Information processing device, information processing method, and information processing program

Abstract

The present invention provides an information processing device, an information processing method, and an information processing program that can improve the accuracy of artifact correction. [Solution] An information processing device comprising a processor, the processor acquires first projection data output from a detector that detects radiation of a first energy that has passed through an object, and second projection data output from a detector that detects radiation of a second energy different from the first energy that has passed through the object, and performs correction processing to correct artifacts in regions where the amount of change between the first projection data and the second projection data is greater than or equal to a threshold.

Description

Technical Field

[0001] The present disclosure relates to an information processing apparatus, an information processing method, and an information processing program.

Background Art

[0002] Radiation is irradiated onto a subject by a CT (Computed Tomography) apparatus or the like to capture a medical image. For example, when a metal is included in the imaging target, such as when there is a bolt used for fixing a bone in the subject, the captured medical image includes artifacts due to the influence of the metal.

[0003] Therefore, techniques for removing artifacts from medical images are known. For example, in the techniques described in Patent Document 1 and Patent Document 2, a metal region is specified from a CT image generated by reconstructing projection data, and the projection data is corrected by forward-projecting the metal region image and using the projection data of the metal region to remove the influence of the artifacts.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The techniques described in References 1 and 2 identify metallic regions from CT images. Because these CT images contain artifacts, errors can occur when identifying metallic regions. Projecting these metallic region images forward introduces errors into the forward projection data, and the interpolation process during forward projection also causes blurring. Therefore, it was sometimes impossible to properly correct the projection data.

[0006] This disclosure has been made in consideration of the above circumstances and aims to provide an information processing device, an information processing method, and an information processing program that can improve the accuracy of artifact correction. [Means for solving the problem]

[0007] To achieve the above objective, the information processing device of the first aspect of this disclosure includes a processor which acquires first projection data output from a detector that detects radiation of a first energy that has passed through an object, and second projection data output from a detector that detects radiation of a second energy different from the first energy that has passed through the object, and performs correction processing to correct artifacts in regions where the amount of change between the first projection data and the second projection data is greater than or equal to a threshold.

[0008] In the second embodiment of the information processing apparatus, the processor performs a correction process on the region of the data to be corrected, which is the difference between the first projection data and the second projection data, or the difference between the first projection data and the second projection data, by correcting the region with interpolated data, and generates a reconstructed image after interpolation by reconstructing the corrected data to be corrected.

[0009] In the third embodiment of the information processing apparatus, the processor generates an interpolation error reduction image obtained by reducing the interpolation error component from the reconstructed image after interpolation processing, generates interpolation error reduction forward projection data obtained by forward projection of the interpolation error reduction image, replaces the region of the data to be corrected based on the interpolation error reduction forward projection data so as to increase the continuity between the region and adjacent regions, and performs residual error reduction processing on the replaced data to be corrected to generate corrected projection data.

[0010] In the fourth embodiment of the information processing apparatus, the processor performs the replacement process using either baseline shift or normalized interpolation, as in the information processing apparatus of the third embodiment.

[0011] In the fifth embodiment of the information processing apparatus, the processor performs residual error reduction processing on error projection data obtained by subtracting the metal component corresponding to the metal and the interpolation error reduction forward projection data from the data to be corrected.

[0012] In the sixth embodiment of the information processing apparatus, the processor performs residual error reduction processing based on frequency information, in the information processing apparatus of the third embodiment.

[0013] The information processing apparatus of the seventh embodiment is an information processing apparatus of the sixth embodiment in which the processor performs weighted addition as residual error reduction processing, in which the weight of frequency components other than high-frequency and low-frequency components is given more weight than the weight of high-frequency components corresponding to noise and low-frequency components corresponding to artifacts.

[0014] The information processing apparatus of the eighth embodiment, in the information processing apparatus of the third embodiment, generates an interpolation error reduction image in which the pixel values ​​of pixels having pixel values ​​within a predetermined range are replaced with pixel values ​​other than the original pixel values.

[0015] An information processing device of the ninth embodiment, in an information processing device of the first embodiment, derives a change amount based on the difference or ratio of first projection data and second projection data.

[0016] To achieve the above object, the information processing method according to the tenth aspect of the present disclosure is such that a processor acquires first projection data output from a detector that has detected radiation of a first energy that has passed through a subject, and second projection data output from a detector that has detected radiation of a second energy different from the first energy that has passed through the subject, and performs a correction process for correcting artifacts on a region where the amount of change between the first projection data and the second projection data is equal to or greater than a threshold value.

[0017] To achieve the above object, the information processing program according to the eleventh aspect of the present disclosure causes a processor to acquire first projection data output from a detector that has detected radiation of a first energy that has passed through a subject, and second projection data output from a detector that has detected radiation of a second energy different from the first energy that has passed through the subject, and execute a process for performing a correction process for correcting artifacts on a region where the amount of change between the first projection data and the second projection data is equal to or greater than a threshold value.

Advantages of the Invention

[0018] According to the present disclosure, the correction accuracy of artifacts can be improved.

Brief Description of the Drawings

[0019] [Figure 1] It is a configuration diagram showing an example of the configuration of the CT apparatus of the embodiment. [Figure 2] It is a configuration diagram showing an example of the configuration of the console of the embodiment. [Figure 3] It is a functional block diagram showing an example of the functions of the console of the embodiment. [Figure 4] It is a flowchart showing an example of the flow of information processing of the embodiment.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that this embodiment does not limit the present invention.

[0021] First, an example of the configuration of a CT (Computed Tomography) apparatus according to this embodiment will be described. FIG. 1 shows a configuration diagram representing an example of the configuration of a CT apparatus 10 according to this embodiment. As shown in FIG. 1, the CT apparatus 10 according to this embodiment includes a gantry 20, a couch 27, and a console 30.

[0022] The gantry 20 has an opening 26, and the subject S to be imaged is placed on the couch 27 and disposed within the opening 26. The gantry 20 and the couch 27 are relatively movable in a direction penetrating the opening 26.

[0023] Inside the gantry 20, a radiation generation device 23 having a radiation tube (not shown), a bowtie filter 24, a collimator 25, and a detector 28 are disposed in a state of facing each other with the subject S interposed therebetween. The radiation R irradiated from the radiation generation device 23 is shaped into a beam shape suitable for the size of the subject S by the bowtie filter 24 and the collimator 25 and irradiated onto the subject S. The detector 28 detects the radiation transmitted through the subject S and generates a projection image according to the dose of the detected radiation. The detector 28 according to this embodiment is a photon counting type photon counting detector in which a plurality of detection elements (not shown) that detect the photon energy, which is the energy of photons of the incident radiation, are arranged in an arc shape centered on the focal point of the radiation tube of the radiation generation device 23. The detector 28, which is a photon counting type detector, outputs a projection image according to the photon energy.

[0024] The radiation generation device 23 and the detector 28 are rotated around the subject S by a rotation drive unit (not shown) of the gantry 20. By repeating the radiation irradiation from the radiation generation device 23 and the detection of the radiation by the detector 28 along with the rotation of both, projection data at various projection angles are acquired. The plurality of projection data detected by the detector 28 are output to the console 30.

[0025] The console 30 in this embodiment performs various controls related to image acquisition and generates medical images. The medical images generated by the console 30 are output via the network to an external device (not shown) such as a PACS (Picture Archiving and Communication System).

[0026] The console 30 of this embodiment is an example of an information processing device of the present disclosure. As an example, the console 30 of this embodiment is a server computer. As shown in Figure 2, the console 30 comprises a control unit 32, a storage unit 34, an I / F (Interface) unit 35, an operation unit 36, and a display unit 38. The control unit 32, storage unit 34, I / F unit 35, operation unit 36, and display unit 38 are connected to each other via a bus 39 such as a system bus or a control bus, enabling the exchange of various types of information.

[0027] The control unit 32 in this embodiment controls the overall operation of the console 30. The control unit 32 includes a CPU (Central Processing Unit) 32A, a ROM (Read Only Memory) 32B, and a RAM (Random Access Memory) 32C. The ROM 32B pre-stores various programs, including the information processing program 33 described later, which is executed by the CPU 32A. The RAM 32C temporarily stores various data.

[0028] The memory unit 34 stores projection data output from the detector 28, as well as various other information. Specific examples of the memory unit 34 include storage media such as HDDs (Hard Disk Drives), SSDs (Solid State Drives), and flash memory.

[0029] The I / F unit 35 communicates various types of information with the rotation drive unit (not shown) of the gantry 20, the radiation generator 23, and the detector 28 via wired or wireless communication. In this embodiment, the console 30 receives projection data from the detector 28 via the I / F unit 35. The received projection data is stored in the storage unit 34.

[0030] The console 30 acquires multiple projection data from the detector 28 via the I / F unit 35. The control unit 32 reconstructs the acquired multiple projection data and generates a tomographic image, which is a reconstructed image of the subject S.

[0031] The operation unit 36 ​​is used by the user to input various information, such as scan conditions for acquiring projection data, instructions for generating images such as parameter settings, and instructions for displaying images. The operation unit 36 ​​is not particularly limited and may include, for example, various switches, buttons, touch panels, styluses, keyboards, and mice. The display unit 38 displays various information, medical images, etc. The operation unit 36 ​​and the display unit 38 may be integrated to form a touch panel display. For example, the operation unit 36 ​​may also accept voice input from the user.

[0032] The CT scanner 10 in this embodiment is a multi-energy CT scanner. In a multi-energy CT scanner, multiple types of projection data can be acquired by detecting each of several different energy levels of radiation with the detector 28. For example, in the case of a dual-energy CT scanner, which is a type of multi-energy CT scanner, two types of projection data are obtained: low-energy projection data corresponding to relatively low-energy radiation and high-energy projection data corresponding to relatively high-energy radiation. By using the multiple types of projection data obtained, for example, a virtual monochromatic X-ray image can be generated.

[0033] The imaging method for multi-energy CT using the CT apparatus 10 of this embodiment, that is, the method for acquiring multiple types of projection data with different energies, is not particularly limited, and known imaging methods can be applied.

[0034] As an example, in this embodiment, the CT apparatus 10 is a dual-energy CT, and at each of the multiple projection angles, relatively low first-energy radiation is irradiated onto the subject S from the radiation generator 23, and low-energy projection data is acquired by the detector 28. In addition, second-energy radiation, which is higher than the first energy, is irradiated onto the subject S from the radiation generator 23, and high-energy projection data is acquired by the detector 28. Therefore, the console 30 outputs multiple low-energy projection data and multiple high-energy projection data from the detector 28. Note that the low-energy projection data in this embodiment is an example of either the first projection data or the second projection data of this disclosure, and the high-energy projection data in this embodiment is an example of either the first projection data or the second projection data of this disclosure.

[0035] Figure 3 shows a functional block diagram illustrating an example of the console 30's functions. The console 30 comprises an acquisition unit 40, a identification unit 42, and a correction unit 44. As an example, in this embodiment, the console 30 executes an information processing program 33, causing the CPU 32A of the control unit 32 to function as the acquisition unit 40, the identification unit 42, and the correction unit 44.

[0036] The acquisition unit 40 has the function of acquiring multiple low-energy projection data and multiple high-energy projection data output from the detector 28. Specifically, as described above, the acquisition unit 40 acquires low-energy projection data and high-energy projection data captured by two types of radiation with different energies sequentially irradiated onto the subject S in each of multiple directions from the detector 28 via the I / F unit 35. In order to observe the changes between the low-energy projection data and the high-energy projection data, it is preferable that both projection data be acquired at approximately the same position. For example, a two-layer detector 28, a two-rotation method, and PCCT (Photon Counting Computed Tomography) are preferred. The acquisition unit 40 may also acquire the low-energy projection data and high-energy projection data acquired from the detector 28 and temporarily stored in the storage unit 34, and then acquire them from the storage unit 34. The acquisition unit 40 outputs the acquired low-energy projection data and high-energy projection data to the identification unit 42.

[0037] The identification unit 42 has the function of identifying a predetermined region in the projection space. In this embodiment, the identification unit 42 identifies metallic regions for each of the multiple low-energy projection data and the multiple high-energy projection data. The identification unit 42 identifies regions as metallic regions where the amount of change between the low-energy projection data and the high-energy projection data is greater than or equal to a threshold. Metals that are reflected in the low-energy projection data and high-energy projection data along with the subject S have a larger amount of change between the low-energy projection data and the high-energy projection data, or a larger amount of change between the high-energy projection data and the low-energy projection data, compared to human tissue. Therefore, a threshold is obtained that makes it possible to distinguish from human tissue, and the identification unit 42 identifies regions as metallic regions where the amount of change between the high-energy projection data and the metal is greater than or equal to the threshold. The specific threshold can be predetermined according to the energy of the radiation irradiated from the radiation generator 23, the type of metal, etc.

[0038] The identification unit 42 may identify metallic regions based on the amount of change between spectral image data. For example, the acquisition unit 40 reconstructs multiple spectral projection data (corrected projection data) having different spectral information to generate multiple spectral image data having different spectral information. The identification unit 42 may identify metallic regions in the image space based on the amount of change between the multiple spectral image data, and then identify metallic regions in high-energy projection data and low-energy projection data by forward projection processing of the identified metallic regions. Here, the spectral information includes any of the following: photon energy, base material information, effective atomic number information, electron density information, and scattered X-ray information.

[0039] The identification unit 42 outputs information representing the metal region identified in each of the multiple low-energy projection data and the multiple high-energy projection data to the correction unit 44.

[0040] The correction unit 44 has the function of performing correction processing to correct artifacts in the metal region identified by the identification unit 42. The correction processing to correct artifacts is a process that reduces errors caused by metal. Errors caused by metal include beam hardening, noise, and errors caused by scattered radiation.

[0041] Specifically, the correction unit 44 performs a process in the projection space to correct the metal regions of the low-energy projection data and the high-energy projection data with interpolation data. This process generates low-energy interpolated projection data corresponding to the low-energy projection data and high-energy interpolated projection data corresponding to the high-energy projection data. The interpolation data can be predetermined data depending on the energy of the irradiated radiation, the subject S, etc. Interpolation data is the data generated by the interpolation process. Interpolation is a process that estimates the projection data of a metal region from projection data with small errors adjacent to the projection data of a metal region with large errors. Specifically, examples include simple linear interpolation from two nearby projection data, or interpolation using forward projection data of an image with reduced artifacts, baseline shift, normalized interpolation, etc. Note that here, when referring collectively to low-energy interpolated projection data and high-energy interpolated projection data, they are simply called "interpolated projection data."

[0042] Furthermore, the correction unit 44 reconstructs the projection data after interpolation to generate a reconstructed image after interpolation. Specifically, the correction unit 44 reconstructs the projection data after low-energy interpolation to generate a reconstructed image after low-energy interpolation, and also reconstructs the projection data after high-energy interpolation to generate a reconstructed image after high-energy interpolation. Here, when referring to both the reconstructed image after low-energy interpolation and the reconstructed image after high-energy interpolation collectively, they are simply called "reconstructed image after interpolation."

[0043] Furthermore, the correction unit 44 performs interpolation error reduction processing on the reconstructed image after interpolation processing to remove any remaining errors (artifacts) after replacing the metal region with interpolation data as described above, thereby generating an interpolation error reduction image. Specifically, the correction unit 44 performs interpolation error reduction processing on the reconstructed image after low-energy interpolation processing to generate a low-energy interpolation error reduction image, and also performs interpolation error reduction processing on the reconstructed image after high-energy interpolation processing to generate a high-energy interpolation error reduction image. Here, when referring to both the low-energy interpolation error reduction image and the high-energy interpolation error reduction image collectively, they are simply referred to as "interpolation error reduction images." In this embodiment, the correction unit 44 generates interpolation error reduction images by replacing the pixel values ​​of pixels having pixel values ​​within a predetermined range with pixel values ​​other than those pixel values. For example, segmentation processing can be used as an example of such processing. The predetermined range of pixel values ​​can be determined according to the pixel values ​​of the errors (artifacts) remaining after replacing the metal region with interpolation data. For example, among the bone tissue, soft tissue, and air tissue that make up human body tissue, a predetermined range can be defined based on the range of pixel values ​​of soft tissue, which is strongly affected by interpolation errors. By replacing pixels whose pixel values ​​fall within this predetermined range with, for example, the average value of the pixel values ​​within the predetermined range, which is a representative CT value of soft tissue, fluctuations in the CT value due to interpolation errors can be suppressed. Alternatively, instead of the average value, a predetermined pixel value may be used depending on the energy of the irradiated radiation or the subject S, etc.

[0044] Furthermore, the correction unit 44 projects the interpolation error reduction image forward into the projection space to generate interpolation error reduction forward projection data. Specifically, the correction unit 44 generates low-energy interpolation error reduction forward projection data by projecting the low-energy interpolation error reduction image forward into the projection space, and generates high-energy interpolation error reduction forward projection data by projecting the high-energy interpolation error reduction image forward into the projection space. Here, when referring to both the low-energy interpolation error reduction forward projection data and the high-energy interpolation error reduction forward projection data collectively, they are simply called "interpolation error reduction forward projection data."

[0045] Furthermore, the correction unit 44 performs residual error reduction processing on the metallic regions of the low-energy projection data and the metallic regions of the high-energy projection data to reduce residual errors (artifacts) remaining after the above processing, and generates corrected projection data. Specifically, the correction unit 44 replaces the metallic regions of the low-energy projection data with adjacent regions based on the interpolated error-reduced forward projection data, so as to improve the continuity between the metallic regions and adjacent regions. It also replaces the metallic regions of the high-energy projection data with adjacent regions based on the interpolated error-reduced forward projection data, so as to improve the continuity between the metallic regions and adjacent regions. For example, baseline shifting or normalized interpolation may be used for the replacement process. Furthermore, the correction unit 44 performs residual error reduction processing on the replaced low-energy projection data and high-energy projection data to generate corrected projection data. As an example, the correction unit 44 in this embodiment performs residual error reduction processing on error projection data obtained by subtracting the metallic components corresponding to the metal and the interpolated error-reduced forward projection data from each of the low-energy projection data and high-energy projection data.

[0046] Furthermore, the correction unit 44 may perform residual error reduction processing based on frequency information. For example, the correction unit 44 removes low-frequency components as noise and removes high-frequency components higher than the reference, such as the highest frequency component, as photon noise. In this embodiment, the error projection data is assumed to consist of noise, interpolation errors, metal artifacts, and structural components, and the highest frequency component corresponding to the beam spacing of the projection data is treated as noise, the low-frequency component as metal artifacts, and the other components (hereinafter referred to as medium-frequency components) as structural information. As residual error reduction processing, the correction unit 44 reduces the residual error by weighting and adding these components. These weights may be those set in advance according to the type of metal to be corrected, or values ​​that have been verified in advance with various data and determined empirically may be used. Specifically, the separation into high-frequency components, low-frequency components, and medium-frequency components may be performed in real space using a smoothing filter, or the separation may be performed by filtering in the frequency space after the Fourier transform. The filtering in the frequency space may be incorporated as frequency modulation in the reconstruction filter. The weights of the medium-frequency components and high-frequency components of the error projection data are set to be high, low, and high-frequency components are also set to be low. The correction unit 44 performs residual error reduction processing on the interpolation error reduction projection data by weighted addition.

[0047] Furthermore, the correction unit 44 reconstructs the corrected projection data to generate a corrected reconstructed image. Specifically, the correction unit 44 reconstructs the low-energy interpolation error reduction forward projection data to generate a low-energy corrected reconstructed image, and also reconstructs the high-energy interpolation error reduction forward projection data to generate a high-energy corrected reconstructed image. Here, when referring to both the low-energy corrected reconstructed image and the high-energy corrected reconstructed image collectively, they are simply called "corrected reconstructed images."

[0048] Next, the operation of the console 30 in this embodiment will be described.

[0049] In this embodiment, the console 30 executes the information processing shown in Figure 4 by having the CPU 32A of the control unit 32 execute the information processing program 33 stored in the ROM 32B. Figure 4 shows a flowchart illustrating an example of the information processing flow in the console 30 of this embodiment.

[0050] First, in step S100 of Figure 4, the acquisition unit 40 acquires multiple low-energy projection data and multiple high-energy projection data, as described above.

[0051] In the next step S102, the identification unit 42 identifies the metallic region in the projection space from the low-energy projection data and the high-energy projection data, respectively, as described above.

[0052] In the next step S104, the correction unit 44 generates interpolated projection data by replacing the metal region with interpolated data, as described above.

[0053] In the next step S106, the correction unit 44 reconstructs the interpolated projection data as described above to generate the reconstructed image after interpolation.

[0054] In the next step S108, the correction unit 44 performs interpolation error reduction processing on the reconstructed image after interpolation processing, as described above, to generate an interpolation error reduction image.

[0055] In the next step S110, the correction unit 44 projects the interpolation error reduction image forward into the projection space as described above, and generates interpolation error reduction forward projection data.

[0056] In the next step S112, the correction unit 44 performs residual error reduction processing on the metal region as described above and generates corrected projection data.

[0057] In the next step S114, the correction unit 44 reconstructs the corrected projection data as described above to generate a corrected reconstructed image.

[0058] In the next step, S116, the correction unit 44 outputs the corrected reconstructed image generated in step S114 to a predetermined output destination. The output destination may be the storage unit 34 of the console 30, or it may be an external device to the console 30. A virtual monochromatic X-ray image can be generated, for example, from the corrected reconstructed image generated in this way.

[0059] Once the process in step S116 is completed, the information processing shown in Figure 4 is finished.

[0060] As described above, in each of the above embodiments, the console 30 has a CPU 32A that functions as an acquisition unit 40 to acquire low-energy projection data output from a detector 28 that detects low-energy radiation that has passed through the subject S, and high-energy projection data output from a detector 28 that detects high-energy radiation that has passed through the subject S. The CPU 32A also functions as an identification unit 42 to identify a region where the amount of change between the low-energy projection data and the high-energy projection data is greater than or equal to a threshold as a metallic region. The CPU 32A also functions as a correction unit 44 to perform correction processing to correct artifacts in the metallic region.

[0061] Thus, in the console 30 of the above embodiment, compared to identifying metallic regions from reconstructed images, metallic regions are identified in the projection space from low-energy projection data and high-energy projection data that are unaffected or have minimal artifact effects. Therefore, the console 30 of the above embodiment improves the accuracy of identifying metallic regions, thereby improving the accuracy of artifact correction. Furthermore, the console 30 of the above embodiment can restore structures that are distorted when artifacts are removed.

[0062] In the above embodiment, the correction unit 44 was described as performing correction on the metallic region of the low-energy projection data and the high-energy projection data. However, it is also possible to perform correction on the metallic region of the difference data between the low-energy projection data and the high-energy projection data. That is, the data to be corrected in this disclosure may be, for example, the low-energy projection data and the high-energy projection data, or it may be the difference data between the low-energy projection data and the high-energy projection data.

[0063] Furthermore, although the above embodiment describes a configuration in which the console 30 acquires projection data of two types of energy, low energy and high energy, from the detector 28 of the CT device 10, it is also possible to acquire projection data of three types of energy. For example, the detector 28 of the CT device 10 may detect three types of projection data, each with different radiation energies: low energy projection data, medium energy projection data, and high energy projection data.

[0064] Furthermore, the correction unit 44 may identify metallic regions in image space based on a change derived from the difference or ratio between a low-energy reconstructed image obtained by reconstructing low-energy projection data and a high-energy reconstructed image obtained by reconstructing high-energy projection data. For example, when acquiring projection data at various projection angles, if low-energy projection data is acquired by irradiating with low-energy radiation at one projection angle, and high-energy projection data is acquired by irradiating with high-energy radiation at the next projection angle, in cases where there is no low-energy projection data and high-energy projection data with the same projection angle, the correction unit 44 may identify metallic regions in image space instead of identifying metallic regions in projection space as described above. For example, as a result of correction processing including interpolation processing in projection space, projection data from which metallic components have been removed may be generated depending on the processing. In such cases, it is preferable to be able to identify metallic regions in image space in order to add metallic information in image space.

[0065] In the above embodiment, the console 30 was described as having three processing units: an acquisition unit 40, a specific unit 42, and a correction unit 44. However, the functions of these processing units may be carried out by two or fewer processing units, or by four or more processing units. For example, one processing unit having the functions of the specific unit 42 and the correction unit 44 may perform correction processing to correct artifacts in a region (the metallic region in the above embodiment) where the amount of change between the low-energy projection data and the high-energy projection data exceeds a threshold.

[0066] Furthermore, in the above embodiment, the identification unit 42 identifies a metallic region, and the correction unit 44 corrects artifacts for the metallic region identified by the identification unit 42. However, the target region for identification and correction is not limited to metallic regions. The target region for identification and correction is any region where the change between the low-energy projection data and the high-energy projection data exceeds a threshold, and may be, for example, a region such as bone.

[0067] In the above embodiment, each process is executed on any computer. Furthermore, any computer may execute these processes using a processor as hardware, a program as software, or a combination thereof. In that case, the processor is configured to work in cooperation with the program to execute the various processes in this embodiment, and can function as a unit or means in this embodiment. Also, the execution order of the processes by the processor is not limited to the order described and may be changed as appropriate. Any computer may be a general-purpose computer, a computer designed for a specific purpose, a workstation, or any other system capable of executing each process.

[0068] A processor may consist of one or more hardware components, and the type of hardware is not limited. For example, a processor may consist of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a programmable logic device such as an FPGA (Field Programmable Gate Array), a dedicated circuit for executing a specific process such as an ASIC (Application Specific Integrated Circuit), a GPU (Graphic Processing Unit), or an NPU (Neural Processing Unit). Furthermore, the type of hardware may be a combination of different types of hardware. When multiple hardware components are configured to execute one or more processes of a given processor, these components may reside in physically separate devices or in the same device. Also, in any embodiment, the order of each process performed by the processor is not limited to the order described above and may be changed as appropriate. Hardware is composed of electrical circuits (circuitry) that combine circuit elements such as semiconductor elements.

[0069] Furthermore, the program may be firmware or software such as microcode. Alternatively, the program may be, for example, a set of program modules, each function of which may be implemented by a processor configured to perform its respective function. The program may be program code or multiple code segments stored on one or more non-temporary computer-readable media (e.g., storage media or other storage). The program may be divided and stored on multiple non-temporary computer-readable media located on physically separate devices. Program code or code segments may represent any combination of procedures, functions, subprograms, routines, subroutines, modules, software packages, classes, or instructions, data structures, or program statements. Program code or code segments may be connected to other code segments or hardware circuits by sending and receiving information, data, arguments, parameters, or memory contents.

[0070] Furthermore, although the above embodiment describes an embodiment in which the information processing program 33 is pre-stored (installed) in the storage unit 34 of the console 30, the embodiment is not limited to this. The information processing program 33 may be provided in the form of a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), and USB (Universal Serial Bus) memory. Alternatively, the information processing program 33 may be provided in the form of a download from an external device via a network.

[0071] Furthermore, the technology disclosed herein extends to all program products. Program products include all forms of products for providing programs. For example, program products include programs provided via networks such as the Internet, and non-temporary computer-readable recording media such as CD-ROMs, DVDs, and USB memory sticks on which programs are stored.

[0072] Furthermore, the configuration and operation of the CT apparatus 10, console 30, etc., described in each of the above embodiments are merely examples and can be modified as needed without departing from the spirit of the present invention. It also goes without saying that the above embodiments may be combined as appropriate.

[0073] The following additional information is disclosed regarding the above-described embodiments. (Note 1) Equipped with a processor, The aforementioned processor, First projection data output from a detector that detected radiation of a first energy that passed through the subject, and second projection data output from a detector that detected radiation of a second energy different from the first energy that passed through the subject are obtained. Correction processing is performed to correct artifacts in regions where the amount of change between the first projection data and the second projection data exceeds a threshold. Information processing device.

[0074] (Note 2) The aforementioned processor, The correction process involves correcting the region of the corrected data, which is the difference between the first projection data and the second projection data, or the difference between the first projection data and the second projection data, with interpolated data. The reconstructed image after interpolation is generated by reconstructing the corrected data. The information processing device described in Appendix 1.

[0075] (Note 3) The aforementioned processor, An interpolation error reduction image is generated from the reconstructed image after the interpolation process by reducing the interpolation error component. The interpolation error reduction forward projection data is generated by forward projection of the aforementioned interpolation error reduction image. Based on interpolation error reduction forward projection data, the region of the data to be corrected is replaced in such a way that the continuity between the region and adjacent regions is increased. After replacement, the corrected data is subjected to residual error reduction processing to generate corrected projected data. The information processing device described in Appendix 2.

[0076] (Note 4) The aforementioned processor, The replacement process is performed using either baseline shifting or normalized interpolation. The information processing device described in Appendix 3.

[0077] (Note 5) The aforementioned processor, The residual error reduction process is applied to the error projection data obtained by subtracting the metal component corresponding to the metal and the interpolation error reduction forward projection data from the corrected data. The information processing device described in Appendix 3 or Appendix 4.

[0078] (Note 6) The aforementioned processor, Based on the frequency information, the residual error reduction process is performed. An information processing device as described in any one of the appendices 3 to 5.

[0079] (Note 7) The aforementioned processor, As part of the residual error reduction process, a weighted sum is performed in which the weights of frequency components other than the high-frequency components and low-frequency components are given greater weight than the weights of the high-frequency components corresponding to noise and the low-frequency components corresponding to artifacts. The information processing device described in Appendix 6.

[0080] (Note 8) The aforementioned processor, An interpolation error reduction image is generated by replacing the pixel values ​​of pixels having a predetermined range of pixel values ​​with pixel values ​​other than those specified. An information processing device as described in any one of the appendices 3 through 7.

[0081] (Note 9) The aforementioned processor, The amount of change is derived based on the difference or ratio between the first projection data and the second projection data. An information processing device as described in any one of the appendices 1 through 8.

[0082] (Note 10) The processor, First projection data output from a detector that detected radiation of a first energy that passed through the subject, and second projection data output from a detector that detected radiation of a second energy different from the first energy that passed through the subject are obtained. Correction processing is performed to correct artifacts in regions where the amount of change between the first projection data and the second projection data exceeds a threshold. Information processing methods.

[0083] (Note 11) In the processor, First projection data output from a detector that detected radiation of a first energy that passed through the subject, and second projection data output from a detector that detected radiation of a second energy different from the first energy that passed through the subject are obtained. Correction processing is performed to correct artifacts in regions where the amount of change between the first projection data and the second projection data exceeds a threshold. An information processing program used to execute a process. [Explanation of Symbols]

[0084] 10 CT device 12 Image Management Systems 14 Workstations 20 Gantry 23 Radiation Generating Devices 24 Bowtie Filters 25 Collimator 26 Opening 27 berths 28 detectors 30 Console 32 control unit, 32A CPU, 32B ROM, 32C RAM 33 Information Processing Programs 34 Storage section 35 I / F section 36 Control section 38 Display section 39 bus 40 Acquisition Department 42 Specific part 44 Correction section R radiation S Subject

Claims

1. Equipped with a processor, The aforementioned processor, First projection data output from a detector that detected radiation of a first energy that passed through the subject, and second projection data output from a detector that detected radiation of a second energy different from the first energy that passed through the subject are obtained. Correction processing is performed to correct artifacts in regions where the amount of change between the first projection data and the second projection data exceeds a threshold. Information processing device.

2. The aforementioned processor, The correction process involves correcting the region of the corrected data, which is the difference between the first projection data and the second projection data, or the difference between the first projection data and the second projection data, with interpolated data. The reconstructed image after interpolation is generated by reconstructing the corrected data. The information processing apparatus according to claim 1.

3. The aforementioned processor, An interpolation error reduction image is generated from the reconstructed image after the interpolation process by reducing the interpolation error component. The interpolation error reduction forward projection data is generated by forward projection of the aforementioned interpolation error reduction image. Based on interpolation error reduction forward projection data, the region of the data to be corrected is replaced in such a way that the continuity between the region and adjacent regions is increased. After replacement, the corrected data is subjected to residual error reduction processing to generate corrected projected data. The information processing apparatus according to claim 2.

4. The aforementioned processor, The replacement process is performed using either baseline shifting or normalized interpolation. The information processing apparatus according to claim 3.

5. The aforementioned processor, The residual error reduction process is applied to the error projection data obtained by subtracting the metal component corresponding to the metal and the interpolation error reduction forward projection data from the corrected data. The information processing apparatus according to claim 3.

6. The aforementioned processor, Based on the frequency information, the residual error reduction process is performed. The information processing apparatus according to claim 3.

7. The aforementioned processor, As part of the residual error reduction process, a weighted sum is performed in which the weights of frequency components other than the high-frequency components and low-frequency components are given greater weight than the weights of the high-frequency components corresponding to noise and the low-frequency components corresponding to artifacts. The information processing apparatus according to claim 6.

8. The aforementioned processor, Generates an interpolation error reduction image by replacing the pixel values ​​of pixels with a specific range of pixel values ​​with pixel values ​​other than those specified. The information processing apparatus according to claim 3.

9. The aforementioned processor, The amount of change is derived based on the difference or ratio between the first projection data and the second projection data. The information processing apparatus according to claim 1.

10. The processor, First projection data output from a detector that detected radiation of a first energy that passed through the subject, and second projection data output from a detector that detected radiation of a second energy different from the first energy that passed through the subject are obtained. Correction processing is performed to correct artifacts in regions where the amount of change between the first projection data and the second projection data exceeds a threshold. Information processing methods.

11. In the processor, First projection data output from a detector that detected radiation of a first energy that passed through the subject, and second projection data output from a detector that detected radiation of a second energy different from the first energy that passed through the subject are obtained. Correction processing is performed to correct artifacts in regions where the amount of change between the first projection data and the second projection data exceeds a threshold. An information processing program used to execute a process.

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