JP2011110245A - Image display device, x-ray ct apparatus, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device which outputs information for achieving both detailed analysis and rough material discrimination relating to the material discrimination in the image of a subject, on the basis of an image obtained by dual energy imaging. <P>SOLUTION: The image display device includes: image acquiring means for acquiring first and second images Gw, Gio mutually different in correspondence relation between a material and a pixel value; scatter diagram generating means for generating a scatter diagram Gg1 where points corresponding to the pixel values of respectively mutually corresponding pixels in the images Gw, Gio are plotted in a coordinate space Kwi where the pixel value Wg in the first image Gw is defined as a horizontal axis and the pixel value Ig in the second image Gio is defined as a vertical axis; storage means for storing plot ranges Rc, Rio, ... to be estimated to indicate prescribed respective materials when the points corresponding to the pixel values of the mutually corresponding pixels in the images Gw, Gio are plotted in the coordinate space Kwi; and display means for displaying the scatter diagram Gg1 and the plot ranges Rc, Rio, ... by superimposition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an X-ray CT (Computed), an image display device for displaying an image obtained by dual energy imaging.
Tomography) apparatus and program for the same.

  Conventionally, a method has been proposed in which dual energy imaging of an object is performed using an X-ray CT apparatus, and an image useful for substance discrimination and diagnosis at an imaging region of the object is generated (see Patent Document 1, etc.).

JP 2009-118887 A

  By the way, in the image display apparatus and X-ray CT apparatus which display the image obtained by dual energy imaging | photography, it is possible to output the assistance information for the substance discrimination | determination.

  There are various types of support information and its output form, but outputting pixel value information in images obtained by dual energy imaging is a detailed analysis of substance discrimination based on the experience and knowledge of the observer. It is very important in terms of making it possible.

  However, depending on the observer, it may be difficult to intuitively grasp the meaning of the information only by such pixel value information, and it is difficult to perform even a rough substance discrimination.

  In view of the above circumstances, the present invention is capable of performing both detailed analysis and rough substance discrimination based on the experience and knowledge of the observer, regarding substance discrimination in an image of a subject, based on an image obtained by dual energy imaging. An object of the present invention is to provide an image display device that outputs various information, an X-ray CT device, and a program therefor.

  In a first aspect, the present invention provides a first X-ray projection data (data) of a subject by a first X-ray and a second X-ray having a different energy spectrum from the first X-ray. Are the first and second images based on the second projection data of the subject, each corresponding to a predetermined part of the subject, and the correspondence relationship between the substance and the pixel value is different from each other Image acquisition means for acquiring the first and second images, and coordinates having one of the horizontal axis and the vertical axis as the pixel value in the first image and the other axis as the pixel value in the second image A diagram generating means for generating a diagram in which points corresponding to the pixel values of the first and second images are plotted for each pixel position in a predetermined region in the image space corresponding to the predetermined part in the space And the first and second in the coordinate space A plot range storage means for storing, for at least one substance, a plot range presumed to represent a predetermined substance when plotting points corresponding to pixel values of the image, and the figure and an image representing the plot range; An image display apparatus is provided that includes display means for displaying the images in a superimposed manner.

  Here, the “corresponding relationship between a substance and a pixel value” means not a corresponding relationship with respect to a specific substance but an overall corresponding relationship with respect to a plurality of substances. For example, it includes not only the correspondence between air and its pixel value, but also the correspondence between water and its pixel value, the correspondence between iodine and its pixel value, and the like. Therefore, even if the correspondence relationship between air and its pixel value is the same in the two images, if the correspondence relationship between water and its pixel value is different, the two images are “the correspondence relationship between the substance and the pixel value is mutually different. Will be different.

  In a second aspect, the present invention provides the image according to the first aspect, further comprising region setting means for setting, as the predetermined region, a region designated by an operator in an image space corresponding to the predetermined portion. A display device is provided.

  In a third aspect, the present invention provides the first aspect or the second aspect further comprising registration means for storing the range in the coordinate space set by the operator in the plot range storage means as the plot range. The image display apparatus of the viewpoint is provided.

  In a fourth aspect, the present invention provides the first and second images obtained by subjecting the first projection data to image reconstruction processing and the second projection data by image reconstruction processing. The image display device according to any one of the first to third aspects is an image obtained by weighting and subtracting the images obtained by the first and second weights different from each other. provide.

  In a fifth aspect, the present invention provides the first and second images, wherein the first projection data and the second projection data are weighted and subtracted by different first and second weights. An image display device according to any one of the first to third aspects is provided, which is two images obtained by performing image reconstruction processing on the two projection data obtained in this way.

  In a sixth aspect, the present invention is directed to the above, wherein the first and second images are two images obtained by performing image reconstruction processing on the first projection data and the second projection data, respectively. An image display device according to any one of the first to third aspects is provided.

  In a seventh aspect, in the present invention, the plot range storage means stores the plot range and the name of a substance corresponding to the plot range in association with each other, and among the stored plot ranges, When plotting points corresponding to average pixel values of the predetermined area in the first and second images in the coordinate space, the plot space specifying means for specifying a plot range in which the points are plotted is further provided. The display means further corresponds to the predetermined portion, the first image, the second image, and a third image based on the first and second projection data. At least one third image different from the first and second images and the image representing the predetermined area are displayed in an overlapping manner and stored in association with the specified plot range. It is the name of the substance is to provide an image display apparatus according to any one aspect of the sixth aspect of the above first aspect to be displayed in association with the image representing the predetermined region.

  In an eighth aspect, the plot range storage means stores the plot range and the name of a substance corresponding to the plot range in association with each other, and among the stored plot ranges, A plot range that specifies a plot range in which the most points are plotted when points corresponding to the pixel values of the first and second images are plotted for each pixel position in the predetermined area in the coordinate space. A specifying unit, and the display unit is a third image based on the first image, the second image, and the first and second projection data, and the predetermined part And at least one third image different from the first and second images and an image representing the predetermined area are displayed in an overlapping manner, and the specified plot range The response with by the name of the material being stored, to provide an image display apparatus according to any one aspect of the sixth aspect of the above first aspect to be displayed in association with the image representing the predetermined region.

  In a ninth aspect, according to the present invention, the plot range storage unit stores the plot range in association with a color for each plot range, and in the coordinate space among the pixel positions of the predetermined region. When a point corresponding to the pixel value of the first and second images is plotted for each pixel position, the predetermined pixel position where the point is plotted in any of the stored plot ranges, Color specifying means for specifying a color stored in association with a plot range in which points corresponding to pixel positions are plotted; and the display means further includes the first image and the second image. An image and a third image based on the first and second projection data and corresponding to the predetermined portion and at least one third image different from the first and second images; display And an image display device according to any one of the first to eighth aspects, wherein the pixel at the predetermined pixel position in the displayed image is displayed in a color specified for the pixel position. To do.

  In a tenth aspect, the present invention provides color storage means for storing colors in association with each possible combination of pixel values of corresponding pixels in the first and second images, and each of the predetermined areas. A color specifying unit that obtains a combination of pixel values of the first and second images with respect to a pixel position and specifies a color that is stored in association with the combination is further provided, and the display unit further includes: A first image, the second image, and a third image based on the first and second projection data, corresponding to the predetermined part and different from the first and second images Displaying at least one of the third images and displaying each pixel in the predetermined region in the displayed image in a color specified for the pixel position of the pixel from the first to eighth aspects Any one Providing perspective image display apparatus.

  In an eleventh aspect, the present invention is plotted in the plot range when points corresponding to the pixel values of the first and second images are plotted in the coordinate space for each pixel position in the predetermined region. Plot point counting means for counting the number of points to be plotted for each plot range, and the display means further displays the number of the plotted plot points or a feature amount corresponding to the number for each plot range. An image display apparatus according to any one of the first to tenth aspects is provided.

  In a twelfth aspect, the present invention provides the image display device according to any one of the first aspect to the eleventh aspect, and the first and second X-rays irradiated to the subject. An X-ray CT apparatus is provided that includes data collection means for collecting first and second projection data.

  In a thirteenth aspect, the present invention provides a program for causing a computer to function as the image display device according to any one of the first to eleventh aspects.

  The predetermined part may be a predetermined slice or a predetermined three-dimensional region. If the predetermined portion is a predetermined slice, the first to third images can be two-dimensional images composed of a plurality of pixels, and the predetermined portion is a predetermined slice. In the case of a three-dimensional region, the first to third images can be three-dimensional images composed of a plurality of voxels.

  According to the image display device of the present invention, a diagram plotting points corresponding to pixel values of pixels corresponding to each other in a predetermined region in the first and second images of the subject obtained by dual energy imaging, and the pixel An image representing a plot range determined to be plotted when the image represents a predetermined substance is displayed in an overlapping manner. Thus, from the figure, the combination of the pixel values for each pixel in the predetermined area can be known in detail, and from the superimposed display of the figure and the plot range, which predetermined area is It is possible to roughly know whether it is composed of such substances. That is, from these pieces of information, detailed analysis based on the experience and knowledge of the observer and rough substance discrimination can be performed with respect to substance discrimination in the subject image.

It is a figure which shows the structure of the X-ray CT apparatus by 1st Embodiment. It is a block diagram which shows roughly the structure of the X-ray CT apparatus by this embodiment. It is a figure which shows roughly the process of producing | generating the 1st and 2nd material density image and a monochrome image. It is a figure which shows an example of the scatter diagram by 1st Embodiment. It is a figure which shows an example of the plot range by 1st Embodiment. It is a figure which shows an example of the image output screen by 1st Embodiment. It is a flowchart which shows the flow of a process in the X-ray CT apparatus of 1st Embodiment. It is a block diagram which shows roughly the structure of the X-ray CT apparatus by a 1st modification. It is a block diagram which shows roughly the structure of the X-ray CT apparatus by the 2nd modification based on a 1st modification. It is a figure which shows a mode that a region of interest is set. It is a figure which shows an example of the scatter diagram produced | generated with respect to the region of interest. It is a flowchart which shows the flow of a process in the X-ray CT apparatus by a 2nd modification. It is a figure which shows an example of the image output screen obtained by the 2nd modification. It is a block diagram which shows roughly the structure of the X-ray CT apparatus by a 3rd modification. It is a flowchart which shows the flow of a process in the X-ray CT apparatus by a 3rd modification. It is a figure which shows an example of the image output screen obtained by the 3rd modification. It is a block diagram which shows roughly the structure of the X-ray CT apparatus by the 4th modification based on 1st Embodiment. It is a flowchart which shows the flow of a process in the X-ray CT apparatus by a 4th modification. It is a figure which shows an example of the image output screen displayed in the 4th modification based on 1st Embodiment. It is a figure which shows an example of the image output screen displayed in the 4th modification based on a 2nd modification. It is a block diagram which shows roughly the structure of the X-ray CT apparatus by a 5th modification. It is a figure which shows an example of the correspondence of the combination of pixel values, and a color. It is a figure which shows schematically the structure of the operation console of the X-ray CT apparatus by the 6th modification based on the 4th modification. It is a figure which shows an example of the image output screen displayed in the 6th modification based on the 4th modification. It is a figure which shows an example of the plot range by a 7th modification.

  Hereinafter, embodiments of the present invention will be described.

(First embodiment)
FIG. 1 is a diagram showing the configuration of the X-ray CT apparatus according to the first embodiment.

  The X-ray CT apparatus 100 includes an operation console 1, an imaging table 10, and a scanning gantry 20. The imaging table 10 and the scanning gantry 20 are examples of data collection means in the present invention.

  The operation console 1 includes an input device 2 that receives input from an operator, a central processing unit 3 that performs control of various units and various calculations for scanning the subject 40, and data acquired by the scanning gantry 20. A data collection buffer (buffer) 5, a monitor 6 for displaying images, and a storage device 7 for storing programs and data.

  The imaging table 10 includes a cradle 12 on which the subject 40 is placed and carried into and out of the opening B of the scanning gantry 20. The cradle 12 is moved up and down and horizontally moved by a motor built in the imaging table 10. Here, the body axis direction of the subject 40, that is, the horizontal linear movement direction of the cradle 12 is the z direction, the vertical direction is the y direction, and the horizontal direction perpendicular to the z direction and the y direction is the x direction.

  The scanning gantry 20 includes a rotating unit 15 and a support unit 16 that rotatably supports the rotating unit 15. The rotating unit 15 includes an X-ray tube 21, an X-ray controller (controller) 22 that controls the X-ray tube 21, and a collimator that collimates and shapes the X-ray 81 generated from the X-ray tube 21. ) 23, an X-ray detector 24 that detects X-rays 81 irradiated from the X-ray tube 21 and transmitted through the subject 40, and a data collection device that converts and collects the output of the X-ray detector 24 into projection data (DAS; Data Acquisition System) 25 and an X-ray controller 22, a collimator 23, and a rotating unit controller 26 that controls the DAS 25 are mounted. The support unit 16 includes a control controller 29 that communicates control signals and the like with the operation console 1 and the imaging table 10. The rotating part 15 and the support part 16 are electrically connected via a slip ring 30.

  FIG. 2 is a block diagram schematically showing the configuration of the X-ray CT apparatus according to the present embodiment. In this figure, the main part of the operation console is functionally represented.

  The operation console 1 of the X-ray CT apparatus 100 includes a scan control unit 51, an image acquisition unit (image acquisition unit) 52, a scatter diagram generation unit (figure generation unit) 53, a plot range storage unit (plot range storage unit) 54, and A display control unit (display means) 55 is provided.

  The scan control unit 51 controls the imaging table 10 and the scanning gantry 20 in order to perform dual energy imaging of the subject 40. In the dual energy imaging, for example, the X-ray tube voltage is alternately switched between a relatively high first X-ray tube voltage HV and a relatively low second X-ray tube voltage LV in units of one view. to scan. In this example, the first X-ray tube voltage HV is 140 [kV], and the second X-ray tube voltage LV is 80 [kV]. When dual energy imaging is performed by switching the X-ray tube voltage, the X-ray tube voltage is converted into the first X-ray tube voltage HV and the second X-ray tube voltage LV in units of several views or rotations. Alternatively, scanning may be performed alternately.

  When dual energy imaging of the subject 40 is performed, the first projection data PHV of the subject 40 by the first X-ray and the subject 40 by the second X-ray having a different energy spectrum from the first X-ray. Of the second projection data PLV is collected. In this example, the first X-ray is an X-ray generated from the X-ray tube 21 when the X-ray tube voltage is the first X-ray tube voltage HV, and the second X-ray is X-rays generated from the X-ray tube 21 when the X-ray tube voltage is the second X-ray tube voltage LV, which is relatively low. The first and second projection data PHV and PLV are each assigned about 1000 views to a rotation angle 2π [radian] of one rotation of the X-ray tube 21, and a π + X-ray beam (beam) in the view angle range. The fan angle is α [radian] or 2π [radian].

  The image acquisition unit 52 is a tomographic image corresponding to a predetermined slice (predetermined part) SL of the subject 40 based on the first and second projection data PHV and PLV, and is a kind of substance. And a plurality of tomographic images having different correspondences between the pixel values. In this example, the image acquisition unit 52 uses the first and second substance density images (first and second substance images) useful for substance discrimination based on the first and second projection data PHV and PLV. Image) and a monochromatic image (third image) useful for interpretation / diagnosis and the like. In dual energy imaging, when scanning is performed by switching the X-ray tube voltage in units of one view or several views, the obtained first and second projection data PHV and PLV are respectively interpolated in the view direction. It is better to make up for missing data.

  The first and second substance density images are respectively an image that strongly represents the density distribution of the first substance in the slice SL of the subject 40 and a density of the second substance that is different from the first substance in the slice SL. It is an image that strongly represents the distribution. The first and second substance density images respectively correspond to the same slice SL of the subject 40, but the combination of pixel values in these two images differs depending on the kind of substance. Therefore, the substance represented by the pixel can be determined from the combination of the pixel values of the corresponding pixels in the first and second substance density images. Any combination of the first and second substances may be used, but a combination of any two of water, iodine (contrast agent) and calcium (bone) is suitable. In this example, the first substance is water, the second substance is iodine (contrast agent), and the image acquisition unit 52 generates a water density image as the first substance density image, and the second substance density image as the second substance density image. Generate an iodine density image.

  The monochrome image is a tomographic image equivalent to a tomographic image obtained when the subject 40 is imaged with monochromatic X-rays having predetermined energy (energy corresponding to a predetermined X-ray tube voltage). Can be set arbitrarily. Therefore, by setting this energy according to the imaging region and purpose, it is possible to obtain a tomographic image having a drawing mode that is optimal for diagnosis and interpretation.

  Here, a method for generating the first and second material density images and the monochrome image will be described.

  FIG. 3 is a diagram schematically showing a process of generating the first and second material density images and the monochrome image.

  As shown in FIG. 3, first, a first slice SL representing a predetermined slice SL of the subject 40 imaged with the first X-ray tube voltage HV using the collected first and second projection data PHV, PLV. The first X-ray tube voltage image GHV and the second X-ray tube voltage image GLV representing the same slice SL of the subject 40 imaged by the second X-ray tube voltage LV are reconstructed. Specifically, first, predetermined preprocessing including logarithmic conversion, correction of radiation quality, correction of sensitivity of the X-ray detector, and the like is performed on the collected first and second projection data PHV and PLV. Next, a predetermined reconstruction function is superimposed on the preprocessed first and second projection data PHV and PLV. The first and second projection data PHV and PLV on which the reconstruction function is superimposed are respectively backprojected to obtain first and second X-ray tube voltage images GHV and GLV.

  Next, the first X-ray tube voltage image GHV and the second X-ray tube voltage image GLV are weighted and subtracted to obtain a first substance density image representing the density distribution of the first substance, A second material density image representing the material density distribution is obtained. In this example, the first substance is water and the second substance is iodine, and a water density image Gw representing the density distribution of water and an iodine density image Gio representing the density distribution of iodine are obtained.

  The projection data of the subject or an image reconstructed based on the projection data can be approximately expressed by the density distributions of two different types of substances and their X-ray absorption coefficients. Based on this approximate model, first and second material density images can be obtained. That is, by subjecting the first X-ray tube voltage image GHV and the second X-ray tube voltage image GLV to weighted subtraction processing so that the pixel value of the pixel corresponding to water as the first substance becomes zero, The component of water as the first substance is suppressed, and an iodine density image Gio representing the density distribution of iodine as the second substance is obtained as the second substance density image. Similarly, the first X-ray tube voltage image GHV and the second X-ray tube voltage image GLV are weighted and subtracted so that the pixel value of the pixel corresponding to iodine as the second substance becomes zero. The component of iodine as the second substance is suppressed, and a water density image Gw representing the density distribution of the water as the first substance is obtained as the first substance density image.

  Note that the pixel values corresponding to the first and second substances in the first and second X-ray tube voltage images GHV and GLV can be estimated based on imaging conditions of dual energy imaging. Therefore, the weight to be used for the weighted subtraction process can be specified from the ratio of these estimated pixel values.

  The water density image Gw and the iodine density image Gio can be obtained, for example, by performing weighted subtraction processing according to the following mathematical formula.

  Here, kw is a conversion coefficient for expressing the pixel value Gw (x, y) of the water density image in terms of water density [mg / ml], and kio is the pixel value Gio (x, y) of the iodine density image. The conversion coefficient for expressing the density [mg / ml], rio is the dual energy ratio of iodine in the first X-ray tube voltage HV and the second X-ray tube voltage LV, and rw is the first X-ray tube voltage HV. And the dual energy ratio of water at the second X-ray tube voltage LV.

  In Equation 1 representing the weighted subtraction process for obtaining the water density image Gw, the weighting factor to be multiplied by the pixel value GLV (x, y) of the second X-ray tube voltage image is kw, and the first X-ray tube The weighting coefficient to be multiplied to the pixel value GHV (x, y) of the voltage image is kW · rio. Further, in Equation 2 representing the weighted subtraction process for obtaining the iodine density image Gio, the weight coefficient to be multiplied by the pixel value GLV (x, y) of the second X-ray tube voltage image is kio, and the first X The weighting coefficient to be multiplied to the pixel value of the tube voltage image GHV (x, y) is kio · rw.

  The dual energy ratio rio is a pixel value (CT value) GCio, LV (x corresponding to iodine on the image GCLV (x, y) obtained when X-rays are taken with the second X-ray tube voltage LV. , y) is divided by a pixel value GCio, HV corresponding to iodine on the image GCHV (x, y) obtained when X-rays are taken with the first X-ray tube voltage HV ( Pixel value ratio). Further, the dual energy ratio rw is obtained by converting the pixel value GCw, LV (x, y) corresponding to the water on the image GCLV (x, y) into the pixel value GCw, LV corresponding to the water on the image GCHV (x, y). A value obtained by dividing by HV (x, y).

  Next, as shown in FIG. 3, the water density image Gw and the iodine density image Gio are weighted and added to obtain a monochrome image Gm corresponding to a predetermined X-ray tube voltage NV (for example, 100 [kV]). obtain.

  The monochromatic image Gm can be obtained, for example, by performing weighted addition processing according to the following formula.

  Here, keV1 is the effective energy of X-rays by the X-ray tube voltage NV, μw (keV1) is the X-ray absorption coefficient of water at the effective energy keV1, μio (keV1) is the X-ray absorption coefficient of iodine at the effective energy keV1, and kc. Is a change coefficient for changing the pixel value of the tomographic image corresponding to the X-ray tube voltage NV to the CT value. As is well known, the CT value is a value indicating the degree of X-ray absorption of a substance, the CT value of air is represented by -1000 [HU], and the CT value of water is represented by 0 [HU].

  In Equation 5 representing weighted addition processing for obtaining the monochromatic image Gm, the weighting coefficient to be multiplied to the water density image Gw is kc · μw (keV1), and the weighting factor to be multiplied to the iodine density image Gio is kc · μio ( keV1).

  In the above method, an image obtained by image reconstruction processing of the first projection data PHV and an image obtained by image reconstruction processing of the second projection data PLV are different from each other. In this method, the first and second material density images are obtained by performing weighted subtraction with a weighting of 2. However, as another method, two pieces of projection data obtained by weighting and subtracting the first projection data PHV and the second projection data PLV with the first and second weights different from each other are respectively image reconstructed. A method of processing to obtain first and second material density images can also be used.

  The scatter diagram generation unit 53 generates a scatter diagram of pixel values in a predetermined region in the water density image Gw and the iodine density image Gio. In this example, this predetermined area is the entire area AR of the tomographic image corresponding to the slice SL of the subject 40.

  FIG. 4 is a diagram illustrating an example of a scatter diagram according to the first embodiment. As shown in FIG. 4, the scatter diagram generation unit 53 sets these two images Gw, Gw, in a coordinate space Kwi having the horizontal axis as the pixel value Wg in the water density image Gw and the vertical axis as the pixel value Ig in the iodine density image Gio. A scatter diagram is generated by plotting the points Dj corresponding to the pixel values of the pixels corresponding to each other for the entire area AR in Gio. The coordinate on the vertical axis and the coordinate on the horizontal axis in the coordinate space Kwi may be interchanged.

  The plot range storage unit 54 is estimated to indicate a predetermined substance when plotting points corresponding to pixel values of pixels corresponding to each other in the water density image Gw and the iodine density image Gio in the coordinate space Kwi. Is remembered. The plot range storage unit 54 stores the plot range for at least one substance in association with the name of the substance. Note that the plot range is obtained, for example, statistically or empirically based on a large number of sample images. The plot range storage unit 54 stores the plot range and the color determined for each plot range in association with each other.

  FIG. 5 is a diagram illustrating an example of a plot range according to the first embodiment. In this example, as shown in FIG. 5, the plot range storage unit 54 plots the plot range and the substance name for each substance of iodine (contrast medium), calcium (bone), soft tissue, water, fat, and air. , And colors are stored in association with each other. In FIG. 5, Rc, Tc, and Cc indicate the plot range, substance name, and color for calcium, respectively. Similarly, Rio, Tio, Cio are iodine, Rs, Ts, Cs are soft tissue, Rw, Tw, Cw are water, Rf, Tf, Cf are fat, Ra, Ta, Ca are plot ranges for air, Name and color are shown.

  The display control unit 55 controls the monitor 6 to display various images and information on the screen. In this example, the display control unit 55 displays the water density image Gw, iodine density image Gio, and monochrome image Gm generated by the image acquisition unit 52. In addition, the display control unit 55 displays the scatter diagram generated by the scatter diagram generation unit 53 and the image representing the plot range stored in the plot range storage unit 54 in an overlapping manner, and associates the scatter diagram with the plot range. The name of the stored substance is displayed in association with an image representing the plot range. At this time, the image representing the plot range and the name of the substance are displayed in a color that is stored in association with the plot range.

  FIG. 6 is a diagram illustrating an example of an image output screen according to the first embodiment. The image output screen SC includes a tomographic image display area SC1 and a scatter diagram display area SC2. For example, as shown in FIG. 6, the tomographic image display area SC1 and the scatter diagram display area SC2 are divided into three divided areas when the screen is divided into four and one remaining divided area. In the tomographic image display area SC1, a water density image Gw, an iodine density image Gio, and a monochrome image Gm are displayed. In the scatter diagram display area SC2, a scatter diagram Gg1 in which points Dj corresponding to pixel values of pixels corresponding to each other in the entire area AR of the water density image Gw and the iodine density image Gio are displayed in the coordinate space Kwi. Is done. Further, the image representing the plot range Rc,..., Ra stored in the plot range storage unit 54 and the substance names Tc,. Displayed in association with each type. At this time, the image representing each plot range and the name of the substance are displayed in a color determined for each plot range.

  Hereafter, the flow of processing in the X-ray CT apparatus 100 of the present embodiment will be described.

  FIG. 7 is a flowchart showing the flow of processing in the X-ray CT apparatus of this embodiment.

  In step S1, dual energy imaging processing is performed. That is, the scan control unit 51 controls the imaging table 10 and the scanning gantry 20 to perform dual energy imaging. Thus, the first projection data PHV of the subject 40 by the first X-ray at the first X-ray tube voltage HV and the subject 40 by the second X-ray at the second X-ray tube voltage LV. Of the second projection data PLV is collected.

  In step S2, a substance density image generation process is performed. That is, as described above, the image acquisition unit 52 generates the water density image Gw and the iodine density image Gio based on the first and second projection data PHV and PLV.

  In step S3, a monochrome image generation process is performed. That is, as described above, the image acquisition unit 52 generates a monochrome image Gm based on the water density image Gw and the iodine density image Gio.

  In step S4, a scatter diagram generation process is performed. That is, the scatter diagram generation unit 53 generates a scatter diagram by plotting points corresponding to pixel values of pixels corresponding to each other in the entire area AR in the water density image Gw and the iodine density image Gio in the coordinate space Kwi.

  In step S5, an image display process is performed. That is, the display control unit 1g controls the monitor 6 to display the above-described image output screen including the generated tomographic image and scatter diagram.

  According to such a first embodiment, a scatter in which points corresponding to pixel values of pixels corresponding to each other in a predetermined region in the first and second substance density images of the subject 40 obtained by dual energy imaging are plotted. FIG. Gg1 and an image representing the plot range Rio, Rc,... Determined to be plotted when the pixel represents a predetermined substance are displayed in an overlapping manner, and the substance is displayed on the image representing the plot range. The names Tio, Tc,. As a result, the combination of the pixel values for each pixel in the predetermined area can be specifically determined from the scatter diagram Gg1, and the scatter diagram Gg1 and the plot ranges Rio, Rc,. From the alignment display, it is possible to roughly know what kind of material the predetermined region is composed of. That is, based on these pieces of information, detailed analysis based on the experience and knowledge of the observer and rough substance discrimination can be performed with respect to substance discrimination in the tomographic image of the subject 40.

  Next, a modification of the first embodiment will be described.

(First modification)
The X-ray CT apparatus according to the first modification further includes a plot range registration unit (registration means) as a component of the operation console based on the first embodiment.

  FIG. 8 is a block diagram schematically showing the configuration of the X-ray CT apparatus according to the first modification. As shown in FIG. 8, the operation console 1a of the X-ray CT apparatus 101 according to this example includes a scan control unit 51, an image acquisition unit 52, a scatter diagram generation unit 53, a plot range storage unit 54, and a display control unit 55. A plot range registration unit 56 is provided.

  The plot range registration unit 56 performs new registration and registration change according to the operation from the operator for the plot range, the name of the substance, and the color that the plot range storage unit 54 stores in association with each other. In the new registration, a desired range in the coordinate space Kwi, a name of a desired substance, and a desired color set by the operator are newly registered. When registered, these are associated with each other and stored in the plot range storage unit 54. In the registration change, the plot range, the name of the substance, and a part or all of the color that have already been registered and stored in the plot range storage unit 54 in association with each other are changed.

  The plot range can be set, for example, in the manner of drawing using a pointer or the like on the image representing the coordinate space Kwi displayed on the screen of the monitor 6, or in each coordinate of the coordinate space Kwi. Set the numerical range directly.

  According to such a first modified example, the plot range and the like can be freely customized according to the application, the operator's preference, etc., and the usability is improved. In addition, the plot range can be corrected in accordance with the wrinkles on image generation possessed by the X-ray CT apparatus, and more accurate substance discrimination can be performed.

(Second modification)
The X-ray CT apparatus according to the second modification further includes a region-of-interest setting unit (region setting means) as a component of the operation console based on the first embodiment and the first modification. Here, as an example, a second modified example based on the first modified example will be described.

  FIG. 9 is a block diagram schematically showing a configuration of an X-ray CT apparatus according to a second modification based on the first modification. As shown in FIG. 9, the operation console 1b of the X-ray CT apparatus 102 according to this example includes a scan control unit 51, an image acquisition unit 52, a scatter diagram generation unit 53, a plot range storage unit 54, a display control unit 55, and a plot. In addition to the range registration unit 56, a region of interest setting unit 57 is provided.

  The region-of-interest setting unit 57 sets a desired region designated by the operator on the tomographic image corresponding to the slice SL of the subject 40 as the region of interest ROI. This region of interest ROI is not set as a region on a specific tomographic image, but as a region in the image space corresponding to the slice SL, that is, a region common to the tomographic image corresponding to the slice SL.

FIG. 10 is a diagram illustrating how a region of interest is set. For example, as shown in FIG. 10, the operator performs a graphical user interface on one of the tomographic images of the water density image Gw, the iodine density image Gio, and the monochrome image Gm displayed on the image output screen SC. (Graphical
A desired area is designated by using the pointer Pt or the like by (User Interface). The region-of-interest setting unit 57 sets the designated desired region as the region of interest ROI.

  In addition, the scatter diagram generation unit 53 in this example plots the scatter diagram by plotting the points Dk corresponding to the pixel values of the pixels corresponding to each other for the region of interest ROI in the water density image Gw and the iodine density image Gio in the coordinate space Kwi. Generate.

  FIG. 11 is a diagram illustrating an example of a scatter diagram generated for a region of interest. The scatter diagram generation unit 53 generates a scatter diagram as shown in FIG. 11, for example.

  Hereafter, the flow of processing in the X-ray CT apparatus according to the second modification will be described.

  FIG. 12 is a flowchart showing the flow of processing in the X-ray CT apparatus according to the second modification.

  In Steps B1 to B3, as in Steps S1 to S3 in the first embodiment, dual energy imaging processing, substance density image generation processing, and monochrome image generation processing are performed.

  In step B4, a tomographic image display process is performed. That is, the display control unit 55 causes the monitor 6 to display an image output screen including the tomographic images generated in steps B2 and B3.

  In step B5, a region of interest setting process is performed. That is, the operator designates a desired area on a tomographic image included in the displayed image output screen by a graphical user interface or the like. The region-of-interest setting unit 57 sets the designated desired region as the region of interest ROI. When the region of interest ROI is set, the display control unit 55 displays an image representing the region of interest ROI in an overlapping manner on all displayed tomographic images.

  In step B6, a scatter diagram generation process is performed. That is, the scatter diagram generation unit 53 performs a scatter diagram generation process similar to that of the first embodiment on the region of interest ROI, and generates a scatter diagram related to the pixel values of the region of interest ROI.

  In step B7, a scatter diagram display process is performed. That is, the display control unit 55 causes the scatter diagram generated in step B6 and the image representing the plot range stored in the plot range storage unit 54 to be displayed over the scatter diagram display area of the image output screen.

  In step B8, the operator is inquired whether to add or change a region of interest. If a request for addition / change is input, the process returns to step B5 to add or change the region of interest. If a request for addition / change is not input, the process ends. To do.

  FIG. 13 is a diagram illustrating an example of an image output screen obtained in this example.

  According to such a second modified example, it is possible to generate a scatter diagram of pixel values for only a portion of the tomographic image of the subject 40 that is of interest to the operator. Useful information can be obtained.

(Third Modification)
The X-ray CT apparatus according to the third modified example further includes a plot range specifying unit (plot range specifying means) as a component of the operation console based on the second modified example.

  FIG. 14 is a block diagram schematically showing the configuration of the X-ray CT apparatus according to the third modification. As shown in FIG. 14, the operation console 1c of the X-ray CT apparatus 103 according to this example includes a scan control unit 51, an image acquisition unit 52, a scatter diagram generation unit 53, a plot range storage unit 54, a display control unit 55, a plot range. In addition to the registration unit 56 and the region of interest setting unit 57, a plot range specifying unit 58 is provided.

  For example, when plotting points corresponding to the average pixel values of the region of interest ROI in the water density image Gw and the iodine density image Gio in the coordinate space Kwi, the plot range specifying unit 58 plots the points. Is identified. Further, for example, for each pixel position in the region of interest ROI, pixel values at the pixel positions in the water density image Gw and iodine density image Gio are obtained, and points corresponding to the obtained pixel values are plotted in the coordinate space Kwi. Specify the plot range where the most points are plotted.

  In addition, the display control unit 55 in this example, in the scatter diagram display area SC2 of the image output screen SC, the substance name stored in association with the plot range specified by the plot range specifying unit 58, and the region of interest ROI. Is displayed in association with an image representing. For example, the name of the substance is displayed in the vicinity of the region of interest, a leader line is displayed on the image representing the region of interest, and the name of the substance is displayed on the tip.

  Hereafter, the flow of processing in the X-ray CT apparatus according to the third modification will be described.

  FIG. 15 is a flowchart showing a flow of processing in the X-ray CT apparatus according to the third modification.

  In steps C1 to C7, as in steps B1 to B7 of the second modification, dual energy imaging processing, substance density image generation processing, monochrome image generation processing, tomographic image display processing, region of interest setting processing, scatter diagram generation processing, And scatter diagram display processing.

  In step C8, a plot range specifying process is performed. That is, the plot range specifying unit 58 specifies the plot range corresponding to the region of interest ROI based on the pixel value of the region of interest ROI in the water density image Gw and the iodine density image Gio as described above.

  In step C9, a substance display process is performed. That is, the display control unit 55 displays the name of the substance stored in association with the plot range specified by the plot range specifying unit 57 in the scatter diagram display region SC2 of the image output screen SC, representing the region of interest ROI. Are displayed in association with each other. At this time, the display control unit 55 causes the image representing the region of interest ROI and the name of the substance to be colored and displayed with a color associated with the specified plot range. In this example, since the image representing the region of interest ROI is displayed over the water density image Gw, the iodine density image Gio, and the monochrome image Gm, the correspondence display of the substance names in this step C9 is performed. The coloring display is performed on the image representing the region of interest ROI displayed on each tomographic image.

  In step C10, the operator is inquired whether to add or change a region of interest. If a request for addition / change is input, the process returns to step C5 to add or change the region of interest. If a request for addition / change is not input, the process ends. To do.

  FIG. 16 is a diagram illustrating an example of an image output screen according to the present example. The example of FIG. 16 is an example when the soft tissue plot range Rs is specified in step C9. In this example, the name Ts of the substance stored in association with the soft tissue plot range Rs, that is, “Soft Tissue” is displayed in association with the image representing the region of interest ROI. The image representing the region of interest ROI and the name of the substance are colored with the color Cs stored in association with the plot range Rs of the soft tissue, that is, orange.

  According to the third modified example, it is possible to confirm the estimation result of the portion of the substance that the operator is interested in in the tomographic image of the subject 40, and to provide information useful for diagnosis such as the presence or absence of a lesion. Obtainable.

(Fourth modification)
The X-ray CT apparatus according to the fourth modification further includes a color specifying unit (color specifying means) as a component of the operation console based on the first embodiment and the first to third modifications.

  Here, as an example, a fourth modification based on the first embodiment will be described.

  FIG. 17 is a block diagram schematically showing a configuration of an X-ray CT apparatus according to a fourth modification based on the first embodiment. As shown in FIG. 17, the operation console 1d of the X-ray CT apparatus 104 according to this example includes a scan control unit 51, an image acquisition unit 52, a scatter diagram generation unit 53, a plot range storage unit 54, and a display control unit 55. The color specifying unit 59 is provided.

  The color specifying unit 59 obtains pixel values at the pixel positions in the water density image Gw and the iodine density image Gio for the pixel positions in the entire area AR of the tomographic image corresponding to the slice SL. Then, when a point corresponding to the obtained pixel value is plotted in the coordinate space Kwi, the color stored in association with the plot range in which the point is plotted is specified as the color for the pixel position. The color specification for such pixel positions is performed for all the pixel positions in the entire area AR. If the plotted point does not belong to any plot range, for example, a predetermined color that is not associated with any plot range is specified as a color for the pixel position.

  In addition, the display control unit 55 in this example uses at least one tomographic image of the water density image Gw, the iodine density image Gio, and the monochrome image Gm based on the color for each pixel position specified by the color specifying unit 58. Color mapping is performed for. That is, with respect to at least one of the water density image Gw, the iodine density image Gio, and the monochromatic image Gm included in the image output screen, the pixel at each pixel position in the entire area AR is set to the pixel position. Colored with the specified color and displayed. In this example, the monochrome image Gm is colored.

Thus, the flow of processing in the X-ray CT apparatus according to the fourth modification will be described.
FIG. 18 is a flowchart showing a flow of processing in the X-ray CT apparatus according to the fourth modification.

  In steps D1 to D5, as in steps S1 to S5 of the first embodiment, dual energy imaging processing, substance density image generation processing, monochrome image generation processing, scatter diagram generation processing, and image display processing are performed.

  In step D6, a color specifying process is performed. That is, the color specifying unit 59 specifies the color for each pixel position in the entire area AR as described above.

  In step D7, a coloring process is performed. That is, as described above, the display control unit 55 displays each pixel of the monochrome image Gm with a color specified for the pixel position of the pixel.

  FIG. 19 is a diagram illustrating an example of an image output screen displayed in the fourth modified example based on the first embodiment. On this image output screen, a scatter diagram Gg1 in which points Dj corresponding to all pixel positions in the entire area of the tomographic image corresponding to the slice SL are plotted is displayed. Further, a water density image Gw and an iodine density image Gio that are not displayed in a color map, and a monochrome image Gm ′ in which the entire region is displayed in a color map are displayed.

  In the fourth modification example based on the second modification example, the color mapping target is limited to the region of interest ROI.

  FIG. 20 is a diagram illustrating an example of an image output screen displayed in a fourth modification based on the second modification. On this image output screen SC, a scatter diagram Gg2 is displayed in which points Dk corresponding to the pixel positions in the region of interest ROI among the tomographic images corresponding to the slice SL are plotted. Further, a water density image Gw and iodine density image Gio that are not displayed in a color map, and a monochrome image Gm ″ in which the region of interest ROI is displayed in a color map are displayed.

  According to such a fourth modified example, the color map display of the entire area of the tomographic image corresponding to the predetermined slice SL of the subject 40 or the area of interest can intuitively grasp the distribution of each substance in the area. Can do.

(5th modification)
The X-ray CT apparatus according to the fifth modification further includes a color storage unit (color storage means) as a component of the operation console based on the fourth modification.

  FIG. 21 is a block diagram schematically showing the configuration of the X-ray CT apparatus according to the fifth modification. As shown in FIG. 21, the operation console 1e of the X-ray CT apparatus 105 according to this example includes a scan control unit 51, an image acquisition unit 52, a scatter diagram generation unit 53, a plot range storage unit 54, a display control unit 55, and a color. In addition to the specifying unit 59, a color storage unit 60 is provided.

  The color storage unit 60 stores colors in association with each combination of values that can be taken as pixel values of pixels corresponding to each other in the water density image Gw and the iodine density image Gio.

  FIG. 22 is a diagram showing an example of a correspondence relationship between the combination of the pixel values and the color, and this correspondence relationship is represented by a color distribution in the coordinate space Kwi. The color is roughly changed for each of the above-mentioned plot ranges, and gradation is applied so that the colors continuously change between the plot ranges and between the plot ranges and the overlapping range.

  Further, the color specifying unit 59 in this example obtains the pixel values of the pixel positions in the water density image Gw and the iodine density image Gio for the pixel positions in the entire area AR in the tomographic image corresponding to the slice SL, and stores the color values. With reference to the correspondence stored in the unit 60, the color stored in association with the obtained combination of pixel values is specified as the color for the pixel position. The color specification for such pixel positions is performed for all the pixel positions in the entire area AR.

  In addition, the display control unit 55 in this example uses at least one tomographic image of the water density image Gw, the iodine density image Gio, and the monochrome image Gm based on the color for each pixel position specified by the color specifying unit 59. Perform color mapping for.

  The image output screen SC displayed in the fifth modified example is similar to the example shown in FIG. 19, but the color near the boundary between the substances changes more smoothly.

  According to the fifth modified example, in the color map display of the tomographic image of the subject 40, the color near the boundary between the substances can be changed smoothly, and the color map display can be made easier to see.

  Further, according to the fifth modified example, an intermediate color between a color corresponding to the substance A and a color corresponding to the substance B is also obtained for a pixel having a combination of pixel values that is likely to be either the substance A or the substance B. Etc. That is, it is possible to indicate in color which pixel is most likely to be a pixel for which it is difficult to clearly identify the substance. Thereby, information useful for substance discrimination and diagnosis in the tomographic image of the subject 40 can be further obtained.

(Sixth Modification)
The X-ray CT apparatus according to the sixth modification further includes a plot point counting unit (plot point counting means) as a component of the operation console based on the first embodiment and the first to fifth modifications. . Here, as an example, a sixth modified example based on the fourth modified example will be described.

  FIG. 23 is a diagram schematically showing a configuration of an operation console of an X-ray CT apparatus according to a sixth modification based on the fourth modification. As shown in FIG. 23, the operation console 1f of the X-ray CT apparatus 106 according to this example includes a scan control unit 51, an image acquisition unit 52, a scatter diagram generation unit 53, a plot range storage unit 54, a display control unit 55, and In addition to the color specifying unit 59, a plot point counting unit 61 is provided.

  The plot point counting unit 61 counts the points plotted for each plot range in the scatter diagram generated by the scatter diagram generation unit 53.

  In addition, the display control unit 55 in this example displays the count result. At this time, the count value may be multiplied by the area in the real space per pixel and displayed as the area ratio of each substance.

  FIG. 24 is a diagram illustrating an example of an image output screen displayed in a sixth modification based on the fourth modification. The count result PN of the plot points for each plot range is displayed on the image output screen SC.

  According to such a sixth modification, the area ratio of each substance in the slice SL of the subject 40 can be grasped from the result of counting the number of plots for each plot range.

(Seventh Modification)
The X-ray CT apparatus according to the seventh modification uses an X-ray tube voltage image instead of the substance density image in the first embodiment and the first to sixth modifications.

  The image acquisition unit 52 in this example generates the first and second X-ray tube voltage images GHV and GLV based on the first and second projection data PHV and PLV, and also generates the monochromatic image Gm. . The first and second X-ray tube voltage images GHV and GLV are two images useful for determination of a substance, like the substance density image. Each of the first and second X-ray tube voltage images GHV and GLV corresponds to the same slice of the subject 40, but the size of the pixel values and the difference or ratio of the pixel values in these two images are different from each other. It depends on the type. Therefore, the substance represented by the pixel can be determined from the combination of the pixel values of the corresponding pixels in the first and second X-ray tube voltage images GHV and GLV and the pixel value itself.

  Further, the scatter diagram generating unit 53 in this example has a coordinate space in which the horizontal axis is the pixel value Hg in the first X-ray tube voltage image GHV and the vertical axis is the pixel value Lg in the second X-ray tube voltage image GLV. The points corresponding to the pixel values of the pixels corresponding to each other for the entire region AR or the region of interest ROI in these two images are plotted on KhL to generate a scatter diagram of pixel values.

  In addition, as shown in FIG. 25, the plot range storage unit 54 in the present example has a plot range and a substance for each substance of iodine (contrast agent), calcium (bone), soft tissue, water, fat, and air. The name and color are stored in association with each other. In this example, the plot range Rio for iodine is a range in which the ratio between the pixel value Hg and the pixel value Lg is a predetermined value rio ± α. The plot range Rc for calcium is a range in which the ratio between the pixel value Hg and the pixel value Lg is a predetermined value rc ± β. Since the range of CT values that can be taken for iodine and calcium overlaps widely, it is difficult to distinguish only from the magnitude of the pixel value, but the ratio between the pixel value Hg and the pixel value Lg is clearly different. Can be determined.

  According to the seventh modified example, it is possible to support substance discrimination in a tomographic image of a subject using an X-ray tube voltage image instead of a substance density image.

(Second Embodiment)
The X-ray CT apparatus according to the first embodiment and its modification has various units (excluding the scan control unit 51) that functionally represent the components of the operation console, and data such as the imaging table 10 and the scan gantry 20 An image display device that does not have a collecting unit is also an embodiment of the present invention. Such an image display apparatus can be realized by causing a computer such as a workstation to execute a predetermined program.

  In this image display device, the image acquisition unit 52 may acquire various images in such a manner that an input of an image already generated based on the projection data collected by the X-ray CT apparatus is received.

(Third embodiment)
A program for causing a computer to function as the above-described image display device is also an embodiment of the present invention.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment and its modification. Forms obtained by freely combining the constituent elements of these embodiments and modifications thereof within the scope of the present invention are also included in the present invention.

  For example, in each of the above-described embodiments and modifications thereof, the target image is a two-dimensional image corresponding to a predetermined slice SL of the subject, but as a three-dimensional image corresponding to a predetermined three-dimensional region of the subject. Also good.

1, 1a to 1f Operation console 2 Input device 3 Central processing unit 5 Data collection buffer 6 Monitor 7 Storage device 10 Imaging table 12 Cradle 15 Rotating unit 16 Supporting unit 20 Scanning gantry 21 X-ray tube 22 X-ray tube controller 23 Collimator 24 X Line detector 25 Data collection device (DAS)
DESCRIPTION OF SYMBOLS 26 Rotation part controller 29 Control controller 30 Slip ring 40 Subject 51 Scan control part 52 Image acquisition part 53 Scatter diagram generation part 54 Plot range memory | storage part 55 Display control part 56 Plot range registration part 57 Region of interest setting part 58 Plot range specification part 59 color identification unit 60 color storage unit 61 plot point counting unit 81 X-ray 100 to 106 X-ray CT apparatus

Claims (13)

First and second projection data based on first projection data of the subject by the first X-ray and second projection data of the subject by the second X-ray having an energy spectrum different from that of the first X-ray. Image acquisition means for acquiring first and second images, each corresponding to a predetermined part of the subject and having a corresponding relationship between a substance and a pixel value;
A predetermined area in the image space corresponding to the predetermined portion in a coordinate space in which one of the horizontal axis and the vertical axis is a pixel value in the first image and the other axis is a pixel value in the second image Generating a diagram in which points corresponding to the pixel values of the first and second images are plotted for each pixel position;
Plot range storage means for storing, for at least one substance, a plot range estimated to indicate a predetermined substance when points corresponding to the pixel values of the first and second images are plotted in the coordinate space; ,
An image display device comprising: display means for displaying the figure and the image representing the plot range in an overlapping manner.   The image display apparatus according to claim 1, further comprising an area setting unit that sets an area designated by an operator in an image space corresponding to the predetermined part as the predetermined area.   The image display device according to claim 1, further comprising a registration unit that stores the range in the coordinate space set by an operator in the plot range storage unit as the plot range.   The first image and the second image are different from each other in an image obtained by image reconstruction processing of the first projection data and an image obtained by image reconstruction processing of the second projection data. The image display device according to any one of claims 1 to 3, wherein the images are two images obtained by weighted subtraction with the first and second weights.   The first and second images include two pieces of projection data obtained by weighting and subtracting the first projection data and the second projection data by different first and second weights, respectively. The image display device according to any one of claims 1 to 3, wherein the images are two images obtained by image reconstruction processing.   The first and second images are two images obtained by performing image reconstruction processing on the first projection data and the second projection data, respectively. The image display device according to item. The plot range storage means stores the plot range and the name of the substance corresponding to the plot range in association with each other,
Of the stored plot ranges, when the points corresponding to the average pixel values of the predetermined region in the first and second images are plotted in the coordinate space, the plot range in which the points are plotted A plot range specifying means for specifying
The display means is further a first image based on the first image, the second image, and a third image based on the first and second projection data, corresponding to the predetermined part, and And at least one third image different from the second image and an image representing the predetermined area are displayed in an overlapping manner, and the name of the substance stored in association with the specified plot range is The image display device according to claim 1, wherein the image display device displays the image in association with the predetermined region. The plot range storage means stores the plot range and the name of the substance corresponding to the plot range in association with each other,
Of the stored plot ranges, when the points corresponding to the pixel values of the first and second images are plotted in the coordinate space for each pixel position of the predetermined region, the number of the points is the largest. A plot range specifying means for specifying a plot range to be plotted;
The display means is further a first image based on the first image, the second image, and a third image based on the first and second projection data, corresponding to the predetermined part, and And at least one third image different from the second image and an image representing the predetermined area are displayed in an overlapping manner, and the name of the substance stored in association with the specified plot range is The image display device according to claim 1, wherein the image display device displays the image in association with the predetermined region. The plot range storage means stores the plot range in association with a color for each plot range,
When the points corresponding to the pixel values of the first and second images for each pixel position are plotted in the coordinate space among the pixel positions of the predetermined area, the points are stored in the plot range. For a predetermined pixel position plotted in any of the above, further comprising a color specifying means for specifying a color stored in association with a plot range in which a point corresponding to the pixel position is plotted;
The display means is further a first image based on the first image, the second image, and a third image based on the first and second projection data, corresponding to the predetermined part, and And at least one third image different from the second image is displayed, and the pixel at the predetermined pixel position in the displayed image is displayed in a color specified for the pixel position. The image display device according to claim 8. Color storage means for storing colors in association with each possible combination of pixel values of corresponding pixels in the first and second images;
A color specifying means for obtaining a combination of pixel values of the first and second images for each pixel position of the predetermined area and specifying a color stored in association with the combination;
The display means is further a first image based on the first image, the second image, and a third image based on the first and second projection data, corresponding to the predetermined part, and And displaying at least one of a third image different from the second image and displaying each pixel of the predetermined area in the displayed image in a color specified for the pixel position of the pixel. The image display device according to claim 8. In the coordinate space, when the points corresponding to the pixel values of the first and second images are plotted for each pixel position in the predetermined region, the number of points plotted in the plot range is determined for each plot range. A plot point counting means for counting;
The image display device according to any one of claims 1 to 10, wherein the display unit further displays the counted number of plot points or a feature amount corresponding to the number for each plot range. An image display device according to any one of claims 1 to 11,
An X-ray CT apparatus comprising: data collection means for irradiating the subject with the first and second X-rays and collecting the first and second projection data.   The program for functioning a computer as an image display apparatus as described in any one of Claims 1-11.

Images