JP4653536B2 - Ultrasonic diagnostic equipment - Google Patents

Description

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

  When forming a three-dimensional ultrasonic image in an ultrasonic diagnostic apparatus, frame data is acquired by transmitting / receiving ultrasonic waves to a three-dimensional transmission / reception space in a living body, and volume data is formed from a plurality of frame data. Is done. The volume data is composed of a plurality of voxel data. When forming a three-dimensional ultrasonic image using such volume data, for example, a volume rendering method is used.

  In this method, generally, a viewpoint and a screen are defined so as to sandwich a three-dimensional data space (a data space in which volume data exists), and a plurality of rays (perspective lines) are defined from the viewpoint to the screen. Then, for each ray, the voxel data existing on that ray is sequentially read out from the three-dimensional data memory, and voxel operation (here, output using the opacity based on the volume rendering method) is performed on each voxel data. Light amount calculation) is executed sequentially. A final voxel calculation result (output light amount) is converted into a pixel value, and a pixel value for each ray is mapped on the screen, thereby forming a three-dimensional ultrasonic image.

  Conventionally, dedicated hardware (a high-speed computing unit with a fixed function) is designed for various computations for forming a three-dimensional image, and the voxel computation and the like are executed by the hardware.

  On the other hand, recently, the processing speed of programmable general-purpose processors (for example, DSP (digital signal processor)) has improved, and functional design and changes are easy. It is requested to do.

  When the above three-dimensional image processing is realized by a general-purpose processor, in general, volume data (a plurality of (x, y, z) coordinate systems) is obtained from a plurality of frame data of (r, θ, φ) coordinate systems by interpolation processing or the like. Voxel data), and the generated volume data is stored in a three-dimensional data memory (external memory). The general-purpose processor accesses the three-dimensional data memory, and the voxel data necessary for the voxel calculation is obtained for each ray. It is necessary to specify each time and import it into a general-purpose processor. If the viewpoint can be set at an arbitrary position, each ray will pass through the volume data diagonally in most cases, but in that case, if voxel calculation is performed simultaneously for each ray, voxels for multiple rays are used. A group of voxel data necessary for the calculation is variously distributed on the volume data, that is, it is necessary to perform random access to obtain the necessary voxel data for the three-dimensional data memory.

  When a memory device such as SRAM is used as a three-dimensional data memory, such random access can be performed at a high speed. Generally, however, an inexpensive and highly integrated DRAM or SDRAM is used. If random access is attempted in the case of a device, the read time increases, which is contrary to the request for high-speed transfer.

  Patent Document 1 below discloses a technique for forming a three-dimensional ultrasonic image based on a volume rendering method in an ultrasonic diagnostic apparatus. However, there is no specific disclosure regarding the data transfer method and how the voxel calculation proceeds for each ray. In Patent Document 2 below, data transfer from a three-dimensional data space (main memory) to an image processor is performed in units of data blocks having a specific address relationship in order to prevent the occurrence of a cache miss. An apparatus is disclosed. In this apparatus, a special calculation is performed at the time of reading data to obtain a set of read addresses, and the necessity of random access can be pointed out.

Japanese Patent No. 2883584 JP-A-9-134447 JP 2002-224109 A Japanese Patent Laid-Open No. 2003-19134

  In the volume rendering method, the reason why random access to the three-dimensional data memory is required is that, as described above, a group of voxel data necessary for voxel calculation is distributed on the volume data. That is, the voxel data necessary for the voxel calculation is randomly stored on the three-dimensional data memory.

  The storage position (address) of voxel data stored in the three-dimensional data memory is mainly determined by the acquisition order of echo data. For example, echo data acquired in stages according to ultrasonic scanning is stored in order from the smallest address in the memory.

  Therefore, as a technique for avoiding random access to the three-dimensional data memory, it is conceivable to appropriately control the scanning of ultrasonic waves (transmission / reception of ultrasonic waves) according to the calculation status of voxel calculation. By the way, by controlling the transmission and reception of ultrasonic waves according to the calculation status of voxel calculation, random access to the 3D data memory can be avoided, and in some cases, the memory capacity of the 3D data memory can be kept small, Ultimately, it is not impossible to lose the 3D data memory.

  In the present invention, attention is focused on the direction of the perspective line set in the data space as an index for knowing the calculation status of the voxel calculation. Incidentally, Patent Document 3 and Patent Document 4 also pay attention to the direction of the line of sight, but the techniques described therein are not intended to control the transmission and reception of ultrasonic waves.

  The present invention has been made in such a background, and an object thereof is to efficiently form a three-dimensional ultrasonic image based on volume data by controlling transmission and reception of ultrasonic waves.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes a transmission / reception unit that transmits and receives ultrasonic waves in a three-dimensional space to acquire a plurality of echo data, and the plurality of echo data. A three-dimensional image forming means for forming a three-dimensional image based on the three-dimensional image forming means, wherein the three-dimensional image forming means is a perspective line from a viewpoint virtually set in a data space corresponding to the three-dimensional space. A ray setting unit that sets a plurality of rays as, and a voxel calculation unit that calculates voxel data on the plurality of set rays from the plurality of echo data and advances voxel calculation for each ray, and The three-dimensional image is formed as a result of the last voxel operation for each ray, and the wave transmitting / receiving unit acquires a plurality of echo data in an order corresponding to the direction of each ray.

  According to the above configuration, since a plurality of echo data can be acquired in order according to the direction of each ray, starting from what is necessary for the voxel calculation, for example, immediately after acquiring the echo data by the ultrasonic probe Calculation can be started. For this reason, for example, compared with the case where voxel calculation is started after acquiring a lot of echo data in the three-dimensional data space, extremely efficient calculation processing can be realized. In addition, the capacity of the three-dimensional memory for storing the echo data in the three-dimensional data space can be reduced, and a configuration in which the three-dimensional memory is deleted as necessary can be realized.

  In the above configuration, the wave transmitting / receiving unit is preferably a wave transmitting / receiving unit that performs two-dimensional electronic scanning. However, it is also possible to use a transducer that uses both electronic scanning and mechanical scanning as the transducer. The plurality of rays may be set parallel to each other or may be set non-parallel. The three-dimensional image forming means is constituted by a program operation type processor, for example.

  Preferably, the direction of each ray is determined from the sign of a predetermined axis component of the ray vector corresponding to each ray. Preferably, the direction of each ray is determined from the position coordinates of the viewpoint in the data space. Preferably, the transmission / reception means forms a plurality of scanning planes in an order corresponding to the direction of each ray, and acquires frame data composed of a plurality of echo data for each scanning plane. . Preferably, the wave transmitting / receiving unit forms a plurality of scanning planes in order from the side closer to the viewpoint, and acquires a plurality of frame data corresponding to the plurality of scanning planes in a stepwise manner.

  Preferably, the voxel calculation unit calculates the voxel data on the plurality of set rays step by step based on the plurality of frame data acquired stepwise, and advances the voxel calculation for each ray. It is characterized by that. Preferably, the voxel calculation unit calculates voxel data from the plurality of frame data by interpolation processing. Preferably, the voxel computing unit is configured to generate two sheets of frame data corresponding to two scanning planes arranged adjacent to each other when the plurality of scanning planes are arranged in the data space according to their positions. Voxel data existing in an inter-frame region between the scanning planes is calculated. Preferably, the voxel calculation unit calculates voxel data corresponding to the voxel coordinates from echo data included in frame data corresponding to the two scanning planes and existing in the vicinity of the voxel coordinates. It is characterized by that.

  Desirably, the three-dimensional image forming means sets the initial coordinate on the first axis in the data space and the initial value on the second axis as a point at which each ray passes through the data space first. An initial coordinate calculator that calculates coordinates and initial coordinates on the third axis, a step component calculator that calculates a step component of the first axis, a step component of the second axis, and a step component of the third axis; For each ray, for each initial coordinate on the first axis, initial coordinate on the second axis, and initial coordinate on the third axis, the step component on the first axis and the second axis, respectively. By cumulatively adding the step component on the upper axis and the step component on the third axis, the target coordinate specifying unit for specifying the voxel calculation target coordinate on each ray and the stepwise acquisition of a plurality of frame data The inter-frame region that moves step by step For each movement position, characterized in that it comprises an interpolation processor for generating by the interpolation voxel data corresponding to the voxel calculation target coordinates in the region between the frame.

  Preferably, the three-dimensional image forming unit further includes a processing plane setting unit that sets a processing plane in the data space and moves the processing plane in stages according to the stepwise acquisition of the plurality of frame data. The voxel calculation unit calculates voxel data on the processing plane from the plurality of frame data for each movement position of the processing plane that moves in stages, and advances the voxel calculation for each ray according to the movement of the processing plane. It is characterized by that.

  Preferably, the processing plane is a plane orthogonal to a predetermined axis of the data space. Preferably, the voxel calculation unit calculates voxel data from the plurality of frame data by interpolation processing. Preferably, the voxel computing unit uses the coordinates of the data space among the plurality of frame data corresponding to the plurality of scanning planes when the plurality of scanning planes are arranged in the data space according to the positions thereof. Voxel data corresponding to the voxel coordinate is calculated from a plurality of frame data arranged in the vicinity of a certain voxel coordinate. Preferably, the voxel computing unit calculates voxel data corresponding to the voxel coordinates from the echo data included in the plurality of frame data and existing in the vicinity of the voxel coordinates. .

  Desirably, the three-dimensional image forming means sets the initial coordinate on the first axis in the data space and the initial value on the second axis as a point at which each ray passes through the data space first. An initial coordinate calculator that calculates coordinates and initial coordinates on the third axis, a step component calculator that calculates a step component of the first axis, a step component of the second axis, and a step component of the third axis; For each ray, for each initial coordinate on the first axis, initial coordinate on the second axis, and initial coordinate on the third axis, the step component on the first axis and the second axis, respectively. By cumulatively adding the step component on the third axis and the step component on the third axis, the target coordinate specifying unit for specifying the voxel calculation target coordinate on each ray and the processing plane moving in stages Corresponds to the voxel calculation target coordinates Characterized in that it comprises an interpolation processor for generating Kuseru data by the interpolation processing, the.

  As described above, according to the present invention, it is possible to efficiently form a three-dimensional ultrasonic image based on volume data by controlling transmission and reception of ultrasonic waves.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a diagram for explaining the principle of the volume rendering method. The three-dimensional data space 36 has volume data obtained from echo data acquired by two-dimensional scanning with an ultrasonic beam, and is virtually constructed in the ultrasonic diagnostic apparatus. Here, the three-dimensional data space 36 has X, Y, and Z coordinate axes orthogonal to each other, and voxel data exists at each coordinate in the three-dimensional data space 36. When the three-dimensional ultrasonic transmission / reception space is configured as a polar coordinate space of r, θ, and φ, the coordinates of (r, θ, φ) that each voxel data has are (X, A process of converting to the coordinates of Y, Z) is performed.

  In volume rendering, a viewpoint VP is normally set outside the three-dimensional data space 36, and a screen 40 as a two-dimensional plane is virtually set on the opposite side of the viewpoint VP through the three-dimensional data space. Set to A plurality of rays (perspective lines) are defined on the basis of the viewpoint VP (one ray 38 is shown as a representative in FIG. 1). The ray 38 penetrates the three-dimensional data space 36, and therefore, the ray 38 corresponds to a voxel data string composed of a plurality of voxel data. When a voxel operation based on the volume rendering method is sequentially executed for each voxel data from the viewpoint VP along the ray 38, a pixel value is determined as a result of the final voxel operation. The pixel value is mapped to a coordinate P corresponding to the ray 38 on the screen.

  The screen has Xs and Ys coordinate axes, that is, each coordinate is defined by Xs and Ys coordinates. A ray is set for each coordinate. As described above, a pixel value obtained for each ray is mapped on the screen 40, whereby a three-dimensional image is formed on the screen. The plurality of rays may be parallel to each other, but the plurality of rays may be non-parallel to each other.

  In the volume rendering method, various types of calculation formulas for voxel calculation for each voxel data are known. Basically, in any arithmetic expression, opacity (opacity) is used as a parameter for each voxel calculation of each voxel data. Using such parameters, an output light amount (output value) is obtained for each voxel operation, and this is used as an input light amount (input value) in the next voxel operation. This is repeated, and the output light amount at the time when the calculation end condition is satisfied is converted into a pixel value. That is, it is based on a model in which light propagates through a medium while being scattered and attenuated. In the present embodiment, for example, the following equation 1 is used as an arithmetic expression for voxel arithmetic.

もちろん、上記の数１式以外を用いるようにしてもよく、例えば、上記特許文献１に記載されたような演算式を用いてもよい。各レイごとのボクセル演算は、例えば、その対象座標が三次元データ空間を越えた場合、又は、各ボクセル演算で用いた不透明度の累積加算値が所定値（例えば１）を越えた場合など、所定の条件を満たす場合に終了する。そして、演算終了時点の出力光量が画素値に対応付けられる。

Of course, a formula other than the above formula 1 may be used. For example, an arithmetic formula as described in Patent Document 1 may be used. The voxel calculation for each ray is, for example, when the target coordinate exceeds the three-dimensional data space, or when the cumulative addition value of opacity used in each voxel calculation exceeds a predetermined value (for example, 1), etc. The process ends when a predetermined condition is satisfied. Then, the output light amount at the end of the calculation is associated with the pixel value.

  The ultrasonic diagnostic apparatus according to the present embodiment is particularly suitable when performing image processing by the volume rendering method as described above, but can also be applied to an image processing method that performs sequential computation along each ray. is there. For example, the integration method, the detection method of the maximum value and the minimum value, and the like.

  FIG. 2 is a block diagram showing the overall configuration of the ultrasonic diagnostic apparatus according to this embodiment. The 3D probe 10 is an ultrasonic probe for acquiring three-dimensional echo data. The 3D probe 10 is used in contact with the body surface or inserted into a body cavity. An ultrasonic beam is formed by the 3D probe 10, and the ultrasonic beam is two-dimensionally scanned. A three-dimensional transmission / reception space 12 is formed by two-dimensional scanning of the ultrasonic beam.

  Here, the transmission / reception space 12 is a three-dimensional space defined by three coordinates of r, θ, and φ. For example, when the ultrasonic beam B is scanned in the θ direction, a scanning surface S is formed. When scanning in the φ direction (elevation direction), a three-dimensional transmission / reception space 12 is formed. The 3D probe 10 may be a combination of electronic scanning and mechanical scanning, but is preferably one that two-dimensionally electronically scans an ultrasonic beam. In the latter case, a known 2D array transducer is used. In FIG. 2, the transmission / reception space 12 having a pyramid shape is shown, but the shape of the transmission / reception space 12 may be a cube or may be other than that.

  The transmission unit 14 functions as a transmission beam former. That is, the transmission unit 14 supplies a transmission signal to each of the plurality of vibration elements constituting the array transducer. The receiving unit 16 functions as a receiving beam former, and executes a phasing addition process on the received signals from each of a plurality of vibrating elements constituting the array transducer. As a result, a reception signal is output from the receiving unit 16 for each ultrasonic beam. The receiving unit 16 includes an A / D converter, and the received signal after phasing addition output from the receiving unit 16 is digital data. Here, each data corresponds to echo data. In the present embodiment, viewpoint position data is provided to the transmission unit 14, and transmission control is performed based on the viewpoint position. The transmission control based on the viewpoint position will be described in detail later.

  The arbitrary cross-section creating unit 18 is a module that forms a two-dimensional tomographic image (B-mode image) corresponding to the scanning plane S. The arbitrary cross-section creating unit 18 is configured by a digital scan converter or the like conventionally used. The arbitrary section creation unit 18 executes processing for converting r, θ coordinates into x, y coordinates on the arbitrary scanning plane S, other interpolation processing, and the like. The data of the two-dimensional tomographic image formed by the arbitrary section creation unit 18 is output to the display processing unit 20.

  The 2D conversion unit 22 performs two-dimensional coordinate conversion on a plurality of echo data for each scanning frame output from the reception unit 16, that is, frame data. Each echo data has polar coordinates defined by r and θ, and the coordinates are converted into orthogonal coordinates of x and y. The frame data after the coordinate conversion is stored in the frame memory 24.

  The frame memory 24 is a memory that stores frame data necessary for generating voxel data in the 3D processor 26 described later. Each address of the frame memory 24 is associated with each coordinate in the frame data space, which will be described in detail later using FIG. The echo data in each input frame data is stored at an address associated with the three-dimensional coordinates that it has. The frame memory 24 corresponds to an external memory in view of the relationship with the 3D processor 26 described later, and this frame memory is constituted by, for example, a DRAM or the like, and is preferably constituted by an SDRAM or the like. That is, it is desirable to use a memory that can block transfer stored data in predetermined data units. In this case, the DMA transfer method can be used as the block transfer method.

  In the present embodiment, the 3D processor 26 is configured by a CPU or DSP (digital signal processor) that performs a program operation, and an internal memory 28 is provided therein. The internal memory 28 functions as a cache memory in the 3D processor 26, and the 3D processor 26 can access the internal memory 28 at high speed. On the other hand, data transfer from the frame memory 24 to the internal memory 28 cannot generally be performed at a high speed.

  The 3D processor 26 incorporates a DMA controller in the present embodiment, and data can be DMA transferred from the frame memory 24 to the internal memory 28 by the DMA controller. As indicated by reference numeral 25, the 3D processor 26 may control the writing of data to the frame memory 24. In this case, the frame data output from the 2D conversion unit 22 is once taken into the 3D processor 26. After that, it is stored in the frame memory 24 via it. Of course, data may be written into the frame memory 24 by another processor, or it may be realized as a function of the control unit 32 shown in FIG.

  In the present embodiment, as will be described in detail later, frame data is acquired according to the ray direction in the voxel calculation. That is, the frame data is appropriately acquired in the order necessary for the voxel calculation. For this reason, the frame memory 24 may store only the frame data necessary for the current voxel calculation. Alternatively, the frame memory 24 may be eliminated, and the 3D processor 26 may directly acquire the frame data output from the 2D conversion unit 22 and execute the voxel calculation using only the internal memory 28.

  The frame data transfer from the frame memory 24 to the internal memory 28 or the frame data transfer from the 2D conversion unit 22 to the internal memory 28 takes into account the direction of the ray as described above, and is a frame necessary for the voxel calculation. Data is selected appropriately. In the 3D processor 26, it is possible to execute voxel data on each ray by interpolation calculation using the received frame data, instead of proceeding with voxel calculation for each ray simultaneously as in the prior art. Voxel operations are executed sequentially. Therefore, although depending on the cross relationship between the three-dimensional data space and the ray, the degree of progress of the voxel operation is usually different for each ray.

  Random access from the 3D processor 26 to the frame memory 24 becomes a bottleneck in image processing because the data transfer rate is low. On the other hand, according to the method of the present embodiment, since frame data is acquired in consideration of the ray direction in the voxel calculation, random access to the frame memory 24 can be desirably eliminated completely. Of course, the random access problem can also be avoided when the frame data output from the 2D conversion unit 22 is directly transferred to the 3D processor 26 without using the frame memory 24. As a result, in the present embodiment, it is possible to efficiently perform image processing. Furthermore, according to the method of the present embodiment, since only the voxel data through which the ray passes is generated by the interpolation process, the calculation of the interpolation process is performed compared to the case where all the voxel data in the three-dimensional space are generated by the interpolation process. The amount can be reduced. The method of this embodiment will be described in detail later.

  In the present embodiment, the 3D processor 26 uses, for example, the expression shown in the above equation 1 as an arithmetic expression for voxel arithmetic. Therefore, the arithmetic expression is sequentially executed for each ray, and the output value when the end condition is satisfied is converted into a pixel value. The pixel value is stored in the memory provided in the display processing unit 20 from the 3D processor 26. Of course, such a memory may be provided in the 3D processor 26. In any case, a three-dimensional image is formed on the screen by repeatedly executing the voxel operation for each ray.

  The display processing unit 20 has a function for synthesizing image data and graphic data and other display processing functions. Depending on the operation mode of the apparatus, the display processing unit 20 can display 2D tomographic image data or 3D image data. Output data. The display unit 30 displays both or one of the two-dimensional tomographic image and the three-dimensional image.

  The control unit 32 is constituted by a CPU and an operation program therefor, and performs operation control of each component shown in FIG. An input unit 34 constituted by an operation panel is connected to the control unit 32. The user can use the input unit 34 to perform various input operations such as mode selection and parameter specification. The user can also set the viewpoint in volume rendering to a desired position using the input unit 34.

  The outline of the configuration of the ultrasonic diagnostic apparatus according to this embodiment has been described above. Incidentally, a configuration for performing Doppler processing may be added to the configuration in FIG. In the following, the part shown in FIG. 2 is denoted by the reference numeral in FIG.

  FIG. 3 shows a frame data space 37 virtually constructed on the frame memory 24. The frame data space 37 is formed by a plurality of frame data, and echo data of the plurality of frame data is stored in coordinates associated therewith. That is, in each frame data, the address of echo data arranged in the x-axis direction is defined by 0 to n-1, the address of echo data arranged in the y-axis direction is defined by 0 to m-1, and a frame is specified. Addresses are defined from 0 to k-1. As described above, the frame memory 24 does not need to store all the frame data in the three-dimensional data space 36 of FIG. 1, and the number of frames necessary to generate voxel data in the 3D processor 26. Only the frame data may be stored. The example shown in FIG. 3 corresponds to k frame data. Even when the frame data is directly transferred from the 2D conversion unit 22 to the 3D processor 26, the concept of the data space by the transferred frame data is the same as the frame data space 37 shown in FIG.

  In this embodiment, the 3D processor 26 arranges each frame in a three-dimensional data space that is a virtual volume space, calculates voxel data on a ray in the virtual volume from echo data of each frame, and performs a volume rendering method. Perform the calculation by.

  FIG. 4 shows the correspondence between the three-dimensional data space 36 and the frames. As shown in the figure, each of the plurality of frames (# 0 to # k-1) corresponds to the acquisition position by electronic scanning. Are virtually arranged in the three-dimensional data space 36. Voxel data on a ray in the three-dimensional data space 36 is generated by interpolation processing from echo data in frames (# 0 to # k-1).

  FIG. 5 shows the correspondence between frames and rays. As shown in the figure, a ray 38 is virtually set through a frame (#f, # f + 1) arranged in the three-dimensional data space 36. Then, the voxel data Pc on the ray 38 is calculated from the frame data (echo data) on the frame (#f, # f + 1) by interpolation processing.

  FIG. 6 shows a conceptual diagram of interpolation processing when generating voxel data, and FIG. 6 corresponds to a partially enlarged view of the XY section of the three-dimensional data space 36 of FIG. In FIG. 6, three rays 38 are shown. Each voxel data on the ray 38 is generated from four echo data located in the vicinity of the voxel data. For example, in FIG. 6, voxel data Pc is generated by interpolation processing from four echo data P1, P2, P3, and P4 in the vicinity thereof. The echo data is frame data on the frame. That is, the echo data P1 and P2 are frame data on the frame #f, and the echo data P3 and P4 are frame data on the frame # f + 1. Moreover, as an interpolation process, the process etc. which multiply and add each of the four echo data P1, P2, P3, and P4 by an interpolation coefficient etc. are mentioned. The interpolation coefficient for each echo data is set according to the relative position between each echo data and voxel data, for example.

  Since the echo data P1 to P4 used for the interpolation processing is an echo data string in two adjacent frame data, the 3D processor 26 reads the two frame data from the frame memory 24 together by DMA transfer, and performs interpolation. Processing can be performed to generate voxel data, and voxel operations based on the volume rendering method can be executed. Since the frame data is acquired in the order necessary for the voxel calculation, the frame data can also be transferred to the 3D processor 26 one after another in the order acquired by the ultrasonic wave transmission / reception. Hereinafter, the voxel operation executed by the 3D processor 26 will be described in detail.

  FIG. 7 shows a unit ray vector V. This unit ray vector V is used for determining the direction of the ray and sequentially obtaining the coordinates to be calculated in each ray. This unit ray vector is set in common when a plurality of rays are set in parallel, and is set for each ray when the plurality of rays are set non-parallel. Of course, even in that case, one unit ray vector may be set as a representative. For example, for a representative ray, this unit ray vector V is defined as a vector having the same direction and a size of 1. The components on each coordinate axis of the unit ray vector are ΔX, ΔY, and ΔZ. Since the unit ray vector has a size of 1, the maximum value of each component (ΔX, ΔY, ΔZ) is 1. For example, the 3D processor 26 can speed up the arithmetic processing by expressing each component in a fixed-point type of s7.8 (sign 1 bit, integer part 7 bit, decimal part 8 bit) type.

  FIG. 8 shows a state in which a plurality of rays are set for the three-dimensional data space 36. Although the three-dimensional data space 36 is a three-dimensional space, in FIG.

  As shown in FIG. 8, when a plurality of rays are set in an oblique direction intersecting the X axis and the Y axis of the three-dimensional data space 36, each ray first intersects with the frame when attention is paid to each ray. The coordinates to be shown are indicated by black circles in FIG. Each black circle corresponds to voxel data. As shown in FIG. 8, the initial coordinates that intersect the frame differ depending on the position of each ray. For example, for the 10 rays from the rays L3 to L12, the approach position exists in the frame (frame number 0) closest to the origin side of the X coordinate in the three-dimensional data space 36, which is voxel data. It is represented by e1 to e10. On the other hand, the rays L1 and L2 have entered two frames close to the end side of the X coordinate, and voxel data at the first entry position is represented by e11 and e12 in FIG. Incidentally, one ray is associated with each coordinate (Xs, Ys) on the screen 40, and in the example of FIG. 8, each ray is parallel, and for convenience, a unit ray vector on the ray L1. V is represented.

  The 3D processor 26 calculates the calculation start point, which is the coordinate at which each ray first intersects the frame, by the number of rendering rays and stores it in the address table. In order to speed up the processing, the address table is accessed frequently, so it is desirable to store it in the internal memory 28. In the apparatus of the present embodiment, a plurality of voxel data (that is, volume data) existing on each ray is calculated by interpolation processing from echo data of each frame as described above. Therefore, the 3D processor 26 first reads two frame data of the zeroth frame closest to the origin side in the X coordinate and the first frame adjacent thereto from the frame memory 24 into the internal memory 28. Then, the 3D processor 26 performs a voxel operation based on the equation 1 on a ray including voxel data (that is, voxel data e1 to e10 in FIG. 8) calculated from the two frame data. At that time, voxel data used for the calculation is generated by interpolating from the frame data.

The output values C _outi and α _outi of the voxel operation are held in a temporary buffer, and the rendered ray for which the operation has been performed adds each element of the ray unit vector to the value in the address table to generate an address indicating the next voxel data. . The rendering ray in which the address indicating the generated next data exists between the 0th frame and the 1st frame and in an area including each frame (hereinafter referred to as an interframe area) Repeat the calculation. When all rendering rays have finished processing the data having the address of the interframe area between the 0th frame and the 1st frame, or when the size of the three-dimensional data space 36 is exceeded, the interframe area Complete the process in.

Further, the first frame, the second frame, the second frame, the third frame, the third frame, the fourth frame,... (That is, the order acquired by the ultrasonic transmission / reception control). ) The inter-frame region is moved, the voxel operation is performed while acquiring the frame data step by step, and the value of C _outi when the processing of the frame data of the last frame is completed is output as the projection data on the screen 40. The output result is subjected to luminance conversion in the display processing unit 20 and output to the display unit 30. As a result, a display image obtained by projecting the three-dimensional image on the screen 40 is displayed on the display unit 30.

  One characteristic of the present embodiment is that frame data is appropriately acquired in the order required for voxel calculation by the transmission unit 14 and the reception unit 16 in accordance with the ray direction in the voxel calculation.

  FIG. 9 is a diagram for explaining transmission / reception control according to the direction of a ray. The viewpoint VP is set at a desired position in the three-dimensional data space 36 by the user, for example. The set position of the viewpoint VP is divided into two cases according to the coordinate value of the X axis in the three-dimensional data space 36. That is, it can be divided into a case where the coordinate value of the X axis is negative (A) and a case where the coordinate value of the X axis is positive (B). Note that the case where the coordinate value of the X axis is zero may be included in either one of the negative case and the positive case.

  When the coordinate value of the viewpoint VP on the X axis is negative, as shown in FIG. 9A, the ray 38 starting from the viewpoint VP is set toward the positive direction of the X axis. For this reason, the X-axis component ΔX of the unit ray vector (see FIG. 7) is positive. That is, when the coordinate value on the X axis of the viewpoint VP is negative, the X axis component of the unit ray vector is positive. As shown in FIG. 9A, when the ray 38 starting from the viewpoint VP is set in the positive direction of the X axis, the frame where the ray 38 first intersects is the frame # 1, and thereafter , Frame # 2, frame # 3,... That is, frames used for interpolation processing when generating voxel data are required in ascending order of frame numbers.

  Therefore, in the present embodiment, when the ray 38 starting from the viewpoint VP is set in the positive direction of the X axis, the transmitter 14 and the receiver 16 perform in the order necessary for the voxel calculation, that is, The frame data is acquired in the ascending order of the frame numbers. That is, the transmission unit 14 determines the ray direction based on the viewpoint position data (or the X-ray component of the unit ray vector), and the 2D array transducer in the 3D probe 10 (a combination of 1D array and mechanical scanning) Control) is performed to scan the ultrasonic beam in ascending order of the frame number, and the receiving unit 16 acquires echo data according to the scanning order.

  On the other hand, when the coordinate value of the X axis of the viewpoint VP is positive, as shown in FIG. 9B, the ray 38 starting from the viewpoint VP is set toward the negative direction of the X axis. When the ray 38 starting from the viewpoint VP is set in the negative direction of the X axis, the frame where the ray 38 first intersects is the frame # k-1, and then the frame # k-2, the frame Cross in the order of # k-3,. That is, frames used for interpolation processing when generating voxel data are required in descending order of frame numbers. For this reason, when the ray 38 starting from the viewpoint VP is set in the negative direction of the X axis, the frame data is acquired in the order required for the voxel calculation, that is, in descending order of the frame numbers.

  As described above, according to the position of the viewpoint VP (or the X-axis component of the unit ray vector), the frame data is acquired in the order necessary for the voxel calculation, and the voxel calculation is executed in stages.

  In FIG. 10, the execution process of the voxel calculation when the ray is set toward the positive direction of the X axis is shown step by step, and (a), (b), (c), (d ) The process proceeds in this order. That is, first, voxel data is generated for the rays L3 to L12 passing through the inter-frame region E1 between the 0th frame and the 1st frame shown in (a), and the voxel operation is executed. At this time, the voxel operations for the other rays L1 and L2 are postponed. Further, as shown in (b), for the inter-frame region E2, voxel data is generated for the rays L3 to L12 passing through the inter-frame region E2, and the voxel calculation is executed. Similarly, as shown in (c) and (d), the voxel calculation is executed for the inter-frame regions E3 and E4.

  Although not shown, after (d), the inter-frame region moves in a stepwise manner, and voxel calculation is performed on the ray that passes through the inter-frame region at each moving position. In addition, necessary voxel operations can be performed for all the rays, and as a result, a three-dimensional image can be constructed on the screen 40. Incidentally, as an end condition of the voxel calculation for each ray, for example, the target coordinates to be subjected to the voxel calculation are out of the three-dimensional data space 36, or the cumulatively added opacity value exceeds a predetermined value. Etc. are set, and the voxel calculation is individually ended for each ray when such an end situation is satisfied.

  On the other hand, FIG. 11 shows a step-by-step process of executing the voxel operation when the ray is set toward the negative direction of the X axis. (A), (b), (c), The process proceeds in the order of (d). That is, first, voxel data is generated for the rays L1 to L8 passing through the inter-frame region E1 between the (k-2) th frame and the (k-1) th frame shown in (a), and the voxel operation is executed. . At this time, the voxel operations for the other rays L9 to L12 are postponed. Further, as shown in (b), for the inter-frame region E2, voxel data is generated for the rays L2 to L9 passing through the inter-frame region E2, and the voxel calculation is executed. Similarly, as shown in (c) and (d), the voxel calculation is executed for the inter-frame regions E3 and E4.

  As described above, according to the present embodiment, even when the viewpoint is set at an arbitrary position with respect to the three-dimensional data space 36, the frame data is acquired along the traveling direction of the voxel calculation, and the inter-frame region is moved. Voxel data can be generated. In this way, volume rendering calculation (voxel calculation) for each ray can be appropriately performed.

  In the present embodiment, the basic length in the ray direction is defined by the unit ray vector, and the basic length is set as the interval of the target coordinates, that is, the pitch. According to such a method, the number or density of voxel operations can be made uniform regardless of the direction of each ray, so that the image quality that occurs when the pitch of voxel operations is indefinite when the viewpoints are different. It is possible to prevent problems such as differences in image quality or changes in image content.

  Next, the operation of the ultrasonic diagnostic apparatus shown in FIG. 2, particularly the operation of the 3D processor, will be described with reference to FIGS. FIG. 12 shows the main routine. In S101, the initialization process shown in FIG. 13 is executed. In S102, the direction of the voxel calculation is selected using the sign of the unit ray vector component ΔX, that is, whether to execute the process of S103 or the process of S104 is selected.

  In S103, the positive direction in the X direction is designated as the voxel calculation direction, frame data is sequentially acquired in the direction in which the frame number increases, voxel data is generated, and image processing is executed. This will be described in detail later with reference to FIG. On the other hand, in S104, the negative direction in the X direction is designated as the direction of voxel calculation, frame data is sequentially acquired in the direction in which the frame number is decreased, and image processing based on the frame data is executed. The process of S103 and the process of S104 are basically the same, but some parameters are set there. This will be described later. In S105, the 3D image generated by any of the above processes is transferred from the 3D processor to the display processing unit.

  FIG. 13 shows a flowchart of the initialization process of S101 shown in FIG. First, in S201, components for each axis, that is, elements ΔX, ΔY, and ΔZ are calculated for the normalized line-of-sight (unit ray) vector. The unit ray vector has a length of 1 and is defined as the direction of viewing the screen from the viewpoint. In S202, 0 is substituted for the parameter Ysc, and in S203, 0 is substituted for the parameter Xsc.

  In S204, for the ray specified by the screen coordinates Xsc and Ysc, the point (Xs, Ys, Zs) at which it first intersects with the three-dimensional data space is calculated as the target coordinate that is the target of the first voxel calculation. In step S205, the target coordinates are stored in an address table configured on the internal memory.

  In S206, the parameter Xsc is incremented by 1. In S207, it is determined whether or not Xsc exceeds the maximum value. If not, each process from S204 is executed.

  In S208, the parameter Ysc is incremented by 1. In S209, it is determined whether or not the parameter Ysc has exceeded its maximum value. If not, each step from S203 is repeatedly executed. That is, while changing the parameters Xsc and Ysc one by one, the first target coordinates are calculated for the rays corresponding to all the coordinates on the screen and stored in the address table.

  FIG. 14 is a flowchart showing specific contents of the process of S103 shown in FIG. In S301, 0 is substituted for the parameter f corresponding to the frame number (in the case of S104 shown in FIG. 12, f = k-1 (maximum value of f) is substituted). Incidentally, 0 is substituted for the parameter f in S301, and f is incremented by 1 as will be described later, and the process proceeds by sequentially moving the process in the direction of increasing the frame number.

  In S302, frame data is transferred. That is, the frame data of the f-th and f + 1-th frames are transferred to the internal memory via the receiving unit 16 and the 2D conversion unit 22 (even if the frame data is transferred via the frame memory 24 as described above). Good). Then, volume data is generated by interpolation processing using the transferred frame data. The two frame data transferred in S302 is a data set continuous in the memory space as described with reference to FIG.

  In S303, 0 is substituted for the parameter Ysc, and in S304, 0 is substituted for the parameter Xsc. In S305, it is determined whether or not the ray corresponding to the screen coordinates specified by Xsc and Ysc is a ray for which all voxel operations have been completed. If Yes, each step from S315 is executed, and if No, each step from S306 is executed.

  In S306, the target coordinates Pc (Xp, Yp, Zp) are read for the ray specified by Xsc and Ysc from the address table. That is, the coordinates currently being calculated for the ray are specified. In S307, it is determined whether or not the coordinate Pc is in the f-th and f + 1-th frames or between these frames. If No, the process proceeds to S315 on the assumption that there is no voxel data to be currently calculated, whereas if Yes, the process proceeds to S308 assuming that there is voxel data to be subjected to voxel calculation for that ray. Migrate to

  In S308, it is determined whether or not the coordinate Pc is not on the f-th or f + 1-th frame but between these frames. If No, that is, if the coordinate Pc exists on the f-th or f + 1-th frame, the process proceeds to S309, whereas if Yes, the process proceeds to S310. In S309, since the coordinate Pc exists on the frame, frame data (echo data) on the frame corresponding to the position of the coordinate Pc is selected as the voxel data at the position of the coordinate Pc. If there is no echo data at a position that completely coincides with the coordinate Pc, the nearest echo data may be selected as the voxel data, or the voxel data may be selected from the nearby echo data by interpolation or the like. It may be calculated.

  In S310, since the coordinate Pc does not exist on the frame, the voxel data at the position of the coordinate Pc is calculated by interpolation processing from the neighborhood echo data on the frame. The details of the interpolation processing executed in S310 will be described later with reference to FIG.

In S311, the output value is calculated by executing the above equation 1 using the voxel data specified by the target coordinates. In S312, the calculation result is stored in a table on the internal memory. That is, according to the above equation 1, C _outXY and α _outXY that are the calculation results for the _ray are stored. Incidentally, in this stage, when a predetermined end condition is satisfied, for example, when the accumulated addition value of the opacity value reaches 1, for example, the process proceeds to S315 without storing the data or after storing the data without shifting the process to S312. It is desirable to migrate.

  In S313, the target coordinates are updated for the ray. That is, ΔX, ΔY, and ΔZ are added for each of the X coordinate, the Y coordinate, and the Z coordinate, thereby updating the target coordinates. In S314, it is determined whether or not such updated target coordinates are in the three-dimensional data space (or an effective processing range). If the target coordinates are in the three-dimensional data space, the process proceeds to S307. On the other hand, if the target coordinates are not within the three-dimensional data space, the process proceeds to S315.

  Here, when the process proceeds from S313 to S307, if there is currently voxel data that can be processed by the voxel calculation, the processes after S308 are repeatedly executed. That is, by such a process, for each data transfer of the frame data, a ray capable of executing the voxel operation is determined, and the voxel operation can be advanced to a place where the voxel operation can be executed for the ray.

  In S315, the parameter Xsc is incremented by 1. In S316, it is determined whether or not the parameter Xsc exceeds the maximum value. If not, the process proceeds to S305. If it exceeds, the parameter Ysc is set in S317. It is incremented by 1, and it is determined in S318 whether or not the parameter Ysc exceeds the maximum value. If Ysc does not exceed the maximum value, the process proceeds to S304, and if it exceeds, the process proceeds to S319. In S319, f is incremented by 1 (f = f-1 in the case of S104 in FIG. 12), and it is determined in S320 whether the parameter f has reached its maximum value k-1 (in FIG. 12). In the case of S104, f = 0 is determined), and if not reached, the process proceeds to S321, the frame data corresponding to the (f + 1) th frame is transferred, and the processes after S303 are executed. On the other hand, if it is determined in S320 that the parameter f has reached its maximum value k-1, the process proceeds to S322.

That is, for each transfer of frame data and for each ray, it is determined whether or not the execution of the voxel operation is possible. If it is possible, the voxel operation proceeds to the point where the voxel operation can be executed. Then, after such verification and calculation are executed for all the rays, the process returns to S303 via S321, and the calculation for the next frame data is performed, which is sequentially repeated for each transfer of the frame data. become. Therefore, when the process from the transfer of the first frame data to the transfer of the last frame data is completed, all the voxel operations that can be executed for all the rays are completed as a result. Therefore, in S322, a process of performing luminance conversion on C _outXY , which is an output value obtained for each ray, and storing it as a pixel value is executed.

数２式において、ｍはフレームのｙ方向のピクセル数であり、ｎはフレームのｘ方向のピクセル数であり、ｋはフレーム数である（図３参照）。また、Ｙｍａｘ，Ｘｍａｘは、それぞれ、三次元データ空間のＹ軸方向サイズ、Ｘ軸方向のサイズである。さらに、φrotは、０番目のフレームと最終番号のフレームとの間の角度（図５参照）である。 FIG. 15 is a flowchart showing the specific contents of the process of S310 shown in FIG. In S401, the interpolation reference point P1 (f, y, x) used to obtain four frame data (echo data) for calculating the interpolation point INTp from the target coordinates Pc (Zp, Yp, Xp) is It calculates | requires based on Formula 2.

In Equation 2, m is the number of pixels in the y direction of the frame, n is the number of pixels in the x direction of the frame, and k is the number of frames (see FIG. 3). Ymax and Xmax are the Y-axis direction size and the X-axis direction size of the three-dimensional data space, respectively. Further, φrot is an angle (see FIG. 5) between the 0th frame and the last numbered frame.

  In S402, with the interpolation reference point P1 (f, y, x) as a reference, the remaining points P2 to P4 are changed to P2 = (f, y + 1, x), P3 = (f + 1, y, x), P4 = (f + 1). , Y + 1, x). Thus, four frame data (echo data) P1 to P4 for calculating the interpolation point INTp are obtained (see FIG. 6).

In S403, interpolation coefficients w _{1 to} w ₄ corresponding to each of P1 to P4 are obtained. The interpolation coefficients w _{1 to} w ₄ are determined from, for example, the positional relationship between the frame data and the interpolation point INTp (such as the distance between each frame data and the interpolation point).

数３式において、Ｐ₁は点Ｐ１のフレームデータ、Ｐ₂は点Ｐ２のフレームデータ、Ｐ₃は点Ｐ３のフレームデータ、Ｐ₄は点Ｐ４のフレームデータである。こうして、レイ上のボクセルデータ（補間点ＩＮＴｐ）が算出される。 In S404, INTp is obtained by the interpolation processing of the following equation (3).

In Equation 3, P ₁ is frame data at point P ₁ , P ₂ is frame data at point P ₂ , P ₃ is frame data at point P ₃ , and P ₄ is frame data at point P ₄ . Thus, voxel data on the ray (interpolation point INTp) is calculated.

  As described above, in the present embodiment, in consideration of the ray direction in the voxel calculation, the frame data is appropriately acquired in the order necessary for the voxel calculation, and the volume rendering calculation is performed. For this reason, compared with the case where voxel calculation is started after acquiring a lot of echo data in the three-dimensional data space, extremely efficient calculation processing can be realized.

  FIG. 16 is a diagram for explaining processing timing from the acquisition of echo data to the display of a three-dimensional image in the present embodiment.

  FIG. 16 shows processing timings for each of the receiving unit 16, the 2D conversion unit 22, the 3D processor 26, and the display unit 30, and the horizontal axis corresponds to the time axis. In FIG. 16, # 0, # 1,..., # K-1 indicate frame numbers (see FIG. 4). That is, the receiving unit 16 obtains frame data step by step in the order of frame # 0, frame # 1, frame # 2,. There are k frames from frame # 0 to frame # k-1 in the three-dimensional data space. One volume is constituted by these k frames. That is, the receiving unit 16 acquires frame data from the frame # 0 step by step, and has acquired all the data of the volume 1 at the time when the frames up to the frame # k−1 are acquired. Acquisition of frame # 0 is started. Although not shown, the receiving unit 16 continues the frame data acquisition operation and acquires frame data in the order of volume 2, volume 3,.

  The 2D conversion unit 22 performs two-dimensional coordinate conversion on the frame data output from the reception unit 16. Therefore, the 2D conversion unit 22 starts processing at frame # 0 immediately after the reception unit 16 acquires the data of frame # 0. Further, when frame # 1, frame # 2,... Are acquired one after another in the receiving unit 16, the 2D conversion unit 22 performs coordinate conversion of the acquired frames immediately after each frame is acquired.

  Note that before the data of frame # 0 is completely acquired by the reception unit 16, the 2D conversion unit 22 may start processing using only the acquired data portion. That is, each of the 2D conversion unit 22, the 3D processor 26, and the display unit 30 starts processing using only the portion that has been processed in the previous stage before the processing for one frame in the previous stage is completely completed. Is also possible. However, in the following description, it is assumed that the processing of one frame is completely completed in the former stage and the subsequent process is started.

  The 3D processor 26 performs a voxel operation based on the frame data subjected to coordinate conversion. However, as described above, frame data corresponding to two adjacent scanning planes is required for voxel calculation (see FIG. 6). For this reason, the voxel calculation by the 3D processor 26 is performed immediately after two frames are processed in the 2D conversion unit 22. That is, the voxel calculation based on the data of these two frames (# 0, # 1) is started immediately after the conversion of the frames # 0 and # 1 is performed in the 2D conversion unit 22. Further, when frames # 1, # 2,... Are successively converted by the 2D conversion unit 22, the 3D processor 26 executes a voxel operation including the converted frames immediately after each frame is converted. .

  When the 3D processor 26 finishes the voxel operation using two frames (# k-2, # k-1), the voxel operation for one volume (volume 1) is completed. As a result, the volume 1 Are displayed on the display unit 30.

  As shown in FIG. 16, according to the present embodiment, only a delay of “data acquisition time for one volume + data acquisition time for two frames” from the start of the acquisition of echo data to the display of the 3D image. Become.

  Conventionally, for example, after all data in one volume is acquired in a three-dimensional memory (data acquisition time for one volume), voxel data in a three-dimensional space is calculated using data in the three-dimensional memory ( For example, it corresponds to the data acquisition time for one volume), and then the voxel calculation is executed for each ray (further, it corresponds to the data acquisition time for one volume). For this reason, there has conventionally been a delay corresponding to, for example, a data acquisition time for 3 volumes. Compared to this, it can be understood that the delay time can be greatly shortened in the present embodiment.

  In the present embodiment described above, a plurality of echo data are acquired in order from those necessary for the voxel calculation according to the direction of the ray, and the 3D processor 26 executes the voxel calculation. The voxel calculation by the 3D processor 26 is as described in detail with reference to FIGS. However, the method of voxel calculation in the present invention is not limited to the method described above. For example, in the 3D processor 26, a voxel operation may be performed after a processing plane is configured. Hereinafter, a modified example in which the voxel calculation is performed after the processing plane is configured will be described.

  Also in the modified example, a plurality of pieces of echo data are acquired in order from those required for voxel calculation according to the direction of the ray. For example, as in the above-described embodiment, frame data (echo data) is acquired in order from the one closest to the viewpoint. Then, the 3D processor 26 arranges each acquired frame in a three-dimensional data space that is a virtual volume space, calculates voxel data on a processing plane in the virtual volume from echo data of each frame, and performs a volume rendering method. Perform the calculation by.

  FIG. 17 shows a conceptual diagram of interpolation processing when the 3D processor 26 generates voxel data in a modified example. FIG. 17 corresponds to a partially enlarged view of the three-dimensional data space 36 of FIG. Each voxel data in the three-dimensional data space 36 is generated from four echo data located in the vicinity of the voxel data. For example, in FIG. 17, voxel data INTp is generated by interpolation processing from four echo data P1, P2, P3, and P4 in the vicinity thereof. As the interpolation process, for example, a process of multiplying each of the four echo data P1, P2, P3, and P4 by an interpolation coefficient and adding them can be cited. The interpolation coefficient for each echo data is set according to the relative position between each echo data and voxel data, for example.

  In the present modification, since the frame data (#j to # j + 3) is arranged perpendicular to the xy plane of the three-dimensional data space 36, the x coordinate value and the y coordinate value are the same and z in the three-dimensional data space 36. The same interpolation coefficient is used for each voxel data in the voxel data sequence arranged in the axial direction.

  FIG. 18 shows a voxel data string on the processing plane generated by the interpolation process. The echo data string P1 ′ in the frame data #j in FIG. 18 is a data string of echo data arranged along the α axis (parallel to the z axis) of the frame data coordinate system from the position of the echo data P1 in FIG. The echo data string P2 ′ in the frame data #j in FIG. 18 is a data string of echo data arranged along the α axis from the position of the echo data P2 in FIG. Further, the echo data string P3 ′ in the frame data # j + 1 in FIG. 18 is a data string of echo data arranged along the α axis from the position of the echo data P3 in FIG. 17, and the echo data string P3 ′ in the frame data # j + 1 in FIG. The echo data string P4 ′ is a data string of echo data arranged along the α axis from the position of the echo data P4 in FIG.

  The voxel data string INTp ′ in FIG. 18 is a data string of voxel data arranged along the z axis (parallel to the α axis) from the position of the voxel data INTp in FIG. Each voxel data on the voxel data string INTp ′ is generated by interpolation processing from echo data on the echo data strings P1 ′ to P4 ′ existing on the xy section including the voxel data. This interpolation processing is executed for all the voxel data on the voxel data string INTp ′. At this time, the same interpolation coefficient is used for all echo data on the echo data string P1 ′. Similarly, the same interpolation coefficient is used for all echo data on the echo data string P2 ′, and the same interpolation coefficient is used for all echo data on the echo data string P3 ′. The same interpolation coefficient is used for all echo data on P4 ′.

  Since the echo data sequences P1 ′ to P4 ′ used for the interpolation processing are echo data sequences in two adjacent frame data, the 3D processor 26 acquires a plurality of pieces of data acquired in stages and stored in the frame memory 24. Of these frame data, two frame data can be read together by DMA transfer or the like, voxel data can be generated by performing an interpolation process, and a voxel operation based on the volume rendering method can be executed. Hereinafter, the voxel operation executed by the 3D processor 26 will be described in detail.

  FIG. 19 shows a state in which a plurality of rays are set for the three-dimensional data space 36. Although the three-dimensional data space 36 is a three-dimensional space, it is represented in a planar manner in FIG. 19 for explanation.

  As shown in FIG. 19, when a plurality of rays are set in an oblique direction intersecting with the x-axis and the y-axis, when attention is paid to each ray, the coordinates at which each ray first enters the three-dimensional data space 36 are shown. Is indicated by a black circle in FIG. Each black circle corresponds to voxel data. As shown in FIG. 19, the initial coordinates that enter the three-dimensional data space 36 differ depending on the position of each ray. For example, for the eight rays from the rays L5 to L12, the approach positions exist on the yz plane (on the first processing plane) crossing the origin in the x coordinate, which is represented by the voxel data e1 to e8. . On the other hand, the rays L1 to L4 enter the xz plane crossing the end in the y direction, and the voxel data at the initial entry position is represented by e9 to e12 in FIG. Incidentally, one ray is associated with each coordinate on the screen 40, and in the example of FIG. 19, each ray is parallel, and for convenience, a unit ray vector V is represented on the ray L1. Yes.

  The 3D processor 26 calculates the calculation start points, which are the coordinates at which each ray first enters the three-dimensional data space 36, by the number of rendering rays and stores the calculation start points in the address table. In order to speed up the processing, the address table is accessed frequently, so it is desirable to store it in the internal memory 28. In the present modification, a plurality of voxel data (that is, volume data) existing in the three-dimensional data space 36 are calculated from the echo data of each frame by interpolation processing as described above. Therefore, the 3D processor 26 first uses the yz plane that crosses the origin in the x coordinate as a processing plane, and the frames necessary for generating voxel data on the processing plane (that is, voxel data e1 to e8 in FIG. 19). Data is read from the frame memory 24 into the internal memory 28. Then, the 3D processor 26 refers to the address table and performs voxel calculation based on the equation 1 on the ray including the voxel data on the yz plane. At that time, voxel data used for the calculation is generated by interpolating from the frame data.

The output values C _outi and α _outi of the voxel operation are held in a temporary buffer, and the rendered ray for which the operation has been performed adds each element of the ray unit vector to the value in the address table to generate an address indicating the next voxel data. . For a rendering ray in which the address indicating the generated next data is x = 0 (on the yz plane), this calculation is repeated until the x address becomes other than 0. When all the rendering rays have finished processing data having an address of x = 0, or when the addresses of y and z exceed the size of the three-dimensional data space 36, the processing on the plane of x = 0 is completed. .

Further, voxel calculation is performed while moving the processing plane in the order of x = 1, 2, 3,..., _And the value of C _outi at the time when the processing of the last surface is completed is output as projection data on the screen 40. . The output result is subjected to luminance conversion in the display processing unit 20 and output to the display unit 30. As a result, a display image obtained by projecting the three-dimensional image on the screen 40 is displayed on the display unit 30.

  FIG. 20 shows the execution process of the voxel operation step by step, and the processes proceed in the order of (a), (b), (c), and (d). That is, first, the voxel data string E1 is generated for the rays L5 to L12 shown in (a), and the voxel operation is executed. At this time, the voxel operations for the other rays L1 to L4 are postponed. Next, as shown in (b), this time, a voxel data string E2 is generated and a voxel operation is performed on the rays L4 to L12. That is, a ray L4 is added as a ray capable of executing the voxel operation compared to the case shown in FIG.

  Next, the voxel data string E3 shown in (c) is generated, and the voxel operation is executed for the rays L4 to L12. At this stage, no ray that can execute the voxel operation is added. Then, as shown in (d), the voxel data string E4 is further generated, and the voxel operation is executed for the rays L3 to L12. If such a process is repeated, the necessary voxel calculation can be finally performed for all the rays, and as a result, a three-dimensional image can be constructed on the screen 40. Incidentally, as an end condition of the voxel calculation for each ray, for example, the target coordinates to be subjected to the voxel calculation are out of the three-dimensional data space 36, or the cumulatively added opacity value exceeds a predetermined value. Etc. are set, and the voxel calculation is individually ended for each ray when such an end situation is satisfied.

  In the example shown in FIG. 20, the direction of each ray is determined in the direction from the upper left to the lower right, and the voxel calculation proceeds sequentially in the positive direction in the x direction. In this case, the viewpoint position corresponds to the state shown in FIG. Therefore, in the example shown in FIG. 20, as shown in FIG. 9A, the frame where the ray 38 starting from the viewpoint VP first intersects is the frame # 1, and thereafter, the frame # 2, the frame # 3 ..,..., So that the transmission unit 14 and the reception unit 16 obtain frame data in ascending order of frame numbers.

  Contrary to FIG. 20, when the direction of each ray is set from the upper right to the lower left, the voxel calculation proceeds sequentially in the negative direction in the x direction. In this case, as shown in FIG. 9B, the frame at which the ray 38 starting from the viewpoint VP first intersects is the frame # k-1, and thereafter, the frame # k-2 and the frame # k- 3 and so on, the frame data is acquired by the transmission unit 14 and the reception unit 16 in the descending order of the frame numbers.

  Also in this modified example, in consideration of the ray direction in the voxel calculation, the frame data is appropriately acquired in the order necessary for the voxel calculation, and the volume rendering calculation is performed. For this reason, compared with the case where voxel calculation is started after acquiring a lot of echo data in the three-dimensional data space, extremely efficient calculation processing can be realized.

  FIG. 21 is a diagram for explaining processing timing from acquisition of echo data to display of a three-dimensional image in the present modification.

  FIG. 21A shows the arrangement relationship between the frame and the processing plane. 21A corresponds to the xy section of the three-dimensional data space 36 in FIG. In FIG. 21A, Frame # 0, Frame # 1,... Frame # k-1 indicate frame numbers (see FIG. 4). Also, Plane # 0, Plane # 1,..., Planet # (Xmax-1) indicate processing plane numbers.

  In this modification, voxel data on the processing plane is obtained by interpolation processing from frame data on a frame (see FIG. 17). For this reason, in order to generate all the voxel data on the processing plane, it is necessary to acquire all the frame data used for generating the processing plane. For example, in FIG. 21A, two frames Frame # 0 and Frame # 1 are required to generate the processing plane Plan # 1. As the number of processing planes increases, the number of frames required to generate a processing plane increases as the number of intersections between processing planes and frames increases. When the frame data up to the frame Frame # ((k−1) / 2) is acquired, the processing plane Plan # ((Xmax−1) / 2) located at the center is on the left side (the negative direction side of the X axis). It is possible to generate the processing plane located at.

  Therefore, in the present modification, voxel calculation (generation of a processing plane) is started after obtaining frame data up to frame Frame # ((k−1) / 2).

  FIG. 21B shows the processing timing for each of the receiving unit 16, the 2D conversion unit 22, the 3D processor 26, and the display unit 30, and the horizontal axis corresponds to the time axis.

  In FIG. 21B, F # 0, F # 1,..., F # (k−1) indicate frame numbers (see FIG. 4). That is, for example, the receiving unit 16 obtains frame data step by step in the order of frame # 0, frame # 1, frame # 2,. There are k frames from frame # 0 to frame # (k-1) in the three-dimensional data space. One volume is constituted by these k frames. That is, the receiving unit 16 acquires frame data from the frame # 0 in stages, and acquires all the data of the volume 1 at the time when the frames up to the frame # (k−1) are acquired. Acquisition of frame # 0 of volume 2 is started. Although not shown, the receiving unit 16 continues the frame data acquisition operation and acquires frame data in the order of volume 2, volume 3,.

  The 2D conversion unit 22 performs two-dimensional coordinate conversion on the frame data output from the reception unit 16. For this reason, the processing of the frame # 0 by the 2D conversion unit 22 starts immediately after the reception unit 16 acquires the data of the frame # 0. Further, when frame # 1, frame # 2,... Are acquired one after another in the receiving unit 16, the 2D conversion unit 22 performs coordinate conversion of the acquired frames immediately after each frame is acquired.

  Note that the processing may be started using only the acquired data before the data of frame # 0 is completely acquired by the receiving unit 16. That is, each of the 2D conversion unit 22, the 3D processor 26, and the display unit 30 starts processing using only the portion that has been processed in the previous stage before the processing for one frame in the previous stage is completely completed. Is also possible. However, in the following description, it is assumed that the processing of one frame is completely completed in the former stage and the subsequent process is started.

  The 3D processor 26 performs a voxel operation based on the frame data subjected to coordinate conversion. However, as described above, in the voxel calculation, it is necessary to acquire all the frame data used for generating the processing plane. Therefore, the voxel calculation by the 3D processor 26 is performed immediately after the frame # ((k−1) / 2) is processed in the 2D conversion unit 22. That is, the first processing plane P # 0 is generated immediately after the frame # ((k−1) / 2) is converted in the 2D conversion unit 22. Further, as the frames are sequentially converted in the 2D conversion unit 22, the 3D processor 26 generates processing planes in the order of processing planes P # 1, P # 2,... Immediately after each frame is converted, Perform voxel operations.

  Then, the voxel operation relating to one volume (volume 1) is completed at the next point where the voxel operation using the processing plane P # (Xmax-1) is completed in the 3D processor 26. As a result, a three-dimensional image of the volume 1 is obtained. It is displayed on the display unit 30.

  As shown in FIG. 21B, according to the present modification, from the start of the acquisition of echo data to the display of the three-dimensional image, “data acquisition time for 1.5 volumes + 1 data acquisition for one frame” Only "time" delay. For this reason, it can be understood that the delay time can be significantly shortened by this modification as compared with the case where there is a delay corresponding to the data acquisition time of the conventional three volumes.

  The three-dimensional image formed by the embodiment described above (including its modifications) can be expected to be used as a monitor in minimally invasive treatment. For example, a surgical instrument monitor in laparoscopic surgery. Usually, in laparoscopic surgery, the instrument is monitored by a small camera, but it is difficult to see the state of the tip when the tip of the surgical instrument is inside the organ or behind the organ. there were. Therefore, it is possible to grasp the state of the distal end of the surgical instrument by displaying the inside of the organ and the back of the organ using the ultrasonic diagnostic apparatus of the present embodiment. In particular, the ultrasonic diagnostic apparatus according to the present embodiment is suitable for capturing movements of instruments and organs since the delay from acquisition of echo data to formation of a three-dimensional image is small.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

It is explanatory drawing for demonstrating the principle of volume rendering. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present embodiment. It is a figure which shows notionally the structure of frame data space. It is a figure which shows the correspondence of a three-dimensional data space and a frame. It is a figure which shows the correspondence of a flame | frame and a ray. It is a figure for demonstrating the interpolation process at the time of producing | generating voxel data. It is explanatory drawing for demonstrating a unit ray vector. It is a figure which shows the relationship between a frame and the voxel calculation for every ray. It is a figure for demonstrating the transmission / reception control according to the direction of a ray. It is explanatory drawing which showed a mode that voxel calculation was carried out in steps. It is explanatory drawing which showed a mode that voxel calculation was carried out in steps. It is a flowchart which shows the operation example of an apparatus. It is a flowchart which shows the specific content of the initialization process. It is a flowchart which shows the specific content of the process of S103 shown in FIG. It is a flowchart which shows the specific content of the process of S310 shown in FIG. It is a figure for demonstrating the processing timing from acquisition of echo data to the display of a three-dimensional image. It is a conceptual diagram of the interpolation process at the time of producing | generating voxel data. It is a figure for demonstrating the voxel data sequence produced | generated by the interpolation process. It is a figure which shows the relationship between a three-dimensional data space and the voxel calculation for every ray. It is explanatory drawing which showed a mode that voxel calculation was carried out in steps. It is a figure for demonstrating the processing timing from acquisition of the echo data in a modification to the display of a three-dimensional image.

Explanation of symbols

  10 3D probe, 12 transmit / receive space, 22 2D converter, 24 frame memory (external memory), 26 3D processor, 28 internal memory, 36 3D data space, 40 screens.

Claims (13)

A wave transmitting / receiving means for transmitting and receiving ultrasonic waves in a three-dimensional space to obtain a plurality of echo data;
Three-dimensional image forming means for forming a three-dimensional image based on the plurality of echo data;
Have
The three-dimensional image forming means includes:
A ray setting unit for setting a plurality of rays as perspective lines from a viewpoint virtually set in a data space corresponding to the three-dimensional space;
A voxel computing unit that computes voxel data on the plurality of set rays from the plurality of echo data and advances voxel computation for each ray; and
Hints, the association with the pixel value the results of voxel calculation at the time that satisfies the operation end condition for each ray, the three-dimensional image is formed based on a plurality of pixel values obtained from the plurality of rays,
The wave transmitting / receiving means forms a plurality of scanning planes in order from the one closest to the viewpoint, and obtains frame data composed of a plurality of echo data for each scanning plane, thereby obtaining a plurality of frame data corresponding to the plurality of scanning planes. Get step by step,
The voxel computing unit computes the voxel data on the plurality of set rays step by step based on the plurality of frame data acquired stepwise, and advances the voxel computation for each ray,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The wave transmitting / receiving means determines a scanning direction in which a plurality of scanning planes are formed in order from a position closer to the viewpoint from a position coordinate of the viewpoint in the data space.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The transmission / reception means determines the direction of the representative ray from the position of the viewpoint for the representative ray that is one of the plurality of rays, and sets the plurality of scanning planes in an order corresponding to the direction of the representative ray. By forming, a plurality of scanning planes are formed in order from the one closer to the viewpoint,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1 ,
The voxel computing unit calculates voxel data by interpolation processing from the plurality of frame data;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 4 ,
The voxel computing unit calculates the two scanning planes from the frame data corresponding to the two scanning planes arranged adjacent to each other when the plurality of scanning planes are arranged in the data space according to their positions. Voxel data existing in the interframe area between
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 5 ,
The voxel computing unit calculates voxel data corresponding to the voxel coordinates from echo data included in frame data corresponding to the two scanning planes and existing in the vicinity of the voxel coordinates.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 6 ,
The three-dimensional image forming means includes:
For each ray, the initial coordinate on the first axis, the initial coordinate on the second axis, and the initial coordinate on the third axis in the data space are calculated as the first points that pass through the data space. An initial coordinate calculation unit,
A step component computing unit that computes the step component of the first axis, the step component of the second axis, and the step component of the third axis;
For each of the rays, with respect to the initial coordinates on the first axis, the initial coordinates on the second axis, and the initial coordinates on the third axis, the step component on the first axis and the second axis, respectively. A target coordinate specifying unit for specifying the voxel calculation target coordinates on each ray by cumulatively adding the step component on the upper axis and the step component on the third axis;
Corresponding to the voxel calculation target coordinates in the inter-frame region for each movement position of the inter-frame region that moves step by step as a plurality of frame data is acquired step by step from the closest to the viewpoint An interpolation processing unit for generating voxel data to be generated by the interpolation processing;
An ultrasonic diagnostic apparatus comprising: A wave transmitting / receiving means for transmitting and receiving ultrasonic waves in a three-dimensional space to obtain a plurality of echo data;
Three-dimensional image forming means for forming a three-dimensional image based on the plurality of echo data;
Have
The three-dimensional image forming means includes:
A ray setting unit for setting a plurality of rays as perspective lines from a viewpoint virtually set in a data space corresponding to the three-dimensional space;
A voxel computing unit that computes voxel data on the plurality of set rays from the plurality of echo data and advances voxel computation for each ray; and
And associating the result of the voxel calculation at the time when the calculation end condition is satisfied for each ray with a pixel value, and forming the three-dimensional image based on a plurality of pixel values obtained from the plurality of rays,
The wave transmitting / receiving means forms a plurality of scanning planes in order from the one closest to the viewpoint, and obtains frame data composed of a plurality of echo data for each scanning plane, thereby obtaining a plurality of frame data corresponding to the plurality of scanning planes. Get step by step,
The three-dimensional image forming unit sets a processing plane in the data space, and moves the processing plane in stages from the viewpoint closer to the viewpoint according to the stepwise acquisition of the plurality of frame data. Further including
The voxel calculation unit calculates voxel data on the processing plane from the plurality of frame data for each movement position of the processing plane that moves in stages, and advances the voxel calculation for each ray according to the movement of the processing plane. ,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 8 ,
The processing plane is a plane orthogonal to a predetermined axis of the data space.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 9 .
The voxel computing unit calculates voxel data by interpolation processing from the plurality of frame data;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 10 ,
The voxel computing unit, when arranging the plurality of scanning planes in the data space according to their positions, out of a plurality of frame data corresponding to the plurality of scanning planes, voxel coordinates that are coordinates of the data space Voxel data corresponding to the voxel coordinates is calculated from a plurality of frame data arranged in the vicinity of
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 11 ,
The voxel computing unit calculates the voxel data corresponding to the voxel coordinates from the echo data included in the plurality of frame data and existing in the vicinity of the voxel coordinates.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 12 ,
The three-dimensional image forming means includes:
For each ray, the initial coordinates on the first axis, the initial coordinates on the second axis, and the initial coordinates on the third axis in the data space are calculated as the first points that pass through the data space. An initial coordinate calculation unit,
A step component computing unit that computes the step component of the first axis, the step component of the second axis, and the step component of the third axis;
For each ray, for each initial coordinate on the first axis, initial coordinate on the second axis, and initial coordinate on the third axis, the step component on the first axis and the second axis, respectively. A target coordinate specifying unit for specifying the voxel calculation target coordinates on each ray by cumulatively adding the step component on the upper axis and the step component on the third axis;
An interpolation processing unit that generates voxel data corresponding to the voxel calculation target coordinates by the interpolation processing on a processing plane that moves step by step in order from the closest to the viewpoint;
An ultrasonic diagnostic apparatus comprising:

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