Calibration device, method, and program

Abstract

To reduce a data amount of correction data acquired by calibration in a calibration device, method and program for a photon counting type detector.SOLUTION: To acquire calibration data of a photon counting type detector composed of a plurality of detection elements for outputting a detection signal corresponding to photon energy of incident radiation. The processor is configured to acquire a plurality of detection signals output from a plurality of detection elements of the photon counting detector according to a predetermined acquisition condition, derive a difference signal indicating a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals, and store the at least one representative detection signal and the difference signal as calibration data according to the acquisition condition.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a calibration apparatus, method, and program. [Background technology]

[0002] In recent years, photon-counting computed tomography (PCCT) devices, which are radiographic imaging devices equipped with photon-counting detectors, have become well known. PCCT devices are capable of obtaining high-resolution images, i.e., cross-sectional images, with higher resolution than conventional computed tomography (CT) devices. In addition, they can measure the energy of each photon and obtain energy information for each of multiple energy bands. Therefore, PCCT devices can obtain more information than conventional CT devices.

[0003] In a photon-counting detector, when X-ray photons are incident on a detector element included in the detector, a detection signal is output according to the number of counts of the incident photons. However, the behavior of each detector element in a photon-counting detector, such as response characteristics, may differ depending on the element. For this reason, calibration is performed to grasp the number of counts output from each detector element for each energy band under various irradiation conditions, and the calibration data for each pixel is stored in a calibration database, and the calibration data is used to correct the projection data obtained by actual imaging.

[0004] As an example of calibration, Patent Document 1 proposes a method of setting X-ray irradiation conditions so that the probability of photon overlap when X-ray photons are incident on a detector consisting of multiple detector modules is equal to or less than a predetermined value, and then equalizing the X-ray detection sensitivity among the multiple detector modules under these irradiation conditions. Furthermore, Patent Document 2 proposes a calibration device for correcting the nonlinearity of the detection signal output from the detector, although it relates to a CT device equipped with a conventional integral type detector rather than a PCCT device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 144589 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-138660 Summary of the Invention [Problem to be solved by the invention]

[0006] On the other hand, when imaging using a PCCT system, various conditions, such as imaging conditions, subject conditions, and environmental conditions, affect imaging. For example, imaging conditions include the X-ray tube voltage and tube current, and subject conditions include the composition and thickness of the subject. Environmental conditions include the ambient temperature of the PCCT system, the degree of polarization in the detector, charge application time, and X-ray exposure history. Note that charge application time and X-ray exposure history affect polarization. Given the multiple imaging conditions and the detector's millions of detector elements, the amount of calibration data obtained through calibration is enormous. Therefore, modeling the correction data obtained through calibration is considered. However, modeling is difficult due to the strong nonlinearity of photon-counting detectors.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to reduce the amount of correction data acquired through calibration. [Means for solving the problem]

[0008] A calibration device according to the present disclosure is a calibration device for acquiring calibration data of a photon counting detector including a plurality of detection elements that outputs a detection signal corresponding to the photon energy of incident radiation, the calibration device comprising: at least one processor; The processor acquiring a plurality of detection signals output from a plurality of detection elements of the photon counting detector according to predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representative of the plurality of detection signals and the plurality of detection signals; At least one representative detection signal and the difference signal are stored as calibration data according to the acquisition conditions.

[0009] In the calibration device according to the present disclosure, the representative detection signal may be a detection signal output from a representative detection element that outputs a detection signal corresponding to a representative value of a plurality of detection signals.

[0010] In the calibration device according to the present disclosure, the representative detection signal may be a representative value of a plurality of detection signals.

[0011] In the calibration device according to the present disclosure, the difference signal may represent the difference or ratio between the representative detection signal and the detection signal.

[0012] In addition, in the calibration device according to the present disclosure, the processor divides the plurality of detection elements into a plurality of detection element groups according to positions on the photon counting detector; deriving a difference signal between a representative detection signal and the plurality of detection signals for each detection element group; The representative detection signal and the difference signal for each detection element group may be stored as calibration data according to the acquisition conditions.

[0013] In the calibration device according to the present disclosure, the processor may divide the plurality of detection elements into a plurality of detection element groups in the channel direction of the photon counting detector.

[0014] In addition, in the calibration device according to the present disclosure, the processor may divide the plurality of detection elements into a plurality of detection element groups including edge regions and non-edge regions in the photon-counting detector or in the plurality of detector modules constituting the photon-counting detector.

[0015] In addition, in the calibration device according to the present disclosure, the processor may derive a representative detection signal of a detection element group included in a plurality of detection element groups based on a representative detection signal of a detection element group located in the vicinity of the detection element group.

[0016] A calibration method according to the present disclosure is a calibration method for acquiring calibration data of a photon-counting detector including a plurality of detection elements that outputs a detection signal corresponding to the photon energy of incident radiation, the method comprising: a computer acquires a plurality of detection signals output from a plurality of detection elements of the photon counting detector in accordance with predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representative of the plurality of detection signals and the plurality of detection signals; At least one representative detection signal and the difference signal are stored as calibration data according to the acquisition conditions.

[0017] A calibration program according to the present disclosure is a calibration program that causes a computer to execute a process of acquiring calibration data for a photon-counting detector that includes a plurality of detection elements and outputs a detection signal corresponding to the photon energy of incident radiation, the program comprising: acquiring a plurality of detection signals output from a plurality of detection elements of the photon counting detector according to predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representative of the plurality of detection signals and the plurality of detection signals; and storing at least one representative detection signal and the difference signal as calibration data according to the acquisition conditions. [Effects of the Invention]

[0018] According to the present disclosure, the amount of correction data acquired through calibration can be reduced. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram illustrating the configuration of a medical imaging system including a calibration device according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view schematically illustrating a configuration of a detector; [Figure 3] FIG. 1 is a diagram showing a hardware configuration of a calibration device according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing the functional configuration of a calibration device according to an embodiment of the present invention; [Figure 5] Diagram for explaining detector calibration [Figure 6] Diagram showing the contents of the calibration database [Figure 7] A flowchart showing the processing performed in this embodiment [Figure 8] Diagram for explaining the division of the detector module [Figure 9] Diagram for explaining the division of the detector module [Figure 10] Diagram for explaining the division of the detector module DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. First, an example of the configuration of a medical image capturing system equipped with a calibration device of this embodiment will be described. Fig. 1 is a schematic diagram of the configuration of a medical image capturing system equipped with a calibration device of this embodiment.

[0021] As shown in Fig. 1, a medical imaging system 1 of this embodiment includes a CT device 2 and a console 3. The CT device 2 includes a gantry 4 and a bed 8. In the following description, the horizontal direction in Fig. 1 is defined as the X-axis, the vertical direction as the Y-axis, and the direction perpendicular to the XY plane as the Z-axis.

[0022] The gantry 4 has an opening 4A, and the subject H to be imaged is placed inside the opening 4A while being placed on a bed 8. The gantry 4 and the bed 8 are capable of moving relatively in the Z-axis direction.

[0023] Inside the gantry 4, a radiation source 5 having a radiation tube 6 and a bowtie filter 7, and a detector 9 are arranged facing each other across the subject H. The bowtie filter 7 optimizes the radiation exposure by increasing the radiation dose near the center and decreasing the radiation dose around the periphery to reduce the radiation exposure dose in the peripheral area. The radiation emitted from the radiation tube 6 is shaped by the bowtie filter 7 into a beam suitable for the size of the subject H and irradiated onto the subject H. The detector 9 detects the radiation that has passed through the subject H and generates projection data corresponding to the detected radiation dose. As an example, the detector 9 in this embodiment is a photon-counting detector in which multiple detection elements 9P that detect photon energy, which is the energy of photons of incident radiation, are arranged in an arc shape centered on the focal point of the radiation tube 6. The detector 9 outputs projection data corresponding to the photon energy. As shown in FIG. 2, the detector 9 is configured by arranging multiple detector modules 9A in an arc shape. The circumferential direction of the detector 9 is referred to as the channel direction.

[0024] In this embodiment, X-rays are used as an example of radiation, but the radiation is not limited to this.

[0025] The radiation tube 6 and the detector 9 are rotated around the subject H by a rotation drive unit (not shown) of the gantry 4. The irradiation of radiation from the radiation tube 6 and the detection of radiation by the detector 9 are repeated as both rotate, thereby obtaining projection data at various projection angles. The multiple projection data obtained by the detector 9 are output to the console 3.

[0026] The dose of radiation emitted from the radiation tube 6, the rotation speed of the gantry 4, and the relative movement speed between the gantry 4 and the bed 8 are set by the console 3 based on the acquisition conditions for acquiring projection data input by a user such as a technician.

[0027] The console 3 of this embodiment controls acquisition of projection data, generation of tomographic images from the projection data, and calibration according to this embodiment, etc. The console 3 is an example of a calibration device of the present disclosure.

[0028] Next, the calibration device according to this embodiment will be described. First, with reference to Fig. 3, the hardware configuration of the calibration device according to this embodiment included in the console 3 will be described. As shown in Fig. 3, the calibration device 10 included in the console 3 is a computer such as a workstation, a server computer, or a personal computer, and includes a CPU (Central Processing Unit) 11, non-volatile storage 13, and memory 16 as a temporary storage area.

[0029] The calibration device 10 also includes a display 14, an input device 15, and an I / F (Interface) 17. The CPU 11, the storage 13, the display 14, the input device 15, the memory 16, and the I / F 17 are connected to a bus 18. The CPU 11 is an example of a processor in the present disclosure.

[0030] The storage 13 is realized by a hard disk drive (HDD), a solid state drive (SSD), a flash memory, etc. The storage 13 as a storage medium stores the calibration program 12 installed in the calibration device 10. The CPU 11 reads the calibration program 12 from the storage 13, loads it into the memory 16, and executes the loaded calibration program 12. The storage 13 also stores a database of calibration data, which will be described later.

[0031] The display 14 is a device that displays various screens, and is, for example, a liquid crystal display or an EL (Electro Luminescence) display.

[0032] The input device 15 is used by the user to input acquisition conditions for acquiring projection data and calibration data, instructions and various information regarding image generation and display, etc. Examples of the input device 15 include various switches, buttons, a touch panel, a touch pen, a keyboard, and a mouse. The display 14 and the input device 15 may be integrated into a touch panel display.

[0033] The I / F 17 communicates various types of information with a rotation drive unit (not shown) of the gantry 4, the radiation source 5, and the detector 9 via wired or wireless communication.

[0034] The calibration program 12 is stored in a state where it can be accessed from outside, either in a storage device of a server computer connected to a network or in network storage, and is downloaded and installed in response to a request into a computer constituting the calibration device 10. Alternatively, the program is recorded on a recording medium such as a DVD (Digital Versatile Disc) or a CD-ROM (Compact Disc Read Only Memory) and distributed, and is installed from the recording medium into a computer constituting the calibration device 10.

[0035] Next, the functional configuration of the calibration device according to this embodiment will be described. Fig. 4 is a diagram showing the functional configuration of the calibration device according to this embodiment. As shown in Fig. 4, the calibration device 10 includes an information acquisition unit 21, a derivation unit 22, and a registration unit 23. The CPU 11 executes the calibration program 12 to function as the information acquisition unit 21, the derivation unit 22, and the registration unit 23.

[0036] In order to calibrate the detector 9, the information acquisition unit 21 acquires a plurality of detection signals output from each of the plurality of detection elements 9P of the detector 9 via the I / F 17 by having the CT device 2 capture an image of a calibration member, which will be described later. The plurality of detection signals are used to register calibration data C0, which will be described later, in a database. The calibration according to this embodiment will be described below.

[0037] A medical imaging system 1 including a detector 9 that is a photon counting detector can acquire a photon energy spectrum related to projection data of a subject H, thereby generating a material decomposition image in which materials with different compositions are decomposed, and a medical image separated into multiple energy components. In order to obtain such a material decomposition image, a known method is to acquire, for each detecting element 9P of the detector 9, calibration data that represents the output when a material with known composition and thickness is measured by the detector 9 under various acquisition conditions when acquiring projection data. In this embodiment, calibration refers to acquiring such calibration data.

[0038] FIG. 5 is a diagram illustrating detector calibration. A calibration member made of a combination of one or more basis materials with known compositions and thicknesses is used to calibrate detector 9, which is a photon-counting detector. In FIG. 5, calibration member 30 is made of a combination of two types of basis materials: a first basis material 30A and a second basis material 30B. First basis material 30A and second basis material 30B have different attenuation coefficients for radiation. In this embodiment, second basis material 30B has a larger attenuation coefficient than first basis material 30A. For example, first basis material 30A can be acrylic, and second basis material 30B can be aluminum, which has a larger attenuation coefficient than acrylic.

[0039] For example, by combining two first basis materials 30A having the same thickness with two second basis materials 30B having the same thickness, nine different calibration members 30 having different thicknesses in the radiation transmission direction can be obtained. Note that the nine combinations of two first basis materials 30A having the same thickness and two second basis materials 30B having the same thickness include a case where the number of first basis materials 30A and second basis materials 30B used is zero, i.e., a case where no first basis materials 30A or second basis materials 30B are used.

[0040] On the other hand, various acquisition conditions are set when acquiring projection data of the subject H. Specifically, imaging conditions for specifying the radiation dose, such as the tube voltage and tube current of the radiation tube 6, are used as acquisition conditions. The composition and thickness of the attenuating body (subject) are also used as acquisition conditions. The composition and thickness of the attenuating body can be set by combining the first basis material 30A and the second basis material 30B. Another acquisition condition is the degree of polarization within the detector 9. Polarization is a phenomenon in which charge accumulates in a semiconductor detector due to use. The duration of charge application and the radiation irradiation history also affect the degree of polarization.

[0041] In this embodiment, the information acquisition unit 21 acquires detection signals from all the detection elements 9P of the detector 9 for various combinations of acquisition conditions and basis substances.

[0042] On the other hand, in this embodiment, the derivation unit 22 derives at least one representative detection signal that represents the plurality of detection signals. The number of representative detection signals may be one or more.

[0043] In the present embodiment, when there is one representative detection signal, the derivation unit 22 derives a representative value of the detection signals output by all the detection elements 9P of the detector 9 as the representative detection signal. The representative value may be an average value, a median value, or the like. Alternatively, one detection element that exhibits typical behavior among the multiple detection elements 9P may be set as the representative detection element 9R, and the detection signal output by the representative detection element 9R may be used as the representative detection signal.

[0044] In the present embodiment, when there is one representative detection signal, the registration unit 23 registers the representative detection signal output under various acquisition conditions as calibration data C0 in a database of calibration data C0 (hereinafter referred to as calibration database DB). Note that, when the representative detection signal is acquired by the representative detection element 9R, the registration unit 23 registers the representative detection signal in the calibration database DB in association with the representative detection element 9R. The calibration database DB is stored in, for example, the storage 13 of the calibration device 10, but is not limited to this. The calibration database DB may also be stored in an external device different from the calibration device 10 (i.e., the console 3).

[0045] Meanwhile, for the detection signals acquired by all the detection elements 9P of the detector 9, the derivation unit 22 derives difference signals between the detection signals and the representative detection signal. Then, the registration unit 23 registers the derived difference signals as calibration data C0 in the calibration database DB in association with each of the multiple detection elements for each of the various acquisition conditions. The difference signal may be, for example, a differential signal derived by subtracting the detection signal of the representative detection element 9R from the detection signals of the other detection elements 9P, but is not limited to this. It may also be a signal representing the ratio of the detection signals of the other detection elements 9P to the detection signal of the representative detection element 9R.

[0046] Fig. 6 is a diagram showing the registered contents of the calibration database DB. As shown in Fig. 6, the calibration database DB registers various acquisition conditions (acquisition conditions 1, 2, 3, ...), representative detection signals for each acquisition condition, and difference signals for multiple detection elements (1, 2, 3, ...) as calibration data C0.

[0047] Next, the processing performed in this embodiment will be described. Fig. 7 is a flowchart showing the processing performed in this embodiment. First, the information acquisition unit 21 sets acquisition conditions (step ST1), and acquires detection signals from the plurality of detection elements of the detector 9 by imaging a combination of basis substances under the set acquisition conditions (step ST2). Next, the derivation unit 22 derives at least one representative detection signal representative of the plurality of detection signals (step ST3). Furthermore, the derivation unit 22 derives a difference signal between each of the plurality of detection signals and the representative detection signal (step ST4). Then, the registration unit 23 registers the representative detection signal and the difference signal for each detection element as calibration data C0 in the calibration database DB (step ST5).

[0048] Next, it is determined whether or not the registration of the calibration data C0 has been completed for all the acquisition conditions (step ST6). If the result of step ST6 is negative, the information acquisition unit 21 sets the next acquisition condition (step ST7) and returns to the processing of step ST2. If the result of step ST6 is positive, the processing ends.

[0049] In this manner, in this embodiment, at least one representative detection signal representing the plurality of detection signals and a difference signal indicating the difference between the plurality of detection signals are derived, and the at least one representative detection signal and the difference signal are registered in the calibration database DB as calibration data C0 according to the acquisition conditions. Therefore, the data volume of the calibration data C0 can be reduced compared to when the acquired detection signals for all detection elements are used as the calibration data C0 as is.

[0050] On the other hand, if the calibration data C0 is modeled (formulated) using a mathematical formula or the like, the capacity of the calibration database DB can be significantly reduced. However, in a photon-counting detector, the relationship between the imaging conditions and the detection signal is nonlinear. For example, the magnitude of the detection signal when the tube current is set to 200 mA is not twice that of the detection signal when the tube current is set to 100 mA. For this reason, it is difficult to model the calibration data C0 for the imaging conditions.

[0051] Here, by deriving a difference signal from the representative detection signal, such as the difference from the representative detection signal, nonlinearity is largely absorbed, and it is therefore possible to model the calibration data C0, which is the difference signal. Therefore, in this embodiment, by modeling the difference signals derived for multiple detection elements based on, for example, the tube current of the imaging conditions, it is possible to register only the representative detection signal as the calibration data C0 in the calibration database DB. Therefore, according to this embodiment, the capacity of the calibration database DB can be significantly reduced.

[0052] In the above embodiment, one representative detection signal is used, but this is not limiting. Multiple representative detection signals may be derived. Here, the bowtie filter 7 used in the CT device 2 optimizes the radiation exposure by increasing the radiation dose near the center and decreasing the radiation dose around the periphery in order to suppress the radiation exposure dose in the peripheral area. Therefore, the behavior of the response characteristics, etc. differs depending on the position of the detection element in the channel direction (i.e., the direction along the arc) of the detector 9.

[0053] In this embodiment, the detector 9 is configured by arranging multiple detector modules 9A in an arc shape as shown in Fig. 2. Therefore, a representative detection signal may be derived in each detector module 9A, and a difference signal between the multiple detection signals and the representative detection signal may be derived for each detector module 9A, thereby deriving calibration data C0 for each detector module 9A. In this case, the representative detection signal and the difference signal are derived as calibration data C0 for each detector module 9A and registered in the calibration database DB. The multiple detection elements included in one detector module 9A correspond to the detection element group in this disclosure.

[0054] When deriving calibration data C0 for each detector module 9A, a detector element that behaves typically in each detector module 9A may be identified as a representative detector element 9R, and the detection signal output by the representative detector element 9R may be used as the representative detection signal.

[0055] Furthermore, when deriving the calibration data C0 for each detector module 9A, a representative signal of a certain detector module 9A may be derived using representative detection signals of neighboring detector modules 9A. The neighboring detector modules may be one or two detector modules adjacent to a single detector module, or may include one or more detector modules further adjacent to these neighboring detector modules.

[0056] 8, when first to third detector modules 91 to 93 are adjacent to each other, the representative detection signal of the second detector module 92 located in the middle may be derived from the representative detection signal 91S of the first detector module 91 and the representative detection signal 93S of the third detector module 93. In this case, for example, the average value of the representative detection signal 91S and the representative detection signal 93S may be derived as the representative detection signal 92S of the second detector module 92. Note that in the second detector module 92, the difference signal may be derived using the derived representative detection signal 92S.

[0057] Alternatively, multiple representative detection signals may be derived from one detector module. For example, as shown in FIG. 9, when first to third detector modules 91-93 are adjacent to each other, each of the first to third detector modules 91-93 may be divided into two regions 91A, 91B, 92A, 92B, 93A, and 93B, and a representative detection signal may be derived from each of the divided regions 91A, 91B, 92A, 92B, 93A, and 93B. The multiple detection elements included in each of the regions 91A, 91B, 92A, 92B, 93A, and 93B correspond to the detection element group in the present disclosure. In this case, a difference signal between the representative detection signal and the detection signal is derived for each of the regions 91A, 91B, 92A, 92B, 93A, and 93B.

[0058] Furthermore, the detection signals output from the detector elements included in the detector module 9A behave differently, such as in response characteristics, between the detector elements in the edge region and the detector elements in the non-edge region. The edge region is a region including a range within a few pixels from the edge of the detector module 9A. In this case, although not limited thereto, when the first, second, and third detector modules 91-93 are adjacent to each other as shown in FIG. 10, the first detector module 91 may be divided into a first edge region 91C, a second edge region 91D, a third edge region 91E, a fourth edge region 91F, and a non-edge region 91G. The second detector module 92 may be divided into a first edge region 92C, a second edge region 92D, a third edge region 92E, a fourth edge region 92F, and a non-edge region 92G. The third detector module 93 may be divided into a first edge region 93C, a second edge region 93D, a third edge region 93E, a fourth edge region 93F, and a non-edge region 93G.

[0059] The plurality of detection elements included in each edge region and each non-edge region correspond to a detection element group in the present disclosure. In this case, a representative detection signal is derived for each edge region and each non-edge region, and a difference signal between the representative detection signal and the detection signal is derived for each edge region and each non-edge region.

[0060] In this case, the fourth edge region 91F of the first detector module 91 and the first edge region 92C of the second detector module 92 are adjacent to each other. Therefore, the behavior of the detector elements in the fourth edge region 91F of the first detector module 91 and the first edge region 92C of the second detector module 92 is similar. Therefore, the same representative detection signal may be derived from the fourth edge region 91F of the first detector module 91 and the first edge region 92C of the second detector module 92. Similarly, the same representative detection signal may be derived from the fourth edge region 92F of the second detector module 92 and the first edge region 93C of the third detector module 93.

[0061] 10, the behavior of the detecting elements in the second edge region 91D and the third edge region 91E is similar. Therefore, the same representative detection signal may be derived in the second edge region 91D and the third edge region 91E of the first detector module 91. Similarly, the same representative detection signal may be derived in the second edge region 92D and the third edge region 92E of the second detector module 92. Similarly, the same representative detection signal may be derived in the second edge region 93D and the third edge region 93E of the third detector module 93.

[0062] Furthermore, in the above embodiment, the hardware structure of the calibration device 10 can use the various processors listed below. The various processors include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as a PLD (Programmable Logic Device) such as an FPGA (Field-Programmable Gate Array) whose circuit configuration can be changed after manufacture, and a dedicated electrical circuit such as an ASIC, which is a processor having a circuit configuration designed specifically for executing specific processing.

[0063] The above-mentioned various processes may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same or different types (for example, a plurality of FPGAs, or a combination of a CPU and an FPGA). Also, a plurality of processing units may be configured by a single processor. An example of configuring a plurality of processing units by a single processor is a form in which a processor is used that realizes the functions of an entire system including a plurality of processing units by a single IC (Integrated Circuit) chip, such as an SoC (System on a Chip).

[0064] The following are appendices to the present disclosure. (Additional note 1) A calibration device for acquiring calibration data of a photon counting detector including a plurality of detection elements that outputs a detection signal corresponding to the photon energy of incident radiation, the calibration device comprising: at least one processor; The processor: acquiring a plurality of detection signals output from the plurality of detection elements of the photon counting detector according to predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals; a calibration device that stores the at least one representative detection signal and the difference signal as calibration data according to the acquisition conditions; (Additional note 2) 2. The calibration device according to claim 1, wherein the representative detection signal is a detection signal output from a representative detection element that outputs a detection signal corresponding to a representative value of the plurality of detection signals. (Additional note 3) 2. The calibration device according to claim 1, wherein the representative detection signal is a representative value of the plurality of detection signals. (Additional note 4) 4. The calibration device according to any one of claims 1 to 3, wherein the difference signal represents a difference or ratio between the representative detection signal and the detection signal. (Additional note 5) the processor divides the plurality of detector elements into a plurality of detector element groups according to positions on the photon-counting detector; deriving a difference signal between the representative detection signal and the plurality of detection signals for each of the detection element groups; 5. The calibration device according to any one of appendixes 1 to 4, wherein the representative detection signal and the difference signal for each of the detection element groups are stored as calibration data according to the acquisition conditions. (Additional note 6) 6. The calibration device according to claim 5, wherein the processor divides the plurality of detection elements into a plurality of detection element groups in a channel direction of the photon counting detector. (Additional note 7) The calibration device according to claim 5, wherein the processor divides the plurality of detection elements into a plurality of detection element groups including edge regions and non-edge regions in the photon counting detector or a plurality of detector modules constituting the photon counting detector. (Additional note 8) The calibration device according to any one of appendix 5 to 7, wherein the processor derives the representative detection signal of one detection element group included in the plurality of detection element groups based on the representative detection signals of detection element groups located in the vicinity of the one detection element group. (Additional note 9) A calibration method for acquiring calibration data of a photon-counting detector including a plurality of detection elements that outputs a detection signal corresponding to the photon energy of incident radiation, the method comprising: a computer acquires a plurality of detection signals output from the plurality of detection elements of the photon counting detector in accordance with predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals; A calibration method in which the at least one representative detection signal and the difference signal are stored as calibration data according to the acquisition conditions. (Additional note 10) A calibration program that causes a computer to execute a process of acquiring calibration data for a photon counting detector that includes a plurality of detection elements and outputs a detection signal corresponding to the photon energy of incident radiation, the program comprising: acquiring a plurality of detection signals output from the plurality of detection elements of the photon counting detector according to predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals; and a procedure of storing the at least one representative detection signal and the difference signal as calibration data according to the acquisition conditions. [Explanation of symbols]

[0065] 1 Medical imaging system 2 equipment 3 Console 4 Gantry 4A opening 5 Radiation source 6 Radiation tube 7 Bowtie Filter 8 berths 9 Detector 9A Detector Module 9P detector element 10 Calibration Device 11 CPU 12 Calibration Program 13. Storage 14 Display 15 Input Devices 16 memory 17 Interfaces 18 Bus 21 Information Acquisition Department 22 Derivation part 23 Registration Department 30 Calibration member 30A,30B Base material 91,92,93 Detector Module 91A,91B,92A,92B,93A,93B area 91C, 91D, 91E, 91F, 92C, 92D, 92E, 92F, 93C, 93D, 93E, 93F Edge area 91G, 92G, 93G Non-edge area H Subject

Claims

1. A calibration device for acquiring calibration data of a photon counting detector including a plurality of detection elements that outputs a detection signal corresponding to the photon energy of incident radiation, the calibration device comprising: at least one processor; The processor: acquiring a plurality of detection signals output from the plurality of detection elements of the photon counting detector according to predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals; a calibration device that stores the at least one representative detection signal and the difference signal as calibration data according to the acquisition conditions;

2. 2. The calibration device according to claim 1, wherein the representative detection signal is a detection signal output from a representative detection element that outputs a detection signal corresponding to a representative value of the plurality of detection signals.

3. The calibration device according to claim 1 , wherein the representative detection signal is a representative value of the plurality of detection signals.

4. 4. The calibration device according to claim 1, wherein the difference signal represents a difference or a ratio between the representative detection signal and the detection signal.

5. the processor divides the plurality of detector elements into a plurality of detector element groups according to positions on the photon-counting detector; deriving a difference signal between the representative detection signal and the plurality of detection signals for each of the detection element groups; The calibration device according to claim 1 , wherein the representative detection signal and the difference signal are stored as calibration data according to the acquisition conditions for each of the detection element groups.

6. The calibration device according to claim 5 , wherein the processor divides the plurality of detection elements into a plurality of detection element groups in a channel direction of the photon-counting detector.

7. 6. The calibration device according to claim 5, wherein the processor divides the plurality of detector elements into a plurality of detector element groups including edge regions and non-edge regions in the photon-counting detector or in a plurality of detector modules constituting the photon-counting detector.

8. The calibration device according to claim 5 , wherein the processor derives the representative detection signal of one detection element group included in the plurality of detection element groups based on the representative detection signals of detection element groups located in the vicinity of the one detection element group.

9. A calibration method for acquiring calibration data of a photon-counting detector including a plurality of detection elements that outputs a detection signal corresponding to the photon energy of incident radiation, the method comprising: a computer acquires a plurality of detection signals output from the plurality of detection elements of the photon counting detector in accordance with predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals; A calibration method in which the at least one representative detection signal and the difference signal are stored as calibration data according to the acquisition conditions.

10. A calibration program that causes a computer to execute a process of acquiring calibration data for a photon counting detector that includes a plurality of detection elements and outputs a detection signal corresponding to the photon energy of incident radiation, the program comprising: acquiring a plurality of detection signals output from the plurality of detection elements of the photon counting detector according to predetermined acquisition conditions; deriving a difference signal representing a difference between at least one representative detection signal representing the plurality of detection signals and the plurality of detection signals; and a procedure of storing the at least one representative detection signal and the difference signal as calibration data according to the acquisition conditions.

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