WO2016194432A1

WO2016194432A1 - Ultrasonic diagnostic apparatus

Info

Publication number: WO2016194432A1
Application number: PCT/JP2016/057902
Authority: WO
Inventors: 村下　賢; 裕哉宍戸; 小林　正樹; みか佐藤
Original assignee: 株式会社日立製作所
Priority date: 2015-06-02
Filing date: 2016-03-14
Publication date: 2016-12-08
Also published as: JP2016221076A; JP5985007B1

Abstract

In the present invention, a three-dimensional image generation unit 20 generates, on the basis of volume data of a plurality of time phases obtained by transmitting and receiving ultrasonic waves, a three-dimensional ultrasonic image of a plurality of frames corresponding to the time phases. An intermediate image generation unit 50 generates three-dimensional intermediate images of one or more frames to be added between the frames of the three-dimensional ultrasonic image on the basis of movement vectors between the frames of the image. A display image generation unit 80 generates a three-dimensional moving image, on the basis of the three-dimensional ultrasonic image of a plurality of frames and the three-dimensional intermediate images of a plurality of frames added between the former frames, and displays the three-dimensional moving image on a display unit 82.

Description

Ultrasonic diagnostic equipment

The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an apparatus for forming a three-dimensional ultrasonic image.

There is known an ultrasonic diagnostic apparatus that forms a three-dimensional ultrasonic image representing a diagnostic object in three dimensions based on volume data obtained by three-dimensionally transmitting and receiving ultrasonic waves to a space including the diagnostic object. For example, a volume rendering image can be obtained as a three-dimensional ultrasound image in which a fetus is projected three-dimensionally by performing rendering processing on volume data obtained from the mother's body.

In forming a three-dimensional ultrasonic image, an ultrasonic beam is scanned two-dimensionally by electronic scanning or a combination of electronic scanning and mechanical scanning, and volume data is constructed from within the scanning space (volume). A large number of data (voxel data) is collected. Therefore, compared to a B-mode image that forms a tomographic image corresponding to the scanning surface by scanning an ultrasonic beam in a one-dimensional manner, formation of a three-dimensional ultrasonic image requires a lot of transmission / reception time. This is one problem in dynamically displaying a three-dimensional ultrasonic image.

Incidentally, in the field of image processing related to a general image such as a television image as a representative example, a technique for improving a frame rate when an image is dynamically displayed has been proposed. For example, Patent Documents 1 and 2 disclose a technique (FRC: frame rate control) for increasing the frame rate by increasing the number of frames of an image by generating an interpolation frame using an image motion vector. .

JP 2011-216935 A JP 2010-57010 A

The present invention has been made in view of the background art described above, and an object thereof is to improve the dynamic display of a three-dimensional ultrasonic image.

An ultrasonic diagnostic apparatus suitable as a specific example of the present invention is based on volume data of a plurality of time phases obtained by transmitting and receiving ultrasound three-dimensionally, and a plurality of frames of three-dimensional ultrasound corresponding to the plurality of time phases. An ultrasonic image forming unit that forms an image, and one or a plurality of frames of three-dimensional intermediate images that are added between the frames based on movement information of the images between the frames of the plurality of frames of the three-dimensional ultrasound images An intermediate image forming unit, and a display processing unit that displays a three-dimensional moving image based on the three-dimensional ultrasonic image of the plurality of frames and the three-dimensional intermediate image of the plurality of frames added between the plurality of frames. It is characterized by having.

In the above configuration, volume data is obtained for each time phase, for example, over a plurality of time phases by transmitting and receiving ultrasonic waves three-dimensionally. The volume data obtained for each time phase is composed of, for example, a plurality of data (voxel data) collected from the space (volume) in which ultrasonic waves are transmitted and received.

Then, based on the volume data obtained for each time phase, a three-dimensional ultrasonic image of each frame corresponding to that time phase is formed. A preferred specific example of the three-dimensional ultrasonic image is a rendered image obtained by rendering processing on volume data, but the specific example of the three-dimensional ultrasonic image is not limited to the rendered image.

Furthermore, in the above configuration, one or a plurality of frames of three-dimensional intermediate images are added between the frames of a plurality of frames of three-dimensional ultrasound images. For example, one or more three-dimensional intermediate images are added between one frame and the other frame (between each frame) adjacent to each other in the three-dimensional ultrasound image. The number of frames of the three-dimensional intermediate image added between the frames of the three-dimensional ultrasound image is determined according to, for example, the frame rate to be targeted. For example, if you want to double the frame rate of a 3D ultrasound image of multiple frames, you want to add a 1D 3D intermediate image between each frame of the 3D ultrasound image and quadruple the frame rate. In this case, three frames of three-dimensional intermediate images are added between the frames of the three-dimensional ultrasound image. In other words, if you want to increase the frame rate of a 3D ultrasound image of multiple frames by M times (M is an integer greater than or equal to 2), between each frame of the 3D ultrasound image, (M-1) 3D intermediate Add an image.

In the above configuration, a three-dimensional moving image is displayed based on a plurality of frames of three-dimensional ultrasound images and a plurality of frames of three-dimensional intermediate images added between the plurality of frames. A three-dimensional moving image is an image that dynamically reproduces a three-dimensional ultrasonic image and a three-dimensional intermediate image.For example, a three-dimensional ultrasonic image and a plurality of added three-dimensional intermediate images are A three-dimensional moving image is realized by displaying one after another in phase order. Note that 3D video is realized by slow playback (low-speed playback) and frame-by-frame playback in addition to normal playback (single-speed playback) that displays images corresponding to multiple time phases one after another in real time. Alternatively, rewind playback or the like in which the phase order is reversed may be realized.

According to the apparatus having the above configuration, a 3D moving image is displayed based on a 3D ultrasonic image of a plurality of frames and a 3D intermediate image of the plurality of frames added between the plurality of frames. Compared with the case where a moving image is displayed based only on a three-dimensional ultrasound image, the frame rate of the displayed image is increased.

Incidentally, Patent Documents 1 and 2 only disclose a technique for increasing the frame rate of a general image such as a television image as a representative example, and there is no specific disclosure regarding a three-dimensional ultrasonic image. For example, the content does not suggest that a three-dimensional ultrasonic image is targeted.

In a desirable specific example, the ultrasonic diagnostic apparatus further includes a control unit that controls a volume rate, which is the number of volume data per unit time, in accordance with the degree of reliability of the movement information.

In the above configuration, the degree of reliability of the movement information may be determined by, for example, a continuous degree (e.g., an evaluation value indicating a continuous degree) or, for example, a stepped degree ("high, medium, low") Or “high, low”, etc.). If the degree of reliability of the movement information is determined by a continuous degree, the volume rate can be controlled to be a continuous value according to the continuous degree. If the degree of reliability of the movement information is determined by a stepped degree, for example, the volume rate can be controlled so as to have a stepped value according to the degree.

Since the 3D intermediate image is obtained based on the movement information, the reliability of the 3D intermediate image depends on the reliability of the movement information. Therefore, the volume rate, which is the number of volume data per unit time, is controlled according to the degree of reliability of the movement information. For example, if volume data is collected at a relatively high density for each time phase, the volume rate will be relatively low, but if the reliability of movement information is relatively high, the reliability of the 3D intermediate image is also reliable. Therefore, collection of relatively high-density volume data at a relatively low volume rate is maintained. On the other hand, for example, when the reliability of movement information is relatively low, the reliability of the 3D intermediate image is expected to be low, so control that increases the volume rate and increases the reliability of the 3D intermediate image is realized. Is done. Thus, for example, when obtaining a three-dimensional moving image of a fetus, if the reliability of movement information is relatively high, high-density volume data is collected at a low volume rate. When the reliability of the movement information becomes low due to such reasons, it is possible to improve the reliability of the movement information by increasing the volume rate, for example, to cope with the intense movement of the fetus.

In a preferred embodiment, the control unit increases the volume rate per unit time of the three-dimensional ultrasonic image when it is determined that the reliability of the movement information is low based on a reliability determination condition. The frame rate which is the number of frames is increased.

In a preferred embodiment, the control unit transmits and receives a plurality of transmission / reception including a number of spatial frames in a volume for transmitting and receiving ultrasonic waves three-dimensionally, a number of beam lines constituting each spatial frame, and an ultrasonic pulse repetition period. The volume rate is controlled by changing at least one of the parameters.

In a desirable specific example, the intermediate image forming unit uses, as the movement information, a movement vector based on a correlation calculation between the frames for each image element of a plurality of image elements constituting the three-dimensional ultrasonic image of each frame. And obtaining the plurality of intermediate image elements corresponding to each frame based on the plurality of image elements and their movement vectors, thereby forming the three-dimensional intermediate image composed of the plurality of intermediate image elements. It is characterized by that.

In the above configuration, for the derivation of the movement vector, for example, it is desirable to use pattern matching processing between images between frames, but other known methods such as a gradient method and a phase-only correlation method may be used. Good.

In a preferred embodiment, the ultrasonic diagnostic apparatus is configured such that the reliability of the movement vector derived as the movement information based on the magnitude of the correlation value obtained by the correlation calculation for each image element of the plurality of image elements. An evaluation unit that calculates an evaluation value indicating the degree of the control, and the control unit controls a volume rate that is the number of volume data per unit time based on the evaluation value indicating the reliability of the movement vector. It is characterized by that.

The present invention improves the dynamic display of 3D ultrasound images. For example, according to a preferred embodiment of the present invention, a 3D moving image is displayed based on a 3D ultrasound image of a plurality of frames and a 3D intermediate image of a plurality of frames added between the plurality of frames. For example, the frame rate of the displayed image can be increased as compared with a case where a moving image is displayed based only on a three-dimensional ultrasonic image of a plurality of frames.

1 is an overall configuration diagram of an ultrasonic diagnostic apparatus suitable as an embodiment of the present invention. It is a figure which shows the specific example of a three-dimensional ultrasonic image and a three-dimensional intermediate image. It is a figure which shows the specific example of the process which derives | leads-out a movement vector. It is a figure which shows the specific example of the smoothing process with respect to a movement vector. It is a figure which shows the specific example 1 of the process which forms a three-dimensional intermediate image. It is a figure which shows the specific example 1 of an intermediate vector. It is a figure which shows the specific example 2 of the process which forms a three-dimensional intermediate image. It is a figure which shows the specific example 2 of an intermediate vector. It is a figure which shows the specific example of volume rate control.

FIG. 1 is an overall configuration diagram of an ultrasonic diagnostic apparatus suitable as an embodiment of the present invention. The probe 10 is an ultrasonic probe that transmits and receives ultrasonic waves in a three-dimensional space including a diagnosis target. The probe 10 includes a plurality of vibration elements, and each vibration element transmits an ultrasonic wave in a three-dimensional space according to a transmission signal obtained from the transmission / reception unit 12. In addition, each vibration element that receives an ultrasonic reflected wave (echo) from the three-dimensional space outputs a received signal corresponding to the reflected wave to the transmission / reception unit 12.

The transmission / reception unit 12 controls transmission of the probe 10 by outputting a transmission signal corresponding to each of the plurality of vibration elements included in the probe 10. By the transmission control, an ultrasonic transmission beam is formed, and the transmission beam is scanned in the three-dimensional space.

The beam data processing unit 14 obtains a plurality of received signals corresponding to the plurality of vibration elements included in the probe 10 from the transmission / reception unit 12, and performs beam forming processing such as phasing addition processing on the plurality of received signals. Apply. As a result, an ultrasonic reception beam is formed and scanned in the three-dimensional space. That is, the reception beam is scanned in the three-dimensional space while changing the beam address of the reception beam, and the beam data processing unit 14 forms a plurality of line data corresponding to the plurality of beam addresses. Each line data is composed of a plurality of echo data.

Thus, an ultrasonic beam (transmission beam and reception beam corresponding thereto) is scanned three-dimensionally in the three-dimensional space, and a plurality of echo data are obtained from the three-dimensional space. The probe 10 is a 3D probe that collects echo data three-dimensionally by scanning an ultrasonic beam in a three-dimensional space. For example, the ultrasonic beam is scanned three-dimensionally by mechanically moving a scanning surface formed electronically by a plurality of vibration elements (1D array transducers) arranged one-dimensionally. Alternatively, the ultrasonic beam may be scanned three-dimensionally by electronically controlling a plurality of vibration elements (2D array transducers) arranged two-dimensionally.

The volume data storage unit 16 stores volume data based on a plurality of echo data obtained from the three-dimensional space. For example, the beam data processing unit 14 performs a coordinate conversion process or the like on a plurality of echo data, converts the data to a suitable coordinate system in the subsequent process, and then converts the converted data as volume data into a volume data storage unit 16 is stored.

For example, the beam data processing unit 14 performs a three-dimensional coordinate conversion process, an interpolation process, and the like on a plurality of echo data obtained in an ultrasonic scanning coordinate system (for example, an rθφ coordinate system), thereby obtaining a three-dimensional image. A plurality of voxel data corresponding to the orthogonal coordinate system (xyz coordinate system) is formed, and volume data composed of the plurality of voxel data is stored in the volume data storage unit 16.

The beam data processing unit 14 performs two-dimensional coordinate conversion processing on the plurality of echo data, so that, for example, the rθ coordinate system corresponding to the scanning plane in the scanning coordinate system is an orthogonal coordinate system (xy coordinate system). The converted data may be stored in the volume data storage unit 16 as volume data. In addition, a plurality of echo data obtained by three-dimensionally scanning ultrasonic waves in a three-dimensional space has addresses corresponding to a scanning coordinate system (for example, rθφ coordinate system) corresponding to ultrasonic three-dimensional scanning. And may be stored in the volume data storage unit 16 as volume data.

Volume data is formed one after another for each time phase over a plurality of time phases and stored in the volume data storage unit 16.

The three-dimensional image forming unit 20 forms a three-dimensional ultrasonic image based on the volume data stored in the volume data storage unit 16. The three-dimensional image forming unit 20 forms a three-dimensional ultrasonic image that three-dimensionally displays the diagnosis target based on volume data corresponding to a three-dimensional space including the diagnosis target such as a fetus. A preferred specific example of the three-dimensional ultrasound image is a rendering image obtained by a known volume rendering process.

In the volume rendering process, a virtual virtual viewpoint VP is set outside the volume data corresponding to the three-dimensional space, and the two-dimensional plane is calculated on the opposite side of the viewpoint VP with the volume data in between. The screen is virtually set. A plurality of rays (perspective lines) are defined on the basis of the viewpoint VP. For example, each ray is set so as to reach the screen after penetrating the volume data starting from the viewpoint VP. Thereby, voxel data of a plurality of voxels corresponding to the ray correspond to each ray or in the vicinity of the ray. Then, for each ray, when the voxel operation based on the rendering method is sequentially performed on the plurality of voxels corresponding to the ray from the viewpoint VP side, the pixel value corresponding to the ray is obtained as a result of the final voxel operation. It is determined. A rendering image is obtained by mapping a plurality of pixel values obtained from a plurality of rays on the screen.

The volume data storage unit 16 stores volume data of a plurality of time phases, and the three-dimensional image forming unit 20 performs, for each time phase, a tertiary corresponding to the time phase based on the volume data corresponding to the time phase. An original ultrasonic image (rendered image) is formed. As a result, a plurality of frames of three-dimensional ultrasound images corresponding to a plurality of time phases are successively formed. Then, the intermediate image forming unit 50 forms one or a plurality of frames of a three-dimensional intermediate image added between the frames of the plurality of frames of the three-dimensional ultrasound image.

FIG. 2 is a diagram showing a specific example of a three-dimensional ultrasonic image and a three-dimensional intermediate image. FIG. 2A shows a specific example of a three-dimensional ultrasonic image (3D ultrasonic image) of a plurality of frames. FIG. 2A representatively shows 3D ultrasound images of frames 1 to 5 out of a plurality of frames. Then, one or a plurality of three-dimensional intermediate images (3D intermediate images) are added between the frames of the plurality of frames of the 3D ultrasound image to form a frame sequence for a three-dimensional moving image (3D moving image). The

FIG. 2B shows a specific example of a frame sequence for 3D moving images. In the specific example shown in FIG. 2B, 4 frames of 3D intermediate images are added between the frames of the 3D ultrasound image. That is, 4 frames (4 frames) of 3D intermediate images are added between the frame 1 and the frame 2 of the 3D ultrasonic image, and between the frame 2 and the frame 3 of the 3D ultrasonic image and the frame 3 and the frame. 4 frames and 4 frames are also added between the frames 4 and 5, respectively.

追加 By adding the 3D intermediate image, the frame rate after the addition can be made higher than the frame rate before the addition. That is, the number of frames per unit time (frame) in the 3D moving image frame sequence in which the 3D intermediate image is added to the 3D ultrasound image, rather than the number of frames per unit time (frame rate) in the case of only the 3D ultrasound image. (Rate) increases (higher). For example, in the specific example shown in FIG. 2, the frame rate of the 3D moving image frame sequence shown in FIG. 2B is five times higher than the frame rate of only the 3D ultrasound image shown in FIG. It becomes.

For example, if you want to multiply the frame rate of multiple frames of 3D ultrasound images by M times (M is an integer greater than or equal to 2), add (M-1) frames of 3D intermediate images between each frame of 3D ultrasound images do it.

Returning to FIG. 1, the display image forming unit 80 includes a plurality of frames of three-dimensional ultrasound images (3D ultrasound images) formed in the three-dimensional image forming unit 20 and a plurality of frames formed in the intermediate image forming unit 50. Based on the three-dimensional intermediate image (3D intermediate image), a frame sequence for the three-dimensional moving image (3D moving image frame sequence in FIG. 2) is formed. The display image forming unit 80 then displays a three-dimensional moving image (3D moving image) that dynamically shows a three-dimensional ultrasonic image based on a frame sequence for a three-dimensional moving image (a frame sequence for a 3D moving image). Is displayed on the display unit 82.

The movement vector used for forming the three-dimensional intermediate image (3D intermediate image) is derived by the movement vector calculation unit 30. In addition, the movement vector evaluation unit 40 evaluates the degree of reliability of the movement vector.

The control unit 100 generally controls the inside of the ultrasonic diagnostic apparatus in FIG. The overall control by the control unit 100 also reflects an instruction received from a user such as a doctor or a laboratory technician via the operation device 90.

Among the configurations shown in FIG. 1 (respectively assigned parts), the transmission / reception unit 12, the beam data processing unit 14, the three-dimensional image forming unit 20, the movement vector calculation unit 30, the movement vector evaluation unit 40, and the intermediate image formation unit 50 Each unit of the display image forming unit 80 can be realized by using hardware such as an electric / electronic circuit or a processor, for example, and a device such as a memory may be used as necessary in the realization. In addition, at least some of the functions corresponding to the above-described units may be realized by a computer. That is, at least a part of the functions corresponding to the above-described units may be realized by cooperation between hardware such as a CPU, a processor, and a memory and software (program) that defines the operation of the CPU and the processor.

The volume data storage unit 16 can be realized by a storage device such as a semiconductor memory or a hard disk drive. A preferred specific example of the display unit 82 is a liquid crystal display or the like. The operation device 90 can be realized by at least one of, for example, a mouse, a keyboard, a trackball, a touch panel, and other switches. The control unit 100 can be realized by, for example, cooperation between hardware such as a CPU, a processor, and a memory, and software (program) that defines the operation of the CPU and the processor.

The overall configuration of the ultrasonic diagnostic apparatus in FIG. 1 is as described above. Next, specific examples of functions realized by the ultrasonic diagnostic apparatus of FIG. 1 will be described in detail. In addition, about the structure (each part to which the code | symbol was attached | subjected) shown in FIG. 1, the code | symbol of FIG. 1 is utilized in the following description.

FIG. 3 is a diagram showing a specific example of the process for deriving the movement vector. The movement vector calculation unit 30 derives a movement vector for each of the plurality of pixels constituting the three-dimensional ultrasonic image between two adjacent frames of the three-dimensional ultrasonic image (3D ultrasonic image) of the plurality of frames. (calculate. A pattern matching process is used to derive the movement vector.

FIG. 3 shows 3D ultrasound images of a frame n (n is a natural number) and a frame (n + 1) that are adjacent to each other among a plurality of frames. The movement vector calculation unit 30 calculates a movement vector for each pixel of a plurality of pixels constituting the 3D ultrasound image of the frame n by pattern matching processing, and a plurality of pixels constituting the 3D ultrasound image of the frame n, preferably The movement vector of each pixel is derived for all pixels.

In the pattern matching process, for each pixel of the 3D ultrasonic image of frame n, for example, a template T is set so as to surround the pixel. Then, the search area SA is set so as to include, for example, an image area at a position corresponding to the template T in the 3D ultrasonic image of the frame (n + 1). Various known methods can be used for setting the search area SA. Of course, for example, the entire area in the 3D ultrasound image of the frame (n + 1) may be set as the search area SA.

When the template T and the search area SA are set, the template T is moved in the search area SA. At each movement position, a plurality of pixels in the template T of the 3D ultrasound image of the frame n and the 3D of the frame (n + 1). A correlation calculation is performed based on a plurality of pixels in the template T of the ultrasonic image. For example, a position corresponding to the template T in the frame n is set as an initial position, and a correlation value is calculated for each displacement (dx, dy) from the initial position, and corresponds to a plurality of displacements throughout the search area SA. A correlation value is calculated.

The correlation value is a numerical value indicating the degree of correlation (similarity) between image data (a plurality of pixels and a plurality of pixels), and a known mathematical formula corresponding to each method of correlation calculation is used for calculating the correlation value. . As the correlation value, for example, SSD (Sum of Square Difference) is suitable, and the SSD indicates a smaller value as the degree of similarity increases. Note that, for example, a correlation value indicating a larger value may be used as the degree of similarity increases by a phase-only correlation method, a cross-correlation method, or the like.

When correlation values corresponding to a plurality of displacements over the entire search area SA are calculated, a displacement having the highest degree of similarity is specified from the plurality of displacements, and a movement destination of each pixel to be calculated is determined. .

FIG. 3 shows a pixel A as a representative example of a plurality of pixels constituting the 3D ultrasonic image of the frame n. Then, the pixel B is specified as the movement destination of the pixel A in the 3D ultrasonic image of the frame (n + 1) by the pattern matching process regarding the pixel A. The movement vector calculation unit 30 sets a vector having the position (coordinate) of the pixel A as a start point and the position (coordinate) of the pixel B as an end point as a movement vector AB of the pixel A. The movement vector calculation unit 30 derives a movement vector having a position of the pixel as a start point and a movement destination of the pixel as an end point for each of the plurality of pixels in the frame n, preferably for all the pixels.

Furthermore, it is desirable that the movement vector calculation unit 30 performs a smoothing process on the movement vector of each pixel constituting the 3D ultrasonic image of the frame n.

FIG. 4 is a diagram showing a specific example of the smoothing process for the movement vector. The movement vector calculation unit 30 calculates, for each target pixel, an average vector of a plurality of movement vectors corresponding to the target pixel and a plurality of pixels located in the vicinity thereof, and the calculated average vector is smoothed after the target pixel. The movement vector of

FIG. 4 shows a pixel A as a representative example of a plurality of pixels, and an average vector of nine movement vectors corresponding to nine pixels consisting of the pixel A and eight peripheral pixels is calculated. Is a movement vector after the smoothing of the pixel A. In addition, in the calculation of the average vector, the movement vector calculation unit 30 may calculate the average vector after excluding a specific movement vector from a plurality of movement vectors.

By smoothing the movement vector of each pixel, for example, even when a movement vector of a certain pixel is erroneously detected, it is possible to reduce or eliminate an adverse effect associated with the erroneous detection.

When the movement vector calculation unit 30 calculates a plurality of movement vectors corresponding to a plurality of pixels (preferably a movement vector after smoothing), a three-dimensional intermediate image (3D intermediate image) is generated based on the calculated movement vector. It is formed.

FIG. 5 is a diagram showing a specific example 1 of a process for forming a three-dimensional intermediate image. The intermediate image forming unit 50 is added between the frames based on the movement vector of the plurality of pixels obtained between two adjacent frames of the three-dimensional ultrasound image (3D ultrasound image) of the plurality of frames. One or a plurality of frames of a three-dimensional intermediate image (3D intermediate image) is formed.

FIG. 5 shows a specific example of forming an intermediate image added between a frame n (n is a natural number) and a frame (n + 1) of the 3D ultrasound image. The movement vector AB shown in FIG. 5A is a movement vector corresponding to the pixel A in the 3D ultrasound image of the frame n (see FIGS. 3 and 4). That is, the movement destination of the pixel A is the position (coordinates) of the pixel B in the 3D ultrasonic image of the frame (n + 1). The intermediate image forming unit 50 obtains the intermediate vector AC shown in FIG. 5 (2) from the movement vector AB shown in FIG. 5 (1).

FIG. 6 is a diagram showing a specific example 1 of the intermediate vector. FIG. 6 shows a specific example of an intermediate vector between the 3D ultrasound image of frame n and the 3D ultrasound image of frame (n + 1). The movement vector AB is a movement vector corresponding to the pixel A in the 3D ultrasonic image of the frame n, and the movement destination of the pixel A is the position (coordinate) of the pixel B in the 3D ultrasonic image of the frame (n + 1). .

FIG. 6 shows a specific example in which the frame rate is M times (M is an integer of 2 or more). That is, the 3D intermediate image of (M−1) frames is added between the 3D ultrasound image of frame n and the 3D ultrasound image of frame (n + 1). In the specific example shown in FIG. 6, the 3D intermediate images of frames 1, 2, 3,..., M−1 are arranged in the order close to the 3D ultrasound image of frame n (close to the temporal phase).

The intermediate image forming unit 50 derives an intermediate vector AC (AC1, AC2, AC3,..., AC (M−1)) regarding the pixel A from the movement vector AB corresponding to the pixel A. The start point and direction of the intermediate vector AC are the same as those of the movement vector AB, and the size (vector length) of the intermediate vector AC is determined by the frame number (1, 2, 3,..., M−1) of the 3D intermediate image. ).

For example, in FIG. 6, the intermediate vector AC1 corresponding to the 3D intermediate image of frame 1 has the same starting point and direction as the movement vector AB, and the size (the length of the vector) is 1 / M of the movement vector AB. The Also. The intermediate vector AC2 corresponding to the 3D intermediate image of the frame 2 has the same starting point and direction as the movement vector AB, and the size (the length of the vector) is 2 / M of the movement vector AB. The intermediate vector AC (M-1) corresponding to the 3D intermediate image of the frame (M-1) has the same starting point and direction as the movement vector AB, and the magnitude (vector length) of the movement vector AB. (M-1) / M.

The intermediate image forming unit 50 generates an intermediate vector corresponding to each frame of the 3D intermediate image based on the movement vector corresponding to each pixel of the plurality of pixels constituting the 3D ultrasonic image of the frame n. .

Returning to FIG. 5, the intermediate vector AC shown in FIG. 5 (2) is an intermediate vector related to the pixel A of the 3D ultrasound image of frame n, and is the frame of interest of the 3D intermediate image (for example, frames 1 to M-1 in FIG. 6). Intermediate vector corresponding to any of the 3D intermediate images).

The intermediate image forming unit 50 generates an intermediate vector for each pixel for a plurality of pixels constituting the 3D ultrasonic image of the frame n, preferably for all pixels. Then, the intermediate image forming unit 50 selects an intermediate vector whose end point of the vector is closest to the position (coordinates) of the pixel of interest Z among a plurality of intermediate vectors corresponding to the plurality of pixels. In the specific example shown in FIG. 5 (2), the intermediate vector AC is selected.

Further, the intermediate image forming unit 50 translates the intermediate vector so that the end point of the selected intermediate vector becomes the position of the target pixel. In the specific example of FIG. 5, the intermediate vector A′C ′ of FIG. 5 (3) is obtained as a result of translation of the intermediate vector AC of FIG. 5 (2).

Then, the intermediate image forming unit 50 determines the pixel value of the target pixel based on the pixel values of a plurality of pixels in the vicinity of the start point of the intermediate vector after translation. For example, as shown in FIG. 5 (4), the pixel value of the pixel of interest Z is calculated from the pixel values of the four pixels in the vicinity of the coordinate A ′ in the 3D ultrasound image of the frame n by, for example, linear interpolation processing. Is done. Then, the calculated pixel value of the target pixel Z is set as an intermediate pixel constituting the target frame of the 3D intermediate image.

The intermediate image forming unit 50 executes the processing described with reference to FIG. 5 using each of the pixels constituting the target frame of the 3D intermediate image as the target pixel, and performs the processing for all the pixels constituting the target frame of the 3D intermediate image. By obtaining the pixel value, a 3D intermediate image corresponding to the frame of interest is formed. Further, the intermediate image forming unit 50 performs the processing described with reference to FIG. 5 using each frame of a 3D intermediate image of a plurality of frames (for example, 3D intermediate images from frames 1 to M-1 in FIG. 6) as a frame of interest. By executing this, a 3D intermediate image of a plurality of frames is formed.

FIG. 7 is a diagram showing a specific example 2 of a process for forming a three-dimensional intermediate image. FIG. 7 shows a specific example of forming an intermediate image added between a frame n (n is a natural number) and a frame (n + 1) of the 3D ultrasound image. A movement vector AB shown in FIG. 7A is a movement vector (see FIGS. 3 and 4) corresponding to the pixel A in the 3D ultrasonic image of the frame n. That is, the movement destination of the pixel A is the position (coordinates) of the pixel B in the 3D ultrasonic image of the frame (n + 1). The intermediate image forming unit 50 obtains the intermediate vector CB shown in FIG. 7 (2) from the movement vector AB shown in FIG. 7 (1).

FIG. 8 is a diagram showing a specific example 2 of the intermediate vector. FIG. 8 shows a specific example of an intermediate vector between the 3D ultrasound image of frame n and the 3D ultrasound image of frame (n + 1). The movement vector AB is a movement vector corresponding to the pixel A in the 3D ultrasonic image of the frame n, and the movement destination of the pixel A is the position (coordinate) of the pixel B in the 3D ultrasonic image of the frame (n + 1). .

FIG. 8 shows a specific example in which the frame rate is M times (M is an integer of 2 or more). That is, the 3D intermediate image of (M−1) frames is added between the 3D ultrasound image of frame n and the 3D ultrasound image of frame (n + 1). In the specific example shown in FIG. 8, the 3D intermediate images of frames 1, 2, 3,..., M−1 are arranged in the order close to the 3D ultrasound image of frame n (close in time).

The intermediate image forming unit 50 uses the intermediate vector CB (C1B, C2B, C3B,..., C (M−1) from the movement vector AB corresponding to the pixel A to the pixel B that is the end point of the movement vector AB. B) is derived. The end point and direction of the intermediate vector CB are the same as those of the movement vector AB, and the size (vector length) of the intermediate vector CB is the frame number (1, 2, 3,..., M−1) of the 3D intermediate image. ).

For example, in FIG. 8, the intermediate vector C1B corresponding to the 3D intermediate image of frame 1 has the same end point and direction as the movement vector AB, and the size (the length of the vector) is 1 / M of the movement vector AB. The Also. The intermediate vector C2B corresponding to the 3D intermediate image of the frame 2 has the same end point and direction as the movement vector AB, and the size (the length of the vector) is 2 / M of the movement vector AB. The intermediate vector C (M−1) B corresponding to the 3D intermediate image of the frame (M−1) has the same end point and direction as the movement vector AB, and the size (the length of the vector) is the movement vector AB. (M-1) / M.

Returning to FIG. 7, the intermediate vector CB shown in FIG. 7 (2) is an intermediate vector related to the pixel A of the 3D ultrasound image of the frame n, and is a frame of interest of the 3D intermediate image (for example, frames 1 to M-1 in FIG. 8). Intermediate vector corresponding to any of the 3D intermediate images).

The intermediate image forming unit 50 generates an intermediate vector for each pixel for a plurality of pixels constituting the 3D ultrasonic image of the frame n, preferably for all pixels. Then, the intermediate image forming unit 50 selects, from among a plurality of intermediate vectors corresponding to the plurality of pixels, an intermediate vector whose vector starting point is closest to the position (coordinates) of the target pixel Z. In the specific example shown in FIG. 7B, the intermediate vector CB is selected.

Further, the intermediate image forming unit 50 translates the intermediate vector so that the start point of the selected intermediate vector is the position of the target pixel. In the specific example of FIG. 7, the intermediate vector C′B ′ of FIG. 7 (3) is obtained as a result of translation of the intermediate vector CB of FIG. 7 (2).

Then, the intermediate image forming unit 50 determines the pixel value of the target pixel based on the pixel values of a plurality of pixels in the vicinity of the end point of the intermediate vector after translation. For example, as shown in FIG. 7 (4), the pixel value of the target pixel Z is obtained from the pixel values of the four pixels near the coordinate B ′ in the 3D ultrasound image of the frame (n + 1) by, for example, linear interpolation processing. Calculated. Then, the calculated pixel value of the target pixel Z is set as an intermediate pixel constituting the target frame of the 3D intermediate image.

The intermediate image forming unit 50 executes the processing described with reference to FIG. 7 using each of the pixels constituting the target frame of the 3D intermediate image as the target pixel, and performs the processing for all the pixels constituting the target frame of the 3D intermediate image. By obtaining the pixel value, a 3D intermediate image corresponding to the frame of interest is formed. Further, the intermediate image forming unit 50 performs the processing described with reference to FIG. 7 using each frame of the 3D intermediate image of a plurality of frames (for example, the 3D intermediate images from frames 1 to M-1 in FIG. 8) as the target frame. By executing this, a 3D intermediate image of a plurality of frames is formed.

For example, according to Specific Example 1 described using FIGS. 5 and 6 or Specific Example 2 described using FIGS. 7 and 8, a plurality of frames added between a plurality of frames of a 3D ultrasound image of a plurality of frames. The 3D intermediate image is formed.

As described above, the movement vector derived by the movement vector calculation unit 30 is used to form the three-dimensional intermediate image (3D intermediate image). The movement vector calculation unit 30 is configured to move the pixel from the position of the pixel, starting from the position of each pixel, preferably for all the pixels in the frame n of the three-dimensional ultrasonic image (3D ultrasonic image). A movement vector with ending at is derived (see FIG. 3).

The movement vector evaluation unit 40 evaluates reliability related to a plurality of movement vectors corresponding to a plurality of pixels in each frame of the 3D ultrasound image. For example, in the pattern matching process by the movement vector calculation unit 30, the reliability of the movement vector is evaluated based on the correlation value at the movement destination of each pixel selected as having the strongest correlation (the most similar degree).

Specifically, a correlation value that is smaller as the correlation is stronger (similarity is greater) is used, and when the calculated correlation value exceeds the threshold (or above the threshold), It is determined that the correlation value is not a reliable value and the reliability of the movement vector obtained based on the correlation value is low. For example, for each frame of the 3D ultrasound image, the ratio of the number of pixels determined to be low in the reliability of the movement vector among the plurality of pixels constituting the frame is the reliability of the movement vector in the frame. The evaluation value. In this specific example, the greater the reliability evaluation value obtained for each frame, the lower the reliability of the motion vector of that frame.

For example, when the reliability of the movement vector of each frame is low, for example, when the reliability evaluation value is larger than the threshold, for example, the search area SA (FIG. 3) in pattern matching is expanded, It is desirable to expand the selection range of the movement destination of each pixel and increase the identification accuracy of the movement destination. Note that, since the processing time for pattern matching increases when the search area SA is expanded, for example, the number of frames of 3D intermediate images (frames of frames) added between the frames of the 3D ultrasound image as the processing time increases. (Number of sheets) may be reduced. Further, when the reliability of the movement vector of each frame is low, the template T (FIG. 3) may be enlarged to increase the accuracy of specifying the movement destination of each pixel.

Also, the control unit 100 may control transmission / reception of ultrasonic waves based on the evaluation value of the reliability of the movement vector obtained in the movement vector evaluation unit 40. For example, the control unit 100 may control the volume rate based on the evaluation value of the reliability of the movement vector obtained from the movement vector evaluation unit 40.

FIG. 9 is a diagram showing a specific example of volume rate control. FIG. 9A shows a specific example of volume data obtained for each time phase over a plurality of time phases. That is, a plurality of volume data for time phase 1 to time phase 6 are representatively shown. Note that volume data may be obtained for each time phase even after time phase 7 (not shown).

FIG. 9 (2) shows a specific example of a three-dimensional ultrasonic image (3D ultrasonic image) of a plurality of frames. A 3D ultrasonic image of each frame is formed based on time-phase volume data corresponding to the frame. In the specific example shown in FIG. 9, the 3D ultrasound image of frame 1 is formed based on the volume data of time phase 1, and the 3D ultrasound image of frame 2 is formed based on the volume data of time phase 2. That is, the time number of the volume data and the frame number of the 3D ultrasound image correspond to each other.

FIG. 9 (3) shows a specific example of a three-dimensional intermediate image (3D intermediate image), and FIG. 9 (4) shows a specific example of a three-dimensional moving image (3D moving image). Yes. In the specific example shown in FIG. 9, for example, 3 frames (3 frames) of 3D intermediate images are added between frames 1 and 2 of the 3D ultrasound image, and between the frames 2 and 3 of the 3D ultrasound image. 3D (3 frames) 3D intermediate image is also added, and 3D intermediate images are also added between frames after frame 3 of the 3D ultrasound image to form a 3D moving image frame sequence. ing.

In the specific example shown in FIG. 9, the reliability of the movement vector obtained between the frame 1 and the frame 2 of the 3D ultrasonic image is low. When the reliability of the movement vector is low, the control unit 100 increases the volume rate. However, in the specific example shown in FIG. 9, since acquisition of volume data of time phase 3 is started at a standard rate (standard volume rate) immediately after volume data of time phase 2 is obtained, the standard rate Volume data of time phase 3 is acquired while maintaining the above. Then, immediately after the volume data of time phase 3 is acquired, the volume rate is increased, and the volume data of time phase 4 and time phase 5 are acquired at a high rate (volume rate higher than the standard). Alternatively, the volume data of time phase 3 may be obtained by switching to the high rate immediately after the volume data of time phase 2 is obtained.

In the specific example shown in FIG. 9, the reliability of the movement vector obtained between the frame 3 and the frame 4 of the 3D ultrasonic image is high. When the reliability of the movement vector is high, the control unit 100 may decrease the volume rate. However, in the specific example shown in FIG. 9, since acquisition of volume data of time phase 5 is started at a high rate immediately after the volume data of time phase 4 is obtained, the time phase is maintained while maintaining the high rate. 5 volume data is acquired. Then, immediately after the volume data of time phase 5 is acquired, the volume rate is reduced, that is, returned to the standard rate, and the volume data of time phase 6 is acquired at the standard rate. Alternatively, the volume data of time phase 5 may be obtained by switching to the standard rate immediately after the volume data of time phase 4 is obtained.

The control unit 100 controls the volume rate based on a plurality of transmission / reception parameters related to transmission / reception of ultrasonic waves. The plurality of transmission / reception parameters include, for example, the number of spatial frames (spatial frame density), the number of beam lines (line density), and PRT (pulse repetition time).

The number of spatial frames is the number of spatial frames (spatial frames) constituting a volume (three-dimensional region) in which ultrasonic waves are transmitted and received in three dimensions. For example, when the volume size is constant and the number of spatial frames changes, the spatial frame density also changes. The number of beam lines is the number of reception beam lines constituting each spatial frame. For example, if the size of each spatial frame is constant and the number of beam lines changes, the line density also changes. PRT is an ultrasonic pulse repetition period.

The volume rate is determined by these multiple transmission / reception parameters. The plurality of transmission / reception parameters corresponding to the standard rate (standard volume rate) are set with emphasis on the data density of the volume data, for example. On the other hand, the plurality of transmission / reception parameters corresponding to the high rate are set so that the volume rate is higher than the standard rate (standard volume rate).

For example, the number of high-rate spatial frames is set smaller (less) than the number of standard-rate spatial frames, the number of high-rate beamlines is set smaller (less) than the number of standard-rate beamlines, and the high-rate PRT Is set smaller (shorter) than the standard rate PRT.

The control unit 100 controls the transmission / reception unit 12 with a plurality of transmission / reception parameters corresponding to the standard rate, thereby realizing acquisition of volume data at the standard rate, and controls the transmission / reception unit 12 with a plurality of transmission / reception parameters corresponding to the high rate. By doing so, the acquisition of volume data at a high rate is realized.

As a transmission / reception parameter, the volume rate may be changed by changing parallel reception (the number of parallel receptions (one or more)) or THI (whether or not to perform tissue harmonic imaging).

In the specific example shown in FIG. 9, the frame rate of the 3D moving image can be kept constant regardless of the change of the volume rate.

For example, when the high rate (high volume rate) is twice the standard rate (standard volume rate), 3 frames of 3D intermediate images are added between each frame of the 3D ultrasound image corresponding to the standard rate, By adding one frame of 3D intermediate image between each frame of the 3D ultrasound image corresponding to the high rate, the frame interval (time phase interval) of the 3D moving image is maintained constant, and the frame rate of the 3D moving image is increased. Can be kept constant. Note that the specific example shown in FIG. 9 is merely an example, and the frame rate of the 3D moving image does not necessarily have to be constant.

Further, it is desirable that the frame rate of the 3D moving image is determined according to the display frame rate that can be supported by the display unit 82. For example, if the display frame rate of the display unit 82 is 60 Hz (Hertz), the volume rate and the number of frames of the 3D intermediate image (between each frame of the 3D ultrasound image are set so that the frame rate of the 3D moving image is 60 Hz. The number of frames of 3D intermediate image to be added to the image may be determined.

Further, the display image forming unit 80 may play back the 3D moving image slowly. At the time of slow reproduction, it is desirable to determine the number of frames of the 3D intermediate image (the number of frames of the 3D intermediate image added between each frame of the 3D ultrasound image) according to the reproduction speed.

For example, when the number of 3D intermediate images between frames (the number of frames) during normal playback (1 × speed playback) is K (number of frames K: K is a natural number), the playback speed is ½ times that of normal playback. The number of 3D intermediate images (number of frames) between frames during playback is 2K, and the number of 3D intermediate images (number of frames) between frames during slow playback at 1/3 times normal playback is 3K. The number of 3D intermediate images (number of frames) between each frame during slow playback at 1/4 times the speed of playback is 4K. That is, the number of 3D intermediate images (number of frames) between each frame during slow playback at 1 / S times normal speed (S is a natural number) is S × K.

Generally, in conventional slow playback, each image frame among a plurality of image frames used in normal playback is repeatedly played in association with a plurality of display frames. That is, the same image frame is used in a plurality of display frames.

On the other hand, the number of display frames in which the same image frame (each frame of the 3D moving image) is used can be reduced by the above-described processing for determining the number of frames of the 3D intermediate image according to the playback speed during slow playback. Desirably, it is possible to realize slow reproduction in which each image frame and each display frame are associated one-to-one. Thereby, for example, slow reproduction in which the image content changes smoothly becomes possible.

The preferred embodiments of the present invention have been described above, but the above-described embodiments are merely examples in all respects and do not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

10 probe, 12 transmission / reception unit, 14 beam data processing unit, 16 volume data storage unit, 20 three-dimensional image formation unit, 30 movement vector calculation unit, 40 movement vector evaluation unit, 50 intermediate image formation unit, 80 display image formation unit, 82 display unit, 90 operation device, 100 control unit.

Claims

Based on volume data of a plurality of time phases obtained by transmitting and receiving ultrasound three-dimensionally, an ultrasound image forming unit that forms a three-dimensional ultrasound image of a plurality of frames corresponding to the plurality of time phases;
An intermediate image forming unit that forms one or a plurality of frames of three-dimensional intermediate images added between the frames based on movement information of the images between the frames of the plurality of frames of three-dimensional ultrasound images;
A display processing unit for displaying a three-dimensional moving image based on the three-dimensional ultrasound image of the plurality of frames and the three-dimensional intermediate image of the plurality of frames added between the plurality of frames;
Having
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 1,
According to the degree of reliability of the movement information, further includes a control unit that controls a volume rate that is the number of volume data per unit time.
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 2,
The control unit is the number of frames per unit time of the three-dimensional ultrasound image by increasing the volume rate when it is determined that the reliability of the movement information is low based on a reliability determination condition. Increase the frame rate,
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 2,
The control unit includes at least one of a plurality of transmission / reception parameters including a number of spatial frames in a volume for transmitting and receiving ultrasonic waves three-dimensionally, a number of beam lines constituting each spatial frame, and an ultrasonic pulse repetition period. Controlling the volume rate by changing one;
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 3.
The control unit includes at least one of a plurality of transmission / reception parameters including a number of spatial frames in a volume for transmitting and receiving ultrasonic waves three-dimensionally, a number of beam lines constituting each spatial frame, and an ultrasonic pulse repetition period. Controlling the volume rate by changing one;
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 1,
The intermediate image forming unit derives, as the movement information, a movement vector based on a correlation calculation between the frames for each image element of the plurality of image elements constituting the three-dimensional ultrasonic image of each frame. Forming a plurality of intermediate image elements corresponding to each frame based on the image elements and their movement vectors to form the three-dimensional intermediate image composed of a plurality of intermediate image elements,
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 2,
The intermediate image forming unit derives, as the movement information, a movement vector based on a correlation calculation between the frames for each image element of the plurality of image elements constituting the three-dimensional ultrasonic image of each frame. Forming a plurality of intermediate image elements corresponding to each frame based on the image elements and their movement vectors to form the three-dimensional intermediate image composed of a plurality of intermediate image elements,
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 3.
The intermediate image forming unit derives, as the movement information, a movement vector based on a correlation calculation between the frames for each image element of the plurality of image elements constituting the three-dimensional ultrasonic image of each frame. Forming a plurality of intermediate image elements corresponding to each frame based on the image elements and their movement vectors to form the three-dimensional intermediate image composed of a plurality of intermediate image elements,
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 4,
The intermediate image forming unit derives, as the movement information, a movement vector based on a correlation calculation between the frames for each image element of the plurality of image elements constituting the three-dimensional ultrasonic image of each frame. Forming a plurality of intermediate image elements corresponding to each frame based on the image elements and their movement vectors to form the three-dimensional intermediate image composed of a plurality of intermediate image elements,
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 6,
An evaluation unit that calculates an evaluation value indicating a degree of reliability of the movement vector derived as the movement information based on a correlation value obtained by the correlation calculation for each image element of the plurality of image elements; In addition,
The control unit controls a volume rate, which is the number of volume data per unit time, based on the evaluation value indicating the reliability of the movement vector.
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 7,
An evaluation unit that calculates an evaluation value indicating a degree of reliability of the movement vector derived as the movement information based on a correlation value obtained by the correlation calculation for each image element of the plurality of image elements; In addition,
The control unit controls a volume rate, which is the number of volume data per unit time, based on the evaluation value indicating the reliability of the movement vector.
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 8,
An evaluation unit that calculates an evaluation value indicating a degree of reliability of the movement vector derived as the movement information based on a correlation value obtained by the correlation calculation for each image element of the plurality of image elements; In addition,
The control unit controls a volume rate, which is the number of volume data per unit time, based on the evaluation value indicating the reliability of the movement vector.
An ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus according to claim 9,
An evaluation unit that calculates an evaluation value indicating a degree of reliability of the movement vector derived as the movement information based on a correlation value obtained by the correlation calculation for each image element of the plurality of image elements; In addition,
The control unit controls a volume rate, which is the number of volume data per unit time, based on the evaluation value indicating the reliability of the movement vector.
An ultrasonic diagnostic apparatus.