Image processing apparatus, image processing method, computer readable medium, and computer program product

Abstract

Provided are an image processing device, an image processing method, a computer-readable medium, and a computer program product with which it is possible to determine a stationary phase with high precision while suppressing the time required for processing. A processor provided in an image processing apparatus performs: acquisition of projection data corresponding to a phase determined by an electrocardiogram, the projection data being imaged in synchronization with the electrocardiogram of a subject using radiation sequentially irradiated from a plurality of directions to an imaging site of the subject; specifying, from a first reconstructed image reconstructed from projection data corresponding to phases included in the first phase range among the phases, a temporary stationary phase assumed to be the stationary phase of the subject; generating a second reconstructed image in which the motion of the subject is corrected, the second reconstructed image being reconstructed from projection data corresponding to a phase included in the first phase range and included in a second phase range including the temporary stationary phase among the phases; and determining a stationary phase of the subject on the basis of the second reconstructed image.

Description

Technical Field

[0001] The present invention relates to an image processing device, an image processing method and an image processing program. Background Art

[0002] A known technique for analyzing the periodic motion of the heart based on electrocardiographic information obtained during imaging of a subject using a radiographic CT (Computed Tomography) apparatus is described. The technique identifies the phase with the least motion, i.e., the stationary phase (see, for example, Patent Document 1). Using the identified stationary phase, imaging is performed, for example, in synchronization with the stationary phase, or diagnostic images are reconstructed using projection data from the stationary phase.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-204961

[0004] However, in conventional technologies, attempts to detect the stationary phase with higher accuracy may sometimes require a considerable amount of time for processing. Summary of the Invention

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image processing device, an image processing method, and an image processing program that can suppress the time required for processing and determine a stationary phase with high accuracy.

[0006] In order to achieve the above-mentioned purpose, the image processing device of the first mode of the present invention has at least one processor, and the processor performs the following processing: acquiring projection data, wherein the projection data is photographed synchronously with the electrocardiogram of the subject using radiation sequentially irradiated to the photographing part of the subject from multiple directions and corresponds to the phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be the stationary phase of the subject based on a first reconstructed image reconstructed by the projection data corresponding to the phase included in the first phase range; generating a second reconstructed image reconstructed by the projection data and with the movement of the subject corrected, wherein the projection data corresponds to the phase included in the first phase range and included in the second phase range including the temporary stationary phase; and determining the stationary phase of the subject based on the second reconstructed image.

[0007] In the image processing device of the second mode, in the image processing device of the first mode, the processor performs the following processing: generates a second reconstructed image according to the first reconstruction condition; determines a third phase range including a stationary phase of the subject from the phase corresponding to the second reconstructed image; and determines the stationary phase of the subject based on the third reconstructed image, wherein the third reconstructed image is reconstructed according to the second reconstruction condition from the projection data corresponding to the phase included in the third phase range and the motion of the subject is corrected, and the second reconstruction condition is a processing condition that can obtain a reconstructed image with higher image quality than the first reconstruction condition.

[0008] The image processing device according to the third aspect is the image processing device according to the second aspect, wherein the processor performs processing for determining a range corresponding to a phase in which the motion of the subject is smaller than a predetermined threshold value as a third phase range.

[0009] In the image processing device of the fourth mode, in the image processing device of the first mode, the processor performs the following processing: generates a first reconstructed image at a first phase interval; generates a second reconstructed image at a second phase interval wider than the first phase interval; generates a third reconstructed image reconstructed from projection data corresponding to the phase in which the second reconstructed image was generated; and determines the static phase of the object based on the deviation between the second reconstructed image and the third reconstructed image for each corresponding phase.

[0010] The image processing device according to the fifth aspect is the image processing device according to the fourth aspect, wherein the processor performs processing for identifying a phase at which a deviation between the second reconstructed image and the third reconstructed image is minimized as the stationary phase of the subject.

[0011] The image processing device according to a sixth aspect is the image processing device according to the first aspect, wherein the first phase range is a range corresponding to at least one of a diastole and a systole of the subject.

[0012] In order to achieve the above-mentioned purpose, in the image processing method of the seventh mode of the present invention, the processor possessed by the image processing device performs the following processing: acquiring projection data, wherein the projection data is photographed synchronously with the electrocardiogram of the subject using radiation sequentially irradiated from multiple directions to the photographing part of the subject and corresponds to the phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be the stationary phase of the subject based on a first reconstructed image reconstructed by the projection data corresponding to the phase included in the first phase range; generating a second reconstructed image reconstructed by the projection data and with the movement of the subject corrected, wherein the projection data corresponds to the phase included in the first phase range and included in the second phase range including the temporary stationary phase; and determining the stationary phase of the subject based on the second reconstructed image.

[0013] In order to achieve the above-mentioned purpose, the image processing program of the eighth mode of the present invention is used to enable the processor of the image processing device to perform the following processing: acquiring projection data, wherein the projection data is photographed synchronously with the electrocardiogram of the subject using radiation sequentially irradiated to the photographing part of the subject from multiple directions and corresponds to the phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be the stationary phase of the subject based on a first reconstructed image reconstructed by the projection data corresponding to the phase included in the first phase range; generating a second reconstructed image reconstructed by the projection data and with the movement of the subject corrected, wherein the projection data corresponds to the phase included in the first phase range and included in the second phase range including the temporary stationary phase; and determining the stationary phase of the subject based on the second reconstructed image.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to suppress the time required for processing and determine the stationary phase with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a structural diagram showing an example of the structure of a radiation CT imaging apparatus according to the embodiment.

[0017] Figure 2 This is a structural diagram showing an example of the structure of a console according to the embodiment.

[0018] Figure 3 This is a functional block diagram showing an example of the functions of the console according to the embodiment.

[0019] Figure 4A FIG. 1 is a diagram schematically showing an example of an image of a cardiac phase.

[0020] Figure 4B This is a diagram for explaining a method of determining a provisional optimal cardiac phase (optimal cardiac phase in CardioHarmony (registered trademark)).

[0021] Figure 5 This is a flowchart showing an example of the flow of image processing according to the embodiment.

[0022] Explanation of symbols

[0023] 10-Radiation CT imaging device, 20-Gantry, 23-Radiation generating device, 24-Bow-tie filter, 25-Collimator, 26-Aperture portion, 27-Couch, 28-Detector panel, 30-Console, 32-Control unit, 32A-CPU, 32B-ROM, 32C-RAM, 33-Image processing program, 34-Storage unit, 35-I / F unit, 36-Operation unit, 38-Display unit, 39-Bus, 40-Acquisition unit, 42-Temporary static phase determination unit, 44-Correction processing unit, 46-Static phase determination unit, R-Radiation, S-Subject. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, these embodiments do not limit the present invention.

[0025] [First embodiment]

[0026] First, an example of the structure of a radiation CT (Computed Tomography) imaging device according to this embodiment will be described. Figure 1 1 is a structural diagram showing an example of the structure of the radiation CT imaging apparatus 10 according to the present embodiment.

[0027] like Figure 1 As shown in FIG. 1 , the radiation CT imaging apparatus of this embodiment includes a gantry 20, a bed 27, and a console 30. In the following description, Figure 1 The horizontal direction in the figure is set as the X-axis, the vertical direction is set as the Y-axis, and the direction perpendicular to the XY plane is set as the Z-axis.

[0028] The gantry 20 has an opening 26, and a subject S to be imaged is placed on a bed 27 in the opening 26. The gantry 20 and the bed 27 are relatively movable in the Z-axis direction.

[0029] A radiation generator 23 including a radiation tube (not shown), a bowtie filter 24, a collimator 25, and a detector panel 28 are arranged inside the gantry 20 so as to face each other with the subject S interposed therebetween. Radiation R emitted from the radiation generator 23 is shaped into a beam suitable for the size of the subject S by the bowtie filter 24 and the collimator 25 and then irradiated onto the subject S. The detector panel 28 detects radiation that has passed through the subject S and generates projection data corresponding to the dose of the detected radiation.

[0030] The radiation generator 23 and detector panel 28 are rotated around the subject S by a rotation drive unit (not shown) of the gantry 20. As both rotate, radiation irradiation from the radiation generator 23 and detection of radiation by the detector panel 28 are repeated, acquiring projection data at various projection angles. The plurality of projection data acquired by the detector panel 28 is output to the console 30.

[0031] Furthermore, the console 30 sets the radiation dose emitted from the radiation generator 23, the rotational speed of the gantry 20, and the relative movement speed between the gantry 20 and the bed 27, based on scanning conditions input by a user such as a technician. In the case of ECG (electrocardiogram) synchronized imaging, imaging is performed in synchronization with the phase of cardiac motion (cardiac phase) based on information from an electrocardiograph (not shown) worn on the subject S. In the case of asynchronous imaging, imaging is performed under automatic exposure control.

[0032] The console 30 of this embodiment performs control related to acquisition of projection data, determination of a stationary phase, and generation of medical images. The console 30 of this embodiment is an example of an image processing apparatus of the present invention. As an example, the console 30 of this embodiment is a server computer.

[0033] like Figure 2 As shown, the console 30 includes 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, the storage unit 34, the I / F unit 35, the operation unit 36, and the display unit 38 are connected via a bus 39 such as a system bus or a control bus so that they can transmit and receive various information to and from each other.

[0034] The control unit 32 of 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 an image processing program 33 described later, that are executed by the CPU 32A. The RAM 32C temporarily stores various data.

[0035] The storage unit 34 stores projection data output from the detector panel 28 and various other information. Specific examples of the storage unit 34 include storage media such as a HDD (Hard Disk Drive), an SSD (Solid State Drive), and a flash memory.

[0036] The I / F unit 35 communicates various information with the rotation drive unit (not shown) of the gantry 20, the radiation generator 23, and the detector panel 28 via wired or wireless communication. The console 30 of this embodiment receives projection data from the detector panel 28 via the I / F unit 35. The received projection data is stored in the storage unit 34 in a state associated with the cardiac phase.

[0037] The console 30 acquires a plurality of projection data from the detector panel 28 via the I / F unit 35. The control unit 32 generates a tomographic image of the subject S by performing reconstruction processing on the acquired plurality of projection data.

[0038] The operating unit 36 ​​allows the user to input scanning conditions for acquiring projection data, instructions related to image generation and display, and various information. The operating unit 36 ​​is not particularly limited; examples include various switches, buttons, a touch panel, a stylus, a keyboard, and a mouse. The display unit 38 displays various information, medical images, and the like. Alternatively, the operating unit 36 ​​and display unit 38 may be integrated into a touch panel display. Furthermore, for example, the operating unit 36 ​​may accept voice input from the user.

[0039] exist Figure 3 is a functional block diagram illustrating an example of the functions of the console 30. The console 30 includes an acquisition unit 40, a temporary stationary phase determination unit 42, a correction processing unit 44, and a stationary phase determination unit 46. As an example, in the console 30 of this embodiment, the image processing program 33 is executed by the CPU 32A of the control unit 32, and the CPU 32A functions as the acquisition unit 40, the temporary stationary phase determination unit 42, the correction processing unit 44, and the stationary phase determination unit 46.

[0040] The acquisition unit 40 has the function of acquiring projection data from the detector panel 28. Specifically, as described above, the acquisition unit 40 acquires projection data from the detector panel 28 via the I / F unit 35, which is acquired by sequentially irradiating the subject S from multiple directions with radiation synchronized with the subject S's electrocardiogram and corresponding to a phase determined by the electrocardiogram. Alternatively, the acquisition unit 40 may acquire projection data from the storage unit 34, which has been previously acquired from the detector panel 28 and stored in association with cardiac phases. The acquisition unit 40 outputs the acquired projection data to the temporary stationary phase determination unit 42 and the correction processing unit 44.

[0041] The provisional stationary phase determination unit 42 has the function of determining a provisional stationary phase, which is assumed to be a stationary phase, based on a first reconstructed image reconstructed from projection data corresponding to phases included in the diastole and systole of the heart. The stationary phase refers to a phase where the heart moves minimally or is nearly stationary among all phases. The stationary phase is sometimes also referred to as the optimal cardiac phase. In this embodiment, the diastole and systole of the heart are each an example of the first phase range of the present invention. Furthermore, the first reconstructed image reconstructed by the provisional stationary phase determination unit 42 is an example of the first reconstructed image of the present invention.

[0042] In addition, the method by which the temporary stationary phase determination unit 42 determines the temporary stationary phase is not limited. For example, the phase detected as the optimal cardiac phase by CardioHarmony (registered trademark), which is an automatic phase search technology, can be determined as the temporary stationary phase. CardioHarmony (registered trademark) is a technology that extracts the amount of motion of the entire heart from an image (reconstructed image) produced for each cardiac phase and detects the phase with the minimum amount of motion as the optimal cardiac phase. Specifically, first, as Figure 4A As shown in FIG, an image of the cardiac phase of 0 to 99% is generated for the entire heart. Then, the motion amount is extracted at each phase with the contrast portion of the generated image as the center. Figure 4B As shown in the graph, the correspondence between the amount of motion and the phase is determined, and the phase with the minimum amount of motion is detected as the optimal cardiac phase. Furthermore, the optimal cardiac phase is detected for both the diastole and systole phases. That is, two optimal cardiac phases are detected in one cycle of diastole and systole. Furthermore, for example, the technology described in Japanese Patent No. 4157302 can be used.

[0043] The temporary stationary phase determination unit 42 outputs the determined temporary stationary phase to the correction processing unit 44 .

[0044] The correction processing unit 44 has the following function: to generate a second reconstructed image reconstructed from projection data corresponding to phases that are included in the diastole and systole of the heart and are included in the phase range including the temporary stationary phase, and in which the heart motion is corrected. As an example, the correction processing unit 44 of this embodiment generates a second reconstructed image by reconstructing the projection data corresponding to phases that are included in the diastole and systole of the heart and are included in the phase range including the temporary stationary phase. Figure 4B) Correcting for cardiac motion during imaging while reconstructing projection data corresponding to phases within this range, thereby generating a second reconstructed image. As a specific example, when the temporary resting phase during diastole is 77%, projection data corresponding to phases within the phase range of 67% to 87% are used. Furthermore, when the temporary resting phase during systole is 44%, projection data corresponding to phases within the phase range of 34% to 54% are used. The ±10% range of the temporary resting phase in this embodiment is an example of the second phase range of the present invention.

[0045] The method by which the correction processing unit 44 corrects for cardiac motion, in other words, the method by which the projection data is reconstructed while correcting for cardiac motion, is not limited. For example, cardiac motion information may be acquired from an image, and projection data may be reconstructed using the ratio of tube currents used in capturing the image and the motion information, thereby generating a second reconstructed image in which cardiac motion has been corrected.

[0046] Using projection data corresponding to a phase within a range of ±10% of the temporary static phase, a first image and a second image are generated at the facing position. Noise reduction processing and post-noise reduction registration processing are then performed on the second image and the second image, respectively, to obtain motion information of the subject. In this case, at least one of the type and parameters of the noise reduction filter used for the noise reduction processing and the parameters of the non-rigid registration algorithm used for the registration processing can be adjusted based on the tube current ratio when the first and second images were acquired. The motion information is then used to reconstruct the projection data, thereby generating a second reconstructed image. The reconstructed image reconstructed by the static phase determination unit 46 is an example of the second reconstructed image of the present invention.

[0047] The second reconstructed image generated by the correction processing unit 44 is output to the static phase determination unit 46 .

[0048] The stationary phase determination unit 46 has the function of determining the cardiac stationary phase based on the second reconstructed image. The method by which the stationary phase determination unit 46 determines the stationary phase is not limited. For example, the phase detected as the optimal cardiac phase using the aforementioned CardioHarmony (registered trademark) can be determined as the stationary phase. Furthermore, the stationary phase determination unit 46 of this embodiment determines the cardiac stationary phase during diastole and during systole.

[0049] Next, the function of the console 30 of this embodiment will be described.

[0050] For example, when the console 30 of this embodiment receives the display conditions of the radiographic image X and the ultrasonic image U to be displayed inputted by the user through the operation unit 36, the CPU 32A of the control unit 32 executes the image processing program 33 stored in the ROM 32B to perform the display. Figure 5 An example of image processing is shown in FIG. Figure 5 2 is a flowchart showing an example of the flow of image processing in the console 30 according to the present embodiment.

[0051] First, in Figure 5 In step S100 , as described above, the acquisition unit 40 acquires projection data associated with the cardiac phase, which is obtained by imaging the heart of the subject S using the radiation CT imaging apparatus 10 .

[0052] In the next step S102, as described above, the temporary stationary phase determination unit 42 generates the first reconstructed image. The reconstructed phases are respectively included in the diastole and systole of the heart (refer to Figure 4B ) and generates a first reconstructed image based on the projection data corresponding to the phase in ).

[0053] In the next step S104 , as described above, the tentative static phase determination unit 42 determines the tentative static phase using the first reconstructed image generated in the above-described step S102 .

[0054] In addition, when CardioHarmony (registered trademark) is used as the temporary stationary phase determination unit 42 , the processes of steps S102 and S104 are performed together.

[0055] In the next step S106, as described above, the correction processing unit 44 extracts a phase range of ±10% of the temporary static phase determined in the above step S104 from the projection data acquired in the above step S100 (reference Figure 4B )’s phase corresponding to the projection data.

[0056] In the next step S108 , as described above, the correction processing unit 44 reconstructs the projection data extracted in the above-described step S106 while correcting the motion of the heart during imaging, thereby generating a second reconstructed image.

[0057] In the next step S110, the stationary phase determination unit 46 determines the stationary phase based on the second reconstructed image generated in the above-mentioned step S108. The stationary phase determined here is output to a predetermined output destination. For example, when output to the display unit 38 of the console 30, information indicating the stationary phase and the second reconstructed image at the stationary phase can be displayed on the display unit 38. Furthermore, when output to the storage unit 34, a correspondence relationship can be established with at least one of the projection data acquired by the acquisition unit 40 and the second reconstructed image at the stationary phase and stored in the storage unit 34. If the processing of step S110 is completed, then Figure 5 The image processing shown ends.

[0058] Thus, the console 30 of this embodiment determines a provisional resting phase using a method that requires relatively little processing load and requires no processing time. A reconstructed image with cardiac motion corrected is generated for the phase range narrowed by the provisional phase. The resting phase is then determined from the reconstructed image with cardiac motion corrected. Thus, the console 30 of this embodiment can reduce processing time and accurately determine the resting phase.

[0059] [Second embodiment]

[0060] In the present embodiment, the correction processing unit 44 and the static phase determination unit 46 perform different processes, and therefore the different processes will be described.

[0061] When generating the second reconstructed image in which the subject's motion has been corrected, the correction processing unit 44 of this embodiment generates the second reconstructed image based on the first reconstruction condition. The correction processing unit 44 then determines a third phase range that includes the subject's stationary phase from the phases corresponding to the second reconstructed image. This third phase range is a phase range in which cardiac motion is less than a predetermined threshold. Furthermore, the third phase range is within a phase range of ±10% of the provisional stationary phase, meaning it is within the phase range of ±10% of the provisional stationary phase.

[0062] Then, the correction processing unit 44 generates a third reconstructed image in which the motion of the subject is corrected by reconstructing the projection data corresponding to the phase included in the phase range of ±5% of the newly determined temporary phase range based on the second reconstruction condition.

[0063] Here, the second reconstruction condition is a condition for achieving a higher-quality reconstructed image than that obtained under the first reconstruction condition. In this case, the processing load required to obtain a high-quality image increases, and thus the processing time required is relatively longer. Examples of the reconstruction condition in this case include conditions related to slice thickness or slice interval.

[0064] On the other hand, the first reconstruction condition only needs to produce image quality sufficient for phase detection, and is a condition with lower image quality than the reconstructed image obtained under the second reconstruction condition. In this case, the image quality can be reduced, thereby shortening the processing time. Examples of reconstruction conditions in this case include conditions related to FOV (field of view), filter, and matrix size.

[0065] Then, the correction processing unit 44 specifies the cardiac stationary phase as described above based on the generated third reconstructed image.

[0066] Thus, in this embodiment, even when reconstructing a corrected image in which cardiac motion has been corrected, the phase range can be further narrowed using a method that requires relatively little processing time, and the narrowed phase range can be reconstructed with higher image quality. Therefore, according to the console 30 of this embodiment, it is possible to suppress an increase in processing time and determine the stationary phase with higher accuracy.

[0067] Furthermore, unlike the present embodiment, the processing of the temporary stationary phase determination unit 42 can be omitted. That is, the processing of the correction processing unit 44 and the stationary phase determination unit 46 of the present embodiment can be performed on all phase ranges.

[0068] [Third embodiment]

[0069] In the present embodiment, the temporary stationary phase determination unit 42 , the correction processing unit 44 , and the stationary phase determination unit 46 perform different processes, and therefore the different processes will be described.

[0070] The temporary static phase determination unit 42 generates a first reconstructed image at a first phase interval.

[0071] The correction processing unit 44 generates a second reconstructed image at a second phase interval wider than the first phase interval.

[0072] Then, the correction processing unit 44 generates a third reconstructed image reconstructed from the projection data corresponding to the phase in which the second reconstructed image was generated. Note that the third reconstructed image is a reconstructed image in which cardiac motion has not been corrected.

[0073] The stationary phase determination unit 46 then determines the stationary phase of the heart based on the deviation between the second and third reconstructed images for each corresponding phase. In this case, the stationary phase determination unit 46 may determine the phase at which the deviation between the second and third reconstructed images is minimized as the stationary phase of the heart.

[0074] Thus, in this embodiment, the static phase is determined while comparing the motion-corrected second reconstructed image and the motion-uncorrected third reconstructed image.

[0075] As described above, according to the console 30 of each of the above-described embodiments, it is possible to suppress the time required for processing and to determine the stationary phase with high accuracy.

[0076] Furthermore, in each of the above-described embodiments, various processors described below can be used as the hardware configuration of processing units (processing units) that perform various processes, such as the acquisition unit 40, the temporary static phase determination unit 42, the correction processing unit 44, and the static phase determination unit 46. As described above, these various processors include general-purpose processors (CPUs) that function as various processing units by executing software (programs), as well as processors whose circuit configuration can be modified after manufacturing, such as FPGAs (Field Programmable Gate Arrays), programmable logic devices (PLDs), and processors (special-purpose circuits) with circuit configurations specifically designed to perform specific processes, such as ASICs (Application Specific Integrated Circuits).

[0077] A processing unit may be composed of one of these various processors, or a combination of two or more processors of the same or different types (for example, a combination of multiple FPGAs or a combination of a CPU and an FPGA). Furthermore, multiple processing units may be composed of one processor.

[0078] As an example of a single processor constituting multiple processing units, the first example is a method in which a processor is composed of a combination of one or more CPUs and software, as exemplified by computers such as client computers and servers, and functions as multiple processing units. A second example is a method in which a processor is used, such as a system-on-chip (SoC), to implement the overall functionality of a system including multiple processing units using a single integrated circuit (IC) chip. In this manner, various processing units are constructed using one or more of the aforementioned processors as a hardware configuration.

[0079] Furthermore, as the hardware configuration of these various processors, more specifically, a circuit (circuitry) formed by combining circuit elements such as semiconductor elements can be used.

[0080] Furthermore, in the above embodiment, the image processing program 33 is described as being pre-stored (installed) in the storage unit 34 of the console 30, but the present invention is not limited to this. The image processing program 33 may also be provided by being recorded on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory device. Furthermore, the image processing program 33 may be downloaded from an external device via a network.

[0081] Furthermore, the configuration and operation of the radiation CT imaging apparatus 10 and the console 30 described in the above embodiments are merely examples and can be modified according to circumstances without departing from the spirit of the present invention. Furthermore, the above embodiments can be appropriately combined.

[0082] Regarding the above-mentioned embodiment, the following supplementary notes are further disclosed.

[0083] (Note 1)

[0084] An image processing device comprising at least one processor,

[0085] The processor performs the following processing:

[0086] acquiring projection data, the projection data being acquired by sequentially irradiating an imaging portion of the subject from a plurality of directions in synchronization with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram;

[0087] determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range;

[0088] generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and

[0089] The static phase of the object is determined based on the second reconstructed image.

[0090] (Note 2)

[0091] The image processing device according to Supplementary Note 1, wherein:

[0092] The processor performs the following processing:

[0093] generating the second reconstructed image according to the first reconstruction condition;

[0094] determining a third phase range including a stationary phase of the object from the phases corresponding to the second reconstructed image; and

[0095] determining a stationary phase of the subject based on a third reconstructed image, wherein the third reconstructed image is reconstructed from the projection data corresponding to a phase included in the third phase range according to a second reconstruction condition and wherein motion of the subject is corrected;

[0096] The second reconstruction condition is a processing condition that can obtain a reconstructed image with higher image quality than the first reconstruction condition.

[0097] (Note 3)

[0098] The image processing device according to Supplementary Note 2, wherein:

[0099] The processor performs the following processing:

[0100] A range corresponding to a phase in which the motion of the subject is smaller than a predetermined threshold is determined as the third phase range.

[0101] (Note 4)

[0102] The image processing device according to Supplementary Note 1, wherein:

[0103] The processor performs the following processing:

[0104] generating the first reconstructed image at a first phase interval;

[0105] generating the second reconstructed image at a second phase interval wider than the first phase interval;

[0106] generating a third reconstructed image reconstructed from the projection data corresponding to the phase in which the second reconstructed image was generated; and

[0107] The stationary phase of the object is determined based on a deviation between the second reconstructed image and the third reconstructed image at each corresponding phase.

[0108] (Note 5)

[0109] The image processing device according to Supplementary Note 4, wherein:

[0110] The processor performs the following processing:

[0111] A phase at which a deviation between the second reconstructed image and the third reconstructed image is minimized is determined as a stationary phase of the subject.

[0112] (Note 6)

[0113] The image processing device according to any one of Supplementary Notes 1 to 5, wherein:

[0114] The first phase range is a range corresponding to at least one of a diastolic phase and a systolic phase of the subject.

[0115] (Note 7)

[0116] An image processing method, wherein:

[0117] The processor included in the image processing device performs the following processing:

[0118] Acquiring projection data, the projection data being acquired by sequentially irradiating a portion of a subject from a plurality of directions with radiation synchronously with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram;

[0119] determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range;

[0120] generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and

[0121] The static phase of the object is determined based on the second reconstructed image.

[0122] (Note 8)

[0123] An image processing program for causing a processor included in an image processing device to execute the following processing:

[0124] Acquiring projection data, the projection data being acquired by sequentially irradiating a portion of a subject from a plurality of directions with radiation synchronously with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram;

[0125] determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range;

[0126] generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and

[0127] The static phase of the object is determined based on the second reconstructed image.

Claims

1. An image processing device comprising at least one processor, The processor performs the following processing: Acquiring projection data, the projection data being acquired by sequentially irradiating a portion of a subject from a plurality of directions with radiation synchronously with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range; generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and The static phase of the object is determined based on the second reconstructed image.

2. The image processing apparatus according to claim 1, wherein: The processor performs the following processing: generating the second reconstructed image according to the first reconstruction condition; determining a third phase range including a stationary phase of the object from the phases corresponding to the second reconstructed image; and determining a stationary phase of the subject based on a third reconstructed image, wherein the third reconstructed image is reconstructed from the projection data corresponding to a phase included in the third phase range according to a second reconstruction condition and wherein motion of the subject is corrected; The second reconstruction condition is a processing condition that can obtain a reconstructed image with higher image quality than the first reconstruction condition.

3. The image processing apparatus according to claim 2, wherein: The processor performs the following processing: A range corresponding to a phase in which the motion of the subject is smaller than a predetermined threshold is determined as the third phase range.

4. The image processing apparatus according to claim 1, wherein: The processor performs the following processing: generating the first reconstructed image at a first phase interval; generating the second reconstructed image at a second phase interval wider than the first phase interval; generating a third reconstructed image reconstructed from the projection data corresponding to the phase in which the second reconstructed image was generated; and The stationary phase of the object is determined based on a deviation between the second reconstructed image and the third reconstructed image at each corresponding phase.

5. The image processing apparatus according to claim 4, wherein: The processor performs the following processing: A phase at which a deviation between the second reconstructed image and the third reconstructed image is minimized is determined as a stationary phase of the subject. The image processing apparatus according to claim 1 , wherein: The first phase range is a range corresponding to at least one of a diastolic phase and a systolic phase of the subject.

7. An image processing method, wherein: The processor included in the image processing device performs the following processing: Acquiring projection data, the projection data being acquired by sequentially irradiating a portion of a subject from a plurality of directions with radiation synchronously with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range; generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and The static phase of the object is determined based on the second reconstructed image.

8. A computer-readable medium having an image processing program recorded thereon, the image processing program being configured to cause a processor of an image processing device to execute the following processing: Acquiring projection data, the projection data being acquired by sequentially irradiating a portion of a subject from a plurality of directions with radiation synchronously with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range; generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and The static phase of the object is determined based on the second reconstructed image.

9. A computer program product comprising an image processing program, the image processing program being configured to cause a computer to perform the following processing: Acquiring projection data, the projection data being acquired by sequentially irradiating a portion of a subject from a plurality of directions with radiation synchronously with an electrocardiogram of the subject and corresponding to a phase determined by the electrocardiogram; determining a temporary stationary phase assumed to be a stationary phase of the object based on a first reconstructed image reconstructed from the projection data corresponding to a phase included in a first phase range; generating a second reconstructed image reconstructed from the projection data and having the motion of the subject corrected, the projection data corresponding to a phase included in the first phase range and in a second phase range including the temporary stationary phase; and The static phase of the object is determined based on the second reconstructed image.

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