data of the subject 1 in the compressed state. However, since the multiple reflection image of the compression plate 13 is superimposed on the B-mode image of the subject 1, this may hinder the diagnosis of the subject 1.

  In step S16, the first image data acquisition unit 51 of the multiple reflection image extraction unit 47a reads out B-mode image data representing an ultrasonic image in a non-compressed state from the image data storage unit 49, and the multiple reflection image extraction unit 47a The luminance correction calculation unit 52 corrects the luminance of the ultrasonic image in the non-compressed state in consideration of the difference between the acoustic impedance of the air and the acoustic impedance of the subject 1, whereby B-mode image data of the multiple reflection image Is generated.

  In step S17, the subtraction unit 48 calculates the difference between the B-mode image data of the subject 1 in the compressed state generated in step S15 and the B-mode image data of the multiple reflection image generated in step S16. B-mode image data of the subject 1 from which the multiple reflection image has been removed is generated. As shown in FIG. 7C, the multiple reflection image is removed by subtracting the multiple reflection image from the ultrasonic image acquired by pressing the subject (breast) 1 with the compression plate. In step S <b> 18, the B-mode image of the subject 1 from which the multiple reflection image is removed is displayed on the display unit 72.

  Next, a medical imaging method according to the second embodiment of the present invention will be described with reference to FIGS. 1, 2, 4, 8, and 9. FIG. In the medical imaging method according to the second embodiment, the multiple reflection image extraction unit according to the second example is used.

FIG. 8 is a flowchart showing a medical imaging method according to the second embodiment of the present invention.
In step S <b> 21, the movement control unit 20 controls the compression plate moving mechanism 14 to move the compression plate 13, so that the compression plate 13 compresses the subject 1. In step S22, ultrasonic imaging is performed in the compressed state determined in step S21. In step S23, the B-mode image data generation unit 46 generates B-mode image data of the subject 1, and the second image data acquisition unit 54 of the multiple reflection image extraction unit 47b converts the generated B-mode image data. Acquired and stored in the image data storage unit 49.

  In step S24, the movement control unit 20 determines whether or not a predetermined number of ultrasonic imaging has been performed. If the predetermined number of ultrasonic imaging has not been performed, the process returns to step S21, and steps S21 to S24 are repeated. When the process returns to step S21, the movement control unit 20 controls the compression plate moving mechanism 14 to a position where the compression to the subject 1 is strengthened as shown in FIGS. 9 (a) to 9 (c). An ultrasonic image is acquired by moving the compression plate 13 or moving the compression plate 13 to a position where the compression to the subject 1 is weakened. At this time, the ultrasonic probe 16 moves while maintaining an acoustic connection (coupling) to the compression plate 13. In this way, the operation of changing the position of the compression plate 13 and acquiring an ultrasonic image is repeated a predetermined number of times. These ultrasonic images include a multiple reflection image by the compression plate 13.

  When ultrasonic imaging is performed a predetermined number of times, in step S25, the second image data acquisition unit 54 of the multiple reflection image extraction unit 47b changes the position of the compression plate 13 and represents a plurality of ultrasonic images. The mode image data is fetched from the image data storage unit 49. When the compression state of the subject 1 is changed, the tissue image of the subject 1 also changes on the ultrasonic image, but the ultrasonic probe 16 and the compression plate 13 move while maintaining an acoustic connection (coupling). Therefore, the multiple reflection image does not change. Using the difference between the two types of images, the arithmetic mean computing unit 55 of the multiple reflection image extracting unit 47b obtains the arithmetic mean of the values of the B-mode image data representing the plurality of ultrasonic images, thereby obtaining the multiple The reflection image is extracted to generate B-mode image data representing the multiple reflection image.

  In step S26, the subtraction unit 48 removes the multiple reflection image by taking the difference between the value of the B mode image data representing the ultrasonic image of the subject 1 and the value of the B mode image data representing the multiple reflection image. B-mode image data representing the ultrasonic image of the subject 1 thus generated is generated. In step S <b> 27, the image of the subject from which the multiple reflection image has been removed is displayed on the display unit 72.

  Next, a medical imaging method according to the third embodiment of the present invention will be described with reference to FIGS. 1, 2, 5, 10, and 11. In the medical imaging method according to the third embodiment, the multiple reflection image extraction unit according to the third example is used.

FIG. 10 is a flowchart showing a medical imaging method according to the third embodiment of the present invention.
In step S31, the movement control unit 20 controls the probe moving mechanism 17 and moves the ultrasonic probe 16 along the compression plate 13 while the compression plate 13 is compressing the subject 1. The ultrasonic probe 16 changes the imaging position. In step S32, ultrasonic imaging is performed at the imaging position determined in step S21. In step S33, the B-mode image data generation unit 46 generates B-mode image data of the subject 1, and the third image data acquisition unit 57 of the multiple reflection image extraction unit 47c outputs the generated B-mode image data. Acquired and stored in the image data storage unit 49.

  In step S34, the movement control unit 20 determines whether or not a predetermined number of ultrasonic imaging has been performed. If the predetermined number of ultrasonic imaging has not been performed, the process returns to step S31, and steps S31 to S34 are repeated. When the process returns to step S21, the movement control unit 20 controls the probe moving mechanism 17, and the imaging position of the ultrasonic probe 16 as shown in FIGS. 11 (a) to 11 (c). Is changed to obtain an ultrasonic image. At this time, the ultrasonic probe 16 moves while maintaining an acoustic connection (coupling) to the compression plate 13. As described above, the operation of acquiring the ultrasonic image by changing the imaging position of the ultrasonic probe 16 is repeated a predetermined number of times. These ultrasonic images include a multiple reflection image by the compression plate 13.

  When ultrasonic imaging is performed a predetermined number of times, a plurality of ultrasonic images captured by the third image data acquisition unit 57 of the multiple reflection image extraction unit 47c by changing the position of the ultrasonic probe 16 in step S35. B-mode image data representing is taken from the image data storage unit 49. When the position of the ultrasound probe 16 is changed, the tissue image of the subject 1 is also changed on the ultrasound image, but the thickness of the compression plate 13 is uniform and the ultrasound probe 16 and the compression plate 13 are changed. Moves while maintaining an acoustic connection (coupled) state, so that the multiple reflection image does not change. Using the difference between the two types of images, the arithmetic mean computing unit 58 of the multiple reflection image extracting unit 47c obtains the arithmetic mean of the values of the B-mode image data representing the plurality of ultrasonic images, thereby performing the multiplexing. The reflection image is extracted to generate B-mode image data representing the multiple reflection image.

  In step S36, the subtraction unit 48 removes the multiple reflection image by taking the difference between the value of the B mode image data representing the ultrasonic image of the subject 1 and the value of the B mode image data representing the multiple reflection image. B-mode image data representing the ultrasonic image of the subject 1 thus generated is generated. In step S <b> 37, the image of the subject from which the multiple reflection image is removed is displayed on the display unit 72.

  INDUSTRIAL APPLICABILITY The present invention can be used in a medical imaging apparatus and a medical imaging method for imaging breasts and breasts by transmitting and receiving ultrasonic waves while compressing a breast with a compression plate in order to diagnose breast cancer and the like.

It is a block diagram which shows the structure of the medical imaging device which concerns on one Embodiment of this invention. It is a side view which shows the external appearance of the imaging part of the medical imaging device shown in FIG. FIG. 2 is a block diagram illustrating a first example of a multiple reflection image extraction unit in the medical imaging apparatus illustrated in FIG. 1. It is a block diagram which shows the 2nd Example of the multiple reflection image extraction part in the medical imaging device shown in FIG. It is a block diagram which shows the 3rd Example of the multiple reflection image extraction part in the medical imaging device shown in FIG. It is a flowchart which shows the medical imaging method which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the medical imaging method which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the medical imaging method which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the medical imaging method which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the medical imaging method which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating the medical imaging method which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Arm part 3 Base 4 Shaft part 10 X-ray tube 11 Filter 12 Radiation detection part 13 Compression board 131 1st surface of a compression board 132 2nd surface of a compression board 133 Echo jelly 14 Compression board moving mechanism 15 Pressure sensor 16 Ultrasonic probe 17 Probe moving mechanism 18 Position sensor 19 Imaging stand 20 Movement control unit 21 Position adjustment unit 22 Direction adjustment unit 30 X-ray imaging control unit 31 Tube voltage / tube current control unit 32 High voltage generation Unit 33 A / D converter 34 Radiation image data generation unit 40 Ultrasound imaging control unit 41 Scan control unit 42 Transmission circuit 43 Reception circuit 44 A / D converter 45 Signal processing unit 46 B-mode image data generation unit 47 Multiple reflection image Extraction unit 48 Subtraction unit 49 Image data storage unit 51 First image data acquisition unit 52 Luminance correction calculation unit 54 Second image data acquisition Part 55 arithmetic mean calculating section 57 third image data acquisition unit 58 the arithmetic mean calculating unit 60 the image processing unit 71, 72 display unit 80 console 90 control unit 100 storage unit

Claims (11)

A compression plate having a first surface for compressing the subject and a second surface opposite to the first surface, and having ultrasound transmission properties;
A compression plate moving mechanism for moving the compression plate in a direction substantially perpendicular to the first surface of the compression plate;
An ultrasonic probe that transmits an ultrasonic wave according to a drive signal, receives an ultrasonic echo, and outputs a received signal while moving along the second surface of the compression plate;
Image data generation that generates image data representing a plurality of ultrasound images when the compression plate or the ultrasound probe is at a plurality of different positions based on a reception signal output from the ultrasound probe Means,
Based on image data representing at least one ultrasonic image generated by the image data generation means, a multiple reflection image generated by reflection of ultrasonic waves on the first surface and / or the second surface of the compression plate is extracted. A multiple reflection image extracting means for generating image data representing a multiple reflection image,
Subtraction means for generating image data representing an image obtained by subtracting the multiple reflection image from the image of the subject including the multiple reflection image;
A medical imaging apparatus comprising: The multiple reflection image extracting means includes:
Image data acquisition means for acquiring image data representing an ultrasonic image when the first surface of the compression plate is in contact with the air layer from the image data generation means;
Based on the difference in reflectance caused by the difference between the acoustic impedance of the subject and the acoustic impedance of the substance, the image data acquired by the image data acquisition means is subjected to a brightness correction process, whereby a multiple reflection image is obtained. Brightness correction means for generating image data to be represented;
The medical imaging device according to claim 1, comprising: The multiple reflection image extracting means includes:
Image data representing a plurality of ultrasonic images generated while changing the position of the compression plate in a direction substantially perpendicular to the first surface of the compression plate in a state where the compression plate compresses the subject. Image data acquisition means acquired from the generation means;
Image data representing a multiple reflection image is generated based on a difference between an ultrasonic image of the subject that varies with a change in the position of the compression plate and a multiple reflection image that is not affected by the change in the position of the compression plate. Computing means;
The medical imaging device according to claim 1, comprising:   The medical imaging apparatus according to claim 1, further comprising a probe moving mechanism that moves the ultrasonic probe. The multiple reflection image extracting means includes:
Image data representing a plurality of ultrasonic images generated while moving the position of the ultrasonic probe along the second surface of the compression plate in a state where the compression plate compresses the subject. Image data acquisition means acquired from the generation means;
An operation for generating image data representing a multiple reflection image based on a difference between an ultrasonic image of a subject that varies depending on the position of the ultrasonic probe and a multiple reflection image that is not affected by the position of the ultrasonic probe. Means,
The medical imaging device according to claim 4, comprising:   6. The image calculation unit generates image data representing a multiple reflection image by calculating an arithmetic average of values of image data representing a plurality of ultrasonic images acquired by the image data acquisition unit. The medical imaging apparatus described. A radiation generator for generating radiation;
A radiation detector that detects radiation generated by the radiation generator and passed through the subject;
An imaging table disposed between the radiation generation unit and the radiation detection unit;
The medical imaging apparatus according to claim 1, wherein the compression plate has radiolucency and compresses the subject with the imaging table. Based on a received signal output from an ultrasound probe that moves along a second surface of a compression plate having a first surface that compresses the subject and a second surface that opposes the first surface. Generating (a) image data representing a plurality of ultrasonic images when the compression plate or the ultrasonic probe is at a plurality of different positions;
Based on the image data representing at least one ultrasonic image generated in step (a), a multiple reflection image generated by reflection of ultrasonic waves on the first surface and / or the second surface of the compression plate is extracted. A step (b) of generating image data representing a multiple reflection image,
Generating image data representing an image obtained by subtracting the multiple reflection image from the image of the subject including the multiple reflection image;
A medical imaging method comprising: Step (a) includes generating (a ′) image data representing an ultrasound image when the first surface of the compression plate is in contact with the air layer,
Step (b) corrects the luminance of the image data generated in step (a ′) based on the difference in reflectance caused by the difference between the acoustic impedance of the subject and the acoustic impedance of the substance, so that multiple Generating image data representing the reflected image;
The medical imaging method according to claim 8. In step (a), image data representing a plurality of ultrasonic images while changing the position of the compression plate in a direction substantially perpendicular to the first surface of the compression plate in a state where the compression plate compresses the subject. Including the step of generating,
In step (b), based on the difference between the ultrasonic image of the subject that fluctuates with the change in the position of the compression plate and the multiple reflection image that is not affected by the change in the position of the compression plate, a multiple reflection image is obtained. Generating image data representing,
The medical imaging method according to claim 8. Step (a) includes generating image data representing a plurality of ultrasonic images while changing the position of the ultrasonic probe in a state where the compression plate compresses the subject;
Step (b) represents a multiple reflection image based on the difference between the ultrasonic image of the subject that varies depending on the position of the ultrasonic probe and the multiple reflection image that is not affected by the position of the ultrasonic probe. Generating image data,
The medical imaging method according to claim 8.