JP5618230B2 - Image generating apparatus, image generating method, and program - Google Patents

Description

  The present invention relates to a technique for generating an image of a tomographic plane from three-dimensional data.

  For example, in X-ray CT imaging, a tomographic plane image in which a cross section of a subject is imaged is generated based on three-dimensional data (volume data) obtained by collecting X-ray projection data. In such three-dimensional data of the subject, voxel values are recorded for each voxel arranged in three dimensions.

  A technique for generating a tomographic plane image from three-dimensional data is described in Patent Document 1, for example. Specifically, in Patent Document 1, a plurality of slices are generated along a predetermined line-of-sight direction from volume data collected by an ultrasonic probe, and an image (tomographic plane image) is generated from the plurality of slices.

JP 2003-61956 A

  By the way, in the above technique, slices are cut out from the volume data without gaps. The slice thickness always matches the spacing between slices. Therefore, if the slice interval is reduced, it becomes easier to capture the image of the target portion, but the slice thickness is small, so noise in the image increases. Further, if the slice interval is increased, the noise of the image is reduced, but the slice thickness is increased, so that the image of the target portion may be blurred. As described above, in the conventional technique, since the degree of freedom of image generation is low, it is difficult to obtain an image suitable for diagnosis.

  The present invention has been made in view of the above problems, and an object thereof is to provide a technique for generating a tomographic plane image suitable for diagnosis from three-dimensional data.

In order to solve the above-described problem, a first aspect is an image generation apparatus that generates a tomographic plane image from three-dimensional data of a subject obtained by X-ray CT imaging, and sets a line-of-sight direction with respect to the subject. At least one of a direction setting unit, a thickness of an image generation slice acquired from the three-dimensional region represented by the three-dimensional data to generate the tomographic plane image, and an interval at which the image generation slice is acquired Based on conditions set by the slice condition setting unit and the slice condition setting unit that can be individually set, the three-dimensional data included in the plurality of image generation slices acquired from the three-dimensional region, by respectively synthesized, and an image generator for generating a plurality of slice images along the line-of-sight direction as the sectional images, the slice condition setting When the interval for acquiring the image generation slice is the distance between the central points of the thickness of the image generation slice, the slice condition setting unit sets the thickness of the image generation slice to the image generation slice. set the product slice to a value greater than the interval for obtaining the thickness of the image generation slice, either interval for acquiring the image generation slices, that is fixed as a predetermined value.

  Further, according to a second aspect, in the image generation device according to the first aspect, the image generation unit acquires a plurality of unit slices regularly arranged orthogonal to the line-of-sight direction, and the image generation slices The slice image is generated for each of the image generation slices by synthesizing three-dimensional data corresponding to a plurality of unit slices included in the image.

According to a third aspect, in the first or second image generation apparatus, a position-of-interest setting unit that sets a specific position in the three-dimensional region as a position of interest, and a plurality of slices generated by the image generation unit And a display control unit that displays a slice image corresponding to the position of interest on the display unit.

According to a fourth aspect, in the image generation apparatus according to any one of the first to third aspects, the image generation unit converts the three-dimensional data included in the region of the image generation slice to The tomographic plane image is generated by averaging or geometric averaging along the line-of-sight direction.

According to a fifth aspect, in the image generation device according to the second aspect, the image generation unit applies a unit slice located in the center among the plurality of unit slices included in the image generation slice. The slice image is generated from the image generation slice by combining the corresponding three-dimensional data with higher weighting than the three-dimensional data corresponding to other unit slices.

According to a sixth aspect, in the image generation apparatus according to the second aspect, the image generation unit performs the slice evaluation from an image after edge enhancement is performed on three-dimensional data corresponding to the unit slice. Generate an image.

Further, according to a seventh aspect, in the image generation device according to the third aspect, the display control unit generates the image generation unit from the image generation slice orthogonal to the line-of-sight direction for the position of interest. a slice image, and displays on the display unit as a first sectional image, perpendicular to the viewing direction, and from the respective image generating slices perpendicular to each of the two directions orthogonal to each other, the image generation each slice image part is generated, the second sectional image is displayed on the display unit as a third sectional images.

In addition, according to an eighth aspect, in the image generation device according to the seventh aspect, the line-of-sight direction and the two directions are three directions of an x-direction, a y-direction, and a z-direction, respectively, The first tomographic plane image, the second tomographic plane image, and the third tomographic plane image are generated from the image generation slices acquired along the x direction, the y direction, and the z direction. To do.

According to a ninth aspect, in the image generation apparatus according to the eighth aspect, the image generation unit generates images of tomographic planes orthogonal to the x direction, the y direction, and the z direction and orthogonal to each other. The first tomographic plane image, the second tomographic plane image, and the third tomographic plane image, which are generated and displayed as an X tomographic plane image, a Y tomographic plane image, and a Z tomographic plane image, respectively, wherein Y sectional image, the Z sectional images intersect at a common origin.

In a tenth aspect, in the image generation device according to any one of the seventh to ninth aspects, the display control unit includes the first tomographic plane image, the second tomographic plane image, and the third aspect. each sectional images, is displayed on the display unit together with the first indicator is a cursor indicating the position of the other tomographic plane, the point of interest setting unit, the first sectional image, the second sectional image , based on the first indicator moving operation for relatively moving said first indicator to said third sectional image, it sets a new the location of interest.

According to an eleventh aspect, in the image generation device according to the tenth aspect, the line-of-sight direction setting unit displays the first tomographic plane image, the second tomographic plane image, and the third tomographic plane displayed on the display unit. Based on a first index rotation operation for rotating the first index relative to the image, a new line-of-sight direction is set.

In a twelfth aspect, in the image generation device according to any one of the seventh to eleventh aspects, the display control unit displays a three-dimensional image representing the three-dimensional region in three dimensions. And the line-of-sight direction setting unit sets a new line-of-sight direction based on a line-of-sight direction change operation for changing the line-of-sight direction with respect to the three-dimensional region, which is input to the three-dimensional image. .

According to a thirteenth aspect, in the image generating apparatus according to the twelfth aspect, the display control unit is at least one of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image. A second index which is a diagram of a translucent surface indicating the position of the tomographic plane with respect to is displayed on the display unit together with the three-dimensional image, and the line-of-sight direction setting unit is configured to display the second index with respect to the three-dimensional image. A new line-of-sight direction is set based on the index rotation operation for relatively rotating the two indices.

According to a fourteenth aspect, in the image generation device according to any one of the first to thirteenth aspects, the line-of-sight direction setting unit determines the shape of the subject at a specific position from the shape data regarding the subject. A tangent is extracted, and the direction in which the tangent extends is set as the line-of-sight direction.

According to a fifteenth aspect, in the image generation device according to any one of the first to thirteenth aspects, the subject includes a dental arch, and the line-of-sight direction setting unit includes the dental arch on the buccal side. The normal vision direction is set as the line-of-sight direction in accordance with dental arch normal vision information that determines the normal vision direction for normal viewing from the tongue side to the buccal side.

According to a sixteenth aspect, in the image generation device according to the fifteenth aspect, the line-of-sight direction setting unit recognizes the shape of the dental arch and determines the recognized shape of the dental arch. The normal viewing direction is set to the viewing direction.

Further, a seventeenth aspect, in the image generating apparatus according to the twelfth or thirteenth aspect, the viewing direction setting unit is shown displayed on the display unit together with the front Symbol 3-dimensional image was the gaze direction is indicated by an arrow A new line-of-sight direction is set based on the line-of-sight direction changing operation for the third index .

An eighteenth aspect is an image generation method for generating a tomographic plane image from three-dimensional data of a subject obtained by X-ray CT imaging, and (a) a step of setting a line-of-sight direction with respect to the subject; b) At least one of the thickness of the image generation slice acquired from the three-dimensional region represented by the three-dimensional data and the interval for acquiring the image generation slice is individually set to generate the tomographic plane image a step of, by combining each of the three-dimensional data included in (c) above (b) based on the conditions set in the step, a plurality of the image generation slices obtained from previous Symbol 3-dimensional region , look including the step of generating a plurality of slice images along the line-of-sight direction as said sectional image, wherein step (b), the interval of acquiring the image generating slice thickness of the image generation slice in When the distance between points is set, the thickness of the image generation slice is set to a value larger than the interval for acquiring the image generation slice, and the thickness of the image generation slice and the image generation Either one of the intervals for acquiring the slices for use is fixed as a predetermined value .

The nineteenth aspect is the image generation method according to the eighteenth aspect, wherein the step (c) acquires a plurality of unit slices regularly arranged perpendicular to the line-of-sight direction, and In this step, the slice image is generated for each of the image generation slices by synthesizing three-dimensional data corresponding to a plurality of unit slices included in the slice.

Also, aspects of the twentieth, the image generation method according to the eighteenth or nineteenth state like, and setting a specific location in; (d) three-dimensional region of interest position, (e) the (c) A step of displaying a slice image corresponding to the position of interest among the plurality of slice images generated in the step.

Also, aspects of the twenty-first, the image generation method according to any one aspect from the 18th twentieth aspect, wherein the step (c), the three-dimensional data included in the image generation slices in the region, It is a step of generating the tomographic plane image by performing addition averaging or geometric averaging along the line-of-sight direction.

A twenty-second aspect is the image generating method according to the nineteenth aspect, wherein the step (c) includes unit slices positioned at the center among the plurality of unit slices included in the image generation slice. This is a step of generating the slice image from the image generation slice by synthesizing the three-dimensional data corresponding to the above-mentioned three-dimensional data with higher weighting than the three-dimensional data corresponding to other unit slices.

In addition, according to a twenty- third aspect, in the image generation method according to the eighteenth aspect, from the image after the step (c) performs edge enhancement on the three-dimensional data corresponding to the unit slice, This is a step of generating a slice image.

The twenty-fourth aspect is the image generation method according to the twenty-second aspect, wherein the step (e) is generated in the step (c) from the image generation slice orthogonal to the line-of-sight direction for the position of interest. The slice image thus displayed is displayed as a first tomographic plane image, and from each of the image generation slices orthogonal to each of the two directions orthogonal to the line-of-sight direction and orthogonal to each other, (c) In this step, each slice image generated in the process is displayed as a second tomographic plane image and a third tomographic plane image.

According to a twenty-fifth aspect, in the image generation method according to the twenty- fourth aspect, the line-of-sight direction and the two directions are three directions of an x-direction, a y-direction, and a z-direction, respectively, and the step (c) includes The first tomographic plane image, the second tomographic plane image, and the third tomographic plane image are obtained from the image generation slice acquired along the x direction, the y direction, and the z direction. It is a process of generating.

According to a twenty-sixth aspect, in the image generation method according to the twenty- fifth aspect, the step (c) includes tomographic planes orthogonal to the x direction, the y direction, and the z direction, and orthogonal to each other. The images are the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image , which are generated and displayed as an X tomographic plane image, a Y tomographic plane image, and a Z tomographic plane image , respectively. face image, the Y sectional image, a step of crossing the Z sectional images at a common origin.

The twenty-seventh aspect is the image generation method according to any one of the twenty- fourth to twenty- sixth aspects, wherein the step (e) includes the first tomographic plane image, the second tomographic plane image, each of the third sectional image, a step of displaying together with the first indicator is a cursor indicating the position of the other tomographic plane, the first sectional image, the second sectional image, the third sectional images And a step of setting a new position of interest based on a first index movement operation for relatively moving the first index.

Also, aspects of the 28 is an image generating method according to the 27 aspect, step (e) is displayed the first sectional image, the second sectional image, the third sectional images And a step of setting a new line-of-sight direction based on a first index rotation operation for relatively rotating the first index.

Also, aspects of the 29 is an image generating method according to any one aspect of the 24th 28th aspect, step (e) displays the three-dimensional image stereoscopically representing said three-dimensional region as well as a process, is input to the front Symbol 3-dimensional image based on said line-of-sight direction changing operation for changing the viewing direction with respect to the three-dimensional region, comprising the step of setting a new said eye direction.

The thirtieth aspect is the image generating method according to the twenty- ninth aspect, wherein the step (e) includes at least one of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image. A step of displaying a second index, which is a diagram of a translucent surface showing the position of a tomographic plane, together with the three-dimensional image, and rotating the second index relative to the three-dimensional image And setting a new line-of-sight direction based on the index rotation operation.

Also, aspects of the 31 is an image generating method according to any one aspect from the 18th thirtieth aspect, the step (a) the shape data about the object, tangents to the shape of the object at a particular location Is extracted, and the direction in which the tangent line extends is set to the line-of-sight direction.

A thirty-second aspect is the image generation method according to any one of the eighteenth to thirty aspects, wherein the subject includes a dental arch, and the step (a) includes placing the dental arch on the buccal side. In this step, the normal direction is set as the line-of-sight direction according to dental arch normal information that determines the normal direction from the tongue side to the buccal side.

In addition, in a thirty- third aspect, in the image generating method according to the thirty- second aspect, the step (a) includes a step of recognizing the shape of the dental arch, with respect to the recognized shape of the dental arch. Setting the normal viewing direction determined as the viewing direction.

Also, aspects of the 34 is an image generating method according to the 29th or 30th aspect, the third indicator shown step (e) is the line-of-sight direction is displayed with the previous SL 3-dimensional image by an arrow And a step of setting a new line-of-sight direction based on the line-of-sight direction changing operation .

A thirty-fifth aspect is a computer-readable program, and the computer is executed on a memory by the CPU of the computer, so that the computer is changed to any one of the first to seventeenth aspects. It functions as such an image generation apparatus.

According to the image generation apparatus according to the first aspect, since the thickness of the image generation slice acquired to generate the tomographic plane image and the interval between the image generation slices can be individually set, Settings can be adjusted as appropriate according to circumstances, and a tomographic image suitable for diagnosis can be generated with a degree of freedom.
In addition, a tomographic image of the tomographic plane of the three-dimensional area is generated from a plurality of unit slices that share the area around the tomographic plane. That is, since it is generated from a plurality of slice images relatively close to the target site, it is possible to generate a highly accurate tomographic image in which structural features of the tomographic surface are more reflected. More specifically, since it is generated from three-dimensional data of a plurality of unit slices that are relatively close to the target site, high-accuracy tomograms arranged without dropping the image of the target site at a fine pitch A plane image can be generated. Further, by generating one image from a plurality of unit slices, a clear high-quality tomographic image with reduced noise can be acquired.

  In particular, according to the image generation apparatus according to the second aspect, a plurality of unit slices that are orthogonal or substantially orthogonal to the line-of-sight direction are generated. Since a plurality of unit slices are generated, for example, at fine intervals, the slice thickness and interval can be easily set by selecting the unit slice.

In particular, according to the image generation apparatus according to the third aspect, by displaying the tomographic plane image relating to the position of interest on the display unit, the operator can visually grasp the tomographic plane image of the position of interest.

In particular, according to the image generation apparatus according to the fourth aspect, noise in the tomographic plane image can be reduced.

In particular, according to the image generating apparatus according to the fifth aspect, the tomographic plane image more accurately reflects the feature of each position by generating the tomographic plane image by increasing the weight of the three-dimensional data of the central unit slice. Can be generated.

In particular, according to the image generating apparatus according to the sixth aspect, it is possible to acquire a tomographic plane image with emphasized edges.

In particular, according to the image generating apparatus according to the seventh aspect, the operator can visually grasp the tomographic plane image viewed from three directions orthogonal to each other with respect to the position of interest.

In particular, according to the image generating apparatus according to the eighth aspect, it is possible to visually grasp the tomographic plane image viewed from the three directions of the x direction, the y direction, and the z direction that are orthogonal to each other with respect to the position of interest.

In particular, according to the image generation apparatus according to the tenth aspect, the operator can view the tomographic plane image while viewing the specific tomographic plane image and changing the position of the tomographic plane in other directions. This makes it easier to search for and the situation around the area of interest.

In particular, according to the image generation apparatus according to the eleventh aspect, a new line-of-sight direction is set by the operator rotating the first index relative to a specific tomographic plane image, and a new tomographic plane image is obtained. Is generated. Therefore, it becomes easy for the operator to grasp the state around the specific position.

In particular, according to the image generation apparatus according to the twelfth aspect, since the line-of-sight direction can be set for a stereoscopic three-dimensional image, it becomes easy to intuitively set the line-of-sight direction.

In particular, according to the image generating apparatus according to the fourteenth aspect, since the tangential line extending direction is set as the visual line direction, an image generation slice is acquired along the tangent line when generating a tomographic plane image in the visual line direction. It will be. Since the slice for image generation is acquired along the tangent line, the positional relationship of the cross-sectional shapes of the three-dimensional regions is likely to coincide particularly in the portion where the tangent line is set in the slice image generated from each slice. Therefore, the image quality of the tomographic plane image is improved.

It is a figure which illustrates the whole structure of the image display system which concerns on 1st Embodiment. It is a block diagram which shows the structure of an image display system. It is a figure which shows the function structure implement | achieved with an image generation apparatus by CPU operate | moving according to a program with another structure. It is a figure which shows notionally the structure of an X-ray CT imaging apparatus. It is a figure which shows an example of the three-dimensional area | region of the to-be-photographed object which three-dimensional data expresses. It is a flowchart of the operation | movement of the image display of an image display system. It is a figure which shows a mode that a gaze direction is set with respect to a three-dimensional area | region. FIG. 7 is a detailed flowchart of a tomographic plane image generation operation of the image generation apparatus in step S <b> 2 illustrated in FIG. 6. It is a figure which shows notionally the unitary slice acquired from a three-dimensional area | region. It is a figure which shows a mode that a slice image is produced | generated from a unitary slice. It is a schematic diagram which shows a mode that a slice image is produced | generated from a part of area | region of the three-dimensional data in which the unitary slice shown to Fig.10 (a) was set. It is a figure for demonstrating the acquisition method of voxel data when unitary slice is set so that it may pass other than the place where voxel data exists. It is a figure for demonstrating the other example of a setting of the thickness (alpha) of the slice for image generation, and the space | interval (beta). It is a figure for demonstrating the other example of a setting of the thickness (alpha) of the slice for image generation, and the space | interval (beta). FIG. 9 is a detailed flowchart of a slice image synthesis operation of the image generation device in step S <b> 26 shown in FIG. 8. It is a figure which shows an example of the screen displayed on the display apparatus 3 in step S4 shown in FIG. It is a figure for demonstrating operation which changes an interest position. It is a figure for demonstrating the change of a gaze direction. It is a figure for demonstrating the change of a gaze direction. It is a figure for demonstrating the change of a gaze direction. It is a figure which shows the three-dimensional area | region after a gaze direction was changed. It is a figure which shows notionally the process of producing | generating a slice image from each of the several slice for image generation newly acquired after the change of a gaze direction. It is a figure which shows the screen of the display apparatus 3 on which the new tomographic plane image and the volume rendering image were displayed. It is a figure which shows a mode that the process which changes a position of interest is performed after a gaze direction change. It is a figure which shows a mode that an xyz rectangular coordinate system is set with respect to an XYZ rectangular coordinate system. A state in which slice images corresponding to the tomographic plane images Ix, Iy, and Iz as shown in FIG. 16 are cut out for each of the x axis, the y axis, and the z axis of the xyz orthogonal coordinate system is shown. It is a flowchart which shows operation | movement of the image generation apparatus which concerns on 2nd Embodiment. It is a figure for demonstrating a mode that a gaze direction is determined about a cylindrical to-be-photographed object. It is a figure for demonstrating a mode that a gaze direction is determined about a spherical object. It is a flowchart which shows operation | movement of the image generation apparatus in 3rd Embodiment. It is a figure which shows a mode that a gaze direction is set with respect to a dental arch. It is a flowchart which shows operation | movement of the image generation apparatus in 4th Embodiment. It is a figure which shows a mode that a gaze direction is set with respect to a dental arch. It is a figure which shows the volume rendering image in 5th Embodiment. It is a figure which shows the volume rendering image which concerns on a modification.

  Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

<1. First Embodiment>
<1.1. Configuration of Image Display System 1>
FIG. 1 is a diagram illustrating the overall configuration of an image display system 1 according to the first embodiment. FIG. 2 is a block diagram showing the configuration of the image display system 1.

  As shown in FIG. 1, the image display system 1 includes an image generation device 2, a display device 3, an input device 4, and an X-ray CT imaging device 5. In the image display system 1, three-dimensional data (volume data) acquired by imaging a subject with X-rays by the X-ray CT imaging device 5 and reconstructing the processed data is processed by the image generation device 2, and the display device 3 is processed. The (display unit) is configured to display an image of a tomographic plane and the like.

  As shown in FIG. 2, the image generating apparatus 2 includes a CPU 21, a RAM 22, a ROM 23, a fixed disk 24 that stores various data, and a reading unit 25 that reads data from a portable medium 9 such as a CD connected to a bus line 100. Have a typical computer configuration. The bus line 100 is connected to a display device 3 for displaying an image and the like, and an input device 4 including a keyboard and a mouse for receiving an input from an operator via an interface (not shown).

  Further, an X-ray CT imaging apparatus 5 is connected to the bus line 100 via a transmission cable interface. Various data sent from the X-ray CT imaging apparatus 5 can be stored in the fixed disk 24 under the control of the CPU 21.

  The program PG shown in FIG. 2 is stored in the fixed disk 24. Various functions of the image generation device 2 are realized by the CPU 21 operating according to the program PG.

  FIG. 3 is a diagram showing a functional configuration realized by the image generation device 2 by the CPU 21 operating according to the program PG, together with other configurations. In the configuration shown in FIG. 3, the imaging control unit 211, the three-dimensional data acquisition unit 212, the line-of-sight direction setting unit 213, the slice condition setting unit 214, the interest position setting unit 215, the image generation unit 216, and the display control unit 217 are included in the CPU 21. The functions realized by the above are shown.

{Photographing control unit 211}
The imaging control unit 211 controls the start and stop of imaging by transmitting a control signal to the X-ray CT imaging apparatus 5. Here, the configuration of the X-ray CT imaging apparatus 5 will be described with reference to FIG.

  FIG. 4 is a diagram conceptually showing the configuration of the X-ray CT imaging apparatus 5. The X-ray CT imaging apparatus 5 includes an X-ray generator 51 that irradiates, for example, a quadrangular cone-shaped cone beam B1 that is formed of a bundle of X-rays toward the subject Q1, and an X-ray that passes through the subject Q1 and reaches the subject Q1. And an arm 53 that suspends and holds the X-ray generation unit 51 and the X-ray detection unit 52 across the subject Q1.

  One end of a turning shaft 54 is attached to the central portion of the arm 53. A turning drive mechanism 55 provided on the arm 53 is connected to one end portion of the turning shaft 54. The turning drive mechanism 55 includes a turning shaft 54 and a belt (not shown) wound around a motor (not shown), and the arm 53 is centered on the turning shaft 54 by driving the motor of the turning drive mechanism 55. Turn. The turning shaft 54 is connected to the arm 53 via a bearing (not shown), and when the arm 53 turns, the turning shaft 54 does not rotate but only the arm 53 rotates.

  The other end of the turning shaft 54 is connected to a moving mechanism 56 that holds the turning shaft 54 so as to be horizontally movable. The moving mechanism 56 includes, for example, a bolt, a motor, a guide mechanism, and the like. By driving the moving mechanism 56, the turning shaft 54 moves in a horizontal plane, and the arm 53 can be moved to an arbitrary position within a predetermined range.

  Although not shown, the turning drive mechanism 55 may be provided in the moving mechanism 56 so that the turning drive mechanism 55 drives the turning shaft 54 to turn, and the turning arm 53 fixed to the turning shaft 54 turns. In this case, the moving mechanism 56 can be configured to move the turning drive mechanism 55 two-dimensionally in the horizontal plane together with the turning shaft 54.

  The X-ray CT imaging apparatus 5 having such a configuration rotates the arm 53 around the rotation axis 54 while irradiating the imaging area M1 of the subject Q1 with the cone beam B1, and the X-ray projection data on the imaging area M1. To collect. The collected data is transmitted to the image generation device 2.

{3D data acquisition unit 212}
Returning to FIG. 3, the three-dimensional data acquisition unit 212 collects projection data transmitted from the X-ray CT imaging apparatus 5, performs arithmetic processing such as back projection on the projection data, and stores the projection data in the imaging region M <b> 1. Three-dimensional data (volume data) representing a three-dimensional area is acquired. A publicly known method can be applied to this arithmetic processing. The three-dimensional data acquired by the three-dimensional data acquisition unit 212 is stored in the fixed disk 24 and used for image generation processing described later.

  FIG. 5 is a diagram illustrating an example of the three-dimensional area S1 that is the imaging area M1 represented by the three-dimensional data. In the three-dimensional data, data of each point (voxel) constituting the three-dimensional area is recorded for the three-dimensional area of the imaging area M1. As shown in FIG. 5, an XYZ orthogonal coordinate system that is orthogonal to each other is defined for the three-dimensional region S1, and voxel values V (X1, Y1) about a point P (X1, Y1, Z1) in the three-dimensional region S1. , Z1) is determined. The image generation device 2 generates a cross-sectional image (tomographic plane image) or a volume rendering image of the subject based on the three-dimensional data representing the three-dimensional region S1 in this way.

  Note that the three-dimensional region S1 may include a space where the portion of the subject Q1 does not exist. For example, when the region of interest O is near the surface of the subject Q1, X-ray CT imaging is performed around the region of interest O. Therefore, a space outside the surface of the subject Q1 where the portion of the subject Q1 does not exist is also photographed. There is a case where the three-dimensional region S1 included in the target range includes a space where the portion of the subject Q1 does not exist.

{Gaze direction setting unit 213}
Returning to FIG. 3, the line-of-sight setting unit 213 sets the line-of-sight direction with respect to the three-dimensional region of the subject Q <b> 1 when displaying various images on the display device 3. This line-of-sight direction is set based on an operation input from the operator via the input device 4.

{Slice condition setting unit 214}
The slice condition setting unit 214 sets conditions for cutting out a slice from the three-dimensional region represented by the three-dimensional data in order to generate a tomographic plane image. The slice condition setting unit 214 can individually set the slice thickness to be cut and the interval between slices to be cut based on an operation input from the operator via the input device 4. The image generation apparatus 2 generates a slice image that is a two-dimensional planar image by performing arithmetic processing on the voxel values of the three-dimensional data corresponding to each slice. This slice image is displayed on the display device 3 as a tomographic plane image.

{Interested position setting unit 215}
The position-of-interest setting unit 215 sets a position (interesting position) at which the operator wants to observe the tomographic plane in the three-dimensional region based on an operation input from the operator via the input device 4. The image generation device 2 has an image of a cross section perpendicular to the x axis passing through the position of interest (x axis tomographic plane Dx) and a cross section of the three dimensional region S1 perpendicular to the y axis passing through the position of interest (y axis tomographic plane Dy). An image and an image of a cross section (z-axis tomographic plane Dz) perpendicular to the z-axis passing through the position of interest are displayed on the display device 3.

{Image generation unit 216}
The image generation unit 216 generates a tomographic plane image of a three-dimensional region from the three-dimensional data stored in the fixed disk 24 under the conditions set by the line-of-sight direction setting unit 213, the slice condition setting unit 214, and the position-of-interest setting unit 215. , And generate a volume rendering image. A method for generating each image will be described later.

{Display control unit 217}
The display control unit 217 displays the tomographic plane image and volume rendering image generated by the image generation unit 216 on the screen of the display device 3. Further, the display control unit 217 displays the values set by the line-of-sight direction setting unit 213, the slice condition setting unit 214, and the position of interest setting unit 215 for the operator to input to the image generation device 2 via the input device 4. The apparatus 3 also has a function of displaying parts such as a cursor (for example, an x cursor Cx described later) on the screen as an index.

<1.2. Operation of Image Display System 1>
FIG. 6 is a flowchart of the image display operation of the image display system 1. Note that each operation of the image display system 1 described below is controlled by the CPU 21 of the image generation apparatus 2 that executes the program PG unless otherwise specified. Further, the image display system 1 constantly monitors the presence / absence of an end instruction from the operator, and when there is an end instruction, the image display operation is appropriately terminated.

  When the image display system 1 starts an image display operation, the line-of-sight direction setting unit 213 sets the line-of-sight direction to the initial setting direction, and the position-of-interest setting unit 215 sets the predetermined initial position in the three-dimensional region. Set (step S1).

  FIG. 7 is a diagram illustrating a state in which the line-of-sight direction is set for the three-dimensional region S1. In the example illustrated in FIG. 7, the line-of-sight direction setting unit 213 uses an arbitrary point on the X axis in the XYZ orthogonal coordinate system (see FIG. 5) defined for the three-dimensional region S1 as an initial value as the viewpoint P0. And the X-axis direction is set as the line-of-sight direction. Also, the interested position setting unit 215 sets the center of the three-dimensional region S1 as the interested position P1 as an initial value. Of course, the initial values of the line-of-sight direction and the position of interest are not limited to such objects, and can be set arbitrarily.

  When the line-of-sight direction is set, as shown in FIG. 7, the image generating apparatus 2 sets a straight line parallel to the line-of-sight direction passing through the position of interest P1 as the x-axis, and the Y-axis and Z-axis as the y-axis and z-axis. A new xyz orthogonal coordinate system is set for the three-dimensional region S1. This xyz orthogonal coordinate system is used as a display coordinate system.

  Returning to FIG. 6, when the line-of-sight direction and the position of interest are set, and the xyz orthogonal coordinate system is set, the image generation unit 216 executes generation of a tomographic plane image (step S2). Although details will be described later, in order to generate a tomographic plane image, the image generation device 2 uses a plane perpendicular to the x-axis, y-axis, and z-axis of the xyz orthogonal coordinate system from the three-dimensional region S1 to generate a predetermined plane. Thick slices are cut at predetermined intervals. Then, an image of the tomographic plane of the three-dimensional region at the position of interest P1 (tomographic plane images Ix, Iy, Iz) is generated from the slice cut out perpendicular to the three directions.

  When the generation of the tomographic plane image is completed, the image generation unit 216 stereoscopically visualizes the three-dimensional data, and generates a volume rendering image that is a three-dimensional image that three-dimensionally represents the three-dimensional region S1 (step S3). . Since a volume rendering image acquisition method has been proposed in the past, the details thereof will be omitted. For example, by adding voxel values on each line of sight as viewed from the viewpoint P0 for the three-dimensional region S1 (ray casting). A volume rendering image IV is generated. Note that the operation order of step S2 and step S3 can be changed as appropriate.

  When the generation of the volume rendering image is completed, the image generation device 2 causes the display control unit 217 to display the tomographic plane image and the volume rendering image on the display device 3 (step S4).

  When step S4 ends, the image generation device 2 determines whether there is an instruction to end the display process (step S5). If there is an operation input to end the display without changing the image displayed on the display device 3 (YES in step S5), the display process is ended. If there is no instruction to end the display process (NO in step S5), the process proceeds to step S6.

  When the tomographic plane image and the volume rendering image are displayed, the image generation device 2 determines whether the position of interest or the line-of-sight direction has changed (step S6). Specifically, this step S6 is determined based on whether or not the line-of-sight direction setting unit 213 and the position-of-interest setting unit 215 have received a change operation input from the operator via the input device 4. If there is no change operation input (NO in step S6), the display control unit 217 continues to display the screen in step S4 unless there is an instruction to end the display.

  When there is a change operation input (YES in step S6), the line-of-sight direction setting unit 213 or the position-of-interest setting unit 215 sets a new line-of-sight direction or a new position of interest based on the change operation input (step) S7). For example, when there is a change in the line-of-sight direction, the line-of-sight direction setting unit 213 moves the xyz orthogonal coordinate system so that the x-axis of the xyz orthogonal coordinate system matches the new line-of-sight direction. When the position of interest is changed, the xyz rectangular coordinate system is moved so that the origin of the xyz rectangular coordinate system coincides with the changed position of interest.

  When the setting of a new line-of-sight direction or a new position of interest is completed, the image generation device 2 uses the image generation unit 216 to generate a new tomographic plane image (step S8) and a new volume rendering image (step S9). Execute. The order in which step S8 and step S9 are executed can be switched as appropriate.

  When the generation of the new tomographic plane image and the volume rendering image is completed, the image generation device 2 causes the display control unit 217 to display these images on the screen of the display device 3 (step S10). Then, the image generation device 2 determines again whether the line-of-sight direction or the position of interest has changed (step S11). When there is no change operation input, the image generation device 2 determines whether or not there is a display end instruction from the operator (step S12). The image generation device 2 ends the image display operation when the end instruction is given, and continues the image display of step S10 when the end instruction is not given.

  In step S11, when there is a change operation input, the image generating apparatus 2 returns to step S7 and repeatedly executes the subsequent operations. Thereby, every time there is an operation input for changing the line-of-sight direction or the position of interest, the tomographic plane image and the volume rendering image are updated and displayed on the display device 3.

  The above is the description of the flow of the image display operation by the image display system 1. Next, among the operations of the image display system 1 described above, details of the operation of the image generation device 2 will be described.

<1.2.1. Generation operation of tomographic image>
FIG. 8 is a detailed flowchart of the tomographic plane image generation operation of the image generation apparatus 2 in step S2 shown in FIG. When the generation of the tomographic plane image in step S2 is started, the image generation apparatus 2 first prepares a unitary slice (step S20). Here, the unit slice is an extremely thin region extracted from the three-dimensional region S1, and the thickness of the region corresponds to, for example, the thickness of one voxel included in the three-dimensional data. Is set. The unit slice may be composed of two or more voxels. Although details will be described later, in the present embodiment, one tomographic image is generated by combining a plurality of unit slices by a predetermined pixel calculation.

  When the preparation of the unit slice is completed, the image generation apparatus 2 sets the thickness α of the image generation slice by the slice condition setting unit 214 (step S21). This image generation slice is a set of unit slices used for generating the above-mentioned one tomographic image. That is, the tomographic plane image is generated based on the unit slices included in the range of the thickness α set here.

  Further, the slice condition setting unit 214 sets an interval β for generating one image generation slice from the three-dimensional region S1 (step S22). Specifically, in steps S21 and S22, the operator executes a predetermined operation input such as a numerical value input via the input device 4, and the slice condition setting unit 214 receives the operation input, thereby determining the thickness α. An interval β is set. Note that one of the thickness α and the interval β may be fixed as a predetermined value.

  Further, the slice condition setting unit 214 cuts out the image generation slice based on the slice thickness α and the interval β, and sets the acquisition range H of the image generation slice acquired for image generation (step S23). Note that the required number of images may be acquired from the image generation slices prepared by cutting a large number with a margin, or only the number of image generation slices that can be acquired within a certain range may be acquired. Good. In addition, a limited area of the entire area of the three-dimensional area S1 may be set as the acquisition range H. However, the entire area of the three-dimensional area S1 may be set to automatically become the acquisition range H. Good.

  Then, the image generation unit 216 generates a slice image for each of a plurality of image generation slices continuous in the line-of-sight direction (step S24). The slice image generated in this way is stored in a storage unit (fixed disk 24, RAM 22, etc.) and displayed on the display device 3 as a tomographic plane image.

  FIG. 9 is a diagram conceptually showing the unit slice OSx acquired from the three-dimensional region S1. As shown in FIG. 9, a plurality of unit slices OSx (OSx1 to OSx9) arranged at minute intervals along the line-of-sight direction (x-axis) set in step S1 are acquired from the three-dimensional region S1. The

  Such preparation of the unit slice OSx (step S20) may be executed after step S21 (setting of the image generation slice thickness α), and at least from step S24 (slice image generation). May be performed in the previous stage.

  In this embodiment, the imaging region M is subdivided in the axial direction so as to be a minimum unit when the thickness α and the interval β are set in this way, and slices regularly arranged in the line-of-sight direction (axial direction) are unitized. It is sliced. In addition, it is suitable for coordinate calculation that the intervals between adjacent unit slices are equal.

  Here, the preparation of the unit slice OSx means that the three-dimensional data included in each of the unit slices OSx1 to OSx9 is internally associated with position information for each unit slice and managed as image data. Say. The unit slice OSx prepared in this way is a target for acquiring an image generation slice based on a set thickness α and interval β, which will be described later, and calculation is easy. In the example shown in FIG. 9, the unitary slice data OSx are arranged in the order of the numbers assigned to the codes (OSx) as image data.

  The three-dimensional data obtained by X-ray CT imaging may be arranged three-dimensionally as voxel data composed of the above-described voxels of the smallest possible size corresponding to the fineness of the particles of the X-ray detector pixel. it can. Therefore, by setting the minute intervals between the unit slices OSx1, OSx2,... OSx9 to the smallest possible intervals according to the respective intervals of the voxel data, the slice thickness α, the interval β Setting accuracy will increase. The minute interval between the unit slices OSx may match the size in the x-axis or y-axis direction per voxel of the three-dimensional data.

  FIG. 10 is a diagram illustrating a state in which the slice image ISx is generated from the unitary slice OSx. FIG. 10A is a view of the unit slice OSx shown in FIG. 9 viewed from the side (y-axis direction). FIG. 10B shows a slice image ISx.

  As shown in FIG. 10A, a desired range (for each interval β along the line-of-sight direction based on the thickness α and the interval β set in Steps S21 and S22 from a large number of unit slices OSx. A unitary slice OSx contained within the thickness α) is obtained. In FIG. 10A, each of a plurality (three in this case) of unit slices OSx surrounded by a two-dot chain line constitutes image generation slices SLx0, SLx1, and SLx2. In FIG. 10A, the thickness α of the image generation slices SLx0, SLx1, and SLx2 is indicated by the distance between the intermediate points between the unit slice and the adjacent unit slice. The interval β between the image generation slices SLx0, SLx1, and SLx2 is indicated by the distance between the central points of the slice thickness.

  Next, in step S24, the three-dimensional data corresponding to the unit slice OSx within the desired range (thickness α) is synthesized in the direction of the line of sight (here, the x axis) to generate a slice image ISx. . In the example illustrated in FIG. 10A, for example, the slice image ISx1 is generated by combining the voxel data corresponding to the unit slices OSx1, OSx2, OSx3 included in the image generation slice SLx0 along the line-of-sight direction. (See FIG. 10B). Similarly, a slice image ISx0 is generated by combining the voxel data corresponding to the unitary slices OSx4, OSx5, and OSx6, and a slice image ISx2 is generated from the voxel data corresponding to the unitary slices OSx7, OSx8, and OSx9. .

  Note that the voxel values within the range of the thickness α along the line-of-sight direction may be directly combined along the line-of-sight direction without acquiring the unitary slice OSx. In this case, without preparing the unit slice OSx, a flat area corresponding to the thickness α is acquired as an image generation slice from the three-dimensional area S1 at every interval β. Specifically, this will be described with reference to FIG.

  FIG. 11 is a schematic diagram illustrating a state in which the slice image ISx1 is generated from a part of the three-dimensional data area in which the unitary slices OSx1, OSx2, and OSx3 illustrated in FIG. 10A are set. Each of a plurality of points arranged in a lattice form shown in FIG. 11 corresponds to one voxel of three-dimensional data. For each of these voxels, there is a voxel value (such as voxel data Dxa1).

  As shown in FIG. 11, straight lines (lines Lxa, Lxb, Lxc, Lxd) parallel to the line-of-sight direction (x-axis) are assumed, and straight lines (lines Lx1, Lx2, Lx3) orthogonal to the straight line parallel to the line-of-sight direction are assumed. is assumed. When setting unit slices, for example, unit slices are set on this straight line (lines Lx1, Lx2, Lx3). However, in the synthesis processing described here, unit slices are not set directly. Synthesize 3D data. In this case, image data (image data Dxa, Dxa3, etc.) is synthesized by respectively composing three-dimensional data (voxel data Dxa1, Dxa2, Dxa3, etc.) on or near the straight line (lines Lxa, Lxb, Lxc, Lxd) Dxb, Dxc, etc.) are acquired.

  In this way, the image data Dxa, Dxb, Dxc, Dxd... Are obtained by directly synthesizing the three-dimensional data without preparing a unit slice. From this image data Dxa, Dxb, Dxc, Dxd..., One slice image ISx1 is constructed.

  In order to obtain the image data Dxa, it may be configured to take the addition value of the voxel data Dxa1, Dxa2, and Dxa3, but the addition average value and the geometric average value are obtained between the voxel data Dxa1, Dxa2, and Dxa3. Various processes similar to those in the case of synthesizing voxel data corresponding to unit slices described later can be considered. The above is a description of a case where a slice image is generated without acquiring a unitary slice.

  FIG. 12 is a diagram for explaining a method for acquiring voxel data when the unitary slice OSx is set so as to pass other than the position where the voxel data exists. As shown in FIG. 12, when the unitary slice OSx is set obliquely with respect to the direction in which the voxel data is arranged, a method of acquiring the nearest voxel data for each position of the unitary slice OSx is applied. .

  For example, the voxel data Dxaa, Dxbb, Dxcc, Dxdd corresponding to the unitary slice OSx shown in FIG. 12 corresponds to the voxel data Dxa2, Dxb2, Dxc1, Dxd1 of the voxel closest to each position. As described above, the voxel data at each position of the unitary slice OSx is used as the voxel data of the voxel closest to each position, thereby obtaining a slice image (tomographic plane image) that favorably shows the cross-sectional state of the three-dimensional region S1. can do.

  Further, in the example shown in FIG. 10, the thickness α and the interval β are both made equal to three unit slices. However, the method of setting the thickness α and the interval β of the image generation slice is not limited to this.

  13 and 14 are diagrams for explaining other setting examples of the thickness α and the interval β of the image generation slice. In the example shown in FIG. 13, the value of the thickness α is set smaller than the interval β. Specifically, the thickness α is set to two unit slices, while the interval β is set to three unit slices. In such a case, the slice images ISx1, ISx0 shown in FIG. 13B are synthesized by synthesizing the voxel data corresponding to the unit slices OSx1, OSx2, the unit slices OSx4, OSx5 and the unit slices OSx7, OSx8. , ISx2 is generated.

  In the example shown in FIG. 14, the thickness α is set larger than the interval β. Specifically, the thickness α is set to five unit slices, while the interval β is set to two unit slices. In such a case, from the voxel data corresponding to each of the unit slices OSx1 to OSx5, the unit slices OSx3 to OSx7, and the unit slices OSx5 to OSx9 that are continuous in the line-of-sight direction, the slice image ISx1 shown in FIG. ISx0 and ISx2 are generated.

  Thus, when the thickness α of the image generation slice is larger than the interval β between the slices, the advantage is particularly great in that a clearer slice image (tomographic plane image) with less noise can be generated.

  In the examples illustrated in FIGS. 10, 13, and 14, a relatively small number of unit slices OSx are described as examples for easy understanding. However, in actual arithmetic processing, a large number of units are used. It goes without saying that an operation using the target slice OSx may be performed.

  Acquisition of a slice is the setting of the position coordinates occupied by the slice in the three-dimensional space. Considering a slice as a frame, obtaining a slice is setting the position of the frame in the three-dimensional space, that is, the frame of the slice. The shape of the slice is not limited to a quadrangle and a rectangular parallelepiped, and various shapes such as a circle and a cylinder can be considered.

  In addition, expressions such as “cut out a slice” and “acquire a slice” are strictly expressed by three-dimensional data, or a spatial slice position setting with respect to the three-dimensional region S1 corresponding to the three-dimensional data. The process reflected in the three-dimensional data is performed.

  FIG. 15 is a detailed flowchart of the slice image synthesis operation of the image generation apparatus 2 in step S24 shown in FIG. First, in synthesizing voxel data corresponding to a unit slice, the image generation unit 216 uses a slice image among a plurality of unit slices OSx such as unit slices OSx1... OSx9 shown in FIG. Edge enhancement processing is performed on voxel data corresponding to the unitary slice OSx (step S241). Since each of the unit slices OSx can be regarded as an image of a cross section of the three-dimensional region S1, by performing edge processing in advance in this way, a tomographic plane image in which the contour of each part is emphasized is acquired. It becomes possible. For the edge enhancement processing, it is possible to apply filter processing or a known technique.

  When this edge enhancement processing is completed, the image generation unit 216 performs the averaging of the pixel values (specifically, voxel data) of the pixels corresponding to each other in the unit slice, thereby averaging the plurality of synthesized slices. An image (for example, slice images ISx0, ISx1, ISx2) is generated (step S242). By generating one tomographic image from a plurality of unit slices, an image with reduced noise can be acquired.

  Note that the edge emphasis process in step S241 is not necessarily an essential process, and only an addition average or geometric average process of pixel values of pixels corresponding to each other in unit slice data may be performed.

  For example, when the slice image ISx0 is generated from the unit slice data OSx4, OSx5, and OSx6 in FIG. 10A, the center unit slice OSx5 (unit slice closest to the position of interest P1) is the most. A weighted addition process may be performed in which the weighting is performed with a large weight and the other images are weighted with a relatively small weight. In such a case, a tomographic plane image that most strongly reflects the slice image close to the position of interest P1 can be generated.

  Note that weighting is not limited to weighting with a positive number. For example, the central unit slice OSx5 (unit slice closest to the position of interest P1) is weighted with a positive number, but the adjacent unit slices are weighted with a negative number. This is the case.

  The generated plurality of slice images ISx0, ISx1, ISx2 are displayed on the display device 3 as tomographic plane images. In the image display system 1, the tomographic plane image of the position of interest P1 set by the operator is displayed on the display device 3. A slice image corresponding to the position designated by the operator is displayed as a tomographic plane image. Become.

  Of course, the number of unit slices acquired for generating one tomographic image is not limited to the above-described three.

  Although not described in detail, the image generation unit 216 performs a plurality of unit slices cut out perpendicular to the y-axis with the y-axis direction as the line-of-sight direction in the same manner as the operations from step S21 to step S24. A tomographic image is generated from the voxel data. In addition, the image generation unit 216 generates a tomographic plane image from voxel data of a plurality of unit slices cut out perpendicular to the z axis with the z axis direction as the line-of-sight direction. As a result, the image generation unit 216 generates tomographic plane images viewed from three directions at the position of interest P1.

  As described above, in this embodiment, the slice thickness and the slice interval can be set independently. For example, when the thickness is reduced, the definition of the slice image is improved, but the noise increases. When the thickness is increased, the noise of the slice image is reduced, but the definition is reduced. On the other hand, if the interval between slices is increased, the number of all slices can be reduced, so that the amount of data to be handled is reduced, but the possibility that an image of the target part can be obtained decreases. If the slice interval is reduced, it becomes easier to obtain an image of the target part, but the amount of data to be handled increases. Therefore, it is possible to realize generation of a tomographic plane image suitable for diagnosis by determining at least one of the slice thickness and the slice interval based on such characteristics.

  In particular, when the slice thickness is set larger than the slice interval (FIG. 13), the tomographic image of the target site is generated from a plurality of unit slices that share the area around the tomographic plane. . That is, a tomographic plane image is generated from a plurality of unit slices relatively close to the target site, and a high-accuracy tomographic plane image arranged at a fine pitch without dropping the target site image is generated. obtain. In addition, by generating one tomographic image from a plurality of unit slices, a clear and high-quality tomographic image with reduced noise can be acquired.

<1.2.2. Display of tomographic image and volume rendering image>
FIG. 16 is a diagram showing an example of a screen displayed on the display device 3 in step S4 shown in FIG. As shown in FIG. 16, the display control unit 217 displays the tomographic image Ix viewed from the x-axis generated in steps S2 and S3, the tomographic image Iy viewed from the y-axis, and the tomographic image viewed from the z-axis. A total of four images of the plane image Iz and the volume rendering image IV are simultaneously displayed on the display device 3.

  Here, the tomographic plane images displayed as the tomographic plane image Ix, the tomographic plane image Iy, and the tomographic plane image Iz are considered to be examples of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image, respectively. Of course, the tomographic plane image Iy or the tomographic plane image Iz may be considered as the first tomographic plane image, and the other tomographic plane images may be considered as the second tomographic plane image and the third tomographic plane image. What is necessary is just to recognize as a tomographic plane image.

  Further, a tomographic plane image displayed as the tomographic plane image Ix may be referred to as an X tomographic plane image, a tomographic plane image displayed as the tomographic plane image Iy may be referred to as a Y tomographic plane image, and the tomographic plane image Iz. May be referred to as a Z tomographic plane image.

  In this way, by displaying the three tomographic plane images Ix, Iy, and Iz in comparison with respect to the position of interest P1, the operator can intuitively understand the relative relationship between these tomographic plane images Ix, Iy, and Iz. It becomes easy to grasp. Further, by displaying the volume rendering image IV together with the tomographic plane images Ix, Iy, and Iz, the operator can grasp three-dimensionally which position of the subject Q1 is being observed.

  Further, as shown in FIG. 16, the display control unit 217 displays a y-cursor Cy and a z-cursor Cz for the tomographic plane image Ix, a x-cursor Cx and a z-cursor Cz for the tomographic plane image Iy, and a tomographic plane image In Iz, an x cursor Cx and a y cursor Cy are displayed.

  The y cursor Cy displayed in the tomographic plane image Ix indicates the position of the y-axis tomographic plane Dy that passes through the position of interest P1, and the z cursor Cz indicates the position of the z-axis tomographic plane Dz that passes through the position of interest P1. ing. In addition, the x cursor Cx and the z cursor Cz displayed in the tomographic plane image Iy indicate the position of the x-axis tomographic plane Dx and the position of the z-axis tomographic plane Dz that respectively pass through the position of interest P1. Further, the x cursor Cx and the z cursor Cz displayed in the tomographic plane image Iz respectively indicate the position of the x-axis tomographic plane Dx and the position of the y-axis tomographic plane Dy that pass through the position of interest P1.

  By displaying the positions of other tomographic planes on the tomographic plane images Ix, Iy, and Iz in this way, the operator can easily grasp the relative positional relationship between the tomographic plane images Ix, Iy, and Iz.

  In addition, the display control unit 217 displays the x-axis tomographic plane Dx, the y-axis tomographic plane Dy, and the z-axis tomographic plane Dz passing through the position of interest P1 in the volume rendering image IV in a translucent state. By displaying the tomographic plane in this way, the operator can easily grasp the three-dimensional positional relationship between the tomographic plane images Ix, Iy, and Iz.

<1.2.3. Change of interest position and gaze direction>
Next, the change in the position of interest and the line-of-sight direction in step S6 shown in FIG. 6 will be described. First, the change of the position of interest will be described, and then the change of the line-of-sight direction will be described.

{Change of interest position}
FIG. 17 is a diagram for explaining an operation of changing the position of interest P1. As shown in FIG. 17, the positions of the x cursor Cx, the y cursor Cy, and the z cursor Cz displayed in the tomographic plane images Ix, Iy, and Iz can be changed by a predetermined operation by the operator. Yes.

  For example, as shown in FIG. 17, when the operator selects the x cursor Cx of the tomographic plane image Iy and performs an input for moving it in the left direction (−x direction) in the figure, the other tomographic plane image Iz. The x cursor Cx moves in the −x direction in conjunction with the x cursor Cx. Then, the interested position setting unit 215 sets a new interested position P1 at a position where the x cursor Cx is moved. In the case of the figure, since the X axis and the x axis coincide with each other, a new position of interest is set at a position on the −X side from the original position of interest P1.

  Similarly, even when the y cursor Cy or the z cursor Cz is moved, the new position of interest P1 is displayed by the position of interest setting unit 215 according to the moving direction and amount of movement of the y cursor Cy or the z cursor Cz. Is set.

  When a new position of interest P1 is set, the xyz orthogonal coordinate system is translated so that the position of interest P1 is the origin. Thereby, the xyz rectangular coordinate system is redefined.

  The image generation device 2 displays a tomographic plane image at a corresponding position based on the newly set position of interest P1. For example, assuming that the slice image ISx0 shown in FIG. 10 is displayed as the tomographic plane image Ix, the slice image ISx1 is displayed as the tomographic plane image Ix by moving the x cursor Cx in the direction along the x axis. The slice image ISx2 can be displayed as the tomographic plane image Ix.

  As long as the condition setting is performed by the slice condition setting unit 214, a plurality of tomographic plane images, for example, the slice images ISx0, ISx1, ISx2 shown in FIG. Accordingly, the corresponding slice images may be sequentially displayed, or the slice image at the corresponding position may be generated in real time each time the x cursor Cx is moved.

  In addition, a new acquisition range H is set, and the image generation unit 216 executes the same operation as described in FIG. 8 and the generation of the slice image (step S24), so that new tomographic plane images Ix and Iy are obtained. , Iz may be generated.

  Note that there is no change in the line-of-sight direction here, so there is no need to generate a new volume rendering image. Therefore, step S9 may be skipped when there is an operation input for changing the position of interest. However, by moving the x cursor Cx, as shown in FIG. 17, the position of the x-axis tomographic plane Dx is translated in the −X direction so as to pass through the new position of interest P1.

  The new tomographic plane images Ix, Iy, Iz and the volume rendering image IV generated in this way are displayed on the display device 3 as shown in FIG.

{Changing gaze direction}
Next, the change in the viewing direction will be described. In the present embodiment, the operator can observe the cross-sectional layer of the three-dimensional region S1 from any direction for a specific position of interest by changing the line-of-sight direction with respect to the three-dimensional region S1, as described below. it can.

  18-20 is a figure for demonstrating the change of a gaze direction. In FIG. 18, the line-of-sight direction is changed by rotating the indices (x cursor Cx, y cursor Cy, z cursor Cz) with respect to the tomographic plane images Ix, Iy, Iz. In FIG. 19, the line-of-sight direction is changed by rotating the tomographic plane images Ix, Iy, and Iz with respect to the index. In FIG. 20, the line-of-sight direction is changed by rotating the volume rendering image IV with respect to the x-axis tomographic plane Dx, the y-axis tomographic plane Dy, and the z-axis tomographic plane Dz.

  First, as shown in FIG. 18, when the operator rotates the x cursor Cx and the z cursor Cz clockwise with respect to the tomographic plane image Iy, the z cursor Cz of the tomographic plane image Ix and the x cursor Cx of the tomographic plane image Iz. Also, it rotates in conjunction with the rotation in the tomographic plane image Iy.

  In addition, rotating the x cursor Cx and the z cursor Cz clockwise rotates the y-axis tomographic plane Dy with respect to the x-axis tomographic plane Dx and the z-axis tomographic plane Dz. Therefore, when the x cursor Cx and the z cursor Cz are rotated as shown in FIG. 18, the image of the three-dimensional region S1 drawn by the volume rendering image IV is rotated in the xz plane with respect to the viewing direction. . Therefore, the viewpoint set on the x-axis moves to a position rotated by a predetermined angle around the y-axis, and the direction toward the position of interest P1 from the viewpoint of the new position becomes the new line-of-sight direction. .

  As shown in FIG. 19, the operator can also move the viewpoint in the same direction as in the example of FIG. 18 by rotating the tomographic plane image Iy counterclockwise with respect to the x cursor Cx and the z cursor Cz. It is possible to change the line-of-sight direction.

  Furthermore, as shown in FIG. 20, the operator turns the volume rendering image IV about the y axis, thereby moving the viewpoint in the same direction as in the examples of FIGS. 18 and 19 and changing the viewing direction. Can do. Regarding the operation of rotating the volume rendering image IV, for example, dragging the mouse of the input device 4 in the left-right direction is related to rotation around the z-axis, dragging in the vertical direction is related to rotation around the y-axis, Dragging the mouse in the up / down direction (or left / right direction) while a specific button such as a keyboard of the input device 4 is pressed is associated with rotation around the x axis. Thereby, the volume rendering image IV can be rotated in the three-dimensional space by a mouse operation.

  In addition, it may be configured such that an index such as a cursor can be rotated and moved with respect to the displayed X-ray image, or the X-ray image displayed with respect to the index can be rotated and moved. You may comprise so that it can operate. That is, the index rotation operation and the movement operation are relative.

{Image generation after changing eye direction}
FIG. 21 is a diagram illustrating the three-dimensional region S1 after the line-of-sight direction is changed. FIG. 22 is a diagram conceptually illustrating a process of generating slice images ISx0a, ISx1a, and ISx2a from each of a plurality of image generation slices SLx1a, SLx2a, and SLx3a that are newly acquired after the line-of-sight direction is changed. is there.

  When the viewpoint P0 is rotated by an angle (θ1 °) around the y axis by the operation of the operator described in FIGS. 18 to 20, the original viewpoint P0 is rotated about the y axis by θ1 ° as shown in FIG. Rotate and move to a new position. The line-of-sight direction setting unit 213 sets a direction extending from the viewpoint P0 of the new position to the position of interest P1 as a new line-of-sight direction. Then, the image generation apparatus 2 sets the line-of-sight direction as the x-axis, and sets the y-axis and the z-axis that are orthogonal thereto, thereby newly setting the xyz orthogonal coordinate system.

  The new xyz rectangular coordinate system is obtained by rotating the original xyz rectangular coordinate system by an angle θ1 ° around the original y axis. The image generation unit 216 generates the tomographic plane images Ixa, Iya, Iza at the position of interest P1 on the basis of the new xyz orthogonal coordinate system, and also generates the volume rendering image IV viewed from the new viewpoint P0.

  For example, when generating an image of the x-axis tomographic plane Dx perpendicular to the x-axis direction (tomographic plane image Ixa) for the three-dimensional region S1, as shown in FIG. 22, at intervals β along the line-of-sight direction. The image generation slices SLx0a, SLx1a, and SLx2a having a thickness α are acquired, and slice images ISx0a, ISx1a, and ISx2a are generated from the plurality of image generation slices SLx0a, SLx1a, and SLx2a, respectively.

  This series of image generation operations is the same as the operations from step S21 to step S24 shown in FIG. That is, a plurality of slice images ISx0a, ISx1a, ISx2a are generated based on the voxel data corresponding to the image generation slices SLx0a, SLx1a, SLx2a cut out from the three-dimensional region S1. Note that the slice images ISx0a, ISx1a, and ISx2a are subjected to the same edge enhancement processing as that in step S241 shown in FIG. Accordingly, the tomographic plane image Ixa may be generated. In addition, image generation similar to this is executed with the new y-axis direction and z-axis direction as the line-of-sight direction, and tomographic plane images Iya and Iza are generated.

  Similarly to step S7, the volume rendering image IVa is generated by adding the voxel values on each line of sight as viewed from the new viewpoint P0 (ray casting) for the three-dimensional region S1.

  FIG. 23 is a diagram showing a screen of the display device 3 on which new tomographic plane images Ixa, Iya, Iza and a volume rendering image IVa are displayed. Also in the new screen after changing the line-of-sight direction, the y-cursor Cy and the z-cursor Cz are displayed in the new tomographic plane image Ixa as in the screen before the change (FIG. 16), and the new tomographic plane image Iya The x cursor Cx and the z cursor Cz are displayed, and the x cursor Cx and the y cursor Cy are displayed on the new tomographic plane image Iza. Also in the volume rendering image IVa, the x-axis tomographic plane Dx, the y-axis tomographic plane Dy, and the z-axis tomographic plane Dz are displayed in a translucent state.

  FIG. 24 is a diagram illustrating a state in which the process of changing the position of interest P1 is performed after the line-of-sight direction is changed. As shown in FIG. 24, when the x cursor Cx of the tomographic plane image Iya is slid from the position indicated by the broken line to the position indicated by the solid line, the x cursor Cx of the tomographic plane image Iza is also moved in conjunction therewith. Then, the position of the x-axis tomographic plane Dx displayed in the volume rendering image IVa is displaced according to the moving direction and moving amount of the x cursor Cx.

  Then, the position-of-interest setting unit 215 sets the position where the x cursor Cx has moved to a new position of interest P1, and the image generation unit 216 generates the tomographic plane images Ixa, Iya, Iza of the new position of interest P1. It is displayed on the screen of the display device 3. For the volume rendering image IVa, since the line-of-sight direction is not changed, an image similar to that before the change of the position of interest P1 is displayed. However, the x-axis tomographic plane Dx moves according to the movement of the x cursor Cx.

  FIG. 25 is a diagram illustrating how the xyz rectangular coordinate system is set with respect to the XYZ rectangular coordinate system. When the image display system 1 starts image display, the image generation device 2 sets the x-axis, y-axis, and z-axis of the xyz orthogonal coordinate system to the X-axis, Y-axis, and Z-axis of the XYZ orthogonal coordinate system. Match. When there is an operation input for changing the position of interest or changing the line-of-sight direction, the x-axis is adjusted to the new line-of-sight direction, and the y-axis and z-axis are also moved. The x-axis, y-axis, and z-axis are three-dimensional axes in the x-direction, y-direction, and z-direction, respectively, and the x-direction, y-direction, and z-direction are orthogonal to each other.

  For example, as shown in FIG. 25 (a), when there is a change in the viewing direction that moves the viewpoint P0 to a position rotated by θ1 ° around the Y axis and θ2 ° around the Z axis, the xyz orthogonal coordinate system is changed. Arithmetic processing is performed to rotate θ1 ° around the Y axis and θ2 ° around the Z axis from the initial position. As a result, the xyz rectangular coordinate system is moved to a new position, and a slice is acquired along each axis of the new xyz rectangular coordinate system in order to generate a tomographic plane image.

  Further, when the position of interest position P1 set in FIG. 25A (here, the origin of the XYZ orthogonal coordinate system) is moved to a different position as shown in FIG. The displacement can be expressed by a movement amount in each direction of the X axis direction, the Y axis direction, and the Z axis direction. Therefore, by adding the displacement to the xyz rectangular coordinate system before the movement of the position of interest P1, a new xyz rectangular coordinate system having the changed position of interest P1 as the origin can be set.

  In the present embodiment, one tomographic plane image is generated from a plurality of slices even in the image display stage of steps S1 to S4 shown in FIG. 6, but the image display in this initial stage is performed. May generate one tomographic image from a single slice. That is, a single tomographic plane image may be generated from a plurality of slices only when the line-of-sight direction or the position of interest changes.

  Further, when the position of interest P1 and the line-of-sight direction are set, all slice images generated from slices acquired in advance from the three-dimensional region S1 at a predetermined interval β are stored in the fixed disk 24, and in response to a request. Thus, a necessary slice image may be acquired from all slice images and a tomographic plane image may be generated.

  Here, an example in which the thickness α is appropriately set for each of the x-axis, the y-axis, and the z-axis will be described.

  FIG. 26 shows a state in which slice images corresponding to the tomographic plane images Ix, Iy, and Iz as shown in FIG. 16 are cut out for each of the x axis, the y axis, and the z axis of the xyz orthogonal coordinate system. Note that the tomographic plane images Ix, Iy, and Iz in FIG. 16 are images corresponding to the slice image ISx0 perpendicular to the x-axis, the slice image ISy0 perpendicular to the y-axis, and the slice image ISz0 perpendicular to the z-axis, respectively.

  As shown in FIG. 26, when the intersection point of the x-axis, y-axis, and z-axis is the origin OP1, the slice images ISx0, ISy0, and ISz0 displayed on the display device 3 are positioned so as to intersect each other at the common origin OP1. Is set.

  More specifically, a central plane in the axial direction can be considered for each of the slice images ISx0, ISy0, and ISz0. For example, the slice image ISx1 in the example of FIG. 10A corresponds to the unit slice OSx2. It is preferable to set such a central plane so that all slice images intersect at a common origin OP1, since the occurrence of image misalignment can be suppressed.

<2. Second Embodiment>
In the first embodiment, the line-of-sight direction is set based on the operation input from the operator, but the setting of the line-of-sight direction is not limited to this. In the following description, elements having the same functions as those in the first embodiment are appropriately denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 27 is a flowchart showing the operation of the image generation apparatus 2 according to the second embodiment. In step S6 shown in FIG. 6, when the operator changes the position of interest, in this embodiment, the line-of-sight direction setting unit 213 extracts shape data related to the subject (step S71). Then, the line-of-sight direction setting unit 213 calculates the tangent of the outer portion of the three-dimensional region S1a from the extracted shape data (step S72). When the tangent is calculated, the line-of-sight direction setting unit 213 sets the tangent to the line-of-sight direction (step S73). Therefore, in this embodiment, the line-of-sight direction is automatically determined according to the change input operation of the position of interest.

  FIG. 28 is a diagram for explaining how the line-of-sight direction is determined for a cylindrical subject. FIG. 28A shows a three-dimensional area S1a obtained by reconstructing projection data of a cylindrical subject (such as a bone tissue) having a cavity inside, and FIG. 28B shows a three-dimensional area. An image of the z-axis tomographic plane Dz (tomographic plane image Iz) of the region S1a is shown together with the y cursor Cy, and FIG. 28C is for generating a new tomographic plane image Ix from the set line-of-sight direction. Fig. 3 conceptually shows a unit slice obtained.

  In the present embodiment, the line-of-sight direction setting unit 213 extracts shape data (outer edge contour line L1) of the outer portion of the three-dimensional region S1a from the image shown in FIG. As this extraction method, a conventionally proposed image recognition method can be applied. When the y cursor Cy displayed in the tomographic plane image Iz is moved to the position shown in FIG. 28B, the line-of-sight direction setting unit 213 tangents at the intersection P2 between the y cursor Cy and the outer edge contour line L1. L2 is calculated. Although there may be a plurality of intersections between the contour line L1 and the y cursor Cy, only one point is configured as the intersection point P2 based on the position of each intersection point.

  The line-of-sight direction setting unit 213 sets the direction in which the tangent line L2 extends as a new line-of-sight direction. In addition, the image generation unit 216 sets the new line-of-sight direction as the x-axis direction, and sets the y-axis and z-axis that are orthogonal to the x-axis and orthogonal to each other. In the example shown in FIG. 28, the tangent L2 of the outer edge portion of the three-dimensional region S1a in the tomographic plane image Iz is calculated, and the z axis is not changed. Therefore, the x-axis direction and the z-axis direction are determined in advance, and the y-axis direction is set in a direction orthogonal to the x-axis direction and the z-axis direction.

  When the xyz orthogonal coordinate system is set in this way, the image generation unit 216 generates an image of a tomographic plane orthogonal to each axial direction of the xyz orthogonal coordinate system. For example, as shown in FIG. 28C, when generating an image of the x-axis tomographic plane Dx perpendicular to the x-axis direction, slice images are respectively obtained from the plurality of slices SL0, SL1, and SL2 along the x-axis direction. These slice images are generated and displayed on the display device 3 as the tomographic plane image Ix. When the line-of-sight direction is set, a volume rendering image when the three-dimensional region S1a is viewed in this line-of-sight direction is newly generated and displayed on the screen of the display device 3.

  FIG. 29 is a diagram for explaining how the line-of-sight direction is determined for a spherical subject. FIG. 29A shows a three-dimensional region S1b relating to a spherical object having a hollow inside, and FIG. 29B shows a state in which the line-of-sight direction is set for the three-dimensional region S1b. ing.

  Also for the three-dimensional region S1b of such a spherical body, the contour line L1 of the outer edge portion of the three-dimensional region S1b is extracted and the moved y cursor Cy and the contour line L1 are the same as in the aspect shown in FIG. A tangent line L2 of the contour line L1 is calculated at the intersection point P2. The direction in which the tangent L2 extends is set as the line-of-sight direction.

  As described above, since the direction in which the tangent extends is set to the line-of-sight direction, when generating a tomographic image for the line-of-sight direction, a plurality of image generation slices are acquired along the tangent. Therefore, since a plurality of image generation slices are acquired along the tangent line, the positions of the cross-sectional shapes of the three-dimensional regions are likely to coincide with each other, particularly in the portion where the tangent line is set. Therefore, the image quality of the obtained tomographic plane image is improved.

<3. Third Embodiment>
In the second embodiment, the contour line of the outer edge is recognized and the tangent is calculated as the shape data of the subject, but the tangent determination method is not limited to this. In the present embodiment, a case where a dental arch is included in a subject and a tomographic plane image of the dental arch is generated will be described as an example.

  FIG. 30 is a flowchart showing the operation of the image generation apparatus 2 in the third embodiment. In the present embodiment, when the operator performs an operation of changing the position of interest by moving the position of the tomographic plane, the line-of-sight direction setting unit 213 automatically recognizes the shape of the dental arch, thereby providing a dental arch. The curve L3 is extracted (step S71a). Then, the line-of-sight direction setting unit 213 calculates the tangent of the dental arch curve at the intersection of the extracted dental arch curve and the moved tomographic plane (step S72a). Then, the line-of-sight direction setting unit 213 sets the calculated direction of the tangent to the line-of-sight direction (step S73a).

  FIG. 31 is a diagram illustrating a state in which the line-of-sight direction is set with respect to the dental arch. As shown in FIG. 31, when the tomographic plane image Iz of the three-dimensional region showing the dental arch is displayed on the display device 3, the position of the y cursor Cy displayed together with the solid line from the position shown by the broken line. When moved to the position shown, the shape of the dental arch is automatically recognized, and a curve L3 along the dental row is extracted. Then, the tangent line L4 of the curve L3 at the intersection P3 between the curve L3 and the moved y cursor Cy is calculated, and the extending direction of the tangent line L4 is set as the line-of-sight direction.

  When the line-of-sight direction is set, generation of a tomographic plane image is executed as in the second embodiment. As for the volume rendering image, an image of a three-dimensional region viewed in the set viewing direction is generated.

  In this way, for a three-dimensional region in which a specific part is imaged, a shape line representing the structural features of the part is extracted, and the tangent line of the shape line is set in the line-of-sight direction, so that the tomographic plane relating to the specific part The image quality can be improved.

<4. Fourth Embodiment>
FIG. 32 is a flowchart showing the operation of the image generation apparatus 2 in the fourth embodiment. In the present embodiment, when the operator performs an operation of changing the position of interest by moving the position of the tomographic plane, the line-of-sight direction setting unit 213 displays the dental arch model curve stored in the fixed disk 24. This is applied to the tomographic image that has been applied (step S71b).

  When the fitting of the dental arch model is completed, the line-of-sight direction setting unit 213 extracts the intersection of the position of the tomographic plane and the dental arch model, and the direction orthogonal to the tangent line of the dental arch model curve at the intersection The direction is set (step S72b). The line-of-sight direction setting unit 213 sets the normal viewing direction as the line-of-sight direction (step S73b).

  FIG. 33 is a diagram illustrating a state in which a line-of-sight direction is set with respect to the dental arch. As shown in FIG. 33, a tomographic plane image Iz relating to the dental arch is displayed, and when the y cursor Cy indicating the position of the y-axis tomographic plane Dy is moved, the dental arch model curve L3a is represented by the dental arch. Applied to the image. In this fitting, the dental arch model curve L3a is moved, or enlarged or reduced so as to best match the dental arch on the tomographic plane image Iz under a predetermined condition.

  This dental arch model curve L3a is obtained by tracing a general tooth arrangement, and its shape data is stored in advance in the fixed disk 24 or the like. Further, in the data of the dental arch model curve L3a, information on the normal vector at each position of the curve is recorded for each position.

  When the fitting of the dental arch model curve L3a is completed, the line-of-sight direction setting unit 213 extracts the intersection P3a between the y cursor Cy and the fitted dental arch model curve L3a. Then, a normal vector at this intersection P3a is acquired, and the direction of this vector is the normal viewing direction. Further, the line-of-sight direction setting unit 213 sets the normal viewing direction to the line-of-sight direction, and generates a tomographic plane image for each direction of the xyz orthogonal coordinate system and a volume rendering image of the three-dimensional region viewed in the line-of-sight direction. .

  Information for determining the normal viewing direction, such as the dental arch model curve, is dental arch normal viewing information. The normal viewing direction is a normal viewing direction in which the dental arch is viewed from the buccal side toward the tongue side or from the lingual side toward the buccal side, as shown in the example of the normal vector.

<5. Fifth Embodiment>
In the first embodiment, it has been described that the three-dimensional region S1 in the volume rendering image IV is appropriately rotated and displayed by performing a predetermined operation input for changing the viewing direction (see FIGS. 18 to 20). However, the operation method for changing the line-of-sight direction is not limited to this.

  FIG. 34 is a diagram showing a volume rendering image IVb in the fifth embodiment. In the present embodiment, the index 61 indicating the line-of-sight direction is displayed on the display device 3 together with the volume rendering image IVb. The index 61 represents an arrow in three dimensions, and the tip of the index 61 points to the central portion of the three-dimensional area S1. The operator can move the index 61 up and down and left and right around the central portion of the three-dimensional area S1 using the mouse of the input device 4, for example.

  Specifically, the line of sight direction can be changed in the YZ plane by the operator moving the index 61 up and down. In addition, the line of sight direction can be changed in the XY plane by the operator moving the index 61 left and right. When the line-of-sight direction is changed using the index 61, the image of the three-dimensional area S1 in the volume rendering image IVb does not change before and after the change.

  By configuring so that the gaze direction can be set using such an index 61, the operator can change the gaze direction by an intuitive operation. Therefore, a tomographic plane image suitable for diagnosis can be acquired efficiently. Further, since it is not necessary to newly generate the volume rendering image IVb, the image display can be performed efficiently.

  The index 61 may be fixedly displayed and the volume rendering image IVb may be rotated. Even in such a case, the line-of-sight direction can be set based on the relative positional relationship of the index 61 with respect to the volume rendering image IVb.

<6. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  In the first embodiment, as shown in FIG. 16 and the like, the viewpoint is set obliquely upward to display the volume rendering image IV. However, the volume rendering image display method is not limited to this. I can't. For example, as shown in FIG. 35, even if the volume rendering image IVc is displayed so that the line-of-sight direction is always a front view (that is, the direction in which the operator views the image of the three-dimensional region S1 is always the line-of-sight direction). Good.

  In the second to fourth embodiments, when the position of the tomographic plane is moved, when the line-of-sight direction setting unit 213 newly sets the line-of-sight direction, the tangent line or normal line is set as the line-of-sight direction. However, for example, the same method can be applied when setting the line-of-sight direction in the initial stage of step S1 shown in FIG. Specifically, for example, as in the second embodiment, the direction in which the tangent of the contour line extends (tangential direction) at the intersection of the initial tomographic plane and the contour line may be set as the viewing direction. The third and fourth embodiments can also be applied when setting the line-of-sight direction in the initial stage of step S1.

  Further, the indicator may be operable to rotate and move with respect to the displayed X-ray image, or the X-ray image displayed with respect to the indicator may be operable to rotate and move. The index rotation operation and the movement operation are relative.

DESCRIPTION OF SYMBOLS 1 Image display system 2 Image generation apparatus 21 CPU
22 RAM
23 ROM
DESCRIPTION OF SYMBOLS 211 Imaging | photography control part 212 3D data acquisition part 213 Gaze direction setting part 214 Slice condition setting part 215 Interest position setting part 216 Image generation part 217 Display control part 24 Fixed disk 25 Reading part 3 Display apparatus 4 Input apparatus 5 Imaging apparatus 51 X Line generation unit 52 X-ray detection unit 53 Arm 54 Pivot axis 55 Pivot drive mechanism 55 Movement mechanism 61 Index 9 Portable media Cx x cursor Cy y cursor Cz z cursor Dx x axis tomographic plane Dy y axis tomographic plane Dz z axis tomographic plane H Acquisition range ISx0, ISx1, ISx2 Slice image ISx0a, ISx1a, ISx2a Slice image IV, IVa, IVb, IVc Volume rendering image Ix, Iy, Iz Tomographic plane image Ixa, Iya, Iza Tomographic plane image L1 Contour line L2, L4 Tangent L3 curve L3 a Dental arch model curve P0 View point P1 Position of interest PG Program PSL0 Center position S1, S1a, S1b Three-dimensional region SLx0, SLx1, SLx2 Image generation slice SLx0a, SLx1a, SLx2a Image generation slice

Claims (35)

An image generation device that generates a tomographic image from three-dimensional data of a subject obtained by X-ray CT imaging,
A gaze direction setting unit for setting a gaze direction with respect to the subject;
It is possible to individually set at least one of the thickness of the image generation slice acquired from the three-dimensional region represented by the three-dimensional data and the interval for acquiring the image generation slice to generate the tomographic plane image. A slice condition setting section to perform,
Based on the conditions set by the slice condition setting unit, the three-dimensional data included in the plurality of image generation slices acquired from the three-dimensional region are combined to each other, and a plurality along the line-of-sight direction. An image generation unit that generates a slice image of the tomographic plane image,
Equipped with a,
The slice condition setting unit
When the interval for acquiring the image generation slice is the distance between the central points of the thickness of the image generation slice, the slice condition setting unit uses the thickness of the image generation slice as the image generation slice. Set it to a value larger than the interval at which slices are acquired,
Wherein the thickness of the imaging slice, either interval for acquiring the image generation slices, the image generating apparatus that is fixed as a predetermined value. The image generation apparatus according to claim 1,
The image generator
By acquiring a plurality of unit slices regularly arranged perpendicular to the line-of-sight direction, and synthesizing three-dimensional data corresponding to the plurality of unit slices included in the image generation slice, the image generation slice An image generation apparatus that generates the slice image every time.   The image generation apparatus according to claim 1 or 2,
  A position-of-interest setting unit that sets a specific position in the three-dimensional region as a position of interest;
  Among the plurality of slice images generated by the image generation unit, a display control unit that displays a slice image corresponding to the position of interest on a display unit;
An image generation apparatus further comprising:   The image generation apparatus according to any one of claims 1 to 3,
  The image generation device, wherein the image generation unit generates the tomographic plane image by performing averaging or geometric averaging of three-dimensional data included in the region for the image generation slice along the line-of-sight direction.   The image generation apparatus according to claim 2,
  The image generator
    Among the plurality of unit slices included in the image generation slice, three-dimensional data corresponding to the unit slice located at the center is weighted more than three-dimensional data corresponding to other unit slices and synthesized. Thus, an image generation apparatus that generates the slice image from the image generation slice.   The image generation apparatus according to claim 2,
  The image generation apparatus in which the image generation unit generates the slice image from an image after performing edge enhancement on three-dimensional data corresponding to the unit slice.   The image generation apparatus according to claim 3.
  The display control unit, for the position of interest,
  The slice image generated by the image generation unit from the image generation slice orthogonal to the line-of-sight direction is displayed on the display unit as a first tomographic plane image,
  Each slice image generated by the image generation unit from each of the image generation slices orthogonal to each of the two directions orthogonal to the line-of-sight direction and to each other is expressed as a second tomographic plane image, a third An image generation apparatus that displays a tomographic image on the display unit.   The image generation apparatus according to claim 7.
  The line-of-sight direction and the two directions are three directions of an x direction, a y direction, and a z direction, respectively.
  The image generation unit
  The first tomographic plane image, the second tomographic plane image, and the third tomographic plane image are generated from the image generation slices acquired along the x direction, the y direction, and the z direction. An image generating device.   The image generation apparatus according to claim 8, wherein
  The image generating unit converts the tomographic images orthogonal to each of the x direction, the y direction, and the z direction and orthogonal to each other into the first tomographic image, the second tomographic image, and the third tomographic image. A tomographic image is generated as an X tomographic plane image, a Y tomographic plane image, and a Z tomographic plane image, and the displayed X tomographic plane image, the Y tomographic plane image, and the Z tomographic plane image intersect at a common origin. An image generating device.   The image generation apparatus according to any one of claims 7 to 9,
  The display control unit
  Displaying each of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image on the display unit together with a first index that is a cursor indicating the position of another tomographic plane;
  The position of interest setting unit includes:
  The new position of interest is set based on a first index movement operation for moving the first index relative to the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image. Image generation device.   The image generation apparatus according to claim 10.
  The line-of-sight direction setting unit is
  Based on a first index rotation operation for rotating the first index relative to the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image displayed on the display unit, An image generating apparatus for setting the gaze direction.   The image generation apparatus according to any one of claims 7 to 11,
  The display control unit
  Displaying a three-dimensional image that three-dimensionally represents the three-dimensional region on the display unit;
  The image generation apparatus in which the line-of-sight direction setting unit sets a new line-of-sight direction based on a line-of-sight direction change operation for changing the line-of-sight direction with respect to the three-dimensional region, which is input to the three-dimensional image.   The image generation apparatus according to claim 12, wherein
  The display control unit
  A second index that is a diagram of a translucent surface indicating a position of a tomographic plane with respect to at least one of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image, Displayed on the display unit together with the image,
  The line-of-sight direction setting unit is
  An image generation apparatus that sets a new line-of-sight direction based on an index rotation operation for rotating the second index relative to the three-dimensional image.   The image generation apparatus according to any one of claims 1 to 13,
  The line-of-sight direction setting unit is
  An image generation apparatus that extracts a tangent to the shape of the subject at a specific position from shape data related to the subject, and sets a direction in which the tangent extends as the line-of-sight direction.   The image generation apparatus according to any one of claims 1 to 13,
  The subject includes a dental arch;
  The line-of-sight direction setting unit is
An image generation device that sets the normal viewing direction as the line-of-sight direction according to dental arch orthographic information that determines a normal viewing direction for viewing the dental arch from the buccal side to the tongue side or from the tongue side to the buccal side.   The image generation apparatus according to claim 15, wherein
  The line-of-sight direction setting unit is
  An image generating apparatus for recognizing the shape of the dental arch and setting the normal viewing direction determined for the recognized shape of the dental arch to the line-of-sight direction.   The image generation device according to claim 12 or 13,
  The line-of-sight direction setting unit is
  An image generation apparatus that sets a new line-of-sight direction based on a line-of-sight direction change operation for a third index indicated by an arrow with the line-of-sight direction displayed on the display unit together with the three-dimensional image.   An image generation method for generating a tomographic plane image from three-dimensional data of a subject obtained by X-ray CT imaging,
(a) setting a line-of-sight direction with respect to the subject;
(b) At least one of the thickness of the image generation slice acquired from the three-dimensional region represented by the three-dimensional data to generate the tomographic plane image and the interval at which the image generation slice is acquired is individually A setting process;
(c) Based on the conditions set in the step (b), by combining the three-dimensional data included in the plurality of image generation slices acquired from the three-dimensional region, Producing a plurality of slice images along the tomographic plane image,
  In the step (b), when the interval for acquiring the image generation slice is the distance between the central points of the thickness of the image generation slice, the thickness of the image generation slice is set to the image generation slice. A step of setting a value larger than the interval for acquiring slices;
  An image generation method in which one of the thickness of the image generation slice and the interval for acquiring the image generation slice is fixed as a predetermined value.   The image generation method according to claim 18,
  Step (c)
By acquiring a plurality of unit slices regularly arranged perpendicular to the line-of-sight direction, and synthesizing three-dimensional data corresponding to the plurality of unit slices included in the image generation slice, the image generation slice An image generation method which is a step of generating the slice image every time.   The image generation method according to claim 18 or 19,
(d) setting a specific position in the three-dimensional region as a position of interest;
(e) a step of displaying a slice image corresponding to the position of interest among the plurality of slice images generated in the step (c);
An image generation method further comprising:   The image generation method according to any one of claims 18 to 20,
  The image generation in which the step (c) is a step of generating the tomographic plane image by averaging or geometrically averaging three-dimensional data included in the image generation slice area along the line-of-sight direction. Method.   The image generation method according to claim 19, wherein
  Step (c)
    Among the plurality of unit slices included in the image generation slice, three-dimensional data corresponding to the unit slice located at the center is weighted more than three-dimensional data corresponding to other unit slices and synthesized. Accordingly, an image generation method which is a step of generating the slice image from the image generation slice.   The image generation method according to claim 18,
  Step (c)
    An image generation method which is a step of generating the slice image from an image after performing edge enhancement on three-dimensional data corresponding to a unit slice.   The image generation method according to claim 20, wherein
  In step (e), the position of interest
  The slice image generated in the step (c) from the image generation slice orthogonal to the line-of-sight direction is displayed as a first tomographic plane image,
  Each of the slice images generated in the step (c) from each of the image generation slices orthogonal to each of the two directions orthogonal to the line-of-sight direction is defined as a second tomographic image, 3. An image generation method which is a step of displaying as a tomographic image.   The image generation method according to claim 24, wherein:
  The line-of-sight direction and the two directions are three directions of an x direction, a y direction, and a z direction, respectively.
  The step (c)
  The first tomographic plane image, the second tomographic plane image, and the third tomographic plane image are generated from the image generation slices acquired along the x direction, the y direction, and the z direction. An image generation method which is a step of performing.   The image generation method according to claim 25, wherein
  Step (c)
  Images of tomographic planes that are orthogonal to the x direction, the y direction, and the z direction and are orthogonal to each other are defined as the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image, respectively. Image generation that is generated as an X tomographic plane image, a Y tomographic plane image, and a Z tomographic plane image, and is a step of intersecting the displayed X tomographic plane image, the Y tomographic plane image, and the Z tomographic plane image at a common origin. Method.   The image generation method according to any one of claims 24 to 26,
  The step (e)
  Displaying each of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image together with a first index that is a cursor indicating the position of another tomographic plane; and the first tomographic plane image Generating a new position of interest based on a first index moving operation for moving the first index relative to the second tomographic plane image and the third tomographic plane image. Method.   The image generation method according to claim 27,
  The step (e)
  Based on a first index rotation operation for rotating the first index relative to the displayed first tomographic plane image, second tomographic plane image, and third tomographic plane image, the new line-of-sight direction The image generation method including the process of setting.   The image generation method according to any one of claims 24 to 28,
  The step (e)
  A step of displaying a three-dimensional image that three-dimensionally represents the three-dimensional region, and a line-of-sight direction change operation for changing the line-of-sight direction with respect to the three-dimensional region, which is input to the three-dimensional image. An image generation method including a step of setting a new line-of-sight direction.   The image generation method according to claim 29, wherein
  The step (e)
  A second index that is a diagram of a translucent surface indicating a position of a tomographic plane with respect to at least one of the first tomographic plane image, the second tomographic plane image, and the third tomographic plane image, Displaying with the image;
  Setting a new line-of-sight direction based on an index rotation operation for rotating the second index relative to the three-dimensional image;
An image generation method including:   The image generation method according to any one of claims 18 to 30,
  The step (a)
  An image generation method, which is a step of extracting a tangent to the shape of the subject at a specific position from shape data relating to the subject, and setting a direction in which the tangent extends to the line-of-sight direction.   The image generation method according to any one of claims 18 to 30,
  The subject includes a dental arch;
  The step (a)
  An image generation method, which is a step of setting the normal vision direction as the line-of-sight direction according to dental arch normal vision information that determines a normal vision direction in which the dental arch is viewed from the buccal side to the tongue side or from the tongue side to the buccal side.   The image generation method according to claim 32, wherein:
  The step (a)
  An image generation method comprising the step of recognizing the shape of the dental arch, and the step of setting the normal viewing direction determined for the recognized shape of the dental arch as the line-of-sight direction.   The image generation method according to claim 29 or 30,
  The step (e)
  An image generation method including a step of setting a new line-of-sight direction based on a line-of-sight direction changing operation with respect to a third index indicated by an arrow with the line-of-sight direction displayed together with the three-dimensional image.   18. A computer-readable program, which causes the computer to function as the image generation device according to claim 1 when the CPU of the computer executes the program on a memory. .

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