JP2018117779A - X-ray CT apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus capable of setting an optimum spectrum reconfigurable area.SOLUTION: An X-ray CT apparatus includes a calculation part and a control part. The calculation part calculates an output value on energy spectrum from an image of a subject acquired by scanning the subject with an X-ray. The control part predicts a spectrum reconfigurable area corresponding to the subject on the basis of the output value on the energy spectrum, and displays the spectrum reconfigurable area in a display part.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an X-ray CT apparatus.

  In imaging by the X-ray CT apparatus, the amount of X-ray absorption is large and the amount of X-ray photons incident on the detector is small at the center of the subject. For this reason, the energy spectrum of the projection data transmitted through the center of the subject is accurate, and a reconstructed image obtained by accurately discriminating materials can be obtained. On the other hand, X-ray photons incident on the detector increase at the subject edge or a region with little X-ray absorption, and pile-up may occur. As described above, when the energy spectrum of the projection data transmitted through the subject edge or the portion with little X-ray absorption becomes inaccurate, it becomes impossible to obtain a reconstructed image accurately discriminating the substance.

  Further, when the collected projection data includes projection data whose energy spectrum is inaccurate, an image is reconstructed using only projection data in a region where the energy spectrum is accurate. However, there may be a case where a region to be observed is not included in the reconstructed image after shooting. In such a case, re-imaging is required or accurate diagnosis cannot be performed.

US Patent Application Publication No. 2015/117593

  The problem to be solved by the present invention is to provide an X-ray CT apparatus capable of setting an optimum spectrum reconfigurable region.

  The X-ray CT apparatus of the embodiment includes a calculation unit and a control unit. The calculation unit calculates an output value related to an energy spectrum from an image of the subject acquired by scanning the subject with X-rays. The control unit predicts a spectrum reconfigurable region corresponding to the subject based on the output value related to the energy spectrum, and displays the spectrum reconfigurable region on the display unit.

FIG. 1 is a diagram illustrating a configuration example of an X-ray CT apparatus according to the first embodiment. FIG. 2 is a diagram for explaining photographing of a two-dimensional scano. FIG. 3 is a diagram for explaining the shooting condition setting for the main shooting. FIG. 4 is a diagram for explaining the first embodiment. FIG. 5 is a diagram for explaining the first embodiment. FIG. 6 is a diagram for explaining the first embodiment. FIG. 7 is a diagram for explaining the first embodiment. FIG. 8 is a diagram for explaining the first embodiment. FIG. 9 is a flowchart illustrating a procedure of processing for estimating a spectrum reconfigurable region by the X-ray CT apparatus according to the first embodiment. FIG. 10 is a diagram for explaining a modification of the first embodiment. FIG. 11 is a diagram for explaining the second embodiment.

  Hereinafter, an X-ray CT apparatus according to an embodiment will be described with reference to the drawings.

  An X-ray CT apparatus described in the following embodiment is an apparatus capable of performing photon counting CT. That is, the X-ray CT apparatus described in the following embodiment counts X-rays that have passed through the subject using a photon counting type detector instead of a conventional integral type (current mode measurement type) detector. Thus, the X-ray CT image data having a high SN ratio can be reconstructed. In addition, the content described in one embodiment is similarly applied to other embodiments in principle.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of an X-ray CT apparatus according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus according to the first embodiment includes a gantry 10, a bed 20, and a console 30.

  The gantry 10 is a device that irradiates the subject P with X-rays and collects data related to the X-rays transmitted through the subject P. The gantry 10 includes a high voltage generation circuit 11, an X-ray tube 12, a detector 13, and data. The collecting circuit 14, the rotating frame 15, and the gantry driving circuit 16 are included. Further, in the gantry 10, as shown in FIG. 1, an orthogonal coordinate system including an X axis, a Y axis, and a Z axis is defined. That is, the X axis indicates the horizontal direction, the Y axis indicates the vertical direction, and the Z axis indicates the direction of the rotation center axis of the rotating frame 15 when the gantry 10 is not tilted.

  The rotating frame 15 supports the X-ray tube 12 and the detector 13 so as to face each other with the subject P interposed therebetween, and is rotated at a high speed in a circular orbit around the subject P by a gantry driving circuit 16 described later. An annular frame.

  The X-ray tube 12 is a vacuum tube that irradiates the subject P with an X-ray beam by a high voltage supplied by a high voltage generation circuit 11 described later, and the X-ray beam is applied to the subject P as the rotating frame 15 rotates. Irradiate against.

  The high voltage generation circuit 11 is an electric circuit having a function of supplying a high voltage to the X-ray tube 12, and the X-ray tube 12 generates X-rays using the high voltage supplied from the high voltage generation circuit 11. . That is, the high voltage generation circuit 11 adjusts the X-ray dose irradiated to the subject P by adjusting the tube voltage and tube current supplied to the X-ray tube 12. The high voltage generation circuit 11 is controlled by the scan control circuit 33 under the control of the system control circuit 38.

  The gantry driving circuit 16 is an electric circuit having a function of rotating the X-ray tube 12 and the detector 13 on a circular orbit around the subject P by rotating the rotating frame 15. The gantry driving circuit 16 is controlled by the scan control circuit 33 under the control of the system control circuit 38.

  The detector 13 is a photon counting type detector, and a plurality of X-ray detection elements (also referred to as “sensors” or simply “detection elements”) for counting light derived from X-rays transmitted through the subject P. Have For example, the X-ray detection element included in the detector 13 according to the first embodiment is an indirect conversion type surface detector that includes a scintillator and an optical sensor. Here, the optical sensor is, for example, a SiPM (Silicon photomultiplier). Each X-ray detection element of the detector 13 outputs an electrical signal (pulse) corresponding to the incident X-ray photon. The electric signal output by each X-ray detection element is also referred to as a detection signal. That is, the detector 13 has a plurality of detection elements that detect radiation and output detection signals. The peak value of this electric signal (pulse) has a correlation with the energy value of the X-ray photon. The detector 13 may be a direct conversion type surface detector.

  The data collection circuit 14 is an electric circuit having a function of collecting a count result that is a result of a count process using the detection signal of the detector 13. The data collection circuit 14 counts photons (X-ray photons) derived from X-rays irradiated from the X-ray tube 12 and transmitted through the subject P, and collects the results of discriminating the energies of the counted photons as the counting results. To do. Then, the data collection circuit 14 transmits the count result to the console 30. The data acquisition circuit 14 is also referred to as DAS (Data Acquisition System).

  The couch 20 is a device on which the subject P is placed, and includes a couchtop 22 and a couch driving device 21. The couchtop 22 is a plate on which the subject P is placed, and the couch driving device 21 moves the couchtop 22 in the rotary frame 15 by moving the couchtop 22 in the Z-axis direction. The couch driving device 21 can move the top plate 22 also in the X-axis direction.

  For example, the gantry 10 executes a helical scan that rotates the rotating frame 15 while moving the top plate 22 to scan the subject P in a spiral shape. Alternatively, the gantry 10 performs a conventional scan in which the subject P is scanned in a circular orbit by rotating the rotating frame 15 while the position of the subject P is fixed after the top plate 22 is moved. In the following embodiment, a change in the relative position between the gantry 10 and the top plate 22 will be described as being realized by controlling the top plate 22, but the embodiment is not limited to this. For example, when the gantry 10 is self-propelled, a change in the relative position between the gantry 10 and the top plate 22 may be realized by controlling the traveling of the gantry 10.

  The console 30 is a device that accepts the operation of the X-ray CT apparatus by the operator and reconstructs X-ray CT image data using the counting results collected by the gantry 10. As shown in FIG. 1, the console 30 includes an input device 31, a display 32, a scan control circuit 33, a preprocessing circuit 34, a projection data storage circuit 35, an image reconstruction circuit 36, and an image storage circuit 37. And a system control circuit 38.

  The input device 31 includes a mouse, a keyboard, and the like used by the operator of the X-ray CT apparatus to input various instructions and various settings, and transfers the instructions and setting information received from the operator to the system control circuit 38. For example, the input device 31 receives a reconstruction condition when reconstructing the X-ray CT image data, an image processing condition for the X-ray CT image data, and the like from the operator. For example, the input device 31 receives an instruction to perform calibration of the X-ray detection element from the operator. Then, the input device 31 instructs the scan control circuit 33 via the system control circuit 38 to reconstruct the X-ray CT image data and perform calibration.

  The display 32 is a monitor that is referred to by the operator, displays X-ray CT image data to the operator under the control of the system control circuit 38, and provides various instructions and various information from the operator via the input device 31. A GUI (Graphical User Interface) for accepting settings and the like is displayed.

  The scan control circuit 33 controls the operations of the high voltage generation circuit 11, the detector 13, the gantry driving circuit 16, the data collection circuit 14, and the bed driving device 21 under the control of the system control circuit 38 described later. This is an electric circuit having a function of controlling the counting result collection process in the gantry 10. The scan control circuit 33 is, for example, a processor, and realizes a function corresponding to each read program by reading and executing each program. Specifically, the scan control circuit 33 controls projection data collection processing in the photographing for collecting the positioning image (scano image) and the main photographing (scanning) for collecting the image used for diagnosis. Here, the X-ray CT apparatus according to the first embodiment will be described assuming that a two-dimensional scano image (two-dimensional scano) is captured. FIG. 2 is a diagram for explaining photographing of a two-dimensional scano.

  The left figure of FIG. 2 is the figure which looked at CT apparatus from the front (bed 20 side). As shown in the left diagram of FIG. 2, the subject P is disposed on the top plate 22 of the bed 20. Here, for example, when imaging is performed at a position where the X-ray tube 12 is 0 ° (position in the positive direction of the Y axis in the left diagram in FIG. 2 and in the front direction with respect to the subject P), the front of the subject P is captured. The two-dimensional scano as shown in the upper right diagram of FIG. 2 is obtained. In such a case, the scan control circuit 33 captures a two-dimensional scano image by continuously capturing images while fixing the X-ray tube 12a at a 0 degree position and moving the top plate 22 at a constant speed. Alternatively, the scan control circuit 33 fixes the X-ray tube 12a at the 0 degree position and intermittently repeats imaging while synchronizing the movement of the top plate 22 while moving the top plate 22 intermittently. Shoot a 2D scano.

  Further, the scan control circuit 33 can capture a positioning image not only from the front direction but also from an arbitrary direction (for example, a side surface direction) with respect to the subject. For example, when the X-ray tube 12 is imaged at a position of 90 ° (position in the positive direction of the X axis in the left diagram of FIG. 2 and in the lateral direction with respect to the subject P), imaging from the side surface of the subject P is performed. As a result, a two-dimensional scano as shown in the lower right diagram of FIG. 2 is obtained. Note that the position of the X-ray tube 12a can be taken from a plurality of arbitrary positions if necessary.

  The pre-processing circuit 34 performs correction processing such as logarithmic conversion processing, offset correction, sensitivity correction, and beam hardening correction on the count result transmitted from the data collection circuit 14, thereby projecting projection data for each energy discrimination region. Is an electric circuit having a function of generating Further, the preprocessing circuit 34 outputs the counting result transmitted from the data collection circuit 14 to the system control circuit 38 in accordance with an instruction from the system control circuit 38. The preprocessing circuit 34 is, for example, a processor, and realizes a function corresponding to each read program by reading and executing each program.

  The projection data storage circuit 35 is, for example, a NAND (Not AND) type flash memory or an HDD (Hard Disk Drive), and stores the projection data generated by the preprocessing circuit 34. That is, the projection data storage circuit 35 stores projection data for reconstructing X-ray CT image data. The image storage circuit 37 is, for example, a NAND flash memory or an HDD, and stores various image data.

  The image reconstruction circuit 36 is an electric circuit having a function of reconstructing a CT image based on the detection signal of the detector 13. The image reconstruction circuit 36 is a processor, for example, and realizes a function corresponding to each read program by reading and executing each program. That is, the image reconstruction circuit 36 reconstructs X-ray CT image data by performing, for example, back projection processing on the projection data stored in the projection data storage circuit 35. As the back projection process, for example, a back projection process by an FBP (Filtered Back Projection) method can be cited. Note that the image reconstruction circuit 36 may perform reconstruction processing by, for example, a successive approximation method. Further, the image reconstruction circuit 36 generates image data by performing various image processing on the X-ray CT image data. The image reconstruction circuit 36 stores the reconstructed X-ray CT image data and image data generated by various image processes in the image storage circuit 37.

  Here, the projection data generated from the counting result obtained by the photon counting CT includes information on the energy of X-rays attenuated by passing through the subject P. For this reason, the image reconstruction circuit 36 can reconstruct X-ray CT image data of a specific energy component, for example. Further, the image reconstruction circuit 36 can reconstruct X-ray CT image data of each of a plurality of energy components, for example.

  The image reconstruction circuit 36 assigns a color tone corresponding to the energy component to each pixel of the X-ray CT image data of each energy component, for example, and superimposes a plurality of X-ray CT image data color-coded according to the energy component. Image data can be generated. The image reconstruction circuit 36 can generate image data that enables identification of the substance by using, for example, a K absorption edge unique to the substance. Other image data generated by the image reconstruction circuit 36 includes monochromatic X-ray image data, density image data, effective atomic number image data, and the like.

  The system control circuit 38 is an electric circuit having a function of performing overall control of the X-ray CT apparatus by controlling the operations of the gantry 10, the bed 20, and the console 30. Specifically, the system control circuit 38 controls the CT scan performed on the gantry 10 by controlling the scan control circuit 33. Further, the system control circuit 38 controls the pre-processing circuit 34 and the image reconstruction circuit 36 to control image reconstruction processing and image generation processing in the console 30. The system control circuit 38 controls the display 32 to display various image data stored in the image storage circuit 37.

  Further, as shown in FIG. 1, the system control circuit 38 according to the first embodiment executes a calculation function 38a, a control function 38b, and a reception function 38c. Here, for example, each processing function executed by the calculation function 38a, the control function 38b, and the reception function 38c, which are constituent elements of the system control circuit 38 shown in FIG. 1, is controlled in the form of a program executable by a computer. It is recorded in the circuit 38. The system control circuit 38 is, for example, a processor, and realizes a function corresponding to each read program by reading and executing each program. In other words, the system control circuit 38 in a state where each program is read has each function shown in the system control circuit 38 of FIG. The calculation function 38a is an example of a calculation unit, the control function 38b is an example of a control unit, and the reception function 38c is an example of a reception unit. Details of the calculation function 38a, the control function 38b, and the reception function 38c will be described later.

  The overall configuration of the X-ray CT apparatus according to the first embodiment has been described above. Under such a configuration, the X-ray CT apparatus according to the first embodiment reconstructs X-ray CT image data using a photon counting detector.

  Here, the X-ray CT apparatus performs main imaging under imaging conditions set using a scanogram, for example. FIG. 3 is a diagram for explaining the shooting condition setting for the main shooting. FIG. 3 shows a case where the display 32 is divided into a display area 32a and a display area 32c. In the display area 32a of FIG. 3, a two-dimensional scan taken by the X-ray tube 12 at a position of 0 ° is shown. Here, when the operator selects the target cross section 32b on the two-dimensional scano, the X-ray CT apparatus includes a reconstruction area 32d that is a scan FOV (Field of View) in the display area 32c and a scan condition. Display parameters. In the example shown in FIG. 3, the X-ray CT apparatus displays tube voltage x (kV), tube current y (mA), and rotation speed z (R / s) as scan condition parameters.

  By the way, in photon counting CT, the amount of X-rays is measured by counting the number of photons. The more photons per unit time, the stronger the X-rays. In addition, although individual photons have different energies, in photon counting CT, it is possible to obtain information on energy components of X-rays by measuring photon energy. That is, in photon counting CT, data collected by irradiating X-rays with one type of tube voltage can be divided into a plurality of energy components and imaged. For example, in photon counting CT, image data that enables identification of a substance using the difference in the K absorption edge is obtained.

  Here, in the center of the subject, the amount of X-ray absorption is large, and the number of X-ray photons incident on the detector is small. For this reason, the energy spectrum of the projection data transmitted through the center of the subject is accurate, and a reconstructed image obtained by accurately discriminating materials can be obtained. On the other hand, X-ray photons incident on the detector increase at the subject edge or a region with little X-ray absorption, and pile-up may occur. Here, pile-up is a phenomenon in which photons are counted off because the photons are not counted in time at the high count rate. As described above, when the energy spectrum of the projection data transmitted through the subject edge or the portion with little X-ray absorption becomes inaccurate, it becomes impossible to obtain a reconstructed image accurately discriminating the substance.

  Further, when the collected projection data includes projection data whose energy spectrum is inaccurate, an image is reconstructed using only projection data in a region where the energy spectrum is accurate. However, there may be a case where a region to be observed is not included in the reconstructed image after shooting. In such a case, re-imaging is required or accurate diagnosis cannot be performed.

  Therefore, the X-ray CT apparatus according to the first embodiment performs a process of estimating the spectrum reconfigurable region in order to allow the operator to grasp the spectrum reconfigurable region before the main scan. To do. For example, the X-ray CT apparatus calculates an output value related to an energy spectrum from an image of the subject acquired by scanning the subject with X-rays. Then, the X-ray CT apparatus predicts a spectrum reconfigurable region corresponding to the subject based on the output value relating to the energy spectrum, and displays the spectrum reconfigurable region on the display 32. Hereinafter, the operation of the process of estimating the spectrum reconfigurable region according to the first embodiment will be described in detail with reference to FIGS. 4 to 8. 4 to 8 are diagrams for explaining the first embodiment. In the following description, it is assumed that the cross section of interest 32b shown in FIG. 3 is selected in the two-dimensional scano.

  The calculation function 38a calculates an output value related to an energy spectrum from an image of the subject acquired by scanning the subject with X-rays. For example, the calculation function 38 a instructs the preprocessing circuit 34 to acquire a two-dimensional scano from the preprocessing circuit 34. Here, the calculation function 38a acquires a two-dimensional scano from at least one direction as an image. For example, the calculation function 38a acquires a two-dimensional scano imaged at a position of 0 ° by the X-ray tube 12 and a two-dimensional scano imaged at a position of 90 ° by the X-ray tube 12. The calculation function 38a may acquire a two-dimensional scano from one direction. For example, the calculation function 38a acquires a two-dimensional scano imaged by the X-ray tube 12 at a position of 0 °. Alternatively, the calculation function 38a acquires a two-dimensional scan taken by the X-ray tube 12 at a 90 ° position. In addition, the calculation function 38a may acquire a two-dimensional scano imaged by the X-ray tube 12 at an arbitrary position.

  Subsequently, the calculation function 38a calculates an output value in the image for each view. For example, the calculation function 38a calculates an output value related to the energy spectrum from the two-dimensional scano. The upper diagram of FIG. 4 shows the output value according to the incident dose. Here, when the incident dose shown in the upper diagram of FIG. 4 is A1, for example, an X-ray spectrum S1 shown in the lower left diagram of FIG. 4 is obtained. When the incident dose shown in the upper diagram of FIG. 4 is A2, for example, the X-ray spectrum S2 shown in the lower right diagram of FIG. 4 is obtained. The calculation function 38a calculates the output value in the image for each view from each X-ray spectrum. Note that there may be a case where a scan condition at the time of two-dimensional scan imaging is set such that the X-ray irradiation amount is lower than the scan condition of the main scan. Therefore, the calculation function 38a estimates the X-ray spectrum in the scan condition of the main scan using the scan condition and the X-ray spectrum at the time of imaging of the two-dimensional scano, and calculates the output value. For example, the calculation function 38a estimates and outputs an X-ray spectrum at a position where the X-ray tube 12 is 0 ° in the scan conditions of the main scan from a two-dimensional scan image obtained by the X-ray tube 12 at a position of 0 °. Calculate the value. In addition, the calculation function 38a estimates the X-ray spectrum at the position of 90 ° of the X-ray tube 12 under the scanning conditions of the main scan from the two-dimensional scan taken by the X-ray tube 12 at the position of 90 °, and outputs it. Calculate the value.

  Here, the output value is defined as follows. Here, for convenience of explanation, a case will be described in which an output value is calculated with the tube voltage under the scanning conditions of the main scan being 120 kVp and the count of each energy bin being Ci (i = 1 to 120 keV).

  For example, the calculation function 38a calculates the total output value of each energy bin count as an output value. In such a case, the output value is expressed by the following equation (1).

  Further, for example, the calculation function 38a may calculate the pile-up count value of the count of each piled up energy bin as the output value. In such a case, the output value is expressed by the following equation (2).

  Further, for example, the calculation function 38a may calculate an energy integrated value obtained from the count value of energy bins and the representative value as an output value. In this case, for example, when the median value of the energy bin is Ei, the output value is expressed by the following formula (3).

  Further, for example, the calculation function 38a may calculate a pile-up energy integrated value of a representative value of the piled-up energy bin as an output value. In this case, for example, when the median value of the energy bin is Ei, the output value is expressed by the following formula (4).

  An example of output value calculation processing by the calculation function 38a will be described with reference to FIG. FIG. 5 illustrates a case where the output values at the position P1 and the position P2 in the reconstruction area 32d are calculated using a two-dimensional scano imaged by the X-ray tube 12 at a position of 0 °. The position P2 corresponds to a pixel at the subject edge, and the position P1 is a substantially intermediate position between the subject edge and the subject center and corresponds to a pixel at the subject center.

  As shown in FIG. 5, the calculation function 38a acquires the X-ray spectrum S11 at the position P1, and acquires the X-ray spectrum S21 at the position P2. Since X-ray absorption is large in the subject center, the X-ray spectrum 11 at the position P1 corresponding to the subject center does not include an energy count exceeding 120 keV. In addition, since X-ray absorption is small at the subject edge, the X-ray spectrum 21 at the position P2 corresponding to the subject edge includes an energy count exceeding 120 keV. That is, at position P2, X-ray photons with an energy exceeding 120 keV originally do not exist, but an energy count exceeding 120 keV is artificially counted by pileup.

  And the calculation function 38a calculates the output value in an image for every view from each acquired X-ray spectrum. In addition, although FIG. 5 demonstrated the case where the X-ray spectrum was acquired only about the position P1 and the position P2, and the output value was calculated, the calculation function 38a calculates the X-ray spectrum of all the positions in the reconstruction area | region 32d. Obtain and calculate the output value.

  Then, the calculation function 38a calculates output values in all views from the calculated output values for each image. Here, for example, the calculation function 38a is acquired when acquiring a two-dimensional scano imaged at a position of 0 ° by the X-ray tube 12 and a two-dimensional scano imaged at a position of 90 ° by the X-ray tube 12. From the two-dimensional scano, the output value at the position where the X-ray tube 12 is 0 ° and the output value at the position where the X-ray tube 12 is 90 ° are calculated. In addition, the calculation function 38a utilizes the fact that the axial surface of the human body can be approximated to an elliptical shape, and based on the acquired two-dimensional scano, the X-ray tube 12 has a position other than the 0 ° position and the X-ray tube 12 other than the 90 ° position. Guess the output value. The vertical axis in FIG. 6 indicates the output value, and the horizontal axis in FIG. 6 indicates the view direction. FIG. 6 shows output values in all views calculated for the position P1 and the position P2 shown in FIG.

  For example, as shown in FIG. 6, the calculation function 38 a estimates an output value in a view other than the acquired two-dimensional scano using the fact that the human body is an ellipse, and outputs the estimated view in the other view. Plot values in view direction. More specifically, the calculation function 38a generates a graph 12 indicating the output values in all the views at the position P1, and generates a graph 22 indicating the output values in all the views at the position P2. Note that the calculation function 38a uses a count rate (output value per unit time), a pile-up over value (pile-up count value per unit time), or the like as an output value. Note that the calculation function 38a may adjust the estimated output value according to the body shape of the subject P.

  The control function 38b predicts a spectrum reconfigurable region corresponding to the subject based on the output value related to the energy spectrum. As an example, when the graph shown in FIG. 6 is generated by the calculation function 38a, the control function 38b uses the output value Th as a threshold value as shown in FIG. Here, for example, when the tube voltage is 120 kVp, there should theoretically be no photons with energy exceeding 120 keV. For this reason, an area exceeding 120 keV may be considered as pileup, and 120 keV may be set as a threshold value. Alternatively, a threshold value equal to or higher than a predetermined count rate may be set from the time constant of the circuit.

  Then, the control function 38b predicts, as a spectrum reconfigurable region, a region in which output values in all views are equal to or smaller than a predetermined threshold among the reconstructed regions. For example, as shown in the graph 12 of FIG. 6, the control function 38b predicts the position P1 as a spectrum reconfigurable region because the output value at the position P1 is equal to or smaller than the threshold value in all view directions. Further, as shown in the graph 22 of FIG. 6, the control function 38b predicts the position P2 not to be a spectrum reconfigurable region because the output value at the position P2 is not less than or equal to the threshold value in all view directions. The control function 38b determines whether or not the output value is less than or equal to the threshold value for the projection data of all views at each position (pixel) other than the position P1 and the position P2.

  In general, the count rate is low at the center of the scan FOV, and the count rate is higher at the outer edge of the scan FOV. For this reason, for example, the control function 38b may divide the scan FOV region into a central region and an outer edge region, and focus on the region with an inaccurate energy spectrum such as pileup in the outer edge region. For example, the control function 38b may draw a concentric circle from the center of the scan FOV and use an arbitrary position on the concentric circle as a representative point, and determine whether the output value at this representative point is equal to or less than a threshold value. . When the output value exceeds a threshold value at a certain position, the control function 38b predicts the outside of the concentric circle including this position as a region in which spectrum is not reconstructed. In this case, the calculation function 38a may calculate the output value by acquiring the X-ray spectrum from only the representative point without calculating the output value from all positions.

  Then, the control function 38b displays the spectrum reconfigurable region on the display 32. In FIG. 7, only one display area 32c when the display 32 is divided into a plurality of display areas is shown for convenience of explanation. Further, FIG. 7 shows a reconstruction area 32d and a spectrum reconfigurable area 32e for the cross section of interest selected in, for example, the two-dimensional scano. In the left diagram of FIG. 7, the reconstruction area 32d and the spectrum reconfigurable area 32e coincide. For example, when the control function 38b predicts that the output value in all views is equal to or less than a predetermined threshold value in all areas of the reconstruction area 32d, it matches the reconstruction area 32d as shown in the left diagram of FIG. The spectrum reconfigurable area 32e to be displayed is displayed on the display area 32c of the display 32.

  In the right diagram of FIG. 7, a part of the reconstruction area 32d is a spectrum reconfigurable area 32e. For example, when the control function 38b predicts that the output values in all the views are equal to or less than a predetermined threshold in a part of the reconstruction area 32d, as illustrated in the right diagram of FIG. 7, the reconstruction area 32d A spectrally reconfigurable region 32e, which is a partial region, is displayed on the display 32.

  The reception function 38c receives a setting for the predicted spectrum reconfigurable region from the operator. Here, the reception function 38c receives at least one of an operation for determining the spectrum reconfigurable region and an operation for changing the spectrum reconfigurable region as the setting for the predicted spectrum reconfigurable region.

  FIG. 8 shows a case where the display 32 is divided into a display area 32a and a display area 32c. A display area 32a in FIG. 8 shows a two-dimensional scan taken by the X-ray tube 12 at a position of 0 °. FIG. 8 illustrates a case where the attention cross section 32b is selected on the two-dimensional scan by the operator. In this case, the display area 32c of the display 32 displays the reconstruction area 32d, the spectrum reconfigurable area 32e, and the parameters of the scanning conditions. In the example of FIG. 8, the tube voltage x (kV), the tube current y (mA), and the rotation speed z (R / s) are displayed as the scan condition parameters. Further, as shown in FIG. 8, a determination button 32 f is displayed in the display area 32 c of the display 32.

  Here, for example, the operator refers to the reconfigurable region 32d and the spectrum reconfigurable region 32e shown in FIG. 8 and confirms whether or not the region to be observed is included in the spectrum reconfigurable region 32e. If the operator determines that the region to be observed is included in the spectrum reconfigurable region 32e, the operator selects the determination button 32f. When the selection of the determination button 32f is received, the reception function 38c determines that an operation for determining a spectrum reconfigurable region has been received. As a result, the conditions for the main scan are determined.

  The operator accepts an operation for changing the spectrum reconfigurable region 32e. For example, when it is determined that the region to be observed is not included in the spectrum reconfigurable region 32e, the operator performs an operation of changing the spectrum reconfigurable region 32e. More specifically, when the operator determines that the spectrum reconfigurable region 32e shown in FIG. 8 is too small to include the region to be observed, the boundary line of the spectrum reconfigurable region 32e in the display region 32c. And the operation of expanding the spectrum reconfigurable region 32e is performed. In this way, the reception function 38c receives a setting for expanding the spectrum reconfigurable region from the operator.

  On the other hand, even if a part of the reconstruction region 32d is the spectrum reconfigurable region 32e, the predicted spectrum reconfigurable region 32e is wide when the purpose is to observe a small region such as the heart. It may be too much. In such a case, the operator selects the boundary line of the spectrum reconfigurable region 32e in the display region 32c, and performs an operation of reducing the spectrum reconfigurable region 32e. In this way, the reception function 38b receives a setting for reducing the spectrum reconfigurable region from the operator.

  And the control function 38b sets the parameter of the scanning condition according to the change of the spectrum reconfigurable area 32e. In other words, the control function 38b sets parameters for newly scanning the set spectrum reconfigurable region 32e, and displays the set parameters on the display 32. For example, the control function 38b sets a parameter in which the X-ray irradiation amount per unit time is reduced according to the expansion of the spectrum reconfigurable region, and the X-ray per unit time according to the reduction of the spectrum reconfigurable region. Set parameters with increased dose.

  More specifically, when the spectrum reconfigurable region is expanded, the control function 38b slows the gantry rotation speed and sets the tube current low. Further, when the spectrum reconfigurable region is reduced, the control function 38b increases the gantry rotation speed and sets the tube current high. Of the scanning condition parameters, a parameter to be changed may be designated in advance, or a parameter for preferentially fixing the set value may be designated in advance. For example, the control function 38b is set to increase the gantry rotation speed as a scanning condition suitable for an organ having movement such as the heart. In addition, scan condition parameters corresponding to the scan target may be stored as presets.

  The reception function 38c has been described as receiving a change in the spectrum reconfigurable region 32e, but the embodiment is not limited to this. For example, the reception function 38c may receive a parameter change. More specifically, the reception function 38c may receive an operation for changing any numerical value of the tube voltage x (kV), the tube current y (mA), and the rotation speed z (R / s). In such a case, the calculation function 38a calculates output values in all views based on the changed scan condition parameters. For example, the calculation function 38a estimates an X-ray spectrum in each view based on the changed scan condition parameter, and calculates an output value. Then, the control function 38b predicts the spectrum reconfigurable region corresponding to the subject based on the output value related to the energy spectrum, and displays it on the display 32. That is, the control function 38b displays the spectrum reconfigurable region changed according to the change of the parameter on the display 32.

  Next, the procedure of the process of estimating the spectrum reconfigurable region by the X-ray CT apparatus according to the first embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating a procedure of processing for estimating a spectrum reconfigurable region by the X-ray CT apparatus according to the first embodiment. Steps S101 and S102 are steps corresponding to the calculation function 38a. When the system control circuit 38 calls and executes a predetermined program recorded in the system control circuit 38, the calculation function 38a is realized. In step S101, the calculation function 38a acquires a two-dimensional scano. For example, the calculation function 38a acquires a two-dimensional scano imaged at a position of 0 ° by the X-ray tube 12 and a two-dimensional scano imaged at a position of 90 ° by the X-ray tube 12.

  In step S102, the calculation function 38a calculates an output value related to the energy spectrum from the two-dimensional scano. For example, the calculation function 38a calculates an output value in an image for each view from each X-ray spectrum.

  Steps S103 and S104 and steps S107 and S108 are steps corresponding to the control function 38b. The system control circuit 38 calls and executes a predetermined program recorded in the system control circuit 38, thereby realizing the control function 38b. In step S103, the control function 38b predicts a spectrum reconfigurable region. For example, the control function 38b predicts, as a spectrum reconfigurable region, a region in which output values in all views are equal to or smaller than a predetermined threshold among the reconstructed regions.

  In step S104, the control function 38b displays the spectrum reconfigurable region on the display 32. For example, the control function 38b displays the reconstruction area, the spectrum reconfigurable area, and the scan condition parameters on the display 32.

  Steps S105 and S106 are steps corresponding to the reception function 38c. The system control circuit 38 calls and executes a predetermined program recorded in the system control circuit 38, thereby realizing the reception function 38c. In step S105, the reception function 38c determines whether an operation for determining a spectrum reconfigurable region has been received. For example, the reception function 38c determines that an operation for determining the spectrum reconfigurable region has been received when an operation for selecting the determination button 32f illustrated in FIG. 8 is received from the operator. Here, when the reception function 38c determines that an operation for determining a spectrum reconfigurable region has been received (step S105, Yes), the process ends.

  On the other hand, if the reception function 38c does not determine that an operation for determining a spectrum reconfigurable region has been received (No in step S105), the reception function 38c proceeds to step S106. In step S106, the reception function 38c determines whether an operation for changing the spectrum reconfigurable region has been received. For example, when an operation for changing the spectrum reconfigurable region 32e illustrated in FIG. 8 is received from the operator, the reception function 38c determines that an operation for changing the spectrum reconfigurable region has been received. Here, if the reception function 38c does not determine that an operation for changing the spectrum reconfigurable region has been received (step S106, No), the process proceeds to step S105, and an operation for determining the spectrum reconfigurable region is received. It is continuously determined whether or not.

  On the other hand, if the reception function 38c determines that an operation for changing the spectrum reconfigurable region has been received (step S106, Yes), the processing proceeds to step S107. In step S107, the control function 38b sets parameters for scan conditions according to the changed spectrum reconfigurable region. For example, the control function 38b sets a parameter in which the X-ray irradiation amount per unit time is reduced according to the expansion of the spectrum reconfigurable region, and the X-ray per unit time according to the reduction of the spectrum reconfigurable region. Set parameters with increased dose.

  In step S <b> 108, the control function 38 b displays the changed spectrum reconfigurable region and the changed scan condition parameters on the display 32. For example, the control function 38b displays the reconstruction area, the changed spectrum reconfigurable area, and the changed scanning condition parameters on the display 32. After completion of step S108, the process proceeds to step S105, and the reception function 38c determines whether an operation for determining a spectrum reconfigurable region has been received.

  As described above, the X-ray CT apparatus according to the first embodiment calculates an output value related to an energy spectrum from an image of the subject acquired by scanning the subject with X-rays. The X-ray CT apparatus according to the first embodiment predicts a spectrum reconfigurable region corresponding to the subject based on the output value related to the energy spectrum, and displays the spectrum reconfigurable region on the display 32.

  That is, in the first embodiment, an area where the output value of the energy spectrum is equal to or greater than the threshold is estimated by scanography performed prior to the main scan, and an area where the material discrimination image can be reconstructed is displayed on the scan FOV. indicate. Thereby, according to 1st Embodiment, the operator can grasp | ascertain a spectrum reconfigurable area | region before performing this scan, for example.

  If the spectrum reconfigurable region does not cover the range intended by the operator, the operator adjusts the scanning conditions so that the intended range is included. For example, the operator performs an operation for expanding or reducing the spectrum reconfigurable region. In such a case, the X-ray CT apparatus according to the first embodiment can set a scan condition parameter in which the amount of X-ray irradiation per unit time is reduced in accordance with the expansion of the spectrum reconfigurable region, and the spectrum can be reconstructed. A scan condition parameter in which the amount of X-ray irradiation per unit time is increased in accordance with the reduction of the area is set.

  As a result, according to the first embodiment, an optimal spectrum reconfigurable region can be set. In addition, according to the first embodiment, it is possible to set an optimal spectrum reconfigurable region before executing the main scan, thereby reducing re-imaging. Moreover, the image reconstruction circuit 36 can generate a highly accurate spectrum reconstructed image by setting the optimum spectrum reconfigurable region and executing the main scan. As a result, according to the first embodiment, an accurate diagnosis can be performed. The spectrum reconstruction image is, for example, a material discrimination image, a monochromatic X-ray image, or the like.

  Further, the image reconstruction circuit 36 generates a reconstructed image with an energy integration value for regions other than the spectrum reconfigurable region in the scan FOV. In this way, the image reconstruction circuit 36 can improve the reconstruction processing speed.

(Modification of the first embodiment)
In the first embodiment described above, a case has been described in which a candidate region capable of spectrum reconstruction is predicted using one threshold value, but the embodiment is not limited to this. For example, a candidate region capable of spectrum reconstruction may be predicted using a plurality of threshold values. Here, a case where two threshold values, the first threshold value and the second threshold value are used, will be described.

  The first threshold value is the threshold value described in the first embodiment. That is, the first threshold value is used when the output value is predicted to be a spectrum reconfigurable region. A value larger than the first threshold is set as the second threshold. This second threshold value is used when predicting a candidate region in which spectrum reconstruction is possible by correcting the output value. Then, for example, the control function 38b further predicts candidate regions that can be reconstructed by correcting the output value, and further displays the predicted candidate regions on the display 32. FIG. 10 is a diagram for explaining a modification of the first embodiment.

  In FIG. 10, only one display area 32c when the display 32 is divided into a plurality of display areas is shown for convenience of explanation. FIG. 10 shows a reconstruction area 32d, a spectrum reconfigurable area 32e, and a candidate area 32g with respect to the cross section of interest selected in, for example, the two-dimensional scano.

  In FIG. 10, a part of the reconstruction area 32d is a spectrum reconfigurable area 32e. For example, the control function 38b predicts, as shown in FIG. 10, a region where the output values in all views are equal to or less than the first threshold in the reconstruction region 32d as a spectrum reconfigurable region 32e. Further, the control function 38b predicts, as a candidate area 32g, an area in which the output value in all views is not less than or equal to the first threshold value but is less than or equal to the second threshold value in the reconstruction area 32d.

  As described above, in the modified example of the first embodiment, in addition to the spectrum reconfigurable region, candidate regions that can be reconstructed by setting the output value are set. Thereby, according to the modification of the first embodiment, it is possible to set the spectrum reconfigurable region in a wider range before executing the main scan. As a result, it is possible to generate a spectrum reconstructed image even when scanning a wide area.

(Second Embodiment)
The control function 38b predicts a plurality of spectrum reconfigurable regions, sets parameters of scan conditions when newly scanning each spectrum reconfigurable region, and predicts each spectrum reconfigurable region and each spectrum reconfigurable region. You may make it display the parameter of the scanning condition corresponding to a possible area | region on the display 32. FIG.

  FIG. 11 is a diagram for explaining the second embodiment. FIG. 11 illustrates a case where three combinations of the spectrum reconfigurable region and the scan condition parameters corresponding to each spectrum reconfigurable region are displayed on the display 32 in a predetermined order. For example, when a plurality of spectrum reconfigurable regions are predicted, the control function 38b first displays the combinations shown in the upper diagram of FIG. In FIG. 11, only one display area 32 c when the display 32 is divided into a plurality of display areas is shown for convenience of explanation. In FIG. 11, a display area 32c of the display 32 displays a reconstruction area 32d, a spectrum reconfigurable area 32e, a scan condition parameter, a determination button 32f, and a switching button 32h. Note that the reconstruction area 32d shown in FIG. 11 is a cross section of interest selected in, for example, the two-dimensional scano.

  The spectrum reconfigurable region 32e shown in the upper diagram of FIG. 11 has the smallest region among the three combinations. Here, when the operator selects the switching button 32f, the reception function 38c receives a setting for changing the spectrum reconfigurable region from the operator. The control function 38b displays, for example, the combination shown in the middle diagram of FIG.

  The spectrum reconfigurable region 32e shown in the middle diagram of FIG. 11 is larger than the spectrum reconfigurable region 32e shown in the upper diagram of FIG. Here, when the operator selects the switching button 32f, the reception function 38c receives a setting for changing the spectrum reconfigurable region from the operator. Then, the control function 38b displays, for example, the combination shown in the lower diagram of FIG.

  The spectrum reconfigurable region 32e shown in the lower diagram of FIG. 11 has the largest region among the three combinations. Here, when the operator selects the switching button 32f, the reception function 38c receives a setting for changing the spectrum reconfigurable region from the operator. The control function 38b displays, for example, the combination shown in the upper diagram of FIG. In FIG. 11, when the operator selects the determination button 32f, the reception function 38c determines that an operation for determining the spectrum reconfigurable region has been received.

  In this way, in the second embodiment, a plurality of spectrum reconfigurable regions are predicted, and combinations of scan condition parameters corresponding to each spectrum reconfigurable region and each spectrum reconfigurable region are predetermined on the display 32. Display in the order. As a result, the operator can grasp a plurality of spectrum reconfigurable regions before executing the main scan. As a result, according to the second embodiment, the operator can select a spectrum reconfigurable region suitable for diagnosis from a plurality of combinations. In addition, according to the second embodiment, it is possible to set an optimal spectrum reconfigurable region before executing the main scan, thereby reducing re-imaging. Moreover, the image reconstruction circuit 36 can generate a highly accurate spectrum reconstructed image by setting the optimum spectrum reconfigurable region and executing the main scan. As a result, according to the second embodiment, an accurate diagnosis can be performed.

  In the second embodiment, the case has been described in which three combinations of the spectrum reconfigurable region and the scan condition parameters corresponding to each spectrum reconfigurable region are displayed on the display 32 in a predetermined order. The form is not limited to this. For example, the control function 38b may display three combinations on the display 32 in parallel. In addition, when the three combinations are displayed in parallel on the display 32, the control function 38b may display each combination by changing the color, or highlight the recommended combination from the three combinations. It may be. Further, the number of combinations to be displayed is not limited to three and can be arbitrarily set.

  In the second embodiment, the reception function 38c may receive a setting for expanding or reducing the spectrum reconfigurable region from the operator, as in the first embodiment. Then, the control function 38b accepts a setting for expanding or reducing the spectrum reconfigurable region from the operator.

(Other embodiments)
The embodiment is not limited to the above-described embodiment.

  In the above-described embodiment, the control function 38b has been described as a region in which the output values in all the views are equal to or less than the predetermined threshold among the reconstruction regions, and is predicted to be a spectrum reconfigurable region. It is not limited to this. For example, the control function 38b predicts, as a spectrum reconfigurable region, a region in which the output value in a view in a range in which half reconstruction is possible among the reconstruction regions is a predetermined threshold value or less.

  In the above-described embodiment, the calculation function 38a has been described as acquiring a two-dimensional scano from at least one direction as an image, but the embodiment is not limited to this. For example, the calculation function 38a may acquire an image obtained by a main scan executed in the past as an image. In such a case, the calculation function 38a calculates an actual measurement value of the projection data as an output value.

  Further, in the above-described embodiment, the X-ray CT apparatus has been described as capturing a two-dimensional scano. However, for example, when a three-dimensional scan image (three-dimensional scano) is captured in the X-ray CT apparatus, the calculation is performed. The function 38a may acquire a three-dimensional scano as an image. In such a case, the scan control circuit 33 captures a three-dimensional scanogram by collecting projection data for the entire circumference of the subject in scanogram capture. For example, the scan control circuit 33 collects projection data for the entire circumference of the subject by helical scanning or non-helical scanning. Here, the scan control circuit 33 executes a helical scan or a non-helical scan with a lower dose than the main imaging over a wide range such as the entire chest, abdomen, the entire upper body, and the whole body of the subject. As the non-helical scan, for example, the above-described step-and-shoot scan is executed. In this manner, the scan control circuit 33 collects projection data for the entire circumference of the subject, so that the image reconstruction circuit 36 can reconstruct the three-dimensional X-ray CT image data (volume data). The positioning image can be generated from an arbitrary direction using the reconstructed volume data. Whether the positioning image is captured in two dimensions or in three dimensions may be set arbitrarily by the operator, or may be set in advance according to the inspection content.

  Further, the functions of the calculation function 38a, the control function 38b, and the reception function 38c described in the above-described embodiment can be realized by software. For example, the functions of the calculation function 38a, the control function 38b, and the reception function 38c are spectrum reconfigurable regions that define the processing procedures described as being performed by the calculation function 38a, the control function 38b, and the reception function 38c in the above embodiment. This is realized by causing the computer to execute the estimation program. The spectrum reconfigurable region estimation program is stored in, for example, a hard disk or a semiconductor memory device, and is read and executed by a processor such as a CPU or MPU. The spectrum reconfigurable region estimation program is recorded on a computer-readable recording medium such as a CD-ROM (Compact Disc-Read Only Memory), MO (Magnetic Optical disk), DVD (Digital Versatile Disc), Can be distributed.

  The term “processor” used in the above description is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), a programmable logic device (for example, It means circuits such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA). The processor implements a function by reading and executing a program incorporated in the processor circuit. Instead of incorporating the program into the processor circuit, the program may be stored in a storage circuit included in the console 30. In this case, the processor realizes the function by reading and executing the program stored in the storage circuit. Note that each processor of the present embodiment is not limited to being configured as a single circuit for each processor, but may be configured as a single processor by combining a plurality of independent circuits to realize the function. Good. Furthermore, a plurality of components in FIG. 1 may be integrated into one processor to realize the function.

  In the description of the above embodiment, each component of each illustrated apparatus is functionally conceptual and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or a part of the distribution / integration is functionally or physically distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Further, all or a part of each processing function performed in each device may be realized by a CPU and a program that is analyzed and executed by the CPU, or may be realized as hardware by wired logic.

  Moreover, the control method demonstrated by said embodiment is realizable by executing the control program prepared beforehand by computers, such as a personal computer and a workstation. This control program can be distributed via a network such as the Internet. The control program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, and a DVD and being read from the recording medium by the computer.

  According to at least one embodiment described above, an optimum spectrum reconfigurable region can be set.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

30 Console 38 System control circuit 38a Calculation function 38b Control function 38c Reception function

Claims (13)

A calculation unit that calculates an output value related to an energy spectrum from an image of the subject acquired by scanning the subject with X-rays;
A control unit that predicts a spectrum reconfigurable region corresponding to the subject based on an output value related to the energy spectrum, and displays the spectrum reconfigurable region on a display unit;
An X-ray CT apparatus comprising: A reception unit that receives a setting about the predicted spectrum reconfigurable region from an operator;
The X-ray CT apparatus according to claim 1, wherein the control unit sets a parameter for newly scanning the set spectrum reconfigurable region, and displays the set parameter on a display unit. The reception unit receives a setting for expanding or reducing the spectrum reconfigurable region from the operator,
The control unit sets a parameter that reduces the amount of X-ray irradiation per unit time according to the expansion of the spectrum reconfigurable region, and sets the X-ray per unit time according to the reduction of the spectrum reconfigurable region. The X-ray CT apparatus according to claim 2, wherein a parameter with an increased dose is set.   The control unit predicts a plurality of spectrum reconfigurable regions, sets parameters for newly scanning each spectrum reconfigurable region, and predicts each spectrum reconfigurable region and each spectrum reconfigurable region. The X-ray CT apparatus according to claim 1, wherein a parameter corresponding to 1 is displayed on a display unit. The calculation unit calculates the output value in the image for each view, calculates the output value in all views from the calculated output value for each image,
The X-ray CT apparatus according to claim 1, wherein the control unit predicts, as a spectrum reconfigurable region, a region in which the output value in all views is equal to or less than a predetermined threshold among the reconstruction regions. The calculation unit calculates the output value in the image for each view, calculates the output value in all views from the calculated output value for each image,
2. The control unit according to claim 1, wherein the control unit predicts, as a spectrum reconfigurable region, a region in which the output value in a view of a range in which half reconstruction is possible in the reconstruction region is a predetermined threshold value or less. X-ray CT system.   The X-ray CT apparatus according to claim 1, wherein the control unit further predicts a candidate region capable of spectrum reconstruction by correcting the output value, and further displays the predicted candidate region on a display unit.   The X-ray CT apparatus according to claim 1, wherein the calculation unit acquires a two-dimensional scano from at least one direction as the image.   The X-ray CT apparatus according to claim 1, wherein the calculation unit acquires an image obtained by a three-dimensional scan or a main scan executed in the past as the image.   The X-ray CT apparatus according to claim 1, wherein the calculation unit calculates a total output value of each energy bin count as the output value.   The X-ray CT apparatus according to claim 1, wherein the calculation unit calculates a pile-up count value of a count of each piled-up energy bin as the output value.   The X-ray CT apparatus according to claim 1, wherein the calculation unit calculates an energy integrated value obtained from a count value of energy bins and a representative value as the output value.   The X-ray CT apparatus according to claim 1, wherein the calculation unit calculates a pile-up energy integrated value of a representative value of piled-up energy bins as the output value.

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