Radiographic apparatus

Abstract

To provide a radiographic apparatus that enables an effective beam width to be in a predetermined range not less than each of the set beam widths set in a plurality of imaging modes.SOLUTION: A radiographic apparatus can perform imaging in a plurality of imaging modes having different set beam widths in a rotation axis direction of a radioactive ray in a rotation axis. A radiation detector includes a plurality of sub-pixels arranged in a first direction parallel to the rotation axis and a second direction orthogonal to the rotation axis. A plurality of first macro pixels obtained by grouping a first number of sub-pixels arranged in the first direction and a plurality of second macro pixels obtained by grouping a second number of sub-pixels arranged in the first direction are provided, the second number being different from the first number. The second macro pixels are arranged such that an effective beam width determined by the number of the first macro pixels and the number of the second macro pixels for constituting a number of slices corresponding to the set beam width is within a predetermined range not less than each of the set beam widths.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a radiation imaging apparatus. [Background technology]

[0002] In recent years, PCCT (Photon Counting Computed Tomography) devices, which are radiographic imaging devices equipped with photon-counting detectors, have become well known. Unlike the charge-integration detectors used in conventional CT (Computed Tomography) devices, photon-counting detectors are capable of counting the photons of incident radiation. Because PCCT devices can measure the energy of each photon, they can obtain more information than conventional CT devices.

[0003] In a PCCT device, incident photons are converted into electric charges in a semiconductor layer, and the converted electric charges are counted by a photon counting circuit, thereby counting photons. Electrodes for applying a high voltage to the semiconductor layer are formed on the upper and lower surfaces of the semiconductor layer, and multiple sub-pixels are formed by patterning the electrodes on the lower surface. It is also known to form multiple macro-pixels by grouping multiple sub-pixels together (see, for example, Patent Document 1). This allows photons to be counted in units of sub-pixels or macro-pixels.

[0004] Also known as CT devices are multislice CT devices that have multiple imaging modes with different slice thicknesses, such as 40 mm, 20 mm, 10 mm, and 5 mm. The slice thickness corresponds to the beam width in the direction of the rotation axis of the CT device (i.e., the slice direction). Each slice thickness is made up of multiple slices (so-called multi-slices). Hereinafter, the beam width set for each imaging mode will be referred to as the "set beam width." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-039071 Summary of the Invention [Problem to be solved by the invention]

[0006] It is conceivable that a PCCT device can perform multiple imaging modes with different slice thicknesses. When photons are counted in units of macropixels, one slice corresponds to multiple macropixels aligned in the channel direction perpendicular to the slice direction. Furthermore, the number of slices corresponding to the set beam width is composed of multiple macropixels in the slice direction in the area irradiated with radiation. Therefore, the effective beam width on the rotation axis (hereinafter referred to as the effective beam width) is determined by the number of macropixels required to form the number of slices corresponding to the set beam width.

[0007] The total number of subpixels in the slice direction may not be divisible by the number of macropixels to be grouped. For this reason, it is possible to configure multiple first macropixels, each of which is a group of a first number of subpixels aligned in the slice direction, and multiple second macropixels, each of which is a group of a second number of subpixels aligned in the slice direction. For example, the first number is 6, and the second number is 5. In this case, the effective beam width is determined by the number of first macropixels and second macropixels required to configure the number of slices corresponding to the set beam width. Because the first macropixels and the second macropixels each contain a different number of subpixels, the effective beam width varies depending on the number of first macropixels and the arrangement of the second macropixels.

[0008] For example, if the first macro pixels are arranged at equal intervals and the second macro pixels are arranged at unequal intervals, the effective beam width in each imaging mode varies depending on the arrangement of the second macro pixels. That is, in one of the imaging modes, the effective beam width may fall below the set beam width. If the effective beam width falls below the set beam width, the image quality of the tomographic image will be reduced.

[0009] Therefore, the technology according to the present disclosure provides a radiographic imaging apparatus that allows the effective beam width to be set within a predetermined range that does not fall below any of the set beam widths set in a plurality of imaging modes. [Means for solving the problem]

[0010] A radiographic imaging device according to the disclosed technique includes a radiation source that rotates around a rotation axis to emit radiation, and a radiation detector that rotates around the rotation axis facing the radiation source to detect the radiation, and is capable of imaging in multiple imaging modes with different set beam widths in the rotational axis direction of the radiation on the rotation axis. The radiation detector has a plurality of sub-pixels arranged in a first direction parallel to the rotation axis and a second direction perpendicular to the rotation axis, and is provided with a plurality of first macro-pixels each formed by grouping a first number of sub-pixels lined up in the first direction, and a plurality of second macro-pixels each formed by grouping a second number of sub-pixels lined up in the first direction that is different from the first number. The second macro-pixels are arranged so that the effective beam width, determined by the number of first macro-pixels and second macro-pixels required to form slices corresponding to the set beam width, is within a predetermined range that does not fall below each of the set beam widths.

[0011] Preferably, the first number is greater than the second number.

[0012] Preferably, the first number is six and the second number is five.

[0013] It is preferable to include a photon counting circuit that counts photons for each of the first and second macropixels, and an image processing unit that generates a radiographic image based on the count values ​​by the photon counting circuit.

[0014] The image processing unit preferably corrects artifacts having frequencies caused by the arrangement of the second macropixels.

[0015] The image processing unit preferably corrects the count values ​​of the photons counted for each of the first macropixels and each of the second macropixels based on the first number and the second number.

[0016] If the first number is greater than the second number, the image processor preferably distributes a portion of the photon count for the first macro-pixel to the photon count for the adjacent second macro-pixel. [Effects of the Invention]

[0017] According to the technology of the present disclosure, it is possible to provide a radiation imaging device that enables the effective beam width to be set within a predetermined range that does not fall below each of the set beam widths set in multiple imaging modes. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram schematically showing the configuration of a radiation imaging apparatus according to an embodiment; [Figure 2] FIG. 1 is a perspective view showing a schematic configuration of an X-ray detector. [Figure 3] FIG. 2 is a diagram schematically illustrating a configuration example of a detector module. [Figure 4] FIG. 2 is a diagram schematically illustrating a configuration of a semiconductor layer and an ASIC. [Figure 5] FIG. 2 is a diagram schematically showing an arrangement of sub-pixels formed in each of four semiconductor layers. [Figure 6] FIG. 2 is a diagram schematically illustrating an arrangement of first and second macro pixels. [Figure 7] FIG. 10 is a diagram illustrating a set beam width set for each imaging mode. [Figure 8] FIG. 2 is a diagram illustrating a plurality of shooting modes. [Figure 9] FIG. 10 is a diagram showing an example of the arrangement of second macro pixels according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating an effective beam width. [Figure 11] FIG. 10 is a diagram showing calculated values ​​of the effective beam width when the second macro-pixels are arranged as shown in FIG. [Figure 12] FIG. 10 is a diagram showing an example of arrangement of second macro pixels according to a first comparative example. [Figure 13]FIG. 13 is a diagram showing calculated values ​​of the effective beam width when the second macro-pixels are arranged as shown in FIG. [Figure 14] FIG. 10 is a diagram showing an example of arrangement of second macro pixels according to a second comparative example. [Figure 15] FIG. 15 is a diagram showing calculated values ​​of the effective beam width when the second macro pixel is arranged as shown in FIG. [Figure 16] FIG. 10 is a diagram illustrating an example of a process for suppressing artifacts. [Figure 17] FIG. 10 is a diagram illustrating another example of a process for suppressing artifacts. [Figure 18] FIG. 10 is a diagram illustrating a process of distributing a count value. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the technology of the present disclosure will be described with reference to the drawings. The radiographic imaging apparatus of the present disclosure is applied to a PCCT apparatus including a radiation source that rotates around a rotation axis and emits radiation, and a radiation detector that rotates around the rotation axis while facing the radiation source and detects the radiation. In this embodiment, a case where the radiation is X-rays will be described as an example.

[0020] [Embodiment] 1 schematically shows the configuration of a radiographic apparatus 2 according to an embodiment. The radiographic apparatus 2 includes an X-ray source 3, an X-ray detector 4, a gantry 5, a bed 6, a control unit 7, and an image processing unit 8. A circular opening 51 is provided in the center of the gantry 5 for placing the bed 6 on which a subject H is placed. The gantry 5 also includes a rotating plate 52 fixed at a position opposite the X-ray source 3 and the X-ray detector 4, and a drive mechanism (not shown) for rotating the rotating plate 52 about a rotation axis C.

[0021] Hereinafter, in this disclosure, the circumferential direction of the opening 51 is referred to as the X direction, the radial direction as the Y direction, and the central axis direction as the Z direction (see FIG. 2). The Z direction is perpendicular to the X and Y directions and generally corresponds to the body axis direction of the subject H. The rotation axis C is parallel to the Z direction. The subject H is positioned so that the body axis approximately coincides with the rotation axis C.

[0022] The Z direction is the slice direction, and the X direction is the channel direction. The Z direction corresponds to the "first direction" according to the technology of the present disclosure. The X direction corresponds to the "second direction" according to the technology of the present disclosure.

[0023] The X-ray source 3 includes an X-ray tube 31, an aperture 32, an X-ray filter 33, and a bowtie filter 34. The X-ray tube 31 generates X-rays and irradiates the object H with the generated X-rays. The aperture 32 shapes the X-rays irradiated from the X-ray tube 31 into a cone beam having a predetermined fan angle and cone angle. The X-ray filter 33 adjusts the X-ray dose. In order to suppress the radiation dose in the peripheral area, the bowtie filter 34 increases the radiation dose near the center and decreases the radiation dose around the periphery, thereby optimizing the radiation dose.

[0024] 2, the X-ray detector 4 is configured by arranging a plurality of detector modules 40 in an arc shape in the X direction. Each of the detector modules 40 includes a collimator 41, a semiconductor layer 42, and an ASIC (Application Specific Integrated Circuit) 43.

[0025] The collimator 41 is disposed on the X-ray incident side of the semiconductor layer 42, and removes scattered rays by restricting the direction of incidence of the X-rays on the semiconductor layer 42. The semiconductor layer 42 is formed of cadmium zinc telluride (CZT), cadmium telluride (CdTe), or the like, and converts the X-rays that have passed through the subject H and entered into electric charges equivalent to photons and outputs them.

[0026] The ASIC 43 is disposed on the opposite side of the semiconductor layer 42 from the collimator 41. The ASIC 43 is a circuit element having a plurality of photon counting circuits 44. The photon counting circuits 44 count the number of charges output by the semiconductor layer 42 as the number of photons and output a counting signal. As will be described in detail later, the semiconductor layer 42 is configured with a plurality of sub-pixels and a plurality of macro-pixels. The photon counting circuits 44 count photons for each sub-pixel or macro-pixel and output a counting signal.

[0027] The control unit 7 is composed of a processor such as a CPU (Central Processing Unit). The control unit 7 controls the operations of the X-ray source 3, the X-ray detector 4, the gantry 5, and the bed 6. Specifically, the control unit 7 controls the emission of X-rays from the X-ray tube 31 of the X-ray source 3, the change of the fan angle and cone angle by the aperture 32, the X-ray detection by the X-ray detector 4, the rotation of the rotating plate 52 of the gantry 5, and the movement of the bed 6. The X-ray source 3 and the X-ray detector 4 rotate around a rotation axis C while facing each other.

[0028] The control unit 7 is configured to be able to execute a plurality of imaging modes with different slice thicknesses. The slice thickness corresponds to the beam width of the X-rays in the rotation axis direction (i.e., Z direction) on the rotation axis C. The control unit 7 changes the beam width in the rotation axis direction by controlling the aperture 32 to change the cone angle for each imaging mode. In other words, the radiation imaging device 2 is a multi-slice CT device capable of imaging in a plurality of imaging modes with different beam widths in the rotation axis direction, and can acquire a plurality of tomographic images with one rotation.

[0029] The control unit 7 also acquires counting signals output from the photon counting circuit 44 of the ASIC 43 for multiple views. The image processing unit 8 is an image processing processor that generates a tomographic image by performing reconstruction processing based on multiple projection data represented by the counting signals acquired by the control unit 7 from each ASIC 43 for multiple views. The image processing unit 8 may be configured as a part of the control unit 7. The tomographic image is an example of a "radiation image" according to the technology of the present disclosure.

[0030] In addition, the control unit 7 is connected to an input device 9, a display device 10, a storage device 11, and a communication device 12. The input device 9 is a device for an operator to input operation instructions, and is composed of a keyboard, a mouse, etc. The display device 10 is a display such as a liquid crystal display, and displays an operation screen, tomographic images, etc. The storage device 11 is a memory, a storage device, etc., and stores tomographic images, programs, various information, etc.

[0031] The operator can operate the input device 9 to select one of a plurality of imaging modes.

[0032] The communication device 12 is a communication interface for communicating with a radiology information system (RIS), a picture archiving and communication system (PACS), etc. The communication device 12 controls transmission in accordance with communication protocols defined by various wired or wireless communication standards.

[0033] 3 schematically illustrates an exemplary configuration of the detector module 40. For example, the detector module 40 includes four ASICs 43 mounted on a holding substrate 46. The four ASICs 43 are arranged in the Z direction. A semiconductor layer 42 is connected to each ASIC 43. A collimator 41 is disposed on each of the four semiconductor layers 42. Note that the number of semiconductor layers 42 and the number of ASICs 43 included in the detector module 40 are not limited to four, and may be any appropriate number.

[0034] 4 schematically shows the configuration of the semiconductor layer 42 and the ASIC 43. A common electrode 42a is formed on the upper surface of the semiconductor layer 42, and a plurality of individual electrodes 42b are formed on the lower surface of the semiconductor layer 42. The individual electrodes 42b are arranged two-dimensionally in the X and Z directions. Each individual electrode 42b constitutes a sub-pixel SP. The common electrode 42a is an electrode common to each sub-pixel SP, and a bias voltage is applied to the common electrode 42a from a power supply 47.

[0035] When an X-ray photon is incident on the semiconductor layer 42, electron-hole pairs are generated with an amount of charge corresponding to the energy of the photon, and the generated electrons move to the common electrode 42a, while the generated holes move to the individual electrode 42b. When one photon is incident on the individual electrode 42b, it generates a pulse signal having a voltage value corresponding to the energy of the photon.

[0036] Furthermore, a macro pixel MP is formed by grouping a plurality of sub-pixels SP aligned in the Z direction. In this embodiment, a plurality of first macro pixels MP1 are formed by grouping a first number of sub-pixels SP aligned in the Z direction, and a plurality of second macro pixels MP2 are formed by grouping a second number of sub-pixels SP aligned in the Z direction (see FIG. 6). Hereinafter, when there is no need to distinguish between the first macro pixel MP1 and the second macro pixel MP2, they will simply be referred to as macro pixels MP.

[0037] The ASIC 43 includes a plurality of photon-counting circuits 44 and a switching circuit 48. The switching circuit 48 is connected between a plurality of individual electrodes 42b included in the macro pixel MP and a plurality of photon-counting circuits 44. The switching circuit 48 enables switching between a macro-pixel mode in which the plurality of individual electrodes 42b are commonly connected to one photon-counting circuit 44, and a sub-pixel mode in which the plurality of individual electrodes 42b are each connected to a different photon-counting circuit 44.

[0038] The control unit 7 controls the switching circuit 48 to switch between the macro pixel mode and the sub-pixel mode. The macro pixel mode is a mode in which photons are counted for each macro pixel MP. The sub-pixel mode is a mode in which photons are counted for each sub-pixel SP. In this embodiment, the macro pixel mode will be described. For example, the macro pixel mode is used when acquiring a material decomposition image in which materials with different X-ray attenuation coefficients are differentiated and visualized.

[0039] The photon counting circuit 44 is composed of a plurality of energy discriminators and a plurality of counters connected to each energy discriminator, and counts photons for each energy band while discriminating the energy of photons into a plurality of energy bands based on the pulse signals generated by the individual electrodes 42b.

[0040] 5 schematically shows the arrangement of sub-pixels SP formed in each of the four semiconductor layers 42. In one semiconductor layer 42, the sub-pixels SP are arranged at a constant arrangement pitch s in the X and Y directions. In this embodiment, the number Nx of sub-pixels SP in the X direction and the number Nz of sub-pixels SP in the Z direction formed in one semiconductor layer 42 are equal, for example, Nx=Nz=128.

[0041] The four semiconductor layers 42 are arranged in the Z direction, and a gap G exists between two adjacent semiconductor layers 42. The length g of the gap G in the Z direction (hereinafter referred to as the gap length g) is also the distance between two adjacent sub-pixels SP between the two semiconductor layers 42. For example, the gap length g is equal to the arrangement pitch s of the sub-pixels SP.

[0042] 6 schematically shows the arrangement of the first macropixels MP1 and the second macropixels MP2. In this embodiment, the first macropixel MP1 is composed of six subpixels SP, and the second macropixel MP2 is composed of five subpixels SP. That is, the above-mentioned first number is 6, and the second number is 5. When Nz=128, one semiconductor layer 42 has 18 first macropixels MP1 in the Z direction and four second macropixels MP2 in the Z direction. Hereinafter, the first number will be referred to as n1, and the second number will be referred to as n2.

[0043] If n1=8 and n2=8, 128 is divisible by 8, so there is no need to configure the first macro pixel MP1 and the second macro pixel MP2 with different numbers of sub-pixels SP. However, in order to improve resolution, n1=6 and n2=5 are used.

[0044] 7 explains the set beam width WBc set for each imaging mode. The set beam width WBc is the beam width of the X-ray in the rotation axis direction on the rotation axis C, and is set based on the number of macro pixels MP.

[0045] FIG. 8 explains a plurality of imaging modes. In this embodiment, one of four imaging modes, WBc=40 mm, 20 mm, 10 mm, and 5 mm, can be selected. The number of slices corresponding to the set beam width is N. SL and the slice pitch is P SL In all shooting modes, SL = 0.5 mm, when WBc = 40 mm, N SL = 80, WBc = 20 mm, N SL = 40, and when WBc = 10 mm, N SL = 20, WBc = 5 mm, N SL =10.

[0046] Since one slice corresponds to a plurality of macro pixels MP arranged in the X direction (i.e., the channel direction), the set beam width WBc is the number of slices N SL corresponds to a number of macro-pixels MP equal to

[0047] 9 shows an example of the arrangement of second macro-pixels MP2 according to the embodiment. In Fig. 9, the unhatched rectangular areas indicate first macro-pixels MP1, and the hatched rectangular areas indicate second macro-pixels MP2.

[0048] The first macropixels MP1 are arranged at equal intervals in the Z direction except for the locations where the second macropixels MP2 exist. The second macropixels MP2, which are fewer in number than the first macropixels MP1, are arranged at unequal intervals in the Z direction.

[0049] In addition, in FIG. 9, L is the N corresponding to the set beam width WBc. SLIt represents the length in the Z direction (hereinafter referred to as the configuration length) of the plurality of macro-pixels MP (including the first macro-pixel MP1 and the second macro-pixel MP2) that make up a slice. In other words, the configuration length L corresponds to the slice thickness. X-rays are irradiated onto these plurality of macro-pixels MP.

[0050] 9, SL1 indicates the first slice position when WBc=40 mm, and SL80 indicates the 80th slice position when WBc=40 mm. Second macro pixels MP2 are arranged at slice positions SL9, SL18, SL19, SL23, SL27, SL40, SL41, SL54, SL58, SL62, SL63, and SL72.

[0051] Taking into consideration the existence of the gap G, the structural length L is expressed by the following formula (1).

number

[0052] where N MP1 is the number of first macro pixels MP1, N MP2 is the number of second macro-pixels MP2, N G is the number of gaps G.

[0053] N SL =N MP1 +N MP2 Since the above relationship is satisfied, the above equation (1) can be transformed into the following equation (1a).

number

[0054] Fig. 10 explains the effective beam width. In Fig. 10, WBe is the N SL 1 represents the effective beam width determined by the number of macro-pixels MP that constitute this slice.

[0055] The effective beam width WBe is expressed by the following equation (2) based on the geometric relationship using the component length L.

number

[0056] Here, SOD is the length in the Y direction from the X-ray tube 31 to the rotation axis C. SID is the length in the Y direction from the X-ray tube 31 to the detector module 40 (specifically, the semiconductor layer 42).

[0057] As shown in the above formula (1a), the structural length L is the number N of second macro-pixels MP2 MP2 In this embodiment, since n1>n2, the number N of second macro pixels MP2 MP2 The greater the number of beams, the smaller the effective beam width WBe becomes, and there is a possibility that the effective beam width WBe will fall below the set beam width WBc.

[0058] If the effective beam width WBe falls below the set beam width WBc, the image quality of the tomographic image will be reduced. Therefore, in this embodiment, the arrangement of the second macro-pixels MP2 is determined so as to satisfy the following formula (3).

number

[0059] Here, α is a coefficient for defining the upper limit of the effective beam width WBe, and is, for example, α = 1.02. The range defined by the above formula (3) is an example of the "predetermined range" according to the technique of the present disclosure.

[0060] Fig. 11 shows the calculated value of the effective beam width WBe when the second macro pixel MP2 is arranged as shown in Fig. 9. Here, SID = 1079.2 mm, SOD = 612.3 mm, s = 0.15 mm, and g = 0.15 mm. Fig. 11 also shows the calculated value of the effective slice pitch P SLe The calculated values ​​are shown.

number

[0061] As shown in Fig. 11, according to this embodiment, the effective beam width WBe is within the range defined by the above formula (3) in which it does not fall below the set beam width WBc in any imaging mode. SLe is the original slice pitch P SL Therefore, according to this embodiment, it is possible to suppress the deterioration of the image quality of the tomographic image.

[0062] [Comparative Example] A comparative example in which the arrangement of the second macro-pixels MP2 differs from that of the above embodiment will be described below.

[0063] 12 shows an example of the arrangement of second macro pixels MP2 according to a first comparative example. The configuration of a radiographic apparatus 2 according to this comparative example is the same as that of the above-described embodiment, except for the arrangement of the second macro pixels MP2. In this comparative example, the second macro pixels MP2 are arranged at the slice positions SL9, SL18, SL19, SL37, SL39, SL40, SL41, SL43, SL44, SL62, SL63, and SL72.

[0064] In this comparative example, SID=1081.5 mm, SOD=612.3 mm, s=0.15 mm, and g=0.15 mm.

[0065] Fig. 13 shows the calculated values ​​of the effective beam width WBe when the second macro pixel MP2 is arranged as shown in Fig. 12. As shown in Fig. 13, in the first comparative example, when WBc=20 mm, 10 mm, and 5 mm, it can be seen that the effective beam width WBe is smaller than the set beam width WBc.

[0066] 14 shows an example of the arrangement of second macro pixels MP2 according to a second comparative example. The configuration of a radiographic apparatus 2 according to this comparative example is the same as that of the above-described embodiment, except for the arrangement of the second macro pixels MP2. In this comparative example, the second macro pixels MP2 are arranged at the slice positions SL9, SL18, SL19, SL27, SL35, SL40, SL41, SL46, SL54, SL62, SL63, and SL72.

[0067] In this comparative example, SID=1081.5 mm, SOD=612.3 mm, s=0.15 mm, and g=0.15 mm.

[0068] Fig. 15 shows the calculated values ​​of the effective beam width WBe when the second macro pixel MP2 is arranged as shown in Fig. 14. As shown in Fig. 15, in the second comparative example, when WBc=20 mm and 10 mm, it can be seen that the effective beam width WBe is smaller than the set beam width WBc.

[0069] [Image Processing] In the above embodiment, the second macro pixels MP2 are arranged at irregular pitches, and therefore artifacts having frequencies due to the arrangement of the second macro pixels MP2 may occur in the tomographic image reconstructed by the image processing unit 8. These artifacts are expected to appear as ring-shaped artifacts and to reduce the resolution characteristics.

[0070] For this reason, it is preferable that the image processing unit 8 corrects artifacts having a frequency due to the arrangement of the second macro pixels MP2. For example, as shown in Fig. 16, when a tomographic image has a frequency fa due to the arrangement of the second macro pixels MP2, the image processing unit 8 suppresses the artifacts by performing correction according to the frequency fa. A reconstruction filter such as a so-called Ramp filter can be used for this correction.

[0071] Furthermore, as shown in FIG. 17, the image processing unit 8 may correct the tomographic image based on information about frequency components around the artifact frequency fa so that the intensity I1 of the frequency fa approaches the intensity I2 of the surrounding frequency.

[0072] Furthermore, in the above embodiment, multiple slices having a constant slice pitch are generated by multiple macro-pixels MP including the second macro-pixel MP2 having an uneven pitch. Therefore, the sampling positions of the slices in the above embodiment differ from the ideal sampling positions when the macro-pixels MP are arranged at a uniform pitch. This may result in a decrease in resolution.

[0073] For this reason, it is preferable that the image processing unit 8 corrects the count value of photons counted for each first macro pixel MP1 and each second macro pixel MP2 based on the first number n1 and the second number n2. Specifically, it is preferable that the image processing unit 8 distributes a part of the count value of photons for the first macro pixel MP1 to the count value of photons for the adjacent second macro pixel MP2.

[0074] For simplicity, FIG. 18 shows a case where multiple slices are generated by three first macropixels MP1 and one second macropixel MP2 aligned in the Z direction. PC1 to PC4 shown in FIG. 18 represent photon count values. PC1 is the count value for the leftmost first macropixel MP1. PC2 is the count value for the second first macropixel MP1 from the left. PC3 is the count value for the third second macropixel MP2 from the left. PC4 is the count value for the fourth first macropixel MP1 from the left.

[0075] In this case, the image processing unit 8 allocates a part of the count value PC2 and a part of the count value PC4 to the count value PC3. Specifically, the image processing unit 8 adds "0.5 x PC2" to PC3 and subtracts it from PC2. The image processing unit 8 also adds "0.25 x PC4" to PC3 and subtracts it from PC4.

[0076] The image processing unit 8 also distributes part of the count value between adjacent first macro pixels MP1. Specifically, the image processing unit 8 adds "0.25 x PC1" to PC2 and subtracts it from PC1.

[0077] The above 0.5 and 0.25 are distribution coefficients determined based on the constituent length L, the first number n1, and the second number n2.

[0078] As a result, the count data for the three first macro pixels MP1 and one second macro pixel MP2 aligned in the Z direction becomes data spaced at equal intervals, improving the resolution.

[0079] Furthermore, in the above embodiment, X-rays are used as radiation, but gamma rays may also be used as radiation.

[0080] In the above embodiment, the hardware structure of the control unit 7 can use various processors as shown 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 dedicated electrical circuits such as a PLD (Programmable Logic Device) whose circuit configuration can be changed after manufacture, such as an FPGA (Field-Programmable Gate Array), and an ASIC, which is a processor with a circuit configuration designed specifically for executing specific processing.

[0081] 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). Furthermore, 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).

[0082] From the above description, the technology described in the following supplementary paragraphs can be understood.

[0083] [Additional note 1] 1. A radiographic imaging apparatus comprising: a radiation source that rotates around a rotation axis and emits radiation; and a radiation detector that rotates around the rotation axis while facing the radiation source and detects the radiation, wherein the radiographic imaging apparatus is capable of imaging in a plurality of imaging modes in which set beam widths of the radiation in the rotation axis direction on the rotation axis are different, The radiation detector comprises: a plurality of sub-pixels arranged in a first direction parallel to the rotation axis and a second direction perpendicular to the rotation axis; a plurality of first macro pixels each formed by grouping a first number of the sub-pixels aligned in the first direction, and a plurality of second macro pixels each formed by grouping a second number of the sub-pixels aligned in the first direction, the second number being different from the first number, are provided; The second macropixels are arranged so that an effective beam width determined by the number of the first macropixels and the second macropixels for configuring the number of slices corresponding to the set beam width falls within a predetermined range not less than each of the set beam widths. Radiography equipment. [Additional note 2] The first number is greater than the second number Item 1. A radiographic imaging apparatus according to claim 1. [Additional note 3] The first number is 6 and the second number is 5 Item 2. A radiographic imaging apparatus according to claim 2. [Additional note 4] a photon counting circuit that counts photons for each of the first macropixels and each of the second macropixels; an image processing unit that generates a radiation image based on the count value by the photon counting circuit; Equipped with Item 3. A radiographic imaging apparatus according to any one of items 1 to 3. [Additional note 5] The image processing unit corrects artifacts having a frequency caused by the arrangement of the second macro pixels. Item 5. A radiographic imaging apparatus according to claim 4. [Additional note 6] The image processing unit corrects the count values ​​of the photons counted for each of the first macro-pixels and each of the second macro-pixels based on the first number and the second number. Item 6. The radiographic imaging apparatus according to claim 4 or 5. [Additional note 7] If the first number is greater than the second number, The image processing unit distributes a part of the count value of the photons for the first macro-pixel to the count value of the photons for the adjacent second macro-pixel. Item 7. The radiographic imaging apparatus according to claim 6. [Explanation of symbols]

[0084] 2. Radiography equipment 3 X-ray source 4 X-ray detector 5 x Gantries 6 berths 7 Control Unit 8 Image processing section 9 Input Devices 10 Display device 11 Storage device 12. Communications equipment 31 X-ray tube 32 aperture 33 X-ray filter 34 Bowtie Filter 40 detector modules 41 Collimator 42 Semiconductor layer 43 ASIC 42a common electrode 42b Individual electrode 44 Photon counting circuit 46 Holding board 47 Power supply 48 Switching Circuits 51 Opening 52 Rotating Plate C rotation axis G Gap H Subject MP macro pixel MP1 1st macro pixel MP2 2nd macro pixel SP subpixel

Claims

1. 1. A radiographic imaging apparatus comprising: a radiation source that rotates around a rotation axis and emits radiation; and a radiation detector that rotates around the rotation axis while facing the radiation source and detects the radiation, wherein the radiographic imaging apparatus is capable of imaging in a plurality of imaging modes in which set beam widths of the radiation in the rotation axis direction on the rotation axis are different, The radiation detector comprises: a plurality of sub-pixels arranged in a first direction parallel to the rotation axis and a second direction perpendicular to the rotation axis; a plurality of first macro pixels each formed by grouping a first number of the sub-pixels aligned in the first direction, and a plurality of second macro pixels each formed by grouping a second number of the sub-pixels aligned in the first direction, the second number being different from the first number, are provided; The second macropixels are arranged so that an effective beam width determined by the number of the first macropixels and the second macropixels for constituting the number of slices corresponding to the set beam width falls within a predetermined range not less than each of the set beam widths. Radiography equipment.

2. The first number is greater than the second number. The radiographic apparatus according to claim 1 .

3. The first number is 6 and the second number is 5 The radiographic imaging apparatus according to claim 2 .

4. a photon counting circuit that counts photons for each of the first macropixels and each of the second macropixels; an image processing unit that generates a radiation image based on the count value by the photon counting circuit; Equipped with The radiographic imaging apparatus according to any one of claims 1 to 3.

5. The image processing unit corrects artifacts having a frequency caused by the arrangement of the second macropixels. The radiographic apparatus according to claim 4 .

6. The image processing unit corrects the count value of the photons counted for each of the first macro-pixels and each of the second macro-pixels based on the first number and the second number. The radiographic apparatus according to claim 4 .

7. If the first number is greater than the second number, The image processing unit distributes a part of the count value of the photons for the first macro-pixel to the count value of the photons for the adjacent second macro-pixel. The radiographic imaging apparatus according to claim 6 .

Images