JP2018000779A - Ultrasonic image processing device - Google Patents

Abstract

In an ultrasonic image processing apparatus, when a color three-dimensional image is generated according to a function that determines coloring conditions according to depth, a user cannot recognize the depth at which the function acts. A guide image is displayed on a tomographic image displayed together with a color three-dimensional image. The guide image 112 is displayed so that the depth axis of the guide image 112 and the depth axis of the tomographic image 106 are parallel to each other. The guide image 112 has a marker 120 that moves in the depth direction. The marker 120 represents an intermediate depth in the color mixture range in the depth direction defined by the function. The guide image 112 may have a plurality of markers and color samples. [Selection] Figure 11

Description

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

  Examples of the ultrasonic image processing apparatus include an ultrasonic diagnostic apparatus and an information processing apparatus that processes ultrasonic volume data (hereinafter simply referred to as “volume data”) acquired by the ultrasonic diagnostic apparatus. In the ultrasonic image processing apparatus, volume rendering is applied to volume data to form a three-dimensional ultrasonic image (an image representing a target tissue three-dimensionally).

When performing volume rendering, a plurality of rays (line of sight) from the viewpoint are set for the volume data. For each individual ray, that is, for each pixel constituting the color three-dimensional image, a rendering operation is executed to obtain a pixel value. More specifically, the output light amount calculation (voxel calculation) using the opacity (opacity) is repeatedly executed for each voxel along the depth direction from the start point. The output light amount when a predetermined end condition is satisfied, that is, the output light amount at the calculation end point constitutes a pixel value (luminance). The predetermined end condition includes a first end condition that indicates that the accumulated opacity has reached a predetermined value close to 1 or that the output light quantity calculation has reached the last sample point on the ray. The second end condition, etc. are known. The accumulated opacity value is generally obtained by sequentially adding the opacity used for each output light amount calculation. Various formulas are known as output light quantity calculation formulas. A plurality of luminances obtained for a plurality of rays are considered as a luminance map, which constitutes a three-dimensional ultrasonic image.

  A volume rendering method that generates a depth map (distance map) together with a luminance map and forms a color three-dimensional image based on these maps as a special volume rendering method that is different from the general volume rendering method described above. It has been known. In this method, the output light amount (luminance) at the end point and the depth of the end point are specified in the rendering operation in units of rays. Thereby, a luminance map composed of a plurality of luminances corresponding to a plurality of rays and a depth map (distance map) composed of a plurality of depths corresponding to the plurality of rays are generated. The depth map typically represents the three-dimensional morphology of the target tissue. For example, it is possible to increase the sense of depth on a color three-dimensional image by changing the color (for example, a combination of RGB values) according to the depth of the end point.

  Patent Documents 1 and 2 propose coloring according to the depth of the end point when forming a three-dimensional ultrasonic image. Patent Literature 3 shows a three-dimensional region of interest set for volume data. The region of interest has a rendering start surface (hereinafter referred to as a “start surface”) as a clipping surface. The starting surface is a deformable surface (in addition, a surface capable of parallel movement and tilting in the height direction). For example, if the starting surface is deformed according to the shape of the gap between the fetus and the uterine wall (including the placenta), only the fetus can be rendered while excluding the uterine wall from the imaging target. It is.

Japanese Patent No. 5117490 Japanese Patent No. 5525930 JP 2011-83439 A

  As described above, when generating a color three-dimensional image based on the luminance map and the depth map, generally, the mixing ratio of the main color and the sub color determined based on the luminance is changed according to the depth of the end point. A “function” is used. The function functions as a color mixing function, a weighting composition function, or a blend function. Other functions may be used.

  However, there is a problem that even if a color three-dimensional image as a coloring result is observed, it is difficult for the user to recognize the contents and actions of the function itself. It is also desirable to support the adjustment when adjusting one or more parameters included in the function.

  The object of the present invention is to recognize the content or action of a function in a user observing a color 3D image when generating a color 3D image according to a function that defines coloring conditions that change according to depth. There is in doing so. Alternatively, an object of the present invention is to support the work when a user adjusts parameters included in the function.

  The ultrasonic image processing apparatus according to the present invention is a means for applying volume rendering to volume data acquired from a three-dimensional space in a living body, and generates a luminance map and a depth map as a result of the volume rendering. A color processing means for generating a color three-dimensional image from the luminance map and the depth map according to a function for determining a coloring condition according to depth, and a first image representing the content or action of the function. And a guide image generating means for generating a guide image having a depth axis.

  According to the above configuration, the guide image symbolizing the function is displayed together with the color three-dimensional image. The guide image has a first depth axis, and the content or function of the function is represented on the first depth axis, for example, as a depth marker or as a color change sample. Through observation of the guide image, information on the coloring condition applied when generating the color three-dimensional image can be obtained. In the guide image, only a part or one side of the content or function of the function may be represented. In order to be able to recognize the depth at which the function acts or the change in the function action depending on the depth, or to obtain information useful for grasping the coloring conditions applied when generating the color 3D image, It is desirable to generate a guide image. When setting the function, if the setting contents are reflected in the guide image in real time, the function setting work can be supported.

Various methods can be used as the volume rendering method. However, since the normal volume rendering method generates only a luminance map, it is desirable to modify or expand the known volume rendering method so that a depth map (distance map) is generated together with the luminance map. Desirably, the target tissue is a fetus in the uterus, particularly desirably the fetal face.

  Preferably, a tomographic image forming unit that forms a tomographic image having a second depth axis based on the volume data, the first depth axis and the second depth axis being parallel to each other. The guide image is displayed on the screen. According to this configuration, the depth of the target tissue in the tomographic image can be compared with the depth at which the function acts. For example, it is possible to easily determine whether the depth used as a reference for coloring should be smaller (front side, viewpoint side) or larger (back side, non-viewpoint side). . A tomographic image is an image representing a cross section of a three-dimensional space, and is an image corresponding to a ray row in a two-dimensional ray array set for volume data.

  Desirably, the display mode of the guide image changes according to the change of the depth parameter included in the function. According to this configuration, it is possible to manually optimize the depth parameter while observing a change in the display mode of the guide image. In the configuration in which the parameter is automatically determined, the parameter change can be recognized as a change in the display mode of the guide image.

  Preferably, a color mixing range in the depth direction is defined by the function, the guide image has a depth marker that represents the depth of the color mixing range, and the depth marker is changed according to a change in the depth parameter. Move in the right direction. The depth marker is an indicator that moves in the depth axis direction. Preferably, the start depth, intermediate depth, end depth, or other depth for the color mixture range is represented by a depth marker. Preferably, the depth marker represents an intermediate depth in the color mixture range. The depth at which the color mixture ratio is 1: 1 may be displayed by a depth marker, or another specific depth may be displayed by a depth marker.

  Preferably, the guide image includes a first depth marker and a second depth marker, and the first depth marker and the second depth marker are a start depth and an end depth of the color mixture range. Represents According to this configuration, the color mixing range in the depth direction can be specifically specified on the depth axis. In particular, according to the above configuration, the depth and size of the color mixture range can be recognized simultaneously.

  Preferably, the guide image has two color samples representing a main color and a sub color given to the function, and the two color samples are displayed side by side in the depth direction. According to this configuration, two original colors before mixing can be recognized. Desirably, the RGB value of the main color and the RGB value of the sub-color are determined according to the luminance of the pixel, and they are combined at a mixing ratio according to the depth corresponding to the pixel. A depth range in which color mixing occurs may be expressed by a boundary line between two color samples. The boundary line may be configured as a diagonal line, and the range may be expressed by the diagonal line. Preferably, a boundary line between the two color samples moves in the depth direction according to a depth parameter included in the function. Preferably, the inclination angle of the boundary line (an angle with respect to the depth axis) changes according to a range parameter included in the function.

  Preferably, the guide image has a color change sample indicating a color change in the depth direction caused by the function. According to this configuration, it is possible to specifically recognize the function action as a color change (gradation).

  Preferably, the color processing means includes, for each pixel constituting the color three-dimensional image, means for determining a main color based on a luminance level corresponding to the pixel, and pixels constituting the color three-dimensional image. For each pixel, the sub-color is determined based on the magnitude of the luminance corresponding to the pixel, and for each pixel constituting the color three-dimensional image, the depth corresponding to the pixel is determined by giving the function Means for determining the color corresponding to the pixel by mixing the main color and the sub color according to the mixing ratio.

  An ultrasonic image processing method according to the present invention is a step of applying volume rendering to volume data acquired from a three-dimensional space in a living body, and generates a luminance map and a depth map as a result of the volume rendering. A step of generating a color three-dimensional image from the luminance map and the depth map according to a function for determining a coloring condition according to a depth, and generating a guide image as an image representing the content or action of the function And a step of displaying the guide image together with the color three-dimensional image.

  The ultrasonic image processing method described above can be realized as a program operating on a processor. The program is installed in the ultrasonic image processing apparatus via a network or a storage medium.

  According to the present invention, it is possible for a user to recognize the content or action of a function. Accordingly, it is possible to facilitate the observation of the color three-dimensional image and to support the function setting operation.

1 is a block diagram showing an embodiment of an ultrasonic image processing apparatus according to the present invention. It is a figure which shows the production | generation of a brightness | luminance map and a distance map. It is a figure which shows the prior art example which does not have a reference plane. It is a figure which shows the 1st example of a reference plane. It is a figure which shows the 2nd example of a reference plane. It is a figure which shows the 3rd example of a reference plane. It is a flowchart for demonstrating the production | generation of a brightness | luminance map and a depth map. It is a figure which shows the structural example of a color processing part. It is a figure which shows a color mixing function (weighting synthetic | combination function). It is a flowchart which shows the operation example of a display process part. It is a figure which shows the 1st example of a guide image. It is a figure which shows the 2nd example of a guide image. It is a figure which shows the 3rd example of a guide image. It is a figure which shows the 4th example of a guide image. It is a figure which shows the 5th example of a guide image. It is a figure which shows the 6th example of a guide image. It is a figure which shows the 7th example of a guide image. It is a figure which shows the 8th example of a guide image. It is a figure for demonstrating the parameter determination method. It is a figure which shows the 1st example of the depth parameter determination method. It is a figure which shows the 2nd example of the depth parameter determination method. It is a figure which shows the determination of the depth parameter based on the depth of the shallowest point and the depth of the deepest point. It is a figure which shows the 3rd example of the depth parameter determination method. It is a figure which shows the 4th example of the depth parameter determination method. It is a figure which shows the change of a color mixing function. It is a figure which shows the 1st example of the range parameter determination method. It is a figure which shows the change of the color mixing function in the 1st example of the range parameter determination method. It is a figure which shows the 2nd example of the range parameter determination method. It is a figure which shows the change of the color mixing function in the 2nd example of the range parameter determination method. It is a figure which shows the modification of a color calculating part.

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

(1) Apparatus Configuration FIG. 1 shows a preferred embodiment of an ultrasonic image processing apparatus according to the present invention. This ultrasonic image processing apparatus is an ultrasonic diagnostic apparatus in the present embodiment. The ultrasonic image processing apparatus may be configured by an information processing apparatus (computer) that performs image processing. In that case, the volume data acquired by the ultrasonic diagnostic apparatus is passed to the information processing apparatus.

  The ultrasonic diagnostic apparatus shown in FIG. 1 is an apparatus that is installed in a medical institution and forms an ultrasonic image by transmitting / receiving ultrasonic waves to / from a living body. In the present embodiment, as described in detail below, a color three-dimensional image is generated as an ultrasonic image. For example, the image is a three-dimensional representation of the three-dimensional form of the fetus in the uterus by changes in brightness and hue.

  In FIG. 1, a 3D probe 10 is a transducer that acquires volume data by transmitting and receiving ultrasonic waves to and from a three-dimensional space in a living body. The 3D probe 10 includes, for example, a 2D array transducer. The 2D array transducer is composed of a plurality of vibration elements arranged two-dimensionally. According to the 2D array transducer, it is possible to electronically scan an ultrasonic beam two-dimensionally. As an electronic scanning method, an electronic sector scanning method or the like is known. Volume data may be obtained by mechanically scanning the 1D array transducer. In general, one volume data is constituted by a plurality of scanning plane data (frame data), and each scanning plane data is constituted by a plurality of beam data. Each beam data is composed of a plurality of echo data arranged in the depth direction.

  The transceiver unit 12 is an electronic circuit, which functions as a transmission beam former and a reception beam former. That is, at the time of transmission, a plurality of transmission signals are supplied from the transmission / reception unit 12 to the 3D probe 10, thereby forming a transmission beam. At the time of reception, when a reflected wave from the living body is received by the 3D probe 10, a plurality of reception signals are output from the 3D probe 10 to the transmission / reception unit 12. The transmission / reception unit 12 performs phasing addition of a plurality of reception signals, thereby generating beam data corresponding to the reception beam.

  A plurality of beam data are sequentially output from the transmission / reception unit 12 to the beam data processing unit 14. The beam data processing unit 14 is an electronic circuit including a detector, a logarithmic converter, and the like. The processed beam data is sent to the coordinate conversion unit 16.

  The coordinate conversion unit 16 is an electronic circuit having a coordinate conversion function, an interpolation function, and the like. The coordinate conversion unit 16 executes a process for mapping individual echo data constituting each beam data to the three-dimensional storage space. In practice, interpolation data is generated and mapped for each three-dimensional coordinate. Volume data may be generated by executing coordinate transformation in units of frame data corresponding to the scanning plane and repeating the transformation. In that case, a two-dimensional scan converter is used. In any case, in this embodiment, volume data is stored in the memory 18 included in the coordinate conversion unit 16. A two-dimensional tomographic image (B-mode image) is formed based on the plane data cut out from such volume data. In this case, the plane data corresponds to a specific ray row in a ray group described later. In this case, the plane data has a depth axis.

  The volume rendering unit 20 functions as a three-dimensional region-of-interest setting unit, a rendering unit, and the like. It is implemented as an electronic circuit or software function. The three-dimensional region of interest (3D-ROI) is a region for cutting out a portion to be imaged in the volume data, and conversely, a region excluding a portion that is not desired to be imaged. The form and position of the three-dimensional region of interest are determined automatically or by user input. For example, if you want to form a 3D image of the fetus in the uterus, the 3D region of interest is set so that the starting plane is set as the clipping plane in the gap (amniotic fluid) between the fetus and the uterine wall (placenta). Is set. In this case, if the volume data is rotated relative to the viewpoint, the volume data is rotated relative to the three-dimensional region of interest accordingly. The clipping plane, that is, the starting plane is a plane in the default state, but as described in Patent Document 3, it is a plane that can be transformed into a convex surface or a concave surface, for example. Furthermore, the height and inclination can be changed.

  In the present embodiment, the volume rendering unit 20 functions as a reference plane setting unit to be described later. The reference plane is typically a plane provided closer to the viewpoint than the start plane, and is a plane orthogonal to a later-described ray group. The reference plane will be described in detail later with reference to FIGS.

  Based on the volume rendering method, the volume rendering unit 20 sets a ray group for a three-dimensional region of interest, that is, target data, and executes a rendering operation for each ray. The plurality of rays are parallel to each other in the present embodiment, and they extend in the depth direction from the viewpoint (or a surface corresponding thereto). A plurality of rays correspond to a plurality of pixels constituting a three-dimensional image. The volume rendering unit 20 repeatedly executes the output light amount calculation (voxel calculation) at a constant pitch from the start point (rendering start point) to the end point (a point where the rendering end condition is satisfied) in units of rays. More precisely, the output light amount calculation using the opacity (opacity) is repeatedly executed while sequentially shifting the calculation points until a predetermined end condition is satisfied.

The predetermined end condition includes a first end condition and a second end condition. When the accumulated value of the opacity referred to in the output light amount calculation exceeds a predetermined value (for example, 0.98), it is determined that the first end condition is satisfied. On the other hand, when the output light amount calculation reaches the end surface, it is determined that the second end condition is satisfied. If the opacity function is appropriately set, for example, the probability that the first termination condition is satisfied at or near the fetus surface, that is, at the surface of the fetus, is increased. As a result, it is possible to form a three-dimensional image exclusively representing the fetal surface. The output light amount when a predetermined end condition is satisfied, that is, the output light amount at the end point, is the luminance corresponding to the ray. The luminance is mapped on the memory 22. A luminance map is configured on the memory 22 as a result of mapping a plurality of luminances corresponding to a plurality of rays.

  On the other hand, when calculating the output light quantity, as described above, the opacity is sequentially added, and when the accumulated value reaches a predetermined value and the first termination condition is satisfied, or the calculation point on the ray Reaches the end surface of the three-dimensional region of interest and the second end condition is satisfied, the end point depth is specified. In this embodiment, the length from the reference point (reference surface) to the end point is calculated as the depth. Specifically, the first distance from the start surface to the end point is obtained by multiplying the number of output light quantity calculations until the end condition is satisfied by the sample point pitch on the ray. On the other hand, the length from the reference plane to the start plane is obtained as the second distance on the ray or on the extension line. By adding the first distance and the second distance, a depth referred to in color processing (a depth normalized with reference to the reference plane) is obtained. The depth is mapped on the memory 24. A depth map is formed on the memory 24 by a plurality of depths corresponding to a plurality of rays. Similar to the luminance map, it has the same arrangement as the pixel arrangement constituting the three-dimensional image. In the present embodiment, as described above, each depth constituting the depth map is a depth from the reference plane, that is, a standardized distance. However, the distance from the start surface to the end point or another distance may be mapped on the memory 24 as the depth. The volume rendering will be described in detail later with reference to FIGS.

  The display processing unit 30 has various display processing functions such as a coloring function and an image composition function. Among them, a part for generating a color three-dimensional image is shown as a color processing unit 32. Further, a guide image generation unit 26 and a parameter determination unit 28 are shown as functions related thereto. The display processing unit 30 is configured by a processor or an electronic circuit. The display processing unit 30 may be configured by a CPU and a program configuring the control unit 36.

  The color processing unit 32 determines a color as a pixel value from the luminance I and the depth Z for each pixel constituting the color three-dimensional image. For example, a warm color system determined according to the luminance I and a cold color system determined according to the luminance I are mixed according to the coloring condition (mixing ratio) determined according to the depth Z. As a result of the mixing, the color of the pixel is determined. In the example, the former warm color is a main color, that is, a short-distance expression color, which is, for example, an orange color. The latter cold color is a sub-color, that is, a color for long-distance expression, for example, a blue color. The depth corresponding to each pixel typically represents the depth of the surface layer of the target tissue, so that the surface layer present in the shallow position is expressed in a warm color, and the surface layer present in the deep position is represented by It is expressed in a color in which the mixing ratio of the cool color is increased. Of course, the specific colors listed above are exemplary.

  In the present embodiment, the color processing unit 32 has two conversion tables (conversion functions) that determine the main color and the sub color according to the luminance, and the main color and the sub color according to the depth. It has a synthesizer for weighted synthesis. The weighting synthesis condition is defined by a color mixture function. The color mixing function includes a depth parameter indicating the intermediate depth of the color mixing range in the depth direction and a range parameter indicating the size of the color mixing range in the depth direction. However, they are examples. A plurality of parameters instead of them may be included in the color mixing function. In the present embodiment, individual parameters included in the color mixing function are designated by the user while observing the color three-dimensional image and the tomographic image, or are automatically determined based on a depth map or the like. The configuration and operation of the color processing unit 32 will be described in detail later with reference to FIGS.

  The guide image generation unit 26 is a module that generates a guide image displayed together with the tomographic image. As will be described later, the guide image is configured as a graphic element, that is, configured as a figure, a color sample, or the like, and is an image that visually represents a part of the content or function of the color mixing function. The guide image also has a depth axis (first depth axis). The tomographic image has a depth axis (second depth axis). The second depth axis is parallel to the ray group, which usually coincides with the left or right side of the tomographic image. The guide image is displayed in the vicinity of the tomographic image or on the tomographic image so that the first depth axis is parallel to the second depth axis. The first depth axis may be a movement axis of the marker described later. The guide image is referred to when the user sets the depth parameter and the range parameter included in the color mixture function. Thereby, parameter setting can be supported. A guide image is also referred to when a color three-dimensional image is observed. Thereby, grasping | ascertainment of the form of the fetus displayed as a color three-dimensional image can be accelerated | stimulated. The guide image will be described in detail later with reference to FIGS.

  The parameter determination unit 28 automatically (or semi-automatically) the former or both of the depth parameter (specifically Zs shown later) and the range parameter (specifically ΔZ shown later) included in the color mixing function. ) Module to be set. With this configuration, it is possible to reduce the burden on the user and to easily optimize the hue of the color three-dimensional image. The automatic parameter setting will be described in detail later with reference to FIGS.

  The control unit 36 includes a CPU and a program, and the control unit 36 controls the operations of the individual components illustrated in FIG. The operation panel 38 constitutes an input device, and it is possible to manually set a three-dimensional region of interest or set parameters included in the color mixture function using the input panel. The operation panel 38 is also used when manually setting a start surface as a clipping surface. In the present embodiment, the reference plane is automatically set on the viewpoint side with respect to the three-dimensional region of interest. However, the reference plane may be set manually. In addition to the color three-dimensional image, tomographic image, and guide image, an arbitrary tomographic image and the like are displayed on the display unit 34 as necessary. A triplane image may be displayed on the display 34.

(2) Generation of Luminance Map and Depth Map FIG. 2 schematically shows a method for generating a luminance map and a depth map. However, FIG. 2 shows a general generation method, which does not show a depth map generation method using a reference plane.

  A plurality of rays 42 are set in parallel to the three-dimensional region of interest 40. XYZ represents an orthogonal coordinate system. The Z direction is the depth direction. An arrow denoted by reference numeral 41 indicates a projection direction from the viewpoint. A plurality of rays 42 are set parallel to the direction. Note that the viewpoint can be set at an arbitrary position with respect to the volume data.

  In the illustrated example, reference numeral 40A indicates a start surface as a clipping surface. It is drawn as a plane. Actually, the shape and the like of the start surface 40A can be freely changed. In each ray 42, the output light amount calculation is repeatedly executed in the depth direction (Z direction in the illustrated example) from the start point on the start surface 40A. The opacity is cumulatively added for each calculation. When the end condition described above is satisfied, the output light amount calculation stops, that is, the rendering calculation ends. As a result, the end point 44 is specified for each ray 42. The end point 44 corresponds to the surface layer of the fetus, for example. The output light amount at the end of the rendering operation is mapped on the memory as the luminance. A luminance map 46 is formed as a mapping result of a plurality of luminances corresponding to the plurality of rays 42. It corresponds to a monochrome volume rendering image.

On the other hand, the depth of the end point 44 is mapped on the memory in units of rays. A depth map 48 is formed as a mapping result of a plurality of depths corresponding to the plurality of rays 42. As shown in the gray scale 50, in FIG. 2, the minimum depth to the maximum depth is represented as a change in luminance.

  The luminance map 46 and the depth map 48 have the same two-dimensional pixel array as the two-dimensional pixel array constituting the three-dimensional image. Based on the luminance map 46 and the depth map 48, a color three-dimensional image is formed. For example, as described above, for each pixel, two colors corresponding to the luminance are weighted and synthesized according to the depth, thereby determining the color of the pixel. This is repeated over all pixels. Each depth constituting the depth map 48 is preferably a distance from the reference point to the end point, as will be described below. However, it may be the distance from the start point to the end point. These distances all indicate the depth of the target tissue viewed from the viewpoint side.

(3) Depth Calculation Based on Reference Surface FIG. 3 shows a conventional example having no reference surface as a comparative example. Reference numeral 54 denotes a fetus, and reference numeral 56 denotes a placenta. Reference numeral 57 indicates amniotic fluid. Reference numeral 52 represents volume data, and reference numeral 58 represents a three-dimensional region of interest (a cross section of the three-dimensional region of interest appears in FIG. 3). The three-dimensional region of interest 58 is a box having a start surface 60 that functions as a clipping surface, an end surface 65 as a bottom surface (lower surface), and four side surfaces (two side surfaces 62 and 64 appear in FIG. 3). It has a shape. Due to the concave deformation of the start surface 60, the start surface 60 is inserted into the gap between the fetus 54 and the placenta 56. Thus, after the form of the three-dimensional region of interest 58 is determined, a rendering operation is executed for each individual ray set for the region.

In FIG. 3, each downward arrow 63 indicates a rendering calculation path, and the tip of the arrow 63 indicates the end point. Note that FIG. 3 includes a plurality of downward arrows 63 that do not reach the fetal surface, but this is for the convenience of drawing. In the example shown in FIG. 3, the reference plane is not adopted. That is, in each ray, the length from the start surface to the end point is calculated as the depth, and the depth is referred to in the coloring process as it is. Therefore, due to the start surface 60 being curved, a depth change in the depth map that is unrelated to the morphology of the fetal surface occurs. It can cause unwanted hue changes.

  FIG. 4 shows a first example of the reference plane. In addition, the same code | symbol is attached | subjected to the element similar to the element shown in FIG. 3, and the description is abbreviate | omitted. The same applies to FIGS. 5 and 6 described later.

  In FIG. 4, the reference plane 66 is set closer to the viewpoint than the start plane 60. The reference plane 66 is a plane orthogonal to the plurality of rays. The start surface 60 in the default state may be defined as the reference surface. The reference surface 66 covers the entire three-dimensional region of interest 58. Specifically, the reference plane is configured as a plane connected to the upper sides of the four side surfaces of the three-dimensional region of interest 58. However, the reference plane may be set at a position closer to the viewpoint. It is desirable to determine the position of the reference surface 66 so that the reference surface 66 does not cross the target tissue.

  For each ray, a rendering operation is executed as in the conventional case, but the reference plane 66 is used as a reference only for the depth calculation. That is, in each ray, the standardized length from the reference plane 66 to the end point is calculated as the depth. Actually, the first distance from the start point to the end point on the start surface 60 is calculated, while the second distance from the reference surface 66 to the start surface 60 is calculated. Then, by adding the first distance and the second distance, the depth to be mapped is calculated as the addition result. However, the distance from the reference plane to the end point may be directly obtained. In this embodiment, since the depth is defined separately from the rendering calculation range, a standardized depth that does not depend on the form of the start surface can be used in the color processing.

  FIG. 5 shows a second example of the reference surface. In the second example, in consideration of the form of the placenta 56A, the start surface 60A of the three-dimensional region of interest 58A constitutes a convex surface, whereby the reference surface 70 is located on the opposite side to the viewpoint as viewed from the start surface 60A. Is set. However, the reference plane 70 does not cover the fetus 54, and the depth calculated in each ray is a plus depth (see reference numeral 72). However, in the second example shown in FIG. 5, since the reference surface 70 is likely to be applied to the target tissue, for example, the reference surface 70 passes through the apex of the start surface 60A so that the reference surface 70 is positioned higher. It is desirable to change the reference plane setting conditions.

  FIG. 6 shows a third example of the reference plane. In this example, the placenta 56B has a fairly complicated shape, and accordingly, the start surface 60B of the three-dimensional region of interest 58B also has a complicated shape. A reference surface 74 is set on the viewpoint side of the start surface 60B. It is a plane, but it is inclined for each ray. The inclination angle is small, and the amount of change in depth due to the inclination is quite small. Moreover, since it is uniformly inclined, no unnatural depth change or local depth change occurs. Thus, in some cases, it is possible to use the inclined reference plane 74. However, since the apparent depth increases and decreases due to the inclination, it is desirable to adopt the reference plane (reference plane shown as the first example) orthogonal to each ray as much as possible.

(4) Volume Rendering FIG. 7 shows an example of operations related to generation of a luminance map and a depth map. In S10, k indicating the ray number is initialized, and in S12, d indicating the distance is initialized. In S14, an echo value (voxel value) is calculated for a point of interest at a distance d on the kth ray. For example, the echo value of the target point is calculated by three-dimensional linear interpolation based on eight echo values existing in the vicinity of the target point. In S16, an output light amount calculation (voxel calculation) based on the echo value at the point of interest, the corresponding opacity, and the like is executed. As a result, the output light amount at the attention point is obtained, and the output light amount is set as the input light amount at the next attention point. Various algorithms are known as such an algorithm. In S16, cumulative addition of opacity is also executed.

  In S18, it is determined whether or not a predetermined end condition is satisfied. If not satisfied, d is incremented in S28, and each step from S14 is repeatedly executed. On the other hand, when it is determined in S18 that the end condition is satisfied, in S19, the final output light amount is mapped on the memory as luminance.

  In S20, a distance Δd from the reference surface to the start surface is calculated. The distance Δd depends on the position and form of the starting surface. In S22, d which is the distance of the end point and the distance Δd between the reference plane and the start plane are added, and as a result, the normalized depth Z is obtained. In S24, the depth Z is mapped on the memory. In S26, it is determined whether or not k has reached the maximum value. If no, k is incremented in S30, and each step after S12 is repeatedly executed.

  Thereafter, a color three-dimensional image is formed based on the luminance map and the distance map. However, prior to the three-dimensional image formation, at least the depth map is subjected to a smoothing process in S27.

(5) Color Processing FIG. 8 shows a configuration example of the color processing unit 32 shown in FIG. The color processing unit 32 includes two tables 84 and 86 and a weighting synthesizer 88. The table 84 is a front side conversion table and is a lookup table that determines the main color (RGB value) Cf according to the luminance I. In general, an orange color is used as the main color. That is, the tissue existing at a short distance is represented by such a color. The table 86 is a back side conversion table, and is a lookup table that determines a sub color (RGB value) Cb according to the luminance I. In general, a blue color that can increase the perspective by mixing with the main color is adopted as the sub color. However, any of the above colors is merely an example.

  The weighting synthesizer 88 is a module for weighting and synthesizing the color Cf and the color Cb determined according to the luminance I according to the depth Z. The color mixture ratio corresponding to the depth Z is determined by a color mixture function (see reference numeral 88A) described below. The weighted synthesizer 88 outputs a color (RGB value) C after weighted synthesis. However, when a weight of 1.0 is given to the color Cf, the color Cf is output as it is as the color C. Similarly, when a weight of 1.0 is given to the color Cb, the color Cb is used as it is. Output as C. In the present embodiment, the coloring condition is changed by manipulating the two parameters Zs and ΔZ included in the color mixture function.

  FIG. 9 shows an example of the color mixing function. The horizontal axis indicates the depth Z. The vertical axis indicates the weight. Specifically, the left vertical axis indicates the front weight given to the main color (front color) Cf, and the right vertical axis gives the sub color (back color) Cb. Indicates the back weight to be used. The weight given to the main color Cf is determined by the first color mixing function 100. Similarly, the weight given to the sub color Cb by the second color mixing function 102 is determined. The sum of the two weights is 1.0. Therefore, since the other color mixing function is automatically determined from one color mixing function, only one color mixing function may be used. In the following description, only the color mixing function 100 for the main color will be clearly shown out of the two color mixing functions 100 and 102 as necessary.

  In FIG. 9, three sections are set in the horizontal axis direction. In the left section (Z: 0-Z1), the main color is adopted 100%. In the central section (Z: Z1-Z2), the main color and the sub color are mixed at a mixing ratio corresponding to the depth. This section can be said to be a color mixing section or a mixing range in the depth direction. In the right section (Z: Z2-Zmax), 100% of the sub-color is adopted. The intermediate depth in the mixing section is the depth parameter Zs, and the range in the depth direction of the mixing section is the range parameter ΔZ. In the present embodiment, the form of the color mixing functions 100 and 102, that is, the mixing action is defined by these parameters. For example, the depth parameter Zs is set in the vicinity of the average depth in the surface layer of the target tissue, or in particular in the vicinity of the depth of the site where morphological observation is desired. Further, for example, the range parameter ΔZ is set according to the degree of change in the shape of the target tissue.

  When the depth parameter Zs is increased or decreased, the color mixing functions 100 and 102 shift in the horizontal axis direction, and therefore the depth parameter Zs can also be referred to as a shift parameter. When the range parameter ΔZ is increased or decreased, the ratio of the main color and the sub color and the ratio of the mixed color in the color three-dimensional image change. Therefore, the range parameter ΔZ can also be referred to as a contrast parameter. Note that the color mixing function may be defined by other parameters. Further, the color mixing function may be defined by a curve.

  It is difficult to set the above parameters manually only by observing a color three-dimensional image, and it is desirable to support the setting. Therefore, in this embodiment, a guide image is generated and displayed together with a three-dimensional image and a tomographic image. In addition, a mechanism for automatically determining parameters is provided in order to reduce the burden on the user when setting parameters.

  The outline thereof will be described with reference to FIG. FIG. 10 is a flowchart showing the operation of the display processing unit shown in FIG. In S40, the mode is selected. If the parameter is set manually, S42 is executed, and if the parameter is set automatically (or semi-automatically), S50 is executed. In S42, for each pixel, a front color and a back color are determined according to the luminance, and they are weighted and synthesized according to the depth. Thereby, the color of the pixel is determined. The weighting / combining condition (that is, the coloring condition) is determined by a color mixing function. Prior to the weighting synthesis, in S44, the user specifies the depth parameter Zs and the range parameter ΔZ and accepts them. A color mixing function is defined by these parameters Zs and ΔZ. In S46, as an image symbolizing the color mixing function, a guide image representing at least a part or one surface of the content or function of the color mixing function is displayed. You can set parameters while referring to it. When a parameter that affects the guide image is changed, the change is reflected in the guide image in real time. In S48, it is determined whether or not to continue the present process. When the present process is continued, each step after S40 is repeatedly executed.

  If the automatic parameter setting is selected in S40, the depth parameter Zs is automatically determined based on the depth map in S50. Then, in S52, the range parameter ΔZ is automatically determined based on, for example, the depth parameter Zs. However, the range parameter ΔZ may be determined manually. In S56, as in S46, both or one of the determined depth parameter Zs and range parameter ΔZ is reflected in the content of the guide image. In S54, for each pixel, a front color and a back color are determined according to the luminance, and they are weighted and synthesized according to the depth. Thereby, the color of the pixel is determined. Also in this case, the condition for weighting synthesis is determined by the color mixing function.

(6) Guide Image FIG. 11 shows a first example of a guide image. On the display screen 104, a black and white tomographic image 106 and a color three-dimensional image 108 are displayed. The color three-dimensional image 108 is an image generated by applying volume rendering to volume data in a three-dimensional region of interest and further applying color processing. Here, the face of the fetus is represented in three dimensions. The tomographic image 106 shows a vertical section of a three-dimensional space (volume data), which corresponds to a ray train. In this example, in the tomographic image 106, the horizontal axis is the X axis and the vertical axis is the Z axis. Both the left and right vertical sides in the tomographic image 106 correspond to the Z-axis. A three-dimensional region of interest 110 is displayed as a box in the tomographic image 106.

  Specifically, a guide image 112 is displayed near the left vertical side of the three-dimensional region of interest 110 at the left end of the tomographic image 106. The guide image 112 is an image showing the content or function of the color mixing function. In this first example, the guide image has a marker 114 indicating the depth parameter Zs (that is, the intermediate level 120 of the color mixture range). Reference numeral 116 represents a start surface level, and reference numeral 118 represents an end surface level. The marker 114 is a graphic element that moves between them in the vertical direction, that is, in the depth axis direction. In the example shown, the marker 114 has a triangular shape, but this is merely exemplary.

  The guide image 112 has a depth axis as a motion axis, and the depth axis is parallel to the depth axis of the tomographic image. When the knob 122 on the operation panel 38 is operated, the depth parameter Zs changes as indicated by reference numeral 126, and the marker 114 moves in the vertical direction accordingly. At the same time, the color aspect of the color three-dimensional image 108 also changes. The depth parameter Zs can be recognized by the marker 114 on the depth axis. According to the present embodiment, it is possible to optimize the depth parameter Zs while referring to the tissue structure displayed on the tomographic image 106. The operation panel 38 also includes a knob 124 for adjusting the range parameter ΔZ. In the first example shown in FIG. 11, even if the range parameter ΔZ is changed, the display mode of the guide image 112 does not change, but the color expression mode of the color three-dimensional image 108 changes. According to the first example, it is possible to recognize the content of the color mixing function (particularly, main parameters included therein) and the depth at which the color mixing function acts (intermediate level of the color mixing range) in comparison with the tomographic image. .

  FIG. 12 shows a second example of the guide image. In addition, the same code | symbol is attached | subjected to the element similar to the element shown in FIG. 11, and the description is abbreviate | omitted. This is the same in each figure after FIG.

  In FIG. 12, the guide image 128 has a strip shape extending in the depth direction. In this example, the upper end of the guide image 128 matches the start surface level 116, and the lower end of the guide image 128 matches the end surface level 118. The guide image 128 is roughly divided into an inverted trapezoidal upper portion 126a and a trapezoidal lower portion 126b. Between them is a boundary line 126c, which forms a common hypotenuse. The boundary line 126c represents a color mixture range in the color mixture function (color mixture function defining the front weight). The width of the boundary line 126c in the depth direction corresponds to the size of the color mixture range in the depth direction, and the inclination of the boundary line 126c corresponds to the mixing ratio, that is, the gradient. That is, the guide image 128 represents the form of the color mixing function itself.

  The upper part 126a is colored with a representative main color in the main color group generated by the front side conversion table. The lower portion 126b is colored by a representative sub color in the sub color group generated by the back side conversion table. Therefore, the upper part 126a and the lower part 126b each function as a color sample.

  As indicated by reference numeral 126, when the depth parameter Zs is changed by operating the knob 122, the boundary line 126c moves in the depth direction while maintaining the inclination angle. On the other hand, as indicated by reference numeral 134, when the knob 124 is operated to change the range parameter ΔZ, the intermediate depth of the boundary line 126c is maintained, and the depth direction between both ends of the boundary line 126c is maintained. The size changes and the tilt angle changes at the same time. According to the second example, two parameters can be specifically recognized on the depth axis. In other words, according to the second example, it is easy to intuitively recognize the specific content of the mixing function itself and the entire action.

FIG. 13 shows a third example of the guide image. The guide image 136 has a graph-like form, and specifically includes a horizontal axis 136a, a vertical axis 136b, and a broken line 136c. Horizontal axis 136
a indicates the size of the front weight (weight given to the main color). The vertical axis 136b indicates the depth Z. A broken line 136c indicates a color mixing function for the main color. The color mixing function for the sub color can be easily derived from the color mixing function for the main color. According to the fourth example, the content of the color mixing function can be specifically recognized.

  FIG. 14 shows a fourth example of the guide image. The guide image 138 has a strip shape extending in the depth direction. A color change sample is formed in which the color changes in the depth direction from the upper end 138a to the lower end 138b of the guide image. Actually, a color change (gradation) occurs in the mixed color range (between the depth Z1 indicated by reference numeral 130 and the depth Z2 indicated by reference numeral 132). The main color is displayed above the depth Z1, and the sub color is displayed below the depth Z2. With such a color change sample that changes in the depth direction, the action of the color mixing function can be specifically recognized.

  FIG. 15 shows a fifth example of the guide image. The guide image 140 includes a color change sample 142 and two markers 144 and 146. The color change sample 142 has a strip shape extending in the depth direction, and an upper side 142a thereof represents a start surface depth, and a lower side 142b thereof represents an end surface depth. Similar to the guide image 138, the color change sample 142 is configured by a color that changes in the depth direction. Reference numerals 130 and 132 indicate depths Z1 and Z2 at both ends of the color mixture range. Their depths Z1, Z2 are specified by two markers 144, 146. The markers 144 and 146 are graphic elements that move in the depth direction as the depths Z1 and Z2 change. A form other than a triangle (for example, a simple horizontal line) may be adopted as the form. It is possible to set a color mixing function by adjusting the positions of the markers 144 and 146. In that case, the depth parameter Zs and the range parameter ΔZ may be determined by the depths Z1 and Z2, or the depths Z1 and Z2 may be directly given to the color mixing function as parameters. Each marker 144, 146 may be moved directly by a pointing device, or may be moved by a picking operation.

  FIG. 16 shows a sixth example of the guide image. On the display screen 148, three black-and-white tomographic images 150, 152, and 154 that are orthogonal to form a so-called triplane are displayed. Further, a color three-dimensional image 156 is displayed. The tomographic image 150 has an X axis and a Z axis, and represents the A plane as the first vertical section. The tomographic image 152 has a Y axis and a Z axis, and represents the B plane as the second vertical section. The tomographic image 154 has an X axis and a Y axis, and represents the C plane as a horizontal section. In the tomographic image 150, a guide image 158 is displayed near the three-dimensional region of interest. In the tomographic image 152, a guide image 160 is displayed near the three-dimensional region of interest. Thus, a plurality of guide images may be displayed together with a plurality of tomographic images.

  The guide images 158 and 160 have the same mode as the guide image shown in FIG. Of course, other modes may be adopted as the guide images 158 and 160, or these modes may be different from each other.

  FIG. 17 shows a seventh example of the guide image. A three-dimensional region of interest 162 is shown on the tomographic image and has an upper surface 162A that functions as a clipping plane. Separately, a reference plane 164 for calculating a standardized depth is set. The guide image 166 includes a left portion 166L and a right portion 166R. The left portion 166L has a marker 168 indicating a depth parameter Zs. A horizontal line 174 indicating the depth parameter Zs is also displayed. The right portion 166R has two markers 170 and 172 indicating the depths Z1 and Z2 at both ends of the color mixture range.

  Thus, by displaying a plurality of elements constituting the guide image in a distributed manner, visibility and appearance can be improved. Furthermore, if the horizontal line 174 is displayed, the relationship between the tissue structure and the depth parameter Zs can be specifically identified, so that the depth parameter Zs can be easily adjusted.

  FIG. 18 shows an eighth example of the guide image. An upper surface 176A of the three-dimensional region of interest 176 forms a convex surface. In this example, the reference plane is not adopted. That is, the distance from the upper surface 176A to the end point is calculated as the depth. Since the positions of the individual start points in the display area are not aligned (because they are curved), the position of the depth parameter Zs at each position in the horizontal direction is also curved on the screen. Based on this, the guide image 178 includes a curve 186 representing the depth parameter Zs, a curve 188 representing the depth Z1 in addition to the left portion 178L including the marker 180 and the right portion 178R including the markers 182 and 184. A curve 190 representing the depth Z2 is included. These curves 186, 188, 190 cross the tomographic image. According to the eighth example, it is possible to correctly recognize the depth parameter Zs, the depth Z1, and the depth Z2 at each horizontal position.

  As described above, if a guide image is displayed together with a tomographic image (overlaid on or near the tomographic image), the content or function of the function can be intuitively recognized in relation to the tissue displayed on the tomographic image. Is possible. Therefore, if the parameters are set while looking at such a guide image, the burden and confusion of the user can be reduced. The guide image is also useful when observing a color three-dimensional image.

(7) Automatic Parameter Determination As already described, in this embodiment, parameters included in the color mixture function are automatically determined as necessary. In FIG. 19, the depth parameter Zs indicated by reference numeral 194 (hereinafter also simply referred to as “depth Zs”) is determined from the depth map indicated by reference numeral 192. In this case, as will be described below, the depth parameter Zs includes the average value, the depth of the shallowest point, the depth of the deepest point, the depth of the user-specified point, etc. in all or part of the depth map. It is determined. The range parameter ΔZ indicated by reference numeral 196 (hereinafter, also simply referred to as “range ΔZ”) may be set manually. Preferably, it is automatically determined from the depth parameter Zs, or It is automatically determined from the depth map. The range parameter ΔZ may be determined based on the depth corresponding to the designated point on the three-dimensional image.

  Once the depth parameter Zs and the range parameter ΔZ are determined, a color mixing function 198 is defined thereby. As described in detail above, the color mixing function 198 is a function that mixes the main color and the sub color obtained in parallel from the luminance of the pixel according to the depth corresponding to the pixel. A specific example of the parameter determination method will be described below.

  FIG. 20 shows a first example of the depth parameter determination method. A reference area 206 is set in the color three-dimensional image 200 by user setting or automatically. In the example shown in the drawing, a reference area 206 is set as a rectangular area that spreads around the intersection (center point) of the vertical center line 204 and the horizontal center line 202. The reference area 206 excludes a surrounding portion where the echo becomes unstable or the echo is likely to disappear. The entire color three-dimensional image 200 may be set as the reference area 206. However, the size and position of the reference area are adjusted so that the part to be observed is dominantly included and the part not to be observed is excluded. Is desirable.

  In the first example, the same reference area as the reference area 206 is set on the depth map, and the average value of the depth is calculated in the reference area. It can be said that the reference area 206 is an area set for this purpose. The average value in the reference area in the depth map is set as the depth parameter Zs as it is. The range parameter may be set manually, or may be a value linked to the depth parameter Zs as will be described later.

  Since the average value in the reference area can be said to be the average depth of the tissue (surface layer) to be imaged, if it is set as the depth parameter Zs, automatic setting mistakes that increase the possibility of optimizing the color mixture range are necessary. Depending on the manual, fine adjustments may be made manually.

  FIG. 21 shows a second example of the depth parameter determination method. Similar to the first example, a reference area 206 is set for the color three-dimensional image 200. The same reference area as this reference area 206 is set on the depth map. Then, the depth Za of the shallowest point (the shallowest point) A in the reference area and the depth Zb of the deepest point (the deepest point) B in the reference area are automatically specified. Then, for example, the depth parameter Zs is determined by the following equation (1) (see reference numeral 210). Where α is a coefficient.

    Zs = (Zb-Za) × α + Za (1)

  According to this configuration, the depth parameter Zs can be automatically determined in consideration of the depth spread in the reference area. The determined depth parameter Zs can be confirmed through a guide image.

  FIG. 22 shows elements constituting the above expression (1). Reference numeral 212 indicates a three-dimensional region of interest on the tomographic image. It includes the fetal head 214. The depth Zs is determined as a depth that internally divides the depth Za of the shallowest point A and the depth Zb of the deepest point B at a constant ratio α. α may be a parameter instead of a fixed value, and may be variable by the user or the target tissue.

  FIG. 23 shows a third example of the depth parameter determination method. A reference area 206 is set on the color three-dimensional image 200, and a designated point A designated by the user is set on the color three-dimensional image 200. The designated point A may be designated on the tomographic image. The designated point A is designated, for example, on a part considered to be the shallowest in the fetus. A depth Za corresponding to the specified point is specified from the depth map. Further, the deepest point B in the reference area (the same reference area as the reference area 206) in the depth map is specified, and the depth Zb is specified. Then, the depth parameter Zs is determined according to the above equation (1) (see reference numeral 216). The deepest point may be designated by the user, and the shallowest point may be automatically determined.

  FIG. 24 shows a fourth example of the depth parameter determination method. By automatically specifying the shallowest point A and the deepest point B in the color three-dimensional image 200, the depth Za of the shallowest point A and the depth Zb of the deepest point B are determined from the depth map. Then, the depth parameter Zs is determined according to the above equation (1) (see reference numeral 218).

  FIG. 25 shows changes in the color mixing function accompanying changes in the depth parameter Zs. When the depth parameter Zs is changed while the range parameter ΔZ is maintained, the color mixing function is translated (shifted) as indicated by reference numerals 220a, 220b, and 220c. In this case, the weight change rate, that is, the gradient in the color mixture range is not changed. However, as described below, the range parameter ΔZ may be changed according to the depth parameter Zs and the like.

FIG. 26 shows a first example of the range parameter determination method. The horizontal axis indicates the depth Z, and the vertical axis indicates the range ΔZ. The maximum value is ΔZ _max . Zs ₀ indicates the initial value or standard value of the depth parameter Zs, and Zs ₁ indicates the current depth parameter Zs. Under such a premise, the current range parameter ΔZ ₁ is determined according to the following equation (2) (see reference numeral 224). The following β1 is a coefficient.

ΔZ ₁ = ΔZ _max −β1 × | Zs ₁ −Zs ₀ | (2)

In the above equation (2), β1 is a coefficient. However, the above equation (2) is premised on that the lower limit Z1 and the upper limit Z2 of the color mixture range satisfy the conditions of 0 ≦ Z1 and Z2 ≦ MaxZ. In the first example, the range parameter ΔZ _max may take an arbitrary value, and ΔZ1 may be determined using the equation (2) after adjusting the coefficient β1 accordingly.

  According to the first example, the range parameter ΔZ decreases as the depth parameter Zs deviates from its initial value or standard value. That is, the depth range in which the color mixing change occurs is reduced, and at the same time, the rate of change within the range is increased. The state of the change is shown in FIG. As the depth parameter Zs approaches the depth zero or the depth MaxZ, the change rate in the color mixture range becomes steeper as indicated by reference numerals 226A, 226B, and 226C.

  FIG. 28 shows a second example of the range parameter determination method. The horizontal axis indicates the depth Z, and the vertical axis indicates the range ΔZ. As indicated by function 228, the range parameter ΔZ is increased as the depth parameter Zs decreases. When the rate of change is constant β2, the range parameter ΔZ is determined by the following equation (3) (see reference numeral 230).

    ΔZ = β2 (MaxZ−Zs)

  FIG. 29 shows the change of the color mixing function accompanying the change of the range parameter ΔZ. The horizontal axis indicates the depth Z, and the vertical axis indicates the front weight. As indicated by reference numerals 230A, 230B, and 230C, as the depth parameter Zs increases, the color mixture function shifts to the left, and the rate of change within the color mixture range is relaxed.

  The parameter determination methods described above are merely examples, and the depth parameter Zs and the range parameter ΔZ may be determined using a method other than the above, and other parameters (for example, depth) may be used instead of these parameters. Z1, Z2) may be automatically determined. A function composed of a curve (for example, a logistic curve) may be used as the color mixture function. In any case, if at least one parameter is automatically determined among a plurality of parameters that define the color mixing function, the burden on the user can be reduced.

  Several timings can be given as the timing for performing automatic parameter adjustment. For example, automatic parameter adjustment may be executed at the image update timing immediately after the switch for adjusting the color mixing function is turned on. Thereafter, for example, automatic parameter adjustment may be automatically performed at the timing when any operation related to the color mixing function is performed, the timing when the image is updated, and the timing at a certain time interval.

  FIG. 30 shows a modification of the color processing unit 32. The color processing unit 32 includes a front side conversion table 232, a back side conversion table 234, and a weighting synthesizer 236. As described above, the weighting synthesizer 236 is provided with a parameter group such as a depth parameter Zs and a range parameter ΔZ. The front side conversion table 232 and the back side conversion table 234 are each configured as a lookup table. The front side conversion table 232 is a table for determining the main color based on the input luminance I and depth Z. The back side conversion table 234 is a table for determining a sub color based on the input luminance I and depth Z. These colors are combined in a weighting combiner 236 to determine the color of the pixel. The color processing unit 32 may combine three colors determined by three or more tables.

20 volume rendering unit, 26 guide image generating unit, 28 parameter determining unit, 30 display processing unit, 32 color processing unit, 46 luminance map, 48 depth map (distance map).

Claims (11)

Means for applying volume rendering to volume data acquired from a three-dimensional space in a living body, wherein the rendering means generates a luminance map and a depth map as a result of the volume rendering;
Color processing means for generating a color three-dimensional image from the luminance map and the depth map according to a function that defines coloring conditions according to depth;
Guide image generation means for generating a guide image having a first depth axis as an image representing the content or action of the function;
An ultrasonic image processing apparatus comprising: The apparatus of claim 1.
Including tomographic image forming means for forming a tomographic image having a first depth axis based on the volume data;
The guide image has a second depth axis;
The guide image is displayed so that the first depth axis and the second depth axis are parallel;
An ultrasonic image processing apparatus. The apparatus of claim 2.
The display mode of the guide image changes according to the change of the depth parameter included in the function.
An ultrasonic image processing apparatus. The apparatus of claim 3.
The function defines a color mixing range in the depth direction,
The guide image has at least one depth marker representing the depth of the color mixture range;
The depth marker moves along the second depth axis in response to a change in the depth parameter;
An ultrasonic image processing apparatus. The apparatus of claim 4.
The depth marker represents an intermediate depth in the color mixture range.
An ultrasonic image processing apparatus. The apparatus of claim 4.
The guide image has a first depth marker and a second depth marker,
The first depth marker and the second depth marker represent a start depth and an end depth of the color mixture range;
An ultrasonic image processing apparatus. The apparatus of claim 1.
The guide image has two color samples representing a main color and a sub color given to the function;
The two color samples are displayed side by side in the depth direction.
An ultrasonic image processing apparatus. The apparatus of claim 7.
The boundary line between the two color samples moves in the depth direction according to the depth parameter included in the function,
An ultrasonic image processing apparatus. The apparatus of claim 1.
The guide image has a color change sample showing a color change in the depth direction caused by the function,
An ultrasonic image processing apparatus. The apparatus of claim 1.
The color processing means includes
Means for determining a main color for each pixel constituting the color three-dimensional image based on a luminance level corresponding to the pixel;
Means for determining a sub-color for each pixel constituting the color three-dimensional image based on a luminance level corresponding to the pixel;
For each pixel constituting the color three-dimensional image, the main color and the sub-color are mixed according to a mixing ratio determined by giving a depth corresponding to the pixel to the function. Means for determining the color;
An ultrasonic image processing apparatus comprising: A program for causing an ultrasonic image processing apparatus to execute an ultrasonic image processing method,
The ultrasonic image processing method includes:
Applying volume rendering to volume data acquired from a three-dimensional space in a living body, generating a luminance map and a depth map as a result of the volume rendering;
Generating a color three-dimensional image from the luminance map and the depth map according to a function that defines coloring conditions according to depth;
Generating a guide image as an image representing the content or action of the function;
Displaying the guide image together with the color three-dimensional image;
The program characterized by including.