JP2007289569A - Medical image processor and medical image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a medical image processor and a medical image processing method suitable for kinetics observation. <P>SOLUTION: This medical image processor includes: a first image generation part for extracting data on a region of interest from a volume data, and performing volume rendering using the extracted data on the region of interest to obtain a three-dimensional image of the region of interest seen from a predetermined line of sight direction on a two-dimensional projection plane; a distance information generating part for calculating a distance from the two-dimensional projection plane to the boundary surface of the region of interest along the direction of line of sight based on the volume data of time phase before and after in point of time, and generating distance information in every time phase; a differential value calculating part for acquiring the distance information of two time phases before and after in point of time and calculating a differential value of the respective distance information pieces; a second image generating part for generating an additional image changing in density according to the magnitude of the calculated differential value; and a composing part for composing an additional image with the three-dimensional image obtained in the first image generating part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a medical image processing apparatus and a medical image processing method capable of easily observing dynamics of a region of interest when diagnosis is performed using medical image data collected by a medical image diagnostic apparatus.

  Conventionally, a subject is imaged using a medical image diagnostic apparatus such as an X-ray CT apparatus (X-ray computer tomography apparatus), an MRI apparatus (magnetic resonance imaging apparatus), an ultrasonic diagnostic apparatus, and the like, and a medical image diagnostic apparatus is used. Image diagnosis is often used in which a three-dimensional image is displayed using an image to diagnose a disease or the like.

  Also, a VR method (volume rendering method) or the like is used to display a three-dimensional image of a lesioned part or the like inside a subject using continuous data (volume data) that is continuous in the body axis direction. An image reconstructed from data obtained by three-dimensional measurement is called a volume image, and a medical image can be presented to a user (doctor) in an easy-to-understand manner by various image processing.

  For example, X-ray CT image data is composed of a group of pixels called voxels. In VR (volume rendering), a virtual light source is set in the computer device and a single ray (ray) is applied from the line-of-sight direction. An image is generated on the two-dimensional projection plane by calculating light absorption / reflection for each voxel, and various images can be displayed by setting an opacity (opacity) or the like.

  In addition, SVR (Shaded Volume Rendering) selects a threshold value of the surface of an object of interest, extracts only a certain range of CT values, projects light from a virtual point light source onto the object, and distances from the light source The brightness is set according to the display, and the object is shaded and displayed in three dimensions. The SVR method is suitable for dynamic observation, and can display a moving image of heart wall motion, for example.

  By the way, the SVR method is an effective expression method for grasping the three-dimensional positional relationship. However, in order to grasp the movement of the region of interest, it is difficult to understand the movement unless it is observed from the lateral direction. There is a problem that it is difficult to grasp the movement at the time, that is, the vertical movement when the object is viewed from the observer.

  Patent Document 1 describes a three-dimensional ultrasonic apparatus that can diagnose abnormal motion of a target tissue, and includes means for forming a three-dimensional ultrasonic image for each time phase, and each part on the target tissue surface. 2 shows an example provided with means for calculating a displacement amount and forming a displacement actual image. The displacement actual image forming means of this example calculates the distance between each part on the target tissue surface and the reference point in the three-dimensional ultrasonic image for each time phase, and based on the change between the time phases with respect to the distance. The amount of displacement is calculated, and the heart and the like are diagnosed by displaying the displacement actual image in two dimensions.

However, in the example of Patent Document 1, the displacement on the tissue surface is only displayed two-dimensionally, and when the object is in motion, the motion that changes every moment cannot be displayed. In addition, there is a problem that it is difficult to grasp the movement in the viewing direction, and there is a problem that the circuit configuration is complicated.
JP 2004-195082 A

  In the conventional medical image processing apparatus and Patent Document 1, there is a problem that it is difficult to grasp the movement when the object is viewed from the visual field direction.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a medical image processing apparatus and a medical image processing method suitable for dynamic observation.

  The medical image processing apparatus according to claim 1 of the present invention is a medical image processing apparatus that processes volume data including a plurality of voxels to generate an image to be observed, and extracts data of a region of interest from the volume data. A region-of-interest extraction unit that performs volume rendering using the extracted data of the region of interest, and obtains a three-dimensional image of the region of interest viewed from a predetermined visual field direction on a two-dimensional projection plane Based on the image generation unit and temporal phase volume data around the time, the distance from the two-dimensional projection plane to the boundary surface of the region of interest along the line-of-sight direction is calculated, and for each time phase A distance information generation unit that generates distance information, and the distance information generation unit that obtains the distance information of two time phases preceding and following from the distance information generation unit and calculates a difference value of each distance information. A three-dimensional image obtained by the first image generation unit, a second image generation unit that generates an additional image whose density changes according to the magnitude of the difference value calculated by the difference value calculation unit, and the first image generation unit And a synthesis processing unit for synthesizing the additional image with a simple image.

  The medical image processing apparatus according to claim 6 of the present invention is a medical image processing apparatus that generates an image to be observed using volume data composed of a plurality of voxels, and means for generating the volume data. A region-of-interest extracting unit that extracts region-of-interest data from the volume data, and performing the volume rendering process using the extracted region-of-interest data, and the region of interest viewed from a predetermined viewing direction on a two-dimensional projection plane A boundary of the region of interest from each pixel of the two-dimensional projection plane along the line-of-sight direction based on a first image generation unit that obtains a three-dimensional image and temporal volume data that is temporally mixed A distance calculation unit that calculates a distance to the surface and calculates distance information for each time phase; and distance information of a time phase that is calculated by the distance calculation unit and precedes in time An existing memory, distance information from the distance calculation unit, a difference value calculation unit that calculates a difference value of each distance information from the distance information read from the memory, and a difference value calculated by the difference value calculation unit A second image generation unit that generates an additional image whose color density changes according to the size; and a synthesis processing unit that combines the additional image with a three-dimensional image obtained by the first image generation unit; And a display unit for displaying the combined image.

  Furthermore, the medical image processing method according to claim 7 of the present invention is a medical image processing method for processing volume data composed of a plurality of voxels to generate an image to be observed, and data of a region of interest from the volume data. And performing volume rendering using the extracted region-of-interest data to generate a first three-dimensional image of the region of interest viewed from a predetermined viewing direction on a two-dimensional projection plane. Based on the volume data of the temporal phase that moves forward and backward, calculate the distance from the two-dimensional projection surface to the boundary surface of the region of interest along the line-of-sight direction, and generate distance information for each time phase, Obtaining the distance information of two time phases preceding and following from the generated distance information, calculating a difference value of each distance information, and the difference value calculated by the difference value calculation unit A second image whose density changes according to the height is generated, and the first image and the second image are synthesized.

  According to the present invention, by displaying a moving image using a difference value between the current time phase and the previous time phase, it is possible to clearly display a portion having a large change in time series as viewed from the visual field direction, A medical image processing apparatus and a medical image processing method suitable for observation can be provided.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a block diagram showing the overall configuration of an embodiment of the medical image processing apparatus of the present invention. In FIG. 1, reference numeral 10 denotes a medical image diagnostic apparatus, which includes, for example, an X-ray CT apparatus or an MRI apparatus. The X-ray CT apparatus will be described as an example. A gantry 11 is provided. A rotating ring 12 is provided in the gantry 11 and is rotated by a rotating mechanism (not shown). An X-ray tube 13 and an X-ray detector 14 are disposed in the rotating ring 12 so as to face each other. The central portion of the rotating ring 12 is opened and placed on the couch top 15. A subject P is inserted.

 X-rays that have passed through the subject P are converted into electrical signals by the X-ray detector 14, amplified by the data acquisition unit 16, and converted into digital data. The data transmission device 17 transmits digital data (projection data) from the data collection unit 16 to the computer system 20. The gantry 11 is provided with a gantry driving unit 18 and an X-ray control unit 19.

 The computer system 20 includes a pre-processing unit 21 to which data from the data transmission device 17 is sent. The pre-processing unit 21 corrects signal intensity, corrects signal loss, and the like, and sends projection data onto the bus line 201. Output. A system control unit 22, an operation unit 23, a data storage unit 24, a data processing unit 25, a display unit 26, and the like are connected to the bus line 201.

 The system control unit 22 controls the operation of each unit of the computer system 20 and the gantry driving unit 18 and the X-ray control unit 19. The data storage unit 24 stores data such as tomographic images, the data processing unit 25 performs data processing using the data stored in the data storage unit 24, and the display unit 26 uses the medical data obtained by the data processing. Display images and so on.

 The operation unit 23 includes a keyboard, a mouse, and the like. The operation unit 23 is operated by a user (physician or the like), and performs various settings such as a region of interest setting and a line-of-sight direction setting for data processing. In addition, various information such as a patient's condition and examination method is input.

  FIG. 2 is a block diagram showing a specific configuration of the data processing unit 25 which is a main part of the present invention. In FIG. 2, 31 is a data input unit for inputting medical image data acquired by an X-ray CT apparatus, an MRI apparatus, an ultrasonic diagnostic apparatus or the like. For example, medical image data stored in the data storage unit 24 of FIG. 1 is sequentially input.

  The medical image data input from the data input unit 31 is supplied to the volume data generation unit 32. The volume data generation unit 32 processes medical image data of the same time phase, and generates volume data (three-dimensional data) based on information on slice positions and image orientations.

  Volume data from the volume data generation unit 32 is supplied to the region of interest extraction unit 33. A region of interest setting unit 34 is coupled to the region of interest extracting unit 33, and the region of interest setting unit 34 allows the user to designate a region of interest by operating the operation unit 23. The region of interest extraction unit 33 extracts the region of interest data designated by the user from the volume data.

  The volume data extracted by the region of interest extraction unit 33 is supplied to a distance information generation unit 35 and a volume rendering image generation unit 36 (hereinafter referred to as a VR image generation unit 36). A line-of-sight direction setting unit 37 is coupled to the distance information generation unit 35 and the VR image generation unit 36, and the user can set the line-of-sight direction by operating the operation unit 23. The line-of-sight direction setting unit 37 can set the line-of-sight direction with respect to the three-dimensional region of interest, for example, when the user operates the mouse.

  In order to create an image with a three-dimensional effect on the two-dimensional projection plane (screen) from the three-dimensional data, a volume rendering process is generally performed, and the VR image generation unit 36 generates a volume rendering image by, for example, a ray casting method. .

  On the other hand, the distance information generation unit 35 calculates the distance from the line-of-sight direction set by the line-of-sight direction setting unit 37 to the boundary surface of the region of interest viewed from each pixel of the screen. The memory 39 temporarily stores the distance information calculated by the unit 38.

  Further, the distance information from the distance calculation unit 38 and the distance information stored in the memory 39 are supplied to the difference value calculation unit 40, and the difference value of each distance information is extracted. The difference value calculation unit 40 reads the distance information in the previous time phase in each image on the screen from the memory 39 and calculates the difference value with the distance information in the current time phase from the distance calculation unit 38. Further, not only the previous one but also a plurality of distance information before the time phase may be used.

  The output of the difference value calculation unit 40 is supplied to the additional image generation unit 41. The additional image generation unit 41 generates an additional image whose density changes according to the difference value. A color map setting unit 42 is coupled to the additional image generating unit 41, and the user can set the additional image to be displayed in an arbitrary color by operating the operation unit 23.

  The output of the additional image generation unit 41 and the output of the VR image generation unit 36 are supplied to the synthesis processing unit 43, where the user sets the VR image (first image) by the color map setting unit 42. The additional image (second image) is overwritten with the color tone thus synthesized and displayed on the display unit 26.

  Next, the operation of the data processing unit 25 in FIG. 2 will be described with reference to FIGS.

  In FIG. 2, the medical image data input from the data input unit 31 is supplied to the volume data generation unit 32, and volume data that is a collection of three-dimensional data is generated.

  This volume data is supplied to the region of interest extraction unit 33, and volume data of the region of interest set by the region of interest setting unit 34 is extracted. The volume data extracted by the region of interest extraction unit 33 is supplied to the distance information generation unit 35 and the VR image generation unit 36.

  In the VR image generation unit 36, for example, a virtual point light source is set in the computer device, and one ray (ray) is applied to the voxel from the viewing direction to perform ray casting, and the reflected light is calculated for each voxel. Thus, a three-dimensional image (volume rendering image) is generated on the two-dimensional projection surface (screen). In addition, a volume rendering image of a region of interest (for example, the heart) is generated by setting an opacity (opacity) or the like.

  The VR image generation unit 36 projects light from a virtual point light source onto a target, sets brightness according to the distance from the light source, and shades the target to form a three-dimensional SVR (Shaded Volume Rendering). Generate an image. Further, the VR image generation unit 36 generates a volume rendering image when viewed from an arbitrary line-of-sight direction set by the line-of-sight direction setting unit 37.

  The VR image generation unit 36 performs voxel tracking from an arbitrary viewpoint by the ray tracing method as well as the ray casting method, obtains the brightness in the voxel, and projects image information based on the brightness on the projection plane. You may do it.

  FIG. 3 is an explanatory diagram for explaining the operations of the distance information generation unit 35 and the difference value calculation unit 40. FIG. 3 illustrates an image (b) of the current time phase of the region of interest and an image (a) of the previous time phase, the line-of-sight direction is indicated by A, the screen is indicated by B, and the object of the region of interest An object (object) is indicated by C.

  As described above, the VR image generation unit 36 sets a virtual light source in the computer device, applies a ray (ray) from the line-of-sight direction (arrow A) to the voxel, and performs ray casting. An image of the object C (for example, the heart) is generated. The distance calculation unit 38 obtains the distance from the screen B to the boundary surface of the object C for each pixel of the screen B, and calculates each distance data as a difference value. It supplies to the calculation part 40.

  The boundary surface of the object C means a surface on which a ray first hits when viewed from the screen B. The distance information of the previous time phase (time T-1) is (Dt-1), and the current time phase (time T ) Is (Dt). The distance information in each time phase calculated by the distance calculation unit 38 is temporarily stored in the memory 39.

  The difference value calculation unit 40 reads the previous time phase distance information (Dt−1) in each image on the screen B from the memory 39, and the current time phase distance information (Dt) from the distance calculation unit 38. The difference value of is calculated. The difference value of each time phase is defined as a time difference value S.

  Further, not only the previous one but also a plurality of distance data before the time phase may be used. That is, the amount of change along the line-of-sight direction can be calculated for each pixel by obtaining the difference in distance information from two time-phase images of the same region that are temporally changed.

  The time difference value S from the difference value calculation unit 40 is supplied to the additional image generation unit 41, converted into color data set by the color map setting unit 42, and an additional image is generated with an arbitrary color. For example, a pixel with a large time difference value S generates an image expressed in a dark color, a pixel with a small time difference value S generates an image expressed in a light color, and what about a pixel with no difference value (no change)? No image is generated.

  The output of the additional image generation unit 41 is supplied to the synthesis processing unit 43. In the composition processing unit 43, the additional image is overwritten with the color tone set by the user using the color map setting unit 42 on the SVR image generated by the VR image generation unit 36 and displayed on the display unit 26. FIG. 4 shows an example in which the additional images S1 and S2 based on the time difference value S are mapped to the SVR image.

  Since the SVR image is sequentially sent to the composition processing unit 43 and the additional image generated from the images having different time phases is transmitted, the 4D image in which the additional image that changes with time is mapped onto the stereoscopic image. And a medical image can be displayed in 4D on the display unit 26. The display image can be displayed by the line-of-sight direction setting unit 37 as viewed from an arbitrary line-of-sight direction.

  FIG. 4 shows an image of the object C viewed from the line-of-sight direction (perpendicular to the paper surface), and is an example in which the additional images S1 and S2 are mapped and displayed in a color different from the color of the object C. As shown in the legend E in FIG. 4, pixels with a large difference value are displayed in a dark color, and pixels with a small difference value are displayed in a light color.

  As can be seen from this figure, when there is a difference in the distance information of two images at different time phases, the difference is displayed as a movement in the line of sight direction. The movement seen from the direction can be accurately grasped. In addition, since a portion with a large movement and a small portion when viewed from the line-of-sight direction can be displayed with color shading, it is more suitable for performing dynamic observation.

  As described above, according to the present invention, by displaying a moving image using the difference value between the current time phase and the previous time phase, it is possible to clearly display a portion having a large time-series change as viewed from the viewing direction. A medical image processing apparatus and a medical image processing method suitable for region dynamic observation can be provided. Also, the circuit configuration does not require a complicated configuration and can be realized with a simple configuration.

  Although an X-ray CT apparatus has been described as an example of a medical image diagnostic apparatus, it is possible to use an MRI, an ultrasonic diagnostic apparatus, or the like, and various modifications can be made without departing from the scope of the claims. .

1 is a block diagram showing a configuration of an embodiment of a medical image processing apparatus of the present invention. The block diagram which shows the structure of the data processing part in the embodiment. Operation | movement explanatory drawing explaining operation | movement of the data processing part in the embodiment. Explanatory drawing which shows the example of a display of the medical image in the embodiment.

Explanation of symbols

10. Medical diagnostic imaging equipment (X-ray CT equipment)
DESCRIPTION OF SYMBOLS 20 ... Computer system 21 ... Pre-processing part 22 ... System controller 23 ... Operation part 24 ... Data storage part 25 ... Data processing part 26 ... Display part 31 ... Data input part 32 ... Volume data generation part 33 ... Region of interest extraction part 34 ... Region-of-interest setting unit 35 ... distance information generating unit 36 ... VR image generating unit 37 ... gaze direction setting unit 38 ... distance calculating unit 39 ... memory 40 ... difference value calculating unit 41 ... additional image generating unit 42 ... color map setting unit 43 ... Compositing processor

Claims (7)

A medical image processing apparatus that processes volume data composed of a plurality of voxels to generate an image to be observed,
A region of interest extraction unit for extracting data of a region of interest from the volume data;
A first image generating unit that performs volume rendering using the extracted region-of-interest data and obtains a three-dimensional image of the region of interest viewed from a predetermined viewing direction on a two-dimensional projection plane;
Based on volume data of temporal phases that move around in time, the distance from the two-dimensional projection plane to the boundary surface of the region of interest is calculated along the line-of-sight direction, and distance information is generated for each temporal phase A distance information generator;
A difference value calculation unit that obtains the distance information of two time phases preceding and following in time from the distance information generation unit, and calculates a difference value of each distance information;
A second image generation unit that generates an additional image whose density changes according to the magnitude of the difference value calculated by the difference value calculation unit;
A medical image processing apparatus comprising: a synthesis processing unit that synthesizes the additional image with a three-dimensional image obtained by the first image generation unit. The distance information generation unit includes a distance calculation unit that calculates a distance from the two-dimensional projection plane to the boundary surface of the region of interest for each pixel of the two-dimensional projection plane, and temporal distance information that precedes in time. And a memory for storing
The medical image processing apparatus according to claim 1, wherein the difference value calculation unit calculates a difference between distance information from the distance calculation unit and distance information read from the memory.   The medical image processing apparatus according to claim 1, further comprising: a gaze direction setting unit that can be operated by a user in order to set the gaze direction in the first image generation unit and the distance information generation unit.   2. The medical image processing apparatus according to claim 1, wherein the second image generation unit generates an additional image whose color shade changes according to the magnitude of the difference value calculated by the difference value calculation unit. .   The medical image processing apparatus according to claim 4, further comprising a color map setting unit that can be operated by a user in order to set the shade of the color. A medical image processing apparatus that generates an image to be observed using volume data composed of a plurality of voxels,
Means for generating the volume data;
A region of interest extraction unit for extracting data of a region of interest from the volume data;
A first image generating unit that performs volume rendering using the extracted region-of-interest data and obtains a three-dimensional image of the region of interest viewed from a predetermined viewing direction on a two-dimensional projection plane;
Based on time phase volume data that moves around in time, the distance from each pixel of the two-dimensional projection plane to the boundary surface of the region of interest is calculated along the line-of-sight direction, and distance information for each time phase A distance calculation unit for calculating
A memory that is calculated by the distance calculation unit and stores distance information of a temporal phase preceding in time;
A difference value calculation unit that calculates a difference value of each distance information from the distance information from the distance calculation unit and the distance information read from the memory;
A second image generation unit that generates an additional image in which the color density changes according to the magnitude of the difference value calculated by the difference value calculation unit;
A synthesis processing unit that synthesizes the additional image with the three-dimensional image obtained by the first image generation unit;
A medical image processing apparatus comprising: a display unit configured to display the combined image. A medical image processing method for processing volume data composed of a plurality of voxels to generate an image to be observed,
Extracting data of the region of interest from the volume data;
Performing volume rendering using the extracted data of the region of interest, and generating a three-dimensional first image of the region of interest viewed from a predetermined viewing direction on a two-dimensional projection plane;
Based on the temporal volume data before and after, calculate the distance from the two-dimensional projection plane to the boundary surface of the region of interest along the line-of-sight direction, and generate distance information for each temporal phase ,
Obtain the distance information of the two time phases that come back and forth in time from the generated distance information, calculate the difference value of each distance information,
Generating a second image whose density changes according to the magnitude of the difference value calculated by the difference value calculation unit;
A medical image processing method comprising combining the first image and the second image.

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