Patent Publication Number: US-2023157670-A1

Title: Ultrasound diagnostic apparatus and control method of ultrasound diagnostic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-191295 filed on Nov. 25, 2021. The above application is hereby expressly incorporated by reference, in its entirety, into the present application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ultrasound diagnostic apparatus, and a control method of the ultrasound diagnostic apparatus which are used in an examination of a breast of a subject. 
     2. Description of the Related Art 
     In the related art, in order to perform a biopsy on a breast of a subject, a procedure of piercing the breast with a tissue sampling needle while observing the inside of the breast of the subject using a so-called ultrasound diagnostic apparatus has been performed. In such a procedure, for example, a technique as disclosed in JP2021-520935A has been developed so that an examiner can easily reach a target location in the subject with the tissue sampling needle. JP2021-520935A discloses predicting a needle reach position on the basis of characteristics of a tissue sampling needle and tissue characteristics of a subject such as a mammary gland tissue and an adipose tissue in the breast. In JP2021-520935A, the tissue characteristics of the subject are determined by image analysis of an ultrasound image or an input of information by the examiner. 
     SUMMARY OF THE INVENTION 
     However, in the technology disclosed in JP2021-520935A, since the reach position of the tissue sampling needle is predicted on the basis of the characteristics of the tissue sampling needle and the tissue characteristics of a patient determined by the image analysis or the input by the examiner, the predicted reach position of the tissue sampling needle may deviate from the actual reach position of the tissue sampling needle, and it may be difficult for a distal end of the tissue sampling needle to reach the target location unless the examiner is skilled. 
     The present invention has been made in order to solve such a problem in the related art, and an object of the present invention is to provide an ultrasound diagnostic apparatus and a control method of the ultrasound diagnostic apparatus which can reliably perform a biopsy in a short time even by an unskilled examiner. 
     In order to achieve the object, an ultrasound diagnostic apparatus according to an aspect of the present invention comprises an image acquisition unit that acquires an ultrasound image in which a breast of a subject is captured; a sampling target region detection unit that detects a sampling target region in which a tissue is sampled from the subject by a tissue sampling needle on the basis of the ultrasound image; a recommended path calculation unit that calculates a recommended path of the tissue sampling needle passing through the sampling target region; a monitor that displays the ultrasound image and the recommended path in a superimposed manner; a needle detection unit that detects the pierced tissue sampling needle on the basis of the ultrasound image; and a needle passage determination unit that determines whether or not the pierced tissue sampling needle has passed through the sampling target region. 
     The sampling target region detection unit can have a malignancy determination unit that determines malignancy in each portion in a region of interest of the breast of the subject, and a region extraction unit that extracts a region in which the malignancy determined by the malignancy determination unit is equal to or greater than a predetermined threshold value, as the sampling target region. 
     The malignancy determination unit can display a determination result of the malignancy on the monitor. 
     In this case, the malignancy determination unit can display a heat map of the determined malignancy as the determination result on the monitor. 
     The recommended path calculation unit can detect pectoralis major muscle of the subject on the basis of the ultrasound image, and calculate a path that passes through the sampling target region and is parallel to the pectoralis major muscle, as the recommended path until the tissue sampling needle is detected by the needle detection unit. 
     In a case where a length of the tissue sampling needle, which is detected by the needle detection unit, having passed through an inside of the sampling target region is equal to or greater than a predetermined ratio with respect to a length of the recommended path in the sampling target region, the needle passage determination unit can determine that the tissue sampling needle has passed through the sampling target region. 
     The ultrasound diagnostic apparatus can further comprise a warning unit that issues a warning in a case where it is predicted that the tissue sampling needle detected by the needle detection unit advances toward pectoralis major muscle of the subject. 
     The ultrasound diagnostic apparatus can further comprise a final point reach determination unit that determines whether or not the tissue sampling needle has reached a piercing final point on the basis of the detection of the tissue sampling needle by the needle detection unit. 
     In this case, the ultrasound diagnostic apparatus can further comprise an examination result memory that stores the ultrasound image acquired by the image acquisition unit before the tissue sampling needle passes through the sampling target region, the ultrasound image, which is acquired by the image acquisition unit, at a time when the final point reach determination unit determines that the tissue sampling needle has reached the final point, coordinates of the tissue sampling needle detected by the needle detection unit or the ultrasound image of the tissue sampling needle detected by the needle detection unit, and the ultrasound image including the sampling target region acquired by the image acquisition unit after the tissue sampling needle is pulled out from the subject. 
     The image acquisition unit can acquire the ultrasound image in both a cross section including the recommended path and a cross section orthogonal to the cross section including the recommended path. 
     Further, the image acquisition unit can acquire a three-dimensional ultrasound image. 
     In this case, the sampling target region detection unit can calculate a volume of the detected sampling target region, and display the volume on the monitor. 
     The sampling target region detection unit can detect the sampling target region on the basis of the ultrasound image acquired by the image acquisition unit before the piercing of the tissue sampling needle, and detect again the sampling target region on the basis of the ultrasound image acquired by the image acquisition unit after the tissue sampling needle retreats from the sampling target region. 
     The ultrasound diagnostic apparatus can further comprise a deflection detection unit that detects deflection occurring in a path through which the tissue sampling needle has passed in the ultrasound image on the basis of the detection of the tissue sampling needle by the needle detection unit; and an emphasizing unit that emphasizes a continuous region having a brightness value within a predetermined range for a brightness value of the ultrasound image for a position where the deflection is detected by the deflection detection unit, as a deflection occurrence region, and displays the deflection occurrence region on the monitor. 
     A control method of an ultrasound diagnostic apparatus according to another aspect of the present invention comprises acquiring an ultrasound image in which a breast of a subject is captured; detecting a sampling target region in which a tissue is sampled from the subject by a tissue sampling needle on the basis of the ultrasound image; calculating a recommended path of the tissue sampling needle passing through the sampling target region; displaying the ultrasound image and the recommended path on a monitor in a superimposed manner; detecting the pierced tissue sampling needle on the basis of the ultrasound image; and determining whether or not the pierced tissue sampling needle has passed through the sampling target region. 
     According to the present invention, since an ultrasound diagnostic apparatus comprises an image acquisition unit that acquires an ultrasound image in which a breast of a subject is captured; a sampling target region detection unit that detects a sampling target region in which a tissue is sampled from the subject by a tissue sampling needle on the basis of the ultrasound image; a recommended path calculation unit that calculates a recommended path of the tissue sampling needle passing through the sampling target region; a monitor that displays the ultrasound image and the recommended path in a superimposed manner; a needle detection unit that detects the pierced tissue sampling needle on the basis of the ultrasound image; and a needle passage determination unit that determines whether or not the pierced tissue sampling needle has passed through the sampling target region, a biopsy can be reliably performed in a short time even by an unskilled examiner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram illustrating a configuration of an ultrasound diagnostic apparatus according to a first embodiment of the present invention. 
         FIG.  2    is a block diagram illustrating a configuration of a transmission and reception circuit in the first embodiment of the present invention. 
         FIG.  3    is a block diagram illustrating a configuration of an image generation unit in the first embodiment of the present invention. 
         FIG.  4    is a block diagram illustrating a configuration of a sampling target region detection unit in the first embodiment of the present invention. 
         FIG.  5    is a diagram illustrating an example of a recommended path that passes through a sampling target region and is parallel to the pectoralis major muscle in the first embodiment of the present invention. 
         FIG.  6    is a diagram illustrating an example of a recommended path corrected in the first embodiment of the present invention. 
         FIG.  7    is a diagram illustrating an example of a tissue sampling needle that has reached a piercing final point, which is depicted on an ultrasound image in the first embodiment of the present invention. 
         FIG.  8    is a flowchart illustrating an operation of the ultrasound diagnostic apparatus according to the first embodiment of the present invention. 
         FIG.  9    is a block diagram illustrating a configuration of an ultrasound diagnostic apparatus according to a second embodiment of the present invention. 
         FIG.  10    is a diagram illustrating an example of a tissue sampling needle predicted to advance toward the pectoralis major muscle in the second embodiment of the present invention. 
         FIG.  11    is a block diagram illustrating a configuration of an ultrasound diagnostic apparatus according to a third embodiment of the present invention. 
         FIG.  12    is a diagram schematically illustrating an example of a final point of the tissue sampling needle in the third embodiment of the present invention. 
         FIG.  13    is a diagram illustrating an example of a recommended path corrected in the third embodiment of the present invention. 
         FIG.  14    is a block diagram illustrating a configuration of an ultrasound diagnostic apparatus according to a fourth embodiment of the present invention. 
         FIG.  15    is a diagram illustrating an example of a deflection occurrence region in the fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings. 
     The description of configuration requirements described below is given on the basis of the representative embodiment of the present invention, but the present invention is not limited to such an embodiment. 
     In the present specification, a numerical range represented using “to” means a range including the numerical values before and after “to” as a lower limit value and an upper limit value. 
     In the present specification, the terms “same” and “identical” include an error range generally allowed in the technical field. 
     First Embodiment 
       FIG.  1    illustrates a configuration of an ultrasound diagnostic apparatus  1  according to a first embodiment of the present invention. The ultrasound diagnostic apparatus  1  comprises an ultrasound probe  2 , and an apparatus main body  3  connected to the ultrasound probe  2 . The ultrasound diagnostic apparatus  1  is used to observe a tissue sampling needle that is pierced into the breast of a subject and a sampling target region suspected to be a lesion part in a case of performing a biopsy of the breast of the subject. Here, the tissue sampling needle refers to a needle-like instrument used to sample a tissue in the subject. Further, the sampling target region refers to a region which is suspected to be, for example, a lesion part, and in which a target tissue to be sampled by the tissue sampling needle is present. 
     The ultrasound probe  2  comprises a transducer array  21 , and a transmission and reception circuit  22  is connected to the transducer array  21 . 
     The apparatus main body  3  comprises an image generation unit  31 , and the image generation unit  31  is connected to the transmission and reception circuit  22  of the ultrasound probe  2 . The transducer array  21  and the transmission and reception circuit  22  of the ultrasound probe  2 , and the image generation unit  31  of the apparatus main body  3  constitute an image acquisition unit F. 
     Further, a display controller  32  and a monitor  33  are sequentially connected to the image generation unit  31 . An image memory  34  is connected to the image generation unit  31 . Further, a sampling target region detection unit  35  and a needle detection unit  36  are connected to the image memory  34 . A recommended path calculation unit  37  and a needle passage determination unit  38  are connected to the sampling target region detection unit  35 . Similarly to the sampling target region detection unit  35 , the recommended path calculation unit  37  and the needle passage determination unit  38  are also connected to the needle detection unit  36 . The needle passage determination unit  38  is connected to the recommended path calculation unit  37 . Further, each of the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , and the needle passage determination unit  38  is connected to the display controller  32 . 
     In addition, a main body controller  40  is connected to the transmission and reception circuit  22 , the image generation unit  31 , the display controller  32 , the image memory  34 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , and the needle passage determination unit  38 . An input device  41  is connected to the main body controller  40 . 
     Further, the image generation unit  31 , the display controller  32 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , the needle passage determination unit  38 , and the main body controller  40  constitute a processor  42  for the apparatus main body  3 . 
     The transducer array  21  of the ultrasound probe  2  has a plurality of ultrasonic transducers arranged in a one-dimensional or two-dimensional manner. According to a drive signal supplied from the transmission and reception circuit  22 , each of the ultrasonic transducers transmits an ultrasonic wave and receives an ultrasound echo from the subject to output a signal based on the ultrasound echo. For example, each ultrasonic transducer is configured by forming electrodes at both ends of a piezoelectric body consisting of piezoelectric ceramic represented by lead zirconate titanate (PZT), a polymer piezoelectric element represented by poly vinylidene di fluoride (PVDF), piezoelectric single crystal represented by lead magnesium niobate-lead titanate (PMN-PT), or the like. 
     The transmission and reception circuit  22  causes the transducer array  21  to transmit the ultrasonic wave and generates a sound ray signal on the basis of a reception signal acquired by the transducer array  21 , under the control of the main body controller  40 . As illustrated in  FIG.  2   , the transmission and reception circuit  22  has a pulser  23  connected to the transducer array  21 , and an amplification unit  24 , an analog to digital (AD) conversion unit  25 , and a beam former  26  that are sequentially connected in series from the transducer array  21 . 
     The pulser  23  includes, for example, a plurality of pulse generators, and the pulser  23  adjusts the amount of delay of each drive signal so that ultrasonic waves transmitted from the plurality of ultrasonic transducers of the transducer array  21  form an ultrasound beam on the basis of a transmission delay pattern selected according to the control signal from the main body controller  40 , and supplies the obtained signals to the plurality of ultrasonic transducers. Thus, in a case where a pulsed or continuous-wave voltage is applied to the electrodes of the ultrasonic transducers of the transducer array  21 , the piezoelectric body expands and contracts to generate pulsed or continuous-wave ultrasonic waves from each ultrasonic transducer. From the combined wave of these ultrasonic waves, an ultrasound beam is formed. 
     The transmitted ultrasound beam is reflected by a target, for example, a site of the subject, and propagates toward the transducer array  21  of the ultrasound probe  2 . The ultrasound echo propagating toward the transducer array  21  in this manner is received by each ultrasonic transducer constituting the transducer array  21 . In this case, each ultrasonic transducer constituting the transducer array  21  expands and contracts by receiving the propagating ultrasound echo to generate a reception signal that is an electric signal, and outputs the reception signal to the amplification unit  24 . 
     The amplification unit  24  amplifies the signals input from each ultrasonic transducer constituting the transducer array  21 , and transmits the amplified signals to the AD conversion unit  25 . The AD conversion unit  25  converts the signal transmitted from the amplification unit  24  into digital reception data. The beam former  26  performs so-called reception focusing processing in which addition is performed by giving delays to respective pieces of the reception data received from the AD conversion unit  25 . Through the reception focusing processing, a sound ray signal in which each piece of the reception data converted by the AD conversion unit  25  is phased and added and the focus of the ultrasound echo is narrowed is acquired. 
     As illustrated in  FIG.  3   , the image generation unit  31  has a configuration in which a signal processing unit  51 , a digital scan converter (DSC)  52 , and an image processing unit  53  are sequentially connected in series. 
     The signal processing unit  51  generates a B-mode image signal, which is tomographic image information regarding tissues inside the subject, by performing, on the sound ray signal received from the transmission and reception circuit  22 , correction of the attenuation due to the distance according to the depth of the reflection position of the ultrasonic wave using a sound speed value set by the main body controller  40  and then performing envelope detection processing. 
     The DSC  52  converts (raster conversion) the B-mode image signal generated by the signal processing unit  51  into an image signal according to a normal television signal scanning method. 
     The image processing unit  53  performs various kinds of necessary image processing such as gradation processing on the B-mode image signal input from the DSC  52 , and then sends the B-mode image signal to the display controller  32  and the image memory  34 . In the following, the B-mode image signal subjected to the image processing by the image processing unit  53  is simply referred to as an ultrasound image. 
     The main body controller  40  controls the transmission and reception circuit  22  of the ultrasound probe  2  and each unit of the apparatus main body  3  according to a program and the like recorded in advance. 
     The display controller  32  performs predetermined processing on the ultrasound image or the like generated by the image generation unit  31  and displays the ultrasound image or the like on the monitor  33 , under the control of the main body controller  40 . 
     The monitor  33  performs various kinds of display under the control of the display controller  32 . The monitor  33  includes a display device such as a liquid crystal display (LCD), or an organic electroluminescence (EL) display. 
     The input device  41  is for a user to perform an input operation. The input device  41  is configured by, for example, a device for a user to perform an input operation, such as a keyboard, a mouse, a trackball, a touchpad, a touch panel, or the like. 
     Under the control of the main body controller  40 , the image memory  34  stores the ultrasound image generated by the image generation unit  31 , and sends the stored ultrasound image to the sampling target region detection unit  35  and the needle detection unit  36 . Here, as the image memory  34 , for example, recording media such as a flash memory, a hard disk drive (HDD), a solid state drive (SSD), a flexible disk (FD), a magneto-optical disk (MO disk), a magnetic tape (MT), a random access memory (RAM), a compact disc (CD), a digital versatile disc (DVD), a secure digital card (SD card), and a universal serial bus memory (USB memory) can be used. 
     The sampling target region detection unit  35  detects a sampling target region in which a tissue is sampled from the subject by the tissue sampling needle, on the basis of the ultrasound image. As illustrated in  FIG.  4   , the sampling target region detection unit  35  has a configuration in which a malignancy determination unit  54  and a region extraction unit  55  are connected in series. 
     The malignancy determination unit  54  performs an image analysis of the ultrasound image of the breast of the subject to recognize a region suspected to be a lesion part such as a tumor, and sets a region of interest including the recognized region on the ultrasound image. Further, the malignancy determination unit  54  determines the malignancy of each portion in the region of interest of the breast of the subject. 
     Further, for example, the malignancy determination unit  54  can recognize the region suspected to be a lesion part on the ultrasound image by applying a method of using simple pattern matching, a machine learning method described in Csurka et al.: Visual Categorization with Bags of Keypoints, Proc. of ECCV Workshop on Statistical Learning in Computer Vision, pp. 59-74 (2004) or a general image recognition method using deep learning described in Krizhevsk et al.: ImageNet Classification with Deep Convolutional Neural Networks, Advances in Neural Information Processing Systems 25, pp. 1106-1114 (2012). 
     Here, for example, in general, it is said that benign tumors often have a circular or elliptical shape, and malignant tumors such as breast cancer often have a so-called lobed or polygonal shape. The malignancy determined by the malignancy determination unit  54  refers to a probability that the tissue in the set region of interest is malignant, and is calculated, for example, in units of pixels. For example, the higher the malignancy of the pixel, the higher the probability that the pixel represents a tissue in a malignant lesion part, and the lower the malignancy of the pixel, the higher the probability that the pixel represents a tissue in a benign lesion part. 
     The malignancy determination unit  54  determines the malignancy of the tissue in the region of interest by recognizing the shape of the tissue using, for example, an image recognition method including pattern matching and extraction of a so-called feature amount, or a deep learning method. For example, in a case of using a deep learning method, the malignancy determination unit  54  determines the malignancy in units of pixels by performing learning in advance using a plurality of ultrasound images including a malignant tumor and a plurality of ultrasound images including a benign tumor as so-called teacher data, and comparing a relationship between the brightness of a specific pixel in the set region of interest and the brightness of surrounding pixels with the learned data. In this case, the malignancy determination unit  54  displays a determination result of the malignancy on the monitor  33  as a so-called heat map in which colors are assigned to regions on the ultrasound image such that, for example, a region with a higher malignancy is colored red, and a region with a lower malignancy is colored blue. 
     The region extraction unit  55  has a predetermined threshold value regarding the malignancy, and determines whether or not the value of the malignancy determined by the malignancy determination unit  54  is equal to or greater than the predetermined threshold value. The region extraction unit  55  further extracts a region of which the value of the malignancy determined by the malignancy determination unit  54  is equal to or greater than the predetermined threshold value, as a sampling target region. Therefore, the sampling target region is a region including, for example, a set of pixels having a malignancy equal to or greater than the predetermined threshold value in the region suspected to be a lesion part such as a tumor, and can be said to be a region which is highly suspected that a lesion part is positioned, and is a target for the biopsy. 
     The needle detection unit  36  detects the tissue sampling needle pierced into the breast of the subject on the basis of the ultrasound image. The needle detection unit  36  can detect the tissue sampling needle shown in the ultrasound image by using, for example, an image recognition method including pattern matching and extraction of the feature amount, or a deep learning method. 
     The recommended path calculation unit  37  calculates a recommended path of the tissue sampling needle that passes through the sampling target region extracted by the region extraction unit  55 . For example, as illustrated in  FIG.  5   , the recommended path calculation unit  37  can detect a pectoralis major muscle region B 1  in an ultrasound image U 1  by performing an image analysis on the ultrasound image U 1 , and further calculate a recommended path P 1  that passes through a sampling target region A 1  and is parallel to the pectoralis major muscle region B 1 . Note that the recommended path calculation unit  37  can use an image recognition method such as pattern matching or extraction of a feature amount, a deep learning method, or the like in a case of detecting the pectoralis major muscle region B 1 . 
     Further, in a case where the tissue sampling needle is detected by the needle detection unit  36 , the recommended path calculation unit  37  can correct the recommended path P 1  on the basis of the positional relationship between the detected tissue sampling needle and the sampling target region detected by the sampling target region detection unit  35 . For example, as illustrated in  FIG.  6   , in a case where a tissue sampling needle N 1  advancing toward the sampling target region A 1  is detected by the needle detection unit  36 , the recommended path calculation unit  37  can set a straight line passing through both the distal end of the detected tissue sampling needle N 1  and the location with the highest malignancy in the sampling target region A 1 , as the recommended path P 1 . The examiner pierces the breast of the subject with the tissue sampling needle N 1  along the recommended path P 1 , and thereby the distal end of the tissue sampling needle N 1  can pass through the sampling target region A 1  as illustrated in  FIG.  7   . 
     The needle passage determination unit  38  determines whether or not the tissue sampling needle N 1  pierced into the breast of the subject has passed through the sampling target region A 1 . For example, the needle passage determination unit  38  recognizes a positional relationship, on the ultrasound image U 1 , between the sampling target region A 1  detected by the sampling target region detection unit  35  and the tissue sampling needle N 1  detected by the needle detection unit  36 , and can determine that the tissue sampling needle N 1  has passed through the sampling target region A 1  in a case where it is recognized that the tissue sampling needle N 1  passes through the sampling target region A 1  and the distal end of the tissue sampling needle N 1  has reached the outside of the sampling target region A 1 . 
     Further, the needle passage determination unit  38  can display the determination result on the monitor  33  in a case where it is determined that the tissue sampling needle N 1  has passed through the sampling target region A 1 . 
     The processor  42  having the image generation unit  31 , the display controller  32 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , the needle passage determination unit  38 , and the main body controller  40  is configured by a central processing unit (CPU) and a control program for causing the CPU to execute various kinds of processing, but the processor  42  may be configured by using a field programmable gate array (FPGA), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a graphics processing unit (GPU), or other integrated circuits (IC) or may be configured by a combination thereof. 
     In addition, the image generation unit  31 , the display controller  32 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , the needle passage determination unit  38 , and the main body controller  40  of the processor  42  can also be configured by being integrated partially or entirely into one CPU or the like. 
     Next, the operation of the ultrasound diagnostic apparatus  1  according to the first embodiment of the present invention will be described using the flowchart illustrated in  FIG.  8   . 
     First, in Step S 1 , the examiner performs an input operation via the input device  41  so that an instruction to perform a biopsy on the subject is input. As a result, the main body controller  40  activates a biopsy mode according to the instruction from the examiner, and the biopsy for the subject is started. Here, the biopsy mode is a mode in which the ultrasound diagnostic apparatus  1  performs characteristic operations of the present invention, as illustrated in Steps S 2  to S 12  after Step S 1 . 
     Next, in Step S 2 , the examiner brings the ultrasound probe  2  into contact with the breast of the subject, and the ultrasound image U 1  is acquired in this state. In a case where the ultrasound image U 1  is acquired, the transmission and reception circuit  22  performs so-called reception focusing processing under the control of the main body controller  40  to generate sound ray signals. The sound ray signals generated by the transmission and reception circuit  22  are sent to the image generation unit  31 . The image generation unit  31  generates the ultrasound image U 1  using the sound ray signals sent from the transmission and reception circuit  22 . The ultrasound image U 1  acquired in this manner is sent to the display controller  32  and the image memory  34 . The ultrasound image U 1  sent to the display controller  32  is displayed on the monitor  33  after being subjected to predetermined processing. Further, the ultrasound image U 1  sent to the image memory  34  is stored in the image memory  34 . 
     The examiner pierces the breast of the subject with the tissue sampling needle N 1  while observing the ultrasound image U 1  of the inside of the breast of the subject acquired in this manner. 
     Next, in Step S 3 , the sampling target region detection unit  35  detects the sampling target region A 1  in which the tissue is sampled from the subject by the tissue sampling needle N 1 , on the basis of the ultrasound image U 1  that is acquired in Step S 2  and is stored in the image memory  34 . 
     In this case, the malignancy determination unit  54  of the sampling target region detection unit  35  recognizes a region suspected to be a lesion part such as a tumor on the ultrasound image U 1 , and sets a region of interest including the recognized region. The malignancy determination unit  54  determines the malignancy in the set region of interest in units of pixels by using an image analysis method, a machine learning method, or a deep learning method, for example. 
     Further, the region extraction unit  55  of the sampling target region detection unit  35  extracts a region including a set of pixels of which the value of the malignancy determined by the malignancy determination unit  54  is equal to or greater than the predetermined threshold value, as the sampling target region A 1 . In this case, the malignancy determination unit  54  can further display the malignancy determined for each pixel in the region of interest, as a heat map on the monitor  33 . As a result, the examiner can easily understand the region with a high possibility that malignant tissues, that is, tissues to be sampled in the biopsy are distributed. 
     In subsequent Step S 4 , the recommended path calculation unit  37  calculates the recommended path P 1  of the tissue sampling needle N 1  passing through the sampling target region A 1  detected in Step S 3 . In this case, for example, as illustrated in  FIG.  5   , the recommended path calculation unit  37  can detect a pectoralis major muscle region B 1  in an ultrasound image U 1  by performing an image analysis on the ultrasound image U 1 , and further calculate a recommended path P 1  that passes through a sampling target region A 1  and is parallel to the pectoralis major muscle region B 1 . The examiner causes the distal end of the tissue sampling needle N 1  to advance along the calculated recommended path P 1  so as to allow that the distal end of the tissue sampling needle N 1  can safely advance so as to pass through the sampling target region A 1  and not to reach the pectoralis major muscle. 
     In Step S 5 , the ultrasound image U 1  that is acquired is Step S 2  and is displayed on the monitor  33 , and the recommended path P 1  calculated in Step S 3  are displayed on the monitor  33 . In this case, the recommended path calculation unit  37  displays the recommended path P 1  on the monitor  33  such that the recommended path P 1  is superimposed on the ultrasound image U 1 . 
     In Step S 6 , the needle detection unit  36  performs an image analysis on the ultrasound image U 1  acquired in Step S 2  to perform processing of detecting the tissue sampling needle N 1  pierced into the breast of the subject. In a case where the tissue sampling needle N 1  is not detected here, the processing returns to Step S 1 . 
     In this manner, the processing of Steps S 2  to S 6  is repeated until the tissue sampling needle N 1  is detected in Step S 6 . In the second and subsequent Step S 3 , the sampling target region detection unit  35  can set the sampling target region A 1  on the ultrasound image U 1  by aligning the sampling target region A 1  detected in the first Step S 3  on an ultrasound image U 1  newly acquired in Step S 2 , by using, for example, a so-called block matching method or a so-called gradient method. Further, in the second and subsequent Step S 4 , the recommended path calculation unit  37  can set the recommended path P 1  on the ultrasound image U 1  by aligning the recommended path P 1  calculated in the first Step S 4  on a ultrasound image U 1  newly acquired in Step S 2 , by using, for example, a block matching method or a gradient method. 
     In a case where the tissue sampling needle N 1  is detected in Step S 6 , the processing proceeds to Step S 7 . 
     In Step S 7 , the recommended path calculation unit  37  corrects the recommended path P 1  calculated in Step S 3  on the basis of the positional relationship between the sampling target region A 1  detected in Step S 2  and the tissue sampling needle N 1  detected in Step S 5 . In this case, as illustrated in  FIG.  6   , the recommended path calculation unit  37  can set a straight line passing through both the distal end of the detected tissue sampling needle N 1  and the location with the highest malignancy in the sampling target region A 1 , as the recommended path P 1 . 
     In Step S 8 , similarly to Step S 5 , the ultrasound image U 1  acquired in Step S 1  and the recommended path P 1  corrected in Step S 7  are displayed on the monitor  33  in a superimposed manner. The examiner pierces the breast of the subject with the tissue sampling needle N 1  along the recommended path P 1  displayed on the monitor  33 , and thereby the distal end of the tissue sampling needle N 1  can pass through the sampling target region A 1  as illustrated in  FIG.  7   . 
     In Step S 9 , the needle passage determination unit  38  determines whether or not the tissue sampling needle N 1  pierced into the breast of the subject has passed through the sampling target region A 1  detected in Step S 2 . In this case, in a case where it is recognized, for example, that the tissue sampling needle N 1  detected in Step S 5  passes through the sampling target region A 1  detected in Step S 2  and the distal end of the tissue sampling needle N 1  has reached the outside of the sampling target region A 1  on the ultrasound image U 1 , the needle passage determination unit  38  can determine that the tissue sampling needle N 1  has passed through the sampling target region A 1 . 
     In a case where it is determined in Step S 9  that the tissue sampling needle N 1  has not passed through the sampling target region A 1 , the processing proceeds to Step S 10 . In Step S 10 , similarly to Step S 2 , a new ultrasound image U 1  representing a cross-cross section of the breast of the subject is acquired. In this case, the sampling target region detection unit  35  can set the sampling target region A 1  detected in Step S 3  on the ultrasound image U 1  acquired in Step S 10  by aligning the sampling target region A 1  detected in Step S 3  on the ultrasound image U 1  acquired in Step S 10 , by using, for example, a block matching method or a gradient method. Further, the recommended path calculation unit  37  can set the recommended path P 1  corrected in Step S 7  on the ultrasound image U 1  acquired in Step S 10  by aligning the recommended path P 1  corrected in Step S 7  on the ultrasound image U 1  acquired in Step S 10 , by using, for example, a block matching method or a gradient method. 
     In Step S 11 , similarly to Step S 5  and Step S 8 , the recommended path P 1  corrected in Step S 7  and the ultrasound image U 1  acquired in Step S 10  are displayed on the monitor  33  in a superimposed manner. 
     In Step S 12 , the needle detection unit  36  detects the tissue sampling needle N 1  from the ultrasound image U 1  acquired in Step S 10 . In this case, the needle detection unit  36  can detect the tissue sampling needle N 1  by tracing the tissue sampling needle N 1  detected in Step S 6  on the ultrasound image U 1  acquired in Step S 10 , by using, for example, a block matching method or a gradient method. 
     In this manner, the processing of Steps S 9  to S 12  is repeated until it is determined in Step S 9  that the tissue sampling needle N 1  has passed through the sampling target region A 1 . 
     In a case where it is determined in Step S 9  that the tissue sampling needle N 1  has passed through the sampling target region A 1 , the operation of the ultrasound diagnostic apparatus  1  according to the flowchart of  FIG.  8    is ended. Here, in a case where it is determined in Step S 9  that the tissue sampling needle N 1  has passed through the sampling target region A 1 , the needle passage determination unit  38  can notify the examiner that the tissue sampling needle N 1  has passed through the sampling target region A 1  by, for example, displaying a message on the monitor  33  or the like. The examiner can smoothly proceed with the biopsy while understanding that the tissue sampling needle N 1  has passed through the sampling target region A 1  and thus the tissue in the sampling target region A 1  has been sampled by the tissue sampling needle N 1 . 
     As described above, with the ultrasound diagnostic apparatus  1  according to the first embodiment of the present invention, the sampling target region A 1  is detected on the ultrasound image U 1 , the recommended path P 1  of the tissue sampling needle N 1  passing through the sampling target region A 1  is calculated, the recommended path P 1  is displayed to be superimposed on the ultrasound image U 1 , the tissue sampling needle N 1  is detected on the ultrasound image U 1 , and it is determined whether or not the tissue sampling needle N 1  has passed through the sampling target region A 1 . Therefore, the examiner can allow the distal end of the tissue sampling needle N 1  to accurately advance to pass through the sampling target region A 1 , and the biopsy can be reliably performed in a short time even by an unskilled examiner. 
     The description has been made in which in a case where the ultrasound image U 1  is acquired in Step S 10 , the sampling target region A 1  detected in Step S 3  and the recommended path P 1  corrected in Step S 7  are aligned on the ultrasound image U 1  acquired in Step S 10 , so that the sampling target region A 1  and the recommended path P 1  are set on the ultrasound image U 1  acquired in Step S 10 . However, the sampling target region A 1  and the recommended path P 1  can be set on the ultrasound image U 1  by performing the same processing as Step S 3  and Step S 4  after the ultrasound image U 1  is acquired in Step S 10 . 
     Further, the description has been made in which the transmission and reception circuit  22  is included in the ultrasound probe  2 , but the transmission and reception circuit  22  can be included in the apparatus main body  3  instead of being included in the ultrasound probe  2 . 
     Further, the description has been made in which the image generation unit  31  is included in the apparatus main body  3 , but the image generation unit  31  can be included in the ultrasound probe  2  instead of being included in the apparatus main body  3 . 
     Further, the ultrasound probe  2  and the apparatus main body  3  can be connected to each other by so-called wired communication using a cable, or can also be connected to each other by so-called wireless communication. 
     Further, the description has been made in which the needle passage determination unit  38  determines that the tissue sampling needle N 1  has passed through the sampling target region A 1  by recognizing that the tissue sampling needle N 1  detected by the needle detection unit  36  passes through the sampling target region A 1  and the distal end of the tissue sampling needle N 1  has reached the outside of the sampling target region A 1  on the ultrasound image U 1 , but the determination method is not particularly limited. In a case where the length of the tissue sampling needle N 1  having passed through the inside of the sampling target region A 1  is equal to or greater than a predetermined ratio with respect to the length of the recommended path P 1  in the sampling target region A 1 , the needle passage determination unit  38  can determine that the tissue sampling needle N 1  has passed through the sampling target region A 1 . As a result, it can be determined that the tissue sampling needle N 1  has passed through the sampling target region A 1  along the recommended path P 1 . 
     The description has been made in which the region extraction unit  55  of the sampling target region detection unit  35  extracts a region in which the malignancy determined by the malignancy determination unit  54  is equal to or greater than the predetermined threshold value, as the sampling target region A 1 , but the region extraction unit  55  can calculate the threshold value of the malignancy on the basis of the malignancy determined by the malignancy determination unit  54 . The region extraction unit  55  can calculate the threshold value for the value of the malignancy by, for example, multiplying the maximum value of the determined malignancy in the region of interest by a predetermined ratio. As a result, for example, even in a case where only a relatively low value of the malignancy is obtained, the sampling target region A 1  can be reliably set. 
     Further, the sampling target region detection unit  35  can calculate the area of the detected sampling target region A 1 , and display the calculated value of the area on the monitor  33 . The examiner can easily understand the size of the sampling target region A 1  by checking the value of the area of the sampling target region A 1  displayed on the monitor  33 . 
     Further, it is considered that the distribution of the malignancy in the sampling target region A 1  is changed in a case where a part of the tumor or the like in the breast of the subject corresponding to the sampling target region A 1  is sampled by the tissue sampling needle N 1 . Therefore, the sampling target region detection unit  35  can detect the sampling target region A 1  on the basis of the ultrasound image U 1  generated by the image generation unit  31  before the piercing of the tissue sampling needle N 1 , and detect again the sampling target region A 1  on the basis of the ultrasound image U 1  generated by the image generation unit  31  after the tissue sampling needle N 1  retreats from the sampling target region A 1 . Whether or not the tissue sampling needle N 1  has retreated from the sampling target region A 1  can be determined by the needle passage determination unit  38 . 
     In this manner, since the sampling target region A 1  in which the current distribution of the malignancy in the sampling target region A 1  is reflected is detected, the examiner can accurately understand the region to be subjected to the biopsy on the ultrasound image U 1 . 
     In this case, the sampling target region detection unit  35  can calculate both the area of the sampling target region A 1  in the ultrasound image U 1  before the piercing of the tissue sampling needle N 1 , and the area of the sampling target region A 1  in the ultrasound image U 1  after the tissue sampling needle N 1  retreats from the sampling target region A 1 , and display the values of both the areas on the monitor  33 . The examiner can easily understand how much tissue is sampled by comparing the value of the area of the sampling target region A 1  before the piercing of the tissue sampling needle N 1  with the value of the area of the sampling target region A 1  after the tissue sampling needle N 1  retreats. 
     Further, in a case where the transducer array  21  of the ultrasound probe  2  has a plurality of ultrasonic transducers arranged two-dimensionally, the image acquisition unit F can acquire a three-dimensional ultrasound image U 1  by three-dimensionally scanning the inside of the subject. 
     In this case, the sampling target region detection unit  35  can detect the three-dimensional sampling target region A 1  on the basis of the three-dimensional ultrasound image U 1 , calculate the volume of the detected sampling target region A 1 , and display the value of the calculated volume on the monitor  33 . The examiner can easily understand the size of the sampling target region A 1  by checking the value of the volume of the sampling target region A 1  displayed on the monitor  33 . 
     Further, even in a case where the three-dimensional ultrasound image U 1  is acquired, the sampling target region detection unit  35  can detect the sampling target region A 1  on the basis of the ultrasound image U 1  generated by the image generation unit  31  before the piercing of the tissue sampling needle N 1 , and detect again the sampling target region A 1  on the basis of the ultrasound image U 1  generated by the image generation unit  31  after the tissue sampling needle N 1  retreats from the sampling target region A 1 . As a result, since the sampling target region A 1  in which the current distribution of the malignancy is reflected is detected, the examiner can accurately understand the region to be subjected to the biopsy on the ultrasound image U 1 . 
     Further, the description has been made in which the malignancy determination unit  54  recognizes a region suspected to be a lesion part such as a tumor, but the examiner can manually set a region suspected to be a lesion part via the input device  41  by checking the ultrasound image U 1 . In this case, the malignancy determination unit  54  can set a region of interest including the region suspected to be a lesion part set by the examiner, on the ultrasound image U 1 , and determine the malignancy in each portion in the region of interest. 
     Second Embodiment 
     In a case of piercing the breast of the subject with the tissue sampling needle N 1 , in general, the distal end of the tissue sampling needle N 1  is carefully pierced so as not to enter the pectoralis major muscle. The ultrasound diagnostic apparatus  1  can also issue a warning in a case where the tissue sampling needle N 1  is predicted to advance toward the pectoralis major muscle. 
       FIG.  9    illustrates a configuration of an ultrasound diagnostic apparatus  1 A according to a second embodiment. The ultrasound diagnostic apparatus  1 A is obtained by comprising an apparatus main body  3 A instead of the apparatus main body  3  in the ultrasound diagnostic apparatus  1  of the first embodiment illustrated in  FIG.  1   . The apparatus main body  3 A in the second embodiment is obtained by adding a warning unit  61  to the apparatus main body  3  in the first embodiment, and comprising a main body controller  40 A instead of the main body controller  40 . 
     In the apparatus main body  3 A, the sampling target region detection unit  35  and the needle detection unit  36  are connected to the warning unit  61 . Further, the warning unit  61  is connected to the display controller  32  and the main body controller  40 A. Further, the image generation unit  31 , the display controller  32 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , the needle passage determination unit  38 , the main body controller  40 A, and the warning unit  61  constitute a processor  42 A for the apparatus main body  3 A. 
     The sampling target region detection unit  35  detects the sampling target region A 1  and the pectoralis major muscle region B 1  in the ultrasound image U 1  by performing an image analysis on the ultrasound image U 1  stored in the image memory  34 . 
     The warning unit  61  predicts whether or not the tissue sampling needle N 1  advances toward the pectoralis major muscle on the basis of the pectoralis major muscle region B 1  detected by the sampling target region detection unit  35  and the tissue sampling needle N 1  detected on the ultrasound image U 1  by the needle detection unit  36 , and issues a warning in a case where it is predicted that the tissue sampling needle N 1  advances toward the pectoralis major muscle. 
     Here, in a case where the sampling target region A 1  is positioned at a shallow portion in the subject, since there is a sufficient distance between the sampling target region A 1  and the pectoralis major muscle region B 1 , a risk of the tissue sampling needle N 1  entering the pectoralis major muscle is relatively low even in a case where the distal end of the tissue sampling needle N 1  faces the pectoralis major muscle region B 1 . However in a case where the sampling target region A 1  is positioned at a deep portion in the subject, that is, in a case where the sampling target region A 1  is positioned near the pectoralis major muscle region B 1 , and in a case where the distal end of the tissue sampling needle N 1  faces the pectoralis major muscle region B 1 , a risk of the tissue sampling needle N 1  entering the pectoralis major muscle is relatively high when the tissue sampling needle N 1  passes through the sampling target region A 1 . 
     Thus, for example, the warning unit  61  can recognize the positional relationship between pectoralis major muscle region B 1  and the sampling target region A 1  detected by the sampling target region detection unit  35 , and the position and direction of the tissue sampling needle N 1  detected by the needle detection unit  36 , and predict that the tissue sampling needle N 1  advances toward the pectoralis major muscle in a case where an extension line L 1  extending from the distal end of the tissue sampling needle N 1  along the direction of the tissue sampling needle N 1  intersects the pectoralis major muscle region B 1  and the distance between the sampling target region A 1  and the pectoralis major muscle region B 1  is equal to or greater than a certain value, as illustrated in  FIG.  10   . As the distance between the sampling target region A 1  and the pectoralis major muscle region B 1 , the warning unit  61  can evaluate, for example, a distance between the sampling target region A 1  and the pectoralis major muscle region B 1  in a depth direction of the ultrasound image U 1 , and also evaluate a distance between the sampling target region A 1  and the pectoralis major muscle region B 1  along the extension line L 1 . 
     Although not illustrated, the warning unit  61  can issue a warning by displaying a message such as “danger!” on the monitor  33 . 
     As described above, with the ultrasound diagnostic apparatus  1 A according to the second embodiment, since the warning unit  61  issues a warning in a case where it is predicted that the tissue sampling needle N 1  detected by the needle detection unit  36  advances toward the pectoralis major muscle, the examiner can safely pierce the subject with the tissue sampling needle N 1  so that the distal end of the tissue sampling needle N 1  does not enter the pectoralis major muscle, by checking the warning. 
     Third Embodiment 
     In order to check the location where the biopsy has been performed by the tissue sampling needle N 1  after the examination, it is also possible to store information regarding a piercing final point reached by the tissue sampling needle N 1 . 
       FIG.  11    illustrates a configuration of an ultrasound diagnostic apparatus  1 B according to a third embodiment. The ultrasound diagnostic apparatus  1 B is obtained by comprising an apparatus main body  3 B instead of the apparatus main body  3  in the ultrasound diagnostic apparatus  1  of the first embodiment illustrated in  FIG.  1   . The apparatus main body  3 B in the third embodiment is obtained by adding a final point reach determination unit  62  and an examination result memory  63  to the apparatus main body  3  in the first embodiment, and comprising a main body controller  40 B instead of the main body controller  40 . 
     In the apparatus main body  3 B, the final point reach determination unit  62  is connected to the needle detection unit  36 . Further, the examination result memory  63  is connected to the final point reach determination unit  62 . The final point reach determination unit  62  and the examination result memory  63  are connected to the main body controller  40 B. The examination result memory  63  is also connected to the image memory  34 . Further, the image generation unit  31 , the display controller  32 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , the needle passage determination unit  38 , the main body controller  40 B, and the final point reach determination unit  62  constitute a processor  42 B for the apparatus main body  3 B. 
     The final point reach determination unit  62  determines whether or not the tissue sampling needle N 1  has reached the piercing final point on the basis of the detection of the tissue sampling needle N 1  by the needle detection unit  36 . For example, as illustrated in  FIG.  12   , in a case where the advance direction of the distal end of the tissue sampling needle N 1  that has advanced toward the deep portion from the body surface of the subject is changed in the opposite direction, that is, in a direction from the deep portion of the subject toward the body surface, the final point reach determination unit  62  determines that the tissue sampling needle N 1  has reached a piercing final point T by determining a point where the advance direction the distal end of the tissue sampling needle N 1  is changed in the opposite direction, as the final point T. The final point reach determination unit  62  sends the determination result to the main body controller  40 B. 
     Further, the final point reach determination unit  62  can acquire coordinates of the tissue sampling needle N 1  on the ultrasound image U 1  at the time of determining that the tissue sampling needle N 1  has reached the final point T, and send the coordinates to the examination result memory  63 . Here, the coordinates of the tissue sampling needle N 1  are a set of coordinates representing the overall position of the tissue sampling needle N 1 . 
     Further, the final point reach determination unit  62  can extract the ultrasound image of the tissue sampling needle N 1  at the time of determining that the tissue sampling needle N 1  has reached the final point T, and send the extracted ultrasound image of the tissue sampling needle N 1  to the examination result memory  63 . 
     Under the control of the main body controller  40 B, the examination result memory  63  stores various ultrasound image UI and data. Specifically, the examination result memory  63  stores the ultrasound image U 1  acquired by the image acquisition unit F before the tissue sampling needle N 1  passes through the sampling target region A 1 . The examination result memory  63  further stores the ultrasound image U 1 , which is acquired by the image acquisition unit F, the coordinates of the tissue sampling needle N 1  detected by the needle detection unit  36 , or the ultrasound image of the tissue sampling needle N 1  detected by the needle detection unit  36 , which are acquired or detected at the time when the final point reach determination unit  62  determines that the tissue sampling needle N 1  has reached the final point T. The examination result memory  63  further stores the ultrasound image U 1  including the sampling target region A 1  after the tissue sampling needle N 1  is pulled out from the breast of the subject. 
     The ultrasound image U 1  acquired by the image acquisition unit F before the tissue sampling needle N 1  passes through the sampling target region A 1  is stored in order for the examiner or the like to check the region suspected to be a lesion part before the biopsy. Further, the ultrasound image U 1  acquired by the image acquisition unit F and the coordinates of the tissue sampling needle N 1  or the ultrasound image of the tissue sampling needle N 1  at the time when the final point reach determination unit  62  determines that the tissue sampling needle N 1  has reached the final point T are stored in order for the examiner or the like to check the state of the tissue sampling needle N 1  during the biopsy. The ultrasound image U 1  including the sampling target region A 1  after the tissue sampling needle N 1  is pulled out from the breast of the subject is stored in order for the examiner or the like to check the region subject to be a lesion part after the biopsy is performed. 
     In a case where the coordinates of the tissue sampling needle N 1  are stored, the examination result memory  63  can store, for example, the coordinates of the tissue sampling needle N 1  in a so-called Digital Imaging and Communications in Medicine (DICOM) standard format such as grayscale softcopy presentation state (GSPS). For example, an identifier (ID) of the ultrasound image U 1  which is acquired by the image acquisition unit F before the tissue sampling needle N 1  passes through the sampling target region A 1  and is stored in the examination result memory  63  is included in the GSPS. In a case where the ultrasound image U 1  corresponding to the ID is displayed on, for example, an external so-called picture archiving and communication system (PACS) viewer, an image corresponding to the tissue sampling needle N 1  can be depicted in a region corresponding to the coordinates of the tissue sampling needle N 1 , on the ultrasound image U 1 . 
     In this case, since the coordinates of the tissue sampling needle N 1  are only stored as the information of the tissue sampling needle N 1 , the information amount to be stored in the examination result memory  63  can be reduced and the storage capacity of the examination result memory  63  can be saved as compared with a case where the ultrasound image U 1  at the time when the tissue sampling needle N 1  has reached the final point T is stored. 
     In a case where the ultrasound image of the tissue sampling needle N 1  is stored, the examination result memory  63  can store a 1-bit black and white image in a DICOM so-called “overlay” tag for the ultrasound image U 1  acquired by the image acquisition unit F before the tissue sampling needle N 1  passes through the sampling target region A 1 , for example. In this case, in a case where the ultrasound image U 1  acquired before the tissue sampling needle N 1  passes through the sampling target region A 1  is displayed on, for example, an external PACS viewer, the operator of the viewer can superimpose and display the image of the tissue sampling needle N 1  stored in the examination result memory  63  on the ultrasound image U 1 , and display only the ultrasound image U 1  by erasing the image of the tissue sampling needle N 1  that has been superimposed and displayed on the ultrasound image U 1  via the input operation. Therefore, it is possible for the operator of the viewer to easily check the result of the biopsy. 
     Further, in this case, since the 1-bit image of the tissue sampling needle N 1  is only stored as the information of the tissue sampling needle N 1 , the information amount to be stored in the examination result memory  63  can be reduced and the storage capacity of the examination result memory  63  can be saved as compared with a case where the entire ultrasound image U 1  at the time when the tissue sampling needle N 1  has reached the final point T is stored. 
     As described above, with the ultrasound diagnostic apparatus  1 B according to the third embodiment, it is automatically determined that the tissue sampling needle N 1  has reached the piercing final point T. Further, the examination result memory  63  automatically stores the ultrasound image U 1  acquired by the image acquisition unit F before the tissue sampling needle N 1  passes through the sampling target region A 1  and the ultrasound image U 1 , which is acquired by the image acquisition unit F, the coordinates of the tissue sampling needle N 1  detected by the needle detection unit  36 , or the ultrasound image of the tissue sampling needle N 1  detected by the needle detection unit  36 , which are acquired or detected at the time when the final point reach determination unit  62  determines that the tissue sampling needle N 1  has reached the final point T. Therefore, an appropriate examination result can be reliably stored while an examiner performs a biopsy smoothly without interrupting the biopsy. Further, the storage capacity of the examination result memory  63  can also be saved. For example, the operator viewing the ultrasound image U 1  stored in the examination result memory  63  with the external PACS viewer can freely display or delete the image of the tissue sampling needle N 1  on the ultrasound image U 1 , and therefore can easily check the result of the biopsy. 
     When it is determined that the tissue sampling needle N 1  has reached the piercing final point T, in a case where the needle passage determination unit  38  determines that the tissue sampling needle N 1  has not passed through the sampling target region A 1 , the needle detection unit  36  detects an actual path G 1  of the tissue sampling needle N 1 , and the recommended path calculation unit  37  can set a path obtained by the parallel translation of the actual path G 1  of the tissue sampling needle N 1  in any one of upward, downward, left, and right directions on the ultrasound image U 1  to pass through the sampling target region A 1 , as a new recommended path P 2 . The recommended path calculation unit  37  can set the new recommended path P 2  by drawing a plurality of perpendicular lines from the actual path G 1  of the tissue sampling needle N 1  to the linear recommended path P 1  and performing the parallel translation of the actual path G 1  in any one of upward, downward, left, and right directions so that the sum of the lengths of the plurality of perpendicular lines in the sampling target region A 1  is minimized.  FIG.  13    illustrates an example of the deflected path G 1  that has deviated from the sampling target region A 1  due to the deflection or the like of the tissue sampling needle N 1  in the subject, and an example of the new recommended path P 2  set by the parallel translation of the deflected path G 1  in the upward direction. 
     In a case where the new recommended path P 2  is set in this manner, the examiner can retreat the tissue sampling needle N 1  to the shallow portion, that is, the body surface side of the subject once, and pierce the breast of the subject with the tissue sampling needle N 1  along the newly set recommended path P 2 , and thereby the distal end of the tissue sampling needle N 1  can advance to pass through the sampling target region A 1 . 
     Further, the description has been made in which the form of the third embodiment is applied to the form of the first embodiment, but the form of the third embodiment can be appropriately combined with the form of the second embodiment. 
     Fourth Embodiment 
     The tissue sampling needle N 1  pierced into the breast of the subject can be deflected by the tissues in the breast of the subject. The ultrasound diagnostic apparatus  1  can display a deflection occurrence region in an emphasized manner such that the examiner can more accurately perform the biopsy by easily understanding the deflection occurrence region in the breast of the subject where the deflection of the tissue sampling needle N 1  has occurred. 
       FIG.  14    illustrates a configuration of an ultrasound diagnostic apparatus  1 C according to a fourth embodiment. The ultrasound diagnostic apparatus  1 C is obtained by comprising an apparatus main body  3 C instead of the apparatus main body  3  in the ultrasound diagnostic apparatus  1  of the first embodiment illustrated in  FIG.  1   . 
     The apparatus main body  3 C in the fourth embodiment is obtained by adding a deflection detection unit  64  and an emphasizing unit  65  to the apparatus main body  3  in the first embodiment, and comprising a main body controller  40 C instead of the main body controller  40 . In the apparatus main body  3 C, the needle detection unit  36  is connected to the deflection detection unit  64 . The emphasizing unit  65  is connected to the image generation unit  31  and the deflection detection unit  64 . The emphasizing unit  65  is connected to the display controller  32 . The deflection detection unit  64  and the emphasizing unit  65  are connected to the main body controller  40 C. Further, the image generation unit  31 , the display controller  32 , the sampling target region detection unit  35 , the needle detection unit  36 , the recommended path calculation unit  37 , the needle passage determination unit  38 , the main body controller  40 C, the deflection detection unit  64 , and the emphasizing unit  65  constitute a processor  42 C for the apparatus main body  3 C. 
     For example, as illustrated in  FIG.  15   , the deflection detection unit  64  detects the path G 1  through which the tissue sampling needle N 1  has passed in the ultrasound image U 1  on the basis of the detection of the tissue sampling needle N 1  by the needle detection unit  36 , and detects the deflection occurring in the path G 1 . In this case, the deflection detection unit  64  can detect the deflection occurring in the path G 1  through which the tissue sampling needle N 1  has passed by using, for example, an image recognition method including pattern matching and extraction of the feature amount, or a deep learning method. 
     The emphasizing unit  65  detects a brightness value of the ultrasound image U 1  for the position where the deflection is detected by the deflection detection unit  64 , emphasizes a continuous region having a brightness value within a predetermined range for the detected brightness value, as a deflection occurrence region E 1 , and displays the deflection occurrence region E 1  on the monitor  33 . 
     Here, the brightness value within the predetermined range for the detected brightness value refers to a brightness value within a certain range including the detected brightness value, and can be set to a brightness value within a range that is equal to or higher than a brightness value lower than the detected brightness value by a predetermined value and is equal to or lower than a brightness value higher than the detected brightness value by a predetermined value. That is, the lower limit value of the brightness value within the predetermined range for the detected brightness value is a value obtained by subtracting the determined value from the detected brightness value. The upper limit value of the brightness value within the predetermined range for the detected brightness value is a value obtained by adding the determined value to the detected brightness value. 
     Further, the emphasizing unit  65  can emphasize and display the deflection occurrence region E 1  on the monitor  33  by displaying the deflection occurrence region E 1  in a display mode different from the surroundings, such as by displaying a contour line C 1  of the deflection occurrence region E 1  indicated by the dotted line in  FIG.  15    and imparting a color different from the surroundings to the deflection occurrence region E 1 . 
     As described above, with the ultrasound diagnostic apparatus  1 C according to the fourth embodiment, the deflection occurring in the path G 1  through which the tissue sampling needle N 1  has passed is detected, and the continuous region having a brightness value within a predetermined range for the brightness value of the ultrasound image U 1  for the position where the deflection is detected is emphasized and displayed as the deflection occurrence region E 1  on the monitor  33 . Therefore, the examiner can easily understand the position of the deflection occurrence region E 1 , more accurately cause the tissue sampling needle N 1  to advance up to the sampling target region A 1 , and reliably perform the biopsy. 
     In a case where the deflection has occurred in the path G 1  through which the tissue sampling needle N 1  has passed, the advance direction of the tissue sampling needle N 1  in the deflection occurrence region E 1  may deviate from the advance direction desired by the examiner, and as a result, the path G 1  of the tissue sampling needle N 1  may deviate from the sampling target region A 1 . Thus, the recommended path calculation unit  37  can calculate the recommended path P 1  by taking into consideration the position of the deflection occurrence region E 1  detected by the deflection detection unit  64 , for example. 
     In this case, in a case where the tissue sampling needle N 1  advances into the deflection occurrence region E 1 , the recommended path calculation unit  37  can calculate a recommended path P 3  deflected in the deflection occurrence region E 1  on the assumption that the tissue sampling needle N 1  advances along a deflected path similar to the deflection of the actual path G 1  detected by the deflection detection unit  64 . In this case, the recommended path calculation unit  37  can calculate a deflection amount that the path G 1  is deflected for a certain number of pixels in the ultrasound image U 1 , and calculate a deflection amount of the new recommended path P 3  in the deflection occurrence region E 1  according to the number of pixels of a portion where the linear recommended path P 1  before the deflection is considered and the deflection occurrence region E 1  overlap, on the basis of the calculated deflection amount. 
     As a result, the examiner can perform piercing with the tissue sampling needle N 1  while checking the recommended path P 3  in which the deflection of the tissue sampling needle N 1  in the deflection occurrence region E 1  is considered, and therefore can reliably perform the biopsy even in a case where the path G 1  of the tissue sampling needle N 1  is deflected. 
     Further, the description has been made in which the form of the fourth embodiment is applied to the first embodiment, but the form of the fourth embodiment can be appropriately combined with the forms of the second embodiment and the third embodiment. 
     EXPLANATION OF REFERENCES 
       1 ,  1 A,  1 B,  1 C: ultrasound diagnostic apparatus 
       2 : ultrasound probe 
       3 ,  3 A,  3 B,  3 C: apparatus main body 
       21 : transducer array 
       22 : transmission and reception circuit 
       23 : pulser 
       24 : amplification unit 
       25 : AD conversion unit 
       26 : beam former 
       31 : image generation unit 
       32 : display controller 
       33 : monitor 
       35 : sampling target region detection unit 
       36 : needle detection unit 
       37 : recommended path calculation unit 
       38 : needle passage determination unit 
       40 ,  40 A,  40 B,  40 C: main body controller 
       41 : input device 
       42 ,  42 A,  42 B,  42 C: processor 
       51 : signal processing unit 
       52 : DSC 
       53 : image processing unit 
       54 : malignancy determination unit 
       55 : region extraction unit 
       61 : warning unit 
       62 : final point reach determination unit 
       63 : examination result memory 
       64 : deflection detection unit 
       65 : emphasizing unit 
     A 1 : sampling target region 
     B 1 : pectoralis major muscle region 
     C 1 : contour line 
     E 1 : deflection occurrence region 
     F: image acquisition unit 
     G 1 : path 
     L 1 : extension line 
     N 1 : tissue sampling needle 
     P 1 , P 2 : recommended path 
     T: final point 
     U 1 : ultrasound image