Pcct device and control method thereof

Abstract

The present application provides a PCCT device capable of detecting an abnormality occurring in a photon counting type detector and a control method thereof. The PCCT device includes a photon counting type detector that counts photons of X-rays, and is characterized by further including a spectrum generation section that generates a spectrum that is a distribution of photon counts per energy bin, a calculation section that calculates a photon count rate per energy bin from a spectrum at a first time and a spectrum at a second time, and a determination section that determines whether or not the photon counting type detector has an abnormality based on the photon count rate.

Description

Technical Field

[0001] This invention relates to a PCCT (Photon Counting Computed Tomography) device, and more particularly to a technique for determining the cause of abnormalities in the photon counting detector of a PCCT device. Background Technology

[0002] Compared to conventional CT scanners, PCCT (photon-counting computed tomography) scanners equipped with photon-counting detectors can present medical images containing more information. For example, they can present energy chamber images (images created using projection data divided into multiple energy chambers) and substance identification images (images identifying multiple substances). Time-varying variations in X-rays irradiating the subject can sometimes cause artifacts in the medical images presented by PCCT scanners, thus requiring correction.

[0003] Patent Document 1 discloses a technique for calculating the amount of focus shift based on the count of X-ray photons detected by a reference detector, which has an anti-scattering grid for removing scattered rays and is located outside the scanning field of view.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2021-146190

[0005] However, Patent Document 1 does not consider the possibility of anomalies in the photon counting detector. Anomalies in photon counting detectors can sometimes cause artifacts in medical images, and therefore should preferably be detected immediately. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide a PCCT device and a control method thereof capable of detecting abnormalities occurring in a photon counting detector.

[0007] To achieve the above objectives, the PCCT apparatus of the present invention includes a photon counting detector for counting photons of X-rays. The PCCT apparatus is characterized by further comprising: a spectrum generation unit for generating a spectrum, the spectrum being the distribution of photon counts in each energy chamber; a calculation unit for calculating the rate of change of photon counts in each energy chamber based on the spectrum at a first time and the spectrum at a second time; and a determination unit for determining whether the photon counting detector is abnormal based on the rate of change of photon counts.

[0008] The PCCT device of the present invention includes a photon counting detector for counting photons of X-rays. The PCCT device is characterized in that it further includes: a spectrum generation unit for generating a spectrum, the spectrum being the distribution of the number of photons in each energy chamber; a calculation unit for calculating the difference between the spectrum obtained by a first detection element and the spectrum obtained by a second detection element; and a determination unit for determining whether the photon counting detector is abnormal based on the difference.

[0009] Furthermore, the control method of the present invention is a control method for a PCCT device equipped with a photon-counting detector for counting X-ray photons. The control method is characterized by comprising: a spectrum generation step, generating a spectrum, wherein the spectrum is the distribution of the number of photons in each energy chamber; a calculation step, calculating the rate of change of the number of photons in each energy chamber based on the spectrum at a first time moment and the spectrum at a second time moment; and a determination step, determining whether the photon-counting detector is abnormal based on the rate of change of the number of photons.

[0010] Invention Effects

[0011] According to the present invention, a PCCT device and its control method capable of detecting abnormalities occurring in a photon counting detector can be provided. Attached Figure Description

[0012] Figure 1 This is a diagram showing the overall structure of a PCCT device.

[0013] Figure 2 This is a diagram illustrating an example of X-ray photons counted by energy level.

[0014] Figure 3A It is a graph showing the time-dependent changes in the spectrum when polarization occurs.

[0015] Figure 3B It is a graph showing the time-dependent changes in the spectrum when polarization occurs.

[0016] Figure 4 This is a graph showing the time-varying changes in the spectrum when a gain decrease occurs.

[0017] Figure 5 This is a graph showing the time-dependent changes in the spectrum as energy resolution decreases.

[0018] Figure 6 It is a graph showing the time-dependent changes in the spectrum when an energy threshold shift occurs.

[0019] Figure 7 This is a graph showing the time-dependent changes in the spectrum as sensitivity decreases.

[0020] Figure 8 It is a graph showing the time-varying changes in the spectrum when noise increases in a local energy region.

[0021] Figure 9 This is a diagram illustrating an example of the process for handling anomalies in a photon counting detector.

[0022] Figure 10 It is a diagram that indicates the areas where abnormalities are determined when scanning a subject.

[0023] Figure 11 This is an example of a picture showing a scene when polarization is detected.

[0024] Figure 12 This is a diagram illustrating an example of the process for estimating anomalies other than polarization.

[0025] Figure 13 It is a graph showing the difference in spectrum when an anomaly occurs in one of the adjacent detection elements.

[0026] Symbol Explanation

[0027] 100-PCCT device, 101-Subject, 102-Stage, 200-Input / Output unit, 210-Input device, 220-Monitor, 300-Picture unit, 310-X-ray source, 311-Collimator, 320-X-ray detector, 321-Detection element, 330-Rack, 331-Opening, 332-Rotating plate, 340-Picture control unit, 341-X-ray control unit, 342-Rack control unit, 343-Stage control unit, 344-Detector control unit, 400-Central control unit, 401-CPU, 402-Memory, 403-Storage device, 1000-Air area measurement unit, 1100-Notification / instruction screen. Detailed Implementation

[0028] Hereinafter, embodiments of the PCCT (photon counting computed tomography) device according to the present invention will be described with reference to the accompanying drawings. Furthermore, in the following description and drawings, repeated descriptions are omitted by using the same symbols to denote components having the same functional structure.

[0029] [Example 1]

[0030] use Figure 1 The overall structure of the PCCT device 100 will be described. The PCCT device 100 includes an input / output unit 200, an imaging unit 300, and a central control unit 400.

[0031] The input / output unit 200 includes an input device 210 and a monitor 220. The input device 210 is a device used by the operator to input photographic conditions, etc., such as a mouse and keyboard. The monitor 220 is a display device for outputting the input photographic conditions, etc., and in the case of having a touch panel function, it is also used as the input device 210.

[0032] The imaging unit 300 includes an X-ray source 310, an X-ray detector 320, a gantry 330, a worktable 102, and an imaging control unit 340, so as to acquire projection data of the subject 101 at various projection angles. In addition, the acquired projection data is divided into multiple energy chambers.

[0033] X-ray source 310 is a device for irradiating the subject 101 with X-rays. Collimator 311 is provided between X-ray source 310 and subject 101. Collimator 311 is a device for adjusting the irradiation field of X-rays irradiating the subject 101.

[0034] The X-ray detector 320 is a device for detecting X-rays and has multiple detection elements 321. Each detection element 321 is a photon-counting detector consisting of a semiconductor element such as CdTe and a counting circuit element, and approximately 1000 of them are arranged at equal distances (e.g., 1000 mm) from the X-ray focal point of the X-ray source 310. Within each detection element 321, X-ray photons incident on a single element are counted according to their energy level.

[0035] use Figure 2 The X-ray photons counted by energy chamber will be explained. The X-ray photons incident on the detection element 321 are divided into multiple energy chambers according to a preset energy threshold. Figure 2 The diagram illustrates three energy bins (bin1, bin2, and bin3) divided according to energy thresholds T1, T2, and T3. Specifically, X-ray photons from T1 to T2 are counted in bin1, X-ray photons from T2 to T3 are counted in bin2, and X-ray photons from T3 onwards are counted in bin3. Furthermore, by counting X-ray photons by energy bin, a spectrum can be generated showing the distribution of photon counts in each energy bin.

[0036] Return to Figure 1 The description states that a circular opening 331 for arranging a worktable 102, which holds the subject 101, is provided at the center of the frame 330. The diameter of the opening 331 is, for example, 700 mm. A rotating plate 332 is provided inside the frame 330, which carries an X-ray source 310 and an X-ray detector 320, and allows the X-ray source 310 and X-ray detector 320 to rotate around the subject 101. The worktable 102 moves in the z-direction to adjust the position of the subject 101 relative to the frame 330.

[0037] The imaging control unit 340 includes an X-ray control unit 341, a gantry control unit 342, a stage control unit 343, and a detector control unit 344. The X-ray control unit 341 controls the voltage applied to the X-ray source 310, etc. The gantry control unit 342 controls the rotation of the rotating plate 332, for example, causing the rotating plate 332 to rotate one revolution every 1.0 s. The detector control unit 344 controls the detection of X-rays by the X-ray detector 320, for example, causing the X-ray detector 320 to detect X-rays every 0.4 degrees of rotation of the rotating plate 332. The stage control unit 343 controls the movement of the stage 102.

[0038] The central control unit 400 includes a CPU (Central Processing Unit) 401, a memory 402, and a storage device 403. It controls the imaging control unit 340 and performs various processes on projection data of X-rays detected by the X-ray detector 320. For example, the central control unit 400 performs processing to reconstruct a tomographic image based on projection data obtained according to imaging conditions set by the input device 210. The tomographic image can be reconstructed by energy level. Furthermore, the reconstructed tomographic image or the projection data used for reconstruction processing can be displayed on the monitor 220 or stored in the storage device 403, and processed by energy level.

[0039] In the event of an anomaly in the detection element 321 of the X-ray detector 320, the spectrum generated by counting X-ray photons may sometimes change over time, resulting in artifacts in the tomographic image. Therefore, in Embodiment 1, the anomaly occurring in the detection element 321 is detected based on the rate of change of the photon count in each energy chamber, which is calculated based on the spectrum at a first time moment and the spectrum at a second time moment.

[0040] Furthermore, the types of anomalies occurring in the detection element 321 include polarization, gain reduction, energy resolution reduction, energy threshold shift, sensitivity reduction, increased noise in local energy regions, and poor signal output. Moreover, the time-varying pattern of the spectrum varies depending on the type of anomaly occurring in the detection element 321; therefore, each type will be described below.

[0041] use Figure 3A and Figure 3B The time-varying pattern of the spectrum during polarization is illustrated. Polarization is a phenomenon that occurs when the charge generated by the incident X-rays is trapped or released by lattice defects contained in the semiconductor element, causing the spectrum to change as follows: Figure 3A and Figure 3B That's how things changed. Figure 3A The example illustrates the case where the spectrum shifts in the positive direction of energy and in the negative direction of X-ray photon number. Figure 3B The example illustrates a spectral shift towards the negative energy direction and the positive X-ray photon number direction. Furthermore, the spectra before and after the shift exhibit a crossover point. Additionally, the polarization is eliminated by resetting the voltage applied to the semiconductor element.

[0042] use Figure 4 The graph illustrating the time-dependent changes in the spectrum during gain reduction is presented. Gain reduction occurs due to semiconductor component failure or a partial break in the connection between the semiconductor component and the counting circuit elements, resulting in a spectrum similar to... Figure 4 The spectrum changes in the same way. That is, if a decrease in gain occurs, the spectrum shifts in the negative energy direction and in the positive X-ray photon number direction. Furthermore, the spectra before and after the change have an intersection point. Additionally, the direction of the spectral shift is related to... Figure 3B The same, but the displacement is significantly greater than Figure 3B Furthermore, the energy region where the X-ray photon number becomes zero is more than half of the original energy region.

[0043] use Figure 5 The diagram illustrates the temporal change in the spectrum when energy resolution decreases. This decrease in energy resolution occurs due to the degradation of semiconductor components or noise intrusion into the counting circuit elements, causing the spectrum to... Figure 5 That is, if a decrease in energy resolution occurs, the spectrum will expand in both the positive and negative energy directions and shift in the negative direction of X-ray photon number. Furthermore, the spectrum before and after the change will have two intersection points.

[0044] use Figure 6 This section illustrates the time-varying patterns of the spectrum when the energy threshold or counter malfunctions. If the energy threshold or counter malfunctions, then... Figure 6 In that case, the number of X-ray photons will decrease discontinuously within a portion of the energy reservoir of the spectrum.

[0045] use Figure 7 The graph illustrating the temporal change of the spectrum when sensitivity decreases is presented. Sensitivity decrease occurs due to semiconductor component failure or degradation, or a complete disconnection between the semiconductor component and the counting circuit components, resulting in a spectrum similar to... Figure 7 That is, if a decrease in sensitivity occurs, the spectrum will shift in the negative direction of the X-ray photon number. Furthermore, the spectra before and after the change will not have any intersection points.

[0046] use Figure 8 This paper illustrates the time-varying pattern of the spectrum when noise increases in a localized energy region. This noise increase in the localized energy region occurs due to the failure or degradation of semiconductor components or counting circuit elements, causing the spectrum to... Figure 8That is, if an increase in noise occurs in a local energy region, the spectrum will produce noise-induced peaks in a portion of the energy chamber.

[0047] use Figure 9 An example of the processing flow of Example 1 will be described step by step.

[0048] (S901)

[0049] The centralized control unit 400 controls the imaging control unit 340 to count X-ray photons in each energy chamber in all detection elements 321. By counting the X-ray photons in each energy chamber, a spectrum can be generated showing the distribution of photon counts in each energy chamber. The counting of X-ray photons in S901 is preferably performed in the absence of the subject 101.

[0050] Furthermore, when counting X-ray photons in the presence of the subject 101, the device is configured to... Figure 10 The detection element 321 of the air area measuring unit 1000 illustrated in the image becomes the object of subsequent processing. The width of the air area measuring unit 1000 varies depending on the size of the subject 101 or the projection angle, so the air area measuring unit 1000 can be preset based on the scanned image.

[0051] (S902)

[0052] The centralized control unit 400 uses the X-ray photon count obtained in S901 to calculate the photon count change rate for each energy chamber in all detection elements 321. The photon count change rate R(ch, E, t) is calculated, for example, using the following formula.

[0053] R(ch, E, t)=1-C(ch, E, t) / C(ch, E, t0)...(Formula 1)

[0054] Where ch is the channel number of the detection element 321, E is the energy chamber, t is the counting time, and C(ch, E, t) is the number of X-ray photons counted at channel number ch, energy chamber E, and counting time t. Additionally, C(ch, E, t0) is the number of X-ray photons counted at channel number ch, energy chamber E, and counting time t0 (< t) in the absence of the subject 101. The pre-counted C(ch, E, t0) is stored in the storage device 403 and read from the storage device 403 when calculating the photon count change rate R(ch, E, t).

[0055] (S903)

[0056] The centralized control unit 400 determines whether the rate of change of all photons at a certain counting time t calculated in S902 is within the allowable range. If the rate of change of all photons is within the allowable range, the process proceeds to S904. That is, it is determined that the detection element 321 is not abnormal. Furthermore, if at least one of the rates of change of all photons is outside the allowable range, the process proceeds to S905.

[0057] The upper limit R_U and lower limit R_L of the allowable range representing the rate of change of photon number are preset according to the channel number and energy chamber and stored in the storage device 403. For example, in the rotation direction of the rotating plate 332, the shorter the distance from the center of the X-ray detector 320 to the detection element 321, the narrower the allowable range is set. By setting a narrower allowable range for the detection element 321 that is closer to the center of the X-ray detector 320, it is possible to more rigorously determine whether there are any abnormalities in the detection element 321, which is more important for reconstructing tomographic images. Furthermore, the same allowable range can also be used for all detection elements 321. By using the same allowable range, the storage capacity of the storage device 403 can be saved. In addition, the allowable range can also be set according to the tube current or tube voltage of the X-ray source 310.

[0058] (S904)

[0059] The central control unit 400 displays the status of the detection element 321 and the X-ray source 310 as normal on the monitor 220.

[0060] (S905)

[0061] The centralized control unit 400 determines whether the photon number change rate calculated in S902 is outside the allowable range in all detection elements 321 and whether the time-varying pattern of the spectrum is completely identical. If the photon number change rate is outside the allowable range in all detection elements 321 and the pattern is completely identical, the process proceeds to S906. That is, it is determined that the X-ray source 310 is abnormal, but the detection elements 321 are not abnormal. Furthermore, if at least one of the photon number change rates is within the allowable range or the photon number change rates outside the allowable range include different patterns, the process proceeds to S907.

[0062] (S906)

[0063] The central control unit 400 displays the situation on the monitor 220 that the detection element 321 is normal but the X-ray source 310 is abnormal.

[0064] (S907)

[0065] The centralized control unit 400 determines in S903 whether the rate of change of photon count outside the allowable range includes a polarization pattern. If the rate of change of photon count outside the allowable range includes a polarization pattern, the process proceeds to S908. That is, it is determined that the detection element 321 has been polarized. And, if the rate of change of photon count outside the allowable range does not include a polarization pattern, the process proceeds to S909.

[0066] Furthermore, a pattern with a photon number change rate deemed outside the permissible range is considered polarized when the following three conditions are met. The first condition is that the photon number change rate outside the permissible range is not limited to a portion of the energy region. For example, in the case where X-ray photons are divided into three energy chambers, the first condition is met when the photon number change rate is outside the permissible range in more than two energy chambers. Figure 3A and Figure 3B , Figure 4 , Figure 5 , Figure 7 Corresponding to this, the second condition is that the spectra before and after the change have an intersection point. Figure 3A and Figure 3B , Figure 4 The third condition is that the energy region where the number of X-ray photons becomes zero in the changed spectrum is less than half of the energy region before the change. For example, when X-ray photons are divided into three energy chambers, the third condition is satisfied when there is one or fewer energy chambers where the number of X-ray photons becomes zero. Figure 3A and Figure 3B , Figure 5 , Figure 6 , Figure 7 , Figure 8 Corresponding to this. That is, in Figure 3A and Figure 3B It meets three conditions.

[0067] (S908)

[0068] The central control unit 400 notifies the detection element 321 that polarization has occurred and displays a screen indicating a power restart on the monitor 220. Figure 11 The example shown is a notification / instruction screen 1100 displayed on monitor 220 in S908. However, the screen displayed on monitor 220 is not limited to... Figure 11 The notification / instruction screen 1100 illustrated in .

[0069] (S909)

[0070] The centralized control unit 400 estimates the cause of anomalies other than polarization based on the pattern of the rate of change of photon number determined to be outside the allowable range in S903.

[0071] use Figure 12This document describes an example of the process for estimating the cause of an anomaly in S909, step by step.

[0072] (S1201)

[0073] The centralized control unit 400 determines in S903 whether the rate of change of photon count outside the permissible range is part of the energy region. If the rate of change of photon count outside the permissible range is part of the energy region, the process proceeds to S1202. Specifically, Figure 6 and Figure 8 Correspondingly, if the rate of change in photon number outside the permissible range is not limited to a portion of the energy chamber, then processing proceeds to S1205. Specifically, Figure 4 , Figure 5 , Figure 7 Corresponding to this.

[0074] (S1202)

[0075] The centralized control unit 400 determines in S903 whether the rate of change of photon count outside the allowable range is positive. If the rate of change of photon count is positive, the process proceeds to S1203. Specifically, Figure 8 Correspondingly, if the rate of change of photon number is not positive, the process proceeds to S1204. Specifically, Figure 6 Corresponding to this.

[0076] (S1203)

[0077] The central control unit 400 displays the increased noise in the local energy region of the detection element 321 on the monitor 220.

[0078] (S1204)

[0079] The central control unit 400 displays the abnormality of the energy threshold or counter of the detection element 321 on the monitor 220.

[0080] (S1205)

[0081] The centralized control unit 400 determines whether there are more than two intersection points in the spectrum before and after the change. If there are more than two intersection points, the process proceeds to S1206. Specifically, Figure 5 Correspondingly, if there are fewer than two intersection points, the process proceeds to S1207. Specifically, Figure 4 and Figure 7 Corresponding to this.

[0082] (S1206)

[0083] The central control unit 400 displays the decrease in energy resolution of the detection element 321 on the monitor 220.

[0084] (S1207)

[0085] The centralized control unit 400 determines whether the energy region in the changed spectrum where the X-ray photon count is zero is less than a threshold. If the energy region where the X-ray photon count is zero is less than the threshold, the process proceeds to S1208. Specifically, Figure 7 Correspondingly, if the energy region where the X-ray photon number becomes zero is above the threshold, then the process proceeds to S1209. Specifically, Figure 4 Correspondingly, the threshold is set, for example, to half the energy range of the spectrum before the change.

[0086] (S1208)

[0087] The central control unit 400 displays the decrease in sensitivity of the detection element 321 on the monitor 220.

[0088] (S1209)

[0089] The central control unit 400 displays the situation of gain reduction of the detection element 321 on the monitor 220.

[0090] pass Figure 12 The illustrated processing flow is used to estimate anomalies other than polarization. Return to... Figure 9 In the explanation.

[0091] (S910)

[0092] The centralized control unit 400 determines in S903 whether the number of detection elements 321 whose photon count change rate is outside the allowable range is below a threshold. If the number of detection elements 321 outside the allowable range is below the threshold, the process proceeds to S911. Furthermore, if the number of channels outside the allowable range exceeds the threshold, the process proceeds to S912. In addition, the threshold is preset to the number of channels whose artifacts can be prevented by interpolating the output of defective channels.

[0093] (S911)

[0094] The central control unit 400 displays a screen on the monitor 220 indicating that the detection element 321 whose photon number change rate is determined to be outside the allowable range is a faulty channel. The output of the detection element 321 registered as a faulty channel is interpolated by the outputs of the surrounding detection elements 321.

[0095] (S912)

[0096] The central control unit 400 displays a message on the monitor 220 instructing a service engineer to contact the detection component 321 if an abnormality has occurred. The service engineer who receives the notification that the detection component 321 is malfunctioning can repair or replace the X-ray detector 320. The service engineer can refer to the estimated cause of the abnormality in S909 when repairing or replacing the X-ray detector 320.

[0097] pass Figure 9 The processing flow illustrated herein allows the PCCT device 100 to detect anomalies occurring in the detection element 321, which functions as a photon counting detector. Furthermore, by restarting the power supply based on the image displayed when polarization occurs in the detection element 321, polarization can be eliminated, thereby reducing downtime when anomalies occur.

[0098] Furthermore, the centralized control unit 400 performs the function of a spectrum generation unit by executing S901, which generates a spectrum showing the distribution of photon counts in each energy chamber. The centralized control unit 400 also performs the function of a calculation unit by executing S902, which calculates the rate of change of photon counts in each energy chamber based on the spectra at the first and second time points. Finally, the centralized control unit 400 performs the function of a determination unit by executing S905, which determines whether the photon counting detector is malfunctioning based on the rate of change of photon counts.

[0099] [Example 2]

[0100] In Example 1, the detection of anomalies in the detection element based on the time-varying spectrum generated by counting X-ray photons was described. The detection of anomalies in the detection element is not limited to Example 1. In Example 2, the detection of anomalies in the detection element based on the difference between the spectrum obtained by one detection element and the spectra obtained by other detection elements at the same time was described. Furthermore, the overall structure of the PCCT device 100 is the same as in Example 1, therefore, the description is omitted.

[0101] use Figure 13 Example 2 will be described. When both adjacent detection elements P and D are functioning normally, there is no difference in their spectra. However, if either one experiences an anomaly, such as... Figure 13 As illustrated in the example, the spectra of the two differ. That is, an anomaly occurring in a detection element can be detected by the difference between the spectrum obtained by one detection element and the spectrum obtained by other detection elements at the same time. More specifically, when the difference D(ch, E) in the number of X-ray photons calculated using the following formula exceeds a predetermined allowable range, it is determined that an anomaly has occurred in detection element 321.

[0102] D(ch, E)=C(ch, E)-Ave(ch, E)...(Formula 2)

[0103] Where ch is the channel number of detection element 321, E is the energy chamber, and C(ch, E) is the number of X-ray photons counted in energy chamber E within detection element 321 at channel number ch. Furthermore, Ave(ch, E) is the average number of X-ray photons counted in energy chamber E across multiple detection elements 321 near channel number ch. When detection element 321 at channel number ch is... Figure 13 When the detection element P is detected, the detection element 321 near the channel number ch includes, for example, detection elements A to H around the detection element P and detection element J adjacent to the detection elements A to H.

[0104] Furthermore, the cause of the anomaly in the detection element 321 can be estimated based on the differential pattern calculated using (Equation 2). That is, the determination of whether a polarization pattern is included and the estimation of anomalies other than polarization are performed in the same manner as in Embodiment 1 by using a differential pattern instead of a time-varying pattern. Furthermore, when polarization is detected, a screen indicating a power-on restart can be displayed in the same manner as in Embodiment 1.

[0105] According to Embodiment 2, the PCCT device 100 can detect anomalies occurring in the detection element 321, which is a photon counting detector, without relying on time-varying spectral variations. Since detection can be performed without relying on time-varying spectral variations, it eliminates the need for prior counting of X-ray photons, thereby saving storage capacity in the storage device 403. Furthermore, by restarting the power supply based on the image displayed when the detection element 321 becomes polarized, as in Embodiment 1, polarization can be eliminated, thereby reducing downtime when an anomaly occurs.

[0106] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and its constituent elements can be modified and embodied without departing from the spirit of the invention. Furthermore, multiple constituent elements disclosed in the above embodiments can be appropriately combined. Moreover, some constituent elements can be deleted from all the constituent elements shown in the above embodiments.

Claims

1. A PCCT device comprising a photon-counting detector for counting photons of X-rays, characterized in that the PCCT device further comprises: A spectrum generation unit generates a spectrum, which is the distribution of the number of photons in each energy chamber; The computing unit calculates the rate of change of photon count in each energy chamber based on the spectra at the first and second time points; and The determination unit determines whether the photon counting detector is abnormal based on the rate of change of the photon count.

2. The PCCT device according to claim 1, characterized in that, The determination unit estimates the cause of the anomaly in the photon counting detector based on the pattern of the photon number change rate.

3. The PCCT device according to claim 2, characterized in that, The determination unit determines, based on the pattern, whether the anomaly occurring in the photon counting detector includes polarization.

4. The PCCT device according to claim 3, characterized in that, When the abnormality occurring in the photon counting detector is determined to include polarization, the determination unit displays a screen indicating a restart.

5. The PCCT device according to claim 3, characterized in that, When the rate of change of photon count in each energy chamber is outside the allowable range and the rate of change of photon count outside the allowable range is not limited to a part of the energy region, the intersection of the spectrum at the first moment and the spectrum at the second moment is one, and the energy region where the photon count is zero in the spectrum at the second moment is less than half of the energy region in the spectrum at the first moment, the determination unit determines that the abnormality occurring in the photon counting detector includes polarization.

6. The PCCT device according to claim 1, characterized in that, When the number of detection elements whose photon number change rate in each energy chamber is outside the allowable range is below a predetermined threshold, the determination unit displays a screen indicating that the detection elements whose photon number change rate in each energy chamber is outside the allowable range should be registered as faulty channels.

7. The PCCT device according to claim 1, characterized in that, When the rate of change of photon count in each energy chamber is outside the allowable range and the pattern is the same in all detection elements, the determination unit determines that there is an abnormality in the X-ray source.

8. The PCCT device according to claim 1, characterized in that, The spectrum generation unit generates the spectrum for X-rays from air regions that vary depending on the size or projection angle of the subject.

9. The PCCT device according to claim 1, characterized in that, The determination unit uses a narrower allowable range, set so that the distance from the center of the photon counting detector in the rotation direction is as short as possible, to determine whether the abnormality exists.

10. A PCCT device comprising a photon-counting detector for counting photons of X-rays, characterized in that the PCCT device further comprises: A spectrum generation unit generates a spectrum, which is the distribution of the number of photons in each energy chamber; The computing unit calculates the difference between the spectrum obtained by the first detection element and the spectrum obtained by the second detection element; and The determination unit determines whether the photon counting detector is abnormal based on the difference.

11. A control method for a PCCT device equipped with a photon-counting detector for counting X-ray photons, the control method being characterized by comprising: The spectrum generation step generates a spectrum, which is the distribution of the number of photons in each energy chamber; The calculation steps involve calculating the rate of change of photon count in each energy chamber based on the spectra at the first and second time points; and The determination step involves using the rate of change of the number of photons to determine whether the photon counting detector is abnormal.

Images