X-ray CT apparatus, method, and phantom

Abstract

The objective is to efficiently suppress the impact of mount vibrations on the reconstructed image. [Solution] The X-ray CT apparatus according to the embodiment comprises an acquisition unit, an acquisition unit, a correction unit, and a reconstruction processing unit. The acquisition unit collects first detection data in a first scan that scans a subject. The acquisition unit acquires correction data for correcting the rotational balance of the gantry. The correction unit corrects the position of the X-ray detection element that actually received X-rays in the first scan to the position of the X-ray detection element that is predicted to have received X-rays if there were no vibrations, based on the correction data. The reconstruction processing unit generates a reconstructed image based on the first detection data and the corrected position of the X-ray detection element.

Description

Technical Field

[0001] Embodiments of the present invention relate to an X-ray CT apparatus, a method, and a phantom. Background Art

[0002] In recent years, the rotation speed of X-ray CT (Computed Tomography) apparatuses during imaging of a subject has been increasing. Along with this trend, vibration of the gantry also tends to increase. In addition, as the detector pitch becomes higher definition, the vibration of the gantry may affect reconstructed images.

[0003] Conventionally, rotation balance adjustment of the gantry is performed to suppress vibration of the gantry, but due to the above circumstances, high accuracy is now required for rotation balance adjustment. In addition, since rotation balance adjustment needs to be performed for each X-ray CT apparatus, the time required for rotation balance adjustment tends to increase. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2023-039621 Summary of the Invention Problem to be Solved by the Invention

[0005] One of the problems to be solved by the embodiments disclosed in the present specification and the drawings is to efficiently suppress the influence of gantry vibration on reconstructed images. However, the problem to be solved by the embodiments disclosed in the present specification and the drawings is not limited to the above problem. Problems corresponding to respective effects achieved by respective configurations shown in the embodiments described later can be defined as other problems. Means for Solving the Problem

[0006] The X-ray CT apparatus according to the embodiment comprises an acquisition unit, an acquisition unit, a correction unit, and a reconstruction processing unit. The acquisition unit collects first detection data in a first scan that scans a subject. The acquisition unit acquires correction data for correcting the rotational balance of the gantry. The correction unit corrects the position of the X-ray detection element that actually received X-rays in the first scan to the position of the X-ray detection element that is predicted to have received X-rays if there were no vibrations, based on the correction data. The reconstruction processing unit generates a reconstructed image based on the first detection data and the corrected position of the X-ray detection element. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a block diagram showing an example of the configuration of an X-ray CT apparatus according to this embodiment. [Figure 2] Figure 2 shows an example of the positional relationship between the rigging device and the spherical phantom when measuring the deviation of the rigging rotation balance using one spherical phantom according to the embodiment. [Figure 3] Figure 3 shows an example of projection data in the Y-axis direction when there is no rotational balance misalignment according to the embodiment. [Figure 4] Figure 4 shows an example of projection data in the Y-axis direction when there is a rotational balance misalignment according to the embodiment. [Figure 5] Figure 5 shows an example of the Y-axis rotational balance deviation data of the frame according to the embodiment. [Figure 6] Figure 6 shows an example of projection data in the Z-axis direction when there is no rotational balance misalignment according to the embodiment. [Figure 7] Figure 7 shows an example of projection data in the Z-axis direction when there is a rotational balance misalignment according to the embodiment. [Figure 8] Figure 8 shows an example of frame rotation balance deviation data in the Z-axis direction according to the embodiment. [Figure 9]Figure 9 shows an example of the positional relationship between the rigging device and the multiple spherical phantoms when measuring the deviation of the rigging rotation balance using multiple spherical phantoms according to the embodiment. [Figure 10] Figure 10 shows an example of the positional relationship between the mounting device and the multiple spherical phantoms when measuring the deviation of the mounting device rotation balance using multiple spherical phantoms according to the embodiment. [Figure 11] Figure 11 is a diagram illustrating an example of the relationship between the X-ray detection element and the received signal before correction according to the embodiment. [Figure 12] Figure 12 illustrates an example of the relationship between the corrected X-ray detection element and the received signal according to the embodiment. [Figure 13] Figure 13 is a flowchart showing an example of a process performed by an X-ray CT apparatus according to this embodiment. [Figure 14] Figure 14 is a flowchart showing an example of a process performed by an X-ray CT apparatus according to this embodiment. [Figure 15] Figure 15 is a perspective view showing an example of the positional relationship between the mounting device according to Modification 2 and the measuring phantom, which is composed of multiple spherical phantoms. [Figure 16] Figure 16 is a perspective view showing an example of the positional relationship between the top plate and the measuring phantom, which is composed of multiple spherical phantoms, according to Modification 3. [Figure 17] Figure 17 shows an example of the configuration of an X-ray CT apparatus according to Modification 4. [Modes for carrying out the invention]

[0008] The X-ray CT (Computed Tomography) apparatus, method, and phantom according to the embodiment will be described below with reference to the drawings. Note that the embodiments described below are merely examples and are not limited to those described in the embodiments. Furthermore, the contents described in one embodiment generally apply similarly to other embodiments.

[0009] FIG. 1 is a block diagram illustrating an example of a configuration of an X-ray CT apparatus according to an embodiment. As shown in FIG. 1, an X-ray CT apparatus 100 according to the embodiment includes a gantry device 10, a couch device 30, and a console device 40. Note that although the gantry device 10 is depicted at two locations in FIG. 1 for convenience of illustration, one X-ray CT apparatus 1 typically includes one gantry device 10.

[0010] In the present embodiment, the rotation axis of the rotating frame 13 in the non-tilt state or the longitudinal direction of the top plate 33 of the couch device 30 is defined as the Z-axis direction. An axial direction perpendicular to the Z-axis direction and vertical to the floor surface is defined as the X-axis direction. An axial direction perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the Y-axis direction.

[0011] The gantry device 10 includes an X-ray tube 11, an X-ray detector 12, a rotating frame 13, an X-ray high-voltage device 14, a control device 15, a wedge 16, a collimator 17, and a DAS (Data Acquisition System) 18. The gantry device 10 is an example of a gantry.

[0012] The X-ray tube 11 is a vacuum tube that generates X-rays by emitting thermoelectrons from a cathode (filament) toward an anode (target) when a high voltage is applied from the X-ray high-voltage device 14. For example, the X-ray tube 11 may be a rotating anode type X-ray tube that generates X-rays by irradiating thermoelectrons onto a rotating anode.

[0013] The X-ray detector 12 includes a plurality of detection elements that detect X-rays. Each detection element in the X-ray detector 12 detects X-rays emitted from the X-ray tube 11 and passed through the subject P, and outputs a signal corresponding to the detected X-ray dose to the DAS 18.

[0014] Here, the signal corresponding to the X-ray dose detected by each detection element in the X-ray detector 12 can be said to be an example of a reception signal from an X-ray detection element. During examination of the subject P, the correspondence between the X-ray detection elements (detection element identification information) and the reception signals of the X-ray detection elements is corrected by a correction function 446 of a processing circuit 44 described later.

[0015] The X-ray detector 12 has, for example, multiple arrays of detection elements arranged in the channel direction (channel direction) along a single arc centered on the focal point of the X-ray tube 11. The X-ray detector 12 has, for example, a structure in which multiple arrays of detection elements, each arranged in the channel direction, are arranged in the row direction (slice direction, row direction).

[0016] For example, the X-ray detector 12 is an indirect conversion type detector having a grid, a scintillator array, and a photosensor array. The scintillator array has multiple scintillators. The scintillators have scintillator crystals that output light in a quantity of photons corresponding to the amount of incident X-rays. The grid is positioned on the X-ray incident side of the scintillator array and has an X-ray shielding plate that absorbs scattered X-rays.

[0017] The grid is sometimes called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has the function of converting light from the scintillator into an electrical signal, and includes optical sensors such as photodiodes. For example, the X-ray detector 12 is an energy-integrating type detector. The X-ray detector 12 may also be a direct conversion type detector that has a semiconductor element that converts incident X-rays into an electrical signal.

[0018] The rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 opposite each other and rotates the X-ray tube 11 and the X-ray detector 12 by the control device 15. For example, the rotating frame 13 is a casting made of aluminum.

[0019] Furthermore, the rotating frame 13 can also support, in addition to the X-ray tube 11 and X-ray detector 12, an X-ray high-voltage device 14, a wedge 16, a collimator 17, a DAS 18, and the like. Moreover, the rotating frame 13 can also support various other configurations not shown in Figure 1.

[0020] The X-ray high-voltage device 14 includes a high-voltage generator having an electrical circuit such as a transformer and a rectifier, and a function to generate a high voltage to be applied to the X-ray tube 11, and an X-ray control device that controls the output voltage according to the X-rays irradiated by the X-ray tube 11. The high-voltage generator may be of the transformer type or the inverter type.

[0021] The X-ray high-voltage device 14 may be mounted on the rotating frame 13, or it may be mounted on the fixed frame (not shown) side of the rigging device 10. The fixed frame is a frame that rotatably supports the rotating frame 13.

[0022] The control device 15 includes a processing circuit with a CPU and other components, and a drive mechanism with motors and actuators. The control device 15 receives input signals from an input interface 43, which will be described later, attached to the console device 40 or the support device 10, and has the function of controlling the operation of the support device 10 and the bed device 30.

[0023] For example, the control device 15 receives input signals and performs control to rotate the rotating frame 13, control to tilt the support structure 10, and control to operate the bed structure 30 and the top plate 33. The control to tilt the support structure 10 is achieved by the control device 15 rotating the rotating frame 13 around an axis parallel to the Y-axis direction based on tilt angle information input through an input interface attached to the support structure 10.

[0024] The control device 15 may be installed on the mounting device 10 or on the console device 40.

[0025] The wedge 16 is a filter for adjusting the amount of X-rays irradiated from the X-ray tube 11. Specifically, the wedge 16 is a filter that transmits and attenuates the X-rays irradiated from the X-ray tube 11 so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution.

[0026] For example, wedge 16 is a wedge filter or bow-tie filter, which is a filter made by processing aluminum or the like to have a predetermined target angle or thickness.

[0027] The collimator 17 is a lead plate or the like used to narrow the irradiation range of X-rays that have passed through the wedge 16, and a slit is formed by combining multiple lead plates or the like.

[0028] The collimator 17 is sometimes called an X-ray diaphragm. Also, although Figure 1 shows the case where the wedge 16 is placed between the X-ray tube 11 and the collimator 17, the collimator 17 may also be placed between the X-ray tube 11 and the wedge 16. In this case, the wedge 16 transmits and attenuates the X-rays irradiated from the X-ray tube 11, whose irradiation range has been limited by the collimator 17.

[0029] The DAS18 collects X-ray signals detected by each detection element of the X-ray detector 12. For example, the DAS18 has an amplifier that performs amplification processing on the electrical signals output from each detection element, and an A / D converter that converts the electrical signals into digital signals, thereby generating detection data. The DAS18 is implemented, for example, by a processor.

[0030] The data generated by DAS18 is transmitted via optical communication from a transmitter having a light-emitting diode (LED) on the rotating frame 13 to a receiver having a photodiode located on the non-rotating part of the mounting device 10 (for example, a fixed frame, etc., which is not shown in Figure 1), and then transferred to the console device 40.

[0031] Here, the non-rotating part refers to, for example, a fixed frame that rotatably supports the rotating frame 13. The method for transmitting data from the rotating frame 13 to the non-rotating part of the mounting device 10 is not limited to optical communication; any non-contact data transmission method or a contact-type data transmission method may be used.

[0032] The examination bed device 30 is a device for placing and moving the subject P to be scanned. The examination bed device 30 is an example of an examination bed. The examination bed device 30 comprises a base 31, an examination bed drive device 32, a top plate 33, and a support frame 34.

[0033] The base 31 is a housing that supports the support frame 34 so that it can move vertically. The bed drive device 32 is a motor or actuator that moves the top plate 33 on which the subject P is placed in the direction of the long axis of the top plate 33. The top plate 33, which is provided on the upper surface of the support frame 34, is the plate on which the subject P is placed. In addition to moving the top plate 33, the bed drive device 32 may also move the support frame 34 in the direction of the long axis of the top plate 33.

[0034] The console device 40 includes a memory 41, a display 42, an input interface 43, and a processing circuit 44. Although the console device 40 is described separately from the mounting device 10, the mounting device 10 may include the console device 40 or some of its components.

[0035] Memory 41 can be implemented using, for example, semiconductor memory elements such as RAM (Random Access Memory) or flash memory, a hard disk, or an optical disc. Memory 41 stores, for example, projection data or reconstructed image data. Memory 41 is also an example of a storage unit.

[0036] The display 42 displays various types of information. For example, the display 42 outputs medical images (CT images) generated by the processing circuit 44, and a GUI (Graphical User Interface) for receiving various operations from the operator.

[0037] For example, the display 42 may be a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 42 may also be mounted on the mounting device 10. Furthermore, the display 42 may be a desktop type, or it may be composed of a tablet terminal or the like that can communicate wirelessly with the console device 40.

[0038] The input interface 43 receives various input operations from the operator and converts the received input operations into electrical signals, which are then output to the processing circuit 44. For example, the input interface 43 receives data acquisition conditions when collecting projection data, reconstruction conditions when reconstructing CT images, and image processing conditions when generating post-processed images from CT images from the operator.

[0039] For example, the input interface 43 can be implemented using a mouse, keyboard, trackball, switch, button, joystick, etc. Alternatively, the input interface 43 may be provided on the mounting device 10. Furthermore, the input interface 43 may consist of the console device 40 main unit and a wirelessly connected tablet terminal or the like.

[0040] The processing circuit 44 controls the operation of the entire X-ray CT apparatus 1. For example, the processing circuit 44 performs system control functions 441, preprocessing functions 442, reconstruction processing functions 443, image processing functions 444, measurement functions 445, and correction functions 446. The system control function 441 is an example of an acquisition unit. The measurement function 445 is an example of a generation unit and memory control unit. The reconstruction processing function 443 is an example of a reconstruction processing unit. The correction function 446 is an example of an acquisition unit and correction unit.

[0041] The system control function 441 controls various functions of the processing circuit 44 based on input operations received from the operator via the input interface 43. For example, the system control function 441 controls the data acquisition process in the mount device 10 by controlling the operation of the mount device 10. The system control function 441 also controls the operation of the mount device 10 so that the data acquisition process is performed under the shooting conditions specified by the operator.

[0042] The preprocessing function 442 generates data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the detection data output from DAS18. Here, the detection data output from DAS18 by scanning the subject P is an example of the first detection data. Note that the data before preprocessing is sometimes called raw data, and the data after preprocessing is sometimes called projection data.

[0043] The reconstruction processing function 443 generates CT image data by performing reconstruction processing on the projection data generated by the preprocessing function 442, using methods such as filtered back projection and iterative reconstruction, based on the position of the X-ray detection element of the X-ray detector 12 corrected by the correction function 446 described later. The CT image data in this case is an example of a reconstructed image.

[0044] The image processing function 444 converts the CT image data generated by the reconstruction processing function 443 into tomographic image data of an arbitrary cross-section or 3D image data using a known method, based on input operations received from the operator via the input interface 43. The 3D image data may be generated directly by the reconstruction processing function 443.

[0045] The measurement function 445 measures the deviation of the rotational balance of the rotating frame 13 of the rigging device 10 (hereinafter also referred to as the rigging rotational balance). For example, the measurement function 445 acquires projection data obtained by irradiating multiple spherical phantoms with X-rays and measures how the rigging rotational balance is deviated in each angle from 0 to 360° in the view direction in the Y-axis direction (ch direction) and Z-axis direction (row direction).

[0046] The measurement process for the deviation in the rotational balance of the cradle will be explained below using Figures 2 to 8. In this embodiment, raw data is collected by irradiating multiple spherical phantoms with X-rays to measure the deviation in the rotational balance of the cradle. However, for the sake of explanation, Figures 2 to 8 describe an example in which raw data is collected by irradiating a single spherical phantom placed in the center of the opening of the cradle device 10 with X-rays to measure the deviation in the rotational balance of the cradle.

[0047] Figure 2 shows an example of the positional relationship between the mounting device 10 and the spherical phantom F1 when measuring the deviation of the mounting device's rotational balance using a single spherical phantom. In Figure 2, the single spherical phantom F1 is represented by a solid line, and the mounting device 10 is represented by a dashed line.

[0048] As shown in Figure 2, by irradiating a single spherical phantom F1 with X-rays and performing a scan, raw view-row data is collected for each channel in the Y-axis direction. The raw data in this case is an example of second detection data. The view-row raw data shows the relationship between the position in the view direction (mountain rotation angle) and the position in the row direction.

[0049] Here, Figure 3 shows an example of projection data in the Y-axis direction when there is no rotational balance misalignment. Assuming there is no rotational balance misalignment, that is, no vibration of the mounting device 10, an image representing the rectangular spherical phantom F1, as shown by the diagonal lines in Figure 3, is obtained. Hereafter, projection data when there is no rotational balance misalignment will also be referred to as ideal projection data.

[0050] Figure 4 also shows an example of projection data in the Y-axis direction when there is a rotational balance misalignment.

[0051] If there is a misalignment in rotational balance, that is, if the mounting device 10 vibrates, the image representing the spherical phantom F1 will exhibit the kind of wobble shown by the left and right arrows in Figure 4 (for ease of explanation, Figure 4 is a simplified and exaggerated representation of the wobble). This represents the wobble in the row direction when viewed in the view direction. Hereafter, the projection data obtained by actually scanning one spherical phantom F1 will also be referred to as the actual projection data.

[0052] Furthermore, the row-direction oscillations mentioned above indicate a deviation in the Z-axis rotational balance of the support structure. Therefore, the measurement function 445 can measure the deviation in the Z-axis rotational balance of the support structure from the ideal projection data in the Y-axis direction, as shown in Figure 3, and the actual projection data in the Y-axis direction, as shown in Figure 4.

[0053] Specifically, the measurement function 445 generates Z-axis rotational balance deviation data by taking the center position of the image of the measurement phantom F2 in the row direction as the vertical axis and the mount rotation angle (0-360°) as the horizontal axis, from the ideal projection data in the Y-axis direction and the actual projection data in the Y-axis direction.

[0054] Furthermore, by irradiating a single spherical phantom F1, arranged as shown in Figure 2, with X-rays and performing a scan, raw view-ch data is collected for each channel in the Z-axis direction. The raw data in this case is an example of second detection data. The view-ch raw data shows the relationship between the position in the view direction and the position in the channel direction.

[0055] Here, Figure 5 shows an example of frame rotational balance misalignment data in the Z-axis direction. The frame rotational balance misalignment data in the Z-axis direction indicates how much the rotation of the rotating frame 13 is misaligned in the row direction at a certain angle (view). The width of the up and down arrows shown in Figure 5 corresponds to the magnitude of the sway shown by the left and right arrows shown in Figure 4.

[0056] Furthermore, Figure 6 shows an example of projection data in the Z-axis direction when there is no rotational balance misalignment. Assuming there is no rotational balance misalignment, i.e., no vibration of the mounting device 10, an image representing the rectangular spherical phantom F1, as shown by the diagonal lines in Figure 6, is obtained.

[0057] Furthermore, Figure 7 shows an example of projection data in the Z-axis direction when there is a rotational balance misalignment. When there is a rotational balance misalignment, i.e., vibration of the mounting device 10, the image representing the spherical phantom F1 exhibits shaking as shown by the left and right arrows in Figure 7 (for ease of explanation, Figure 7 is a simplified and exaggerated representation of the shaking). This represents the shaking in the ch direction when viewed in the view direction.

[0058] Furthermore, the above-mentioned ch-direction oscillation indicates a deviation in the rotational balance of the frame in the Y-axis direction. Therefore, the measurement function 445 can measure the deviation in the rotational balance of the frame in the Y-axis direction from the ideal projection data in the Z-axis direction as shown in Figure 6 and the actual projection data in the Z-axis direction as shown in Figure 7.

[0059] Specifically, measurement function 445 generates Y-axis rotational balance deviation data for the mounting base, using ideal projection data in the Z-axis direction and actual projection data in the Z-axis direction, with the center position of the image of the measurement phantom F2 in the ch direction on the vertical axis and the mounting base rotation angle (0-360°) on the horizontal axis.

[0060] Figure 8 shows an example of frame rotational balance deviation data in the Y-axis direction. This data indicates how much the rotation of the rotating frame 13 deviates in the ch direction at a given angle. The width of the up and down arrows in Figure 8 corresponds to the magnitude of the sway indicated by the left and right arrows in Figure 7.

[0061] Furthermore, the measurement function 445 stores the generated Z-axis and Y-axis rotational balance misalignment data of the pylon in memory 41 as pylon rotational balance misalignment data. The pylon rotational balance misalignment data is used for position correction processing of the X-ray detection element by the correction function 446.

[0062] In the above explanation, for the sake of clarity, an example was described in which X-rays are irradiated onto a single spherical phantom F1 placed in the center of the opening of the rigging device 10 to measure the deviation in the rigging rotation balance. However, simply placing one phantom may result in some X-ray detection elements of the X-ray detector 12 not being able to measure the deviation in the rigging rotation balance, depending on the arrangement of the X-ray detection elements of the X-ray tube 11 and the X-ray detector 12, as there may be no phantom between the X-ray tube 11 and the X-ray detection elements of the X-ray detector 12.

[0063] Therefore, in this embodiment, the deviation of the rigging rotation balance is measured by irradiating multiple spherical phantoms with X-rays. However, this embodiment is not intended to exclude the form in which the deviation of the rigging rotation balance is measured by irradiating a single spherical phantom with X-rays.

[0064] Here, Figures 9 and 10 show an example of the positional relationship between the mounting device 10 and the multiple spherical phantoms when measuring the deviation of the mounting device rotation balance using multiple spherical phantoms.

[0065] Figure 9 is a perspective view showing an example of the positional relationship between the mounting device 10 and the measurement phantom F2, which is composed of multiple spherical phantoms. Figure 10 is a side view showing an example of the positional relationship between the mounting device 10 and the measurement phantom F2. In Figures 9 and 10, each of the multiple spherical phantoms is represented by a white circle, and the mounting device 10 is represented by a dashed line. Lines illustrating the arrangement of the multiple spherical phantoms are represented by dashed lines.

[0066] As shown in Figures 9 and 10, in this embodiment, the measurement phantom F2 is arranged spirally in the opening of the mounting device 10. By arranging multiple phantoms spirally in this way, a spherical phantom is present between the X-ray tube 11 and the X-ray detection element of the X-ray detector 12 over a wide range of channels and rows. As a result, the measurement function 445 can measure the deviation of the mounting rotation balance over a wide range of channels and rows.

[0067] Furthermore, the measuring phantom may consist of multiple phantoms arranged in a spiral pattern inside the non-rotating section.

[0068] Incidentally, the rotational balance deviation of the gantry may differ depending on the scan speed. For this reason, the measurement function 445 performs the above-mentioned measurement process of the rotational balance deviation of the gantry and the storage process of the rotational balance deviation data for each scan speed that the X-ray CT apparatus 100 can perform.

[0069] The measurement function 445 may perform the measurement process for the deviation of the mount rotation balance described above using only the lowest scan speed and the highest scan speed. In this case, the measurement function 445 may predict the deviation of the mount rotation balance at other scan speeds from the measurement results of the lowest scan speed and the measurement results of the highest scan speed, and generate mount rotation balance deviation data for other scan speeds.

[0070] Furthermore, the measurement function 445 may perform the measurement process for the deviation in the mount rotation balance described above only in two cases: when the rotating frame 13 is stopped and at the maximum scan speed. Here, the measurement process for the deviation in the mount rotation balance when the rotating frame 13 is stopped involves stopping the rotating frame 13 at each mount rotation angle and performing the scan of the measurement phantom F2 described above.

[0071] In this case, the measurement function 445 may predict the deviation of the mount rotation balance at other scan speeds based on the measurement result when the rotating frame 13 is stopped and the measurement result at the highest scan speed, and generate mount rotation balance deviation data for other scan speeds.

[0072] Furthermore, the measurement process for the deviation of the mount rotation balance described above may be performed at any two scan speeds (including the state in which the rotating frame 13 is stopped). In this case, the measurement function 445 may predict the deviation of the mount rotation balance at the other scan speed from the measurement results of the two scan speeds and generate mount rotation balance deviation data for the other scan speed.

[0073] Returning to Figure 1, let's continue the explanation. Based on the rigging rotation balance misalignment data, the correction function 446 corrects the position of the X-ray detection element of the X-ray detector 12 that actually received X-rays during the scan of the subject P to the position of the X-ray detection element of the X-ray detector 12 that is predicted to have received X-rays if there had been no misalignment in the rigging rotation balance of the rigging device 10.

[0074] Here, for example, let's assume that an X-ray CT scanner is designed so that the X-rays emitted from a particular X-ray tube (for the sake of explanation, let's call it X-ray tube a) are received by an X-ray detection element of a particular X-ray detector (for the sake of explanation, let's call it X-ray detection element a).

[0075] Therefore, if there is no misalignment in the rotational balance of the rig, the X-rays emitted from X-ray tube a will naturally be received by the X-ray detection element a. However, if there is a misalignment in the rotational balance of the rig, the rotation of the rotating frame will cause a shift in the positional relationship between X-ray tube a and X-ray detection element a, and there is a possibility that the X-rays emitted from X-ray tube a will not be received by the X-ray detection element a.

[0076] In conventional X-ray CT scanners, even if a misalignment in the gantry rotation balance occurs and the X-rays emitted from X-ray tube a are not received by the X-ray detection element a, the reconstruction process is carried out as if the X-rays emitted from X-ray tube a had been received by the X-ray detection element a. As a result, there is a possibility that projection data different from the projection data that should have been used may be used for reconstruction.

[0077] Furthermore, in recent years, the detector pitch of X-ray CT scanners has become higher resolution. As a result, even a slight deviation in the balance of the gantry rotation can lead to a large difference between the projection data that should have been used and the projection data that was actually used, potentially affecting the image quality of the reconstructed image. For this reason, conventional X-ray CT scanners require a high degree of precision in adjusting the balance of the gantry rotation.

[0078] In this embodiment, the correction function 446 refers to the pylon rotational balance misalignment data in memory 41 and identifies the pylon rotational balance misalignment data in the Z-axis direction and the pylon rotational balance misalignment data in the Y-axis direction that correspond to the scan speed when the subject P is scanned.

[0079] Furthermore, the correction function 446, based on the identified Z-axis rotational balance misalignment data and Y-axis rotational balance misalignment data of the stand, corrects the position of the X-ray detection element of the X-ray detector 12 that actually received X-rays during the scan of the subject P to the position of the X-ray detection element of the X-ray detector 12 that is predicted to have received X-rays if there had been no misalignment in the rotational balance of the stand device 10, and performs reconstruction processing.

[0080] As a result, in the X-ray CT apparatus 100 according to this embodiment, the influence of deviations in the gantry rotation balance on the reconstructed image can be reduced without having to adjust the gantry rotation balance with high precision. In other words, in the X-ray CT apparatus 100 according to this embodiment, the gantry rotation balance only needs to be maintained to the extent that it does not interfere with the scanning of the subject P, and high-precision adjustment of the gantry rotation balance is unnecessary.

[0081] The correction process for the position of the X-ray detection element of the X-ray detector 12 will be explained below using Figures 11 and 12. Figure 11 is a diagram illustrating an example of the relationship between the X-ray detection element and the received signal before correction.

[0082] Each of the grids in Figure 11 represents an X-ray detection element of the X-ray detector 12. For the sake of explanation, each X-ray detection element of the X-ray detector 12 will be represented by a combination of its position in the ch direction and its position in the row direction, such as X-ray detection element C1R1...C4R4. The letters within the grid represent the received signals (raw data) of the X-ray detection elements of the X-ray detector 12. For the sake of explanation, each received signal will be represented as received signal A...Z.

[0083] For the sake of explanation, the following explanation will assume that the deviation in the ch-direction of the gantry rotation balance, corresponding to the scan speed at which the subject P was scanned, was equivalent to -1 X-ray detection element of the X-ray detector 12, and the deviation in the row-direction of the gantry rotation balance was equivalent to -1 X-ray detection element of the X-ray detector 12.

[0084] In this example, for instance, the received signal A, represented in white text on a black background, is received by the X-ray detector element C2R2, but if there had been no misalignment in the mount's rotational balance, it would have been received by the X-ray detector element C1R1. In other words, if the reconstruction process were to be performed using the received signal received by the X-ray detector element C1R1, the received signal Z, which was actually received by the X-ray detector element C1R1, would end up being used in the reconstruction process, even though it was intended to use received signal A.

[0085] Therefore, the correction function 446 corrects the corresponding X-ray detection element of the X-ray detector 12 for each received signal, based on the fact that the deviation in the ch direction of the rig rotation balance is equivalent to -1 X-ray detection element of the X-ray detector 12, and the deviation in the row direction of the rig rotation balance is equivalent to -1 X-ray detection element of the X-ray detector 12.

[0086] Here, Figure 12 illustrates an example of the relationship between the corrected X-ray detection element and the received signal. In the example in Figure 12, the correction function 446 corrects the corresponding X-ray detection element of the X-ray detector 12 for each of the received signals A...Z (received signals T...Z are not shown). For example, the X-ray detection element of the X-ray detector 12 corresponding to received signal A is corrected from X-ray detection element C2R2 to X-ray detection element C1R1.

[0087] This increases the likelihood that the reconstruction processing function 443 can perform the reconstruction process using the assumed projection data.

[0088] Next, we will describe the processes performed by the X-ray CT apparatus 100. First, we will describe the process related to measuring the deviation of the gantry rotation balance. Figure 13 is a flowchart showing an example of the processes performed by the X-ray CT apparatus 100 according to this embodiment.

[0089] First, the system control function 441 irradiates the measurement phantom F2 with X-rays and collects raw data (step S1). For example, the system control function 441 controls each part of the X-ray CT scanner 100 to irradiate the measurement phantom F2 with X-rays and collect raw data.

[0090] Next, the measurement function 445 measures the deviation in the rotational balance of the cradle (step S2). For example, the measurement function 445 measures the deviation in the rotational balance of the cradle from the difference between the projection data that is expected to be obtained when there is no deviation in the rotational balance of the cradle and the projection data generated by the preprocessing function 442 from the raw data collected in step S1.

[0091] Next, the measurement function 445 generates frame rotation balance misalignment data (step S3). For example, from the measurement results of step S2, the measurement function 445 generates frame rotation balance misalignment data in the Z-axis direction and frame rotation balance misalignment data in the Y-axis direction, as shown in Figures 5 and 8.

[0092] Next, the measurement function 445 stores the frame rotation balance misalignment data (step S4) and terminates the process. For example, the measurement function 445 stores the frame rotation balance misalignment data in the Z-axis direction and the frame rotation balance misalignment data in the Y-axis direction generated in step S3 in the memory 41 as frame rotation balance misalignment data.

[0093] Next, we will explain the process related to reconstruction. Figure 14 is a flowchart showing an example of the process performed by the X-ray CT apparatus 100 according to the embodiment.

[0094] First, the system control function 441 irradiates the subject P with X-rays and collects raw data (step S11). For example, the system control function 441 controls each part of the X-ray CT scanner 100 to irradiate the subject P with X-rays and collect raw data.

[0095] Next, the preprocessing function 442 generates projection data (step S12). For example, the preprocessing function 442 generates projection data by applying preprocessing such as logarithmic transformation, offset correction, inter-channel sensitivity correction, and beam hardening correction to the raw data collected in step S11.

[0096] Next, the correction function 446 corrects the position of the X-ray detection element of the X-ray detector 12 that received the X-rays (step S13).

[0097] For example, the correction function 446 refers to the pylon rotational balance deviation data in memory 41 and corrects the corresponding X-ray detection element of the X-ray detector 12 for each of the received signals that formed the basis of the projection data obtained from each of the X-ray detection elements of the X-ray detector 12, based on the pylon rotational balance deviation in the Z-axis direction and the pylon rotational balance deviation in the Y-axis direction.

[0098] Specifically, the correction function 446 corrects the X-ray detection element of the X-ray detector 12 that is currently associated with each projection data obtained from each X-ray detection element of the X-ray detector 12 to the X-ray detection element of the X-ray detector 12 that would have been associated with it if there had been no misalignment in the rigging rotation balance.

[0099] Next, the reconstruction processing function 443 performs reconstruction processing based on the position of the X-ray detection element of the X-ray detector 12 that received the corrected X-rays (step S14). For example, the reconstruction processing function 443 generates CT image data by performing reconstruction processing using methods such as filtered back projection and iterative reconstruction on the projection data in which the X-ray detection element of the X-ray detector 12, which was generated in step S12 and associated in step S13, has been corrected.

[0100] Next, the image processing function 444 generates a display image (step S15) and terminates the process. For example, the image processing function 444 generates a display image by converting the CT image data generated in step S14 into tomographic image data of an arbitrary cross-section or 3D image data using a known method.

[0101] The X-ray CT apparatus 100 according to at least one embodiment described above scans a subject P to collect raw data, corrects the position of the X-ray detection element of the X-ray detector 12 that actually received X-rays during the scan of the subject P, based on the gantry balance misalignment data generated from the raw data obtained by scanning the measurement phantom F2, to the position of the X-ray detection element that is predicted to have received X-rays if there had been no misalignment in the gantry rotation balance, and generates a reconstructed image based on the raw data and the corrected position of the X-ray detection element of the X-ray detector 12.

[0102] As a result, the X-ray CT apparatus 100 according to this embodiment can generate reconstructed images that suppress the effects of misalignment of the gantry rotation balance, even if misalignment occurs. Therefore, the X-ray CT apparatus 100 according to this embodiment can generate reconstructed images that suppress the effects of misalignment of the gantry rotation balance without performing high-precision rotation balance adjustment. In other words, the X-ray CT apparatus 100 according to this embodiment can efficiently suppress the effect of gantry vibration on the reconstructed image.

[0103] The embodiments described above can also be modified and implemented as appropriate by changing some of the configurations or functions of each device. Therefore, several modifications of the embodiments described above will be described below as other embodiments. In the following, we will mainly describe the differences from the embodiments described above, and parts that are common to those already described will be given the same reference numerals and detailed explanations will be omitted. Furthermore, the other embodiments described below may be implemented individually or in combination as appropriate.

[0104] (Variation 1) In the embodiment described above, a configuration was described in which the position of the X-ray detection element of the X-ray detector 12 that received the X-rays was corrected before the reconstruction process. In this modified example, a configuration is described in which the reconstruction process is performed before correcting the position of the X-ray detection element of the X-ray detector 12 that received the X-rays.

[0105] In this modified example, the reconstruction processing function 443 generates CT image data using a filter-corrected back projection method or the like before correcting the position of the X-ray detection elements of the X-ray detector 12 that received the X-rays. Subsequently, the reconstruction processing function 443 checks the generated CT image data and identifies the X-ray detection elements that did not receive the X-rays.

[0106] As a method for identifying X-ray detection elements that are not receiving X-rays, for example, when the reconstruction processing function 443 reconstructs a cross-section of the subject P, it compares the brightness value of each pixel constituting the reconstructed image of that cross-section with the average brightness value of neighboring pixels. The reconstruction processing function 443 identifies pixels among all the pixels constituting the reconstructed image in which the value obtained by subtracting the average value of neighboring pixels from the brightness value of the pixel is less than a threshold.

[0107] The reconstruction processing function 443 identifies the projection data related to the reconstruction processing of the pixels identified above as projection data based on the received signal of an X-ray detection element that has not received X-rays (hereinafter also referred to as missing data). The reconstruction processing function 443 identifies the X-ray detection element associated with the received signal that formed the basis of the identified missing data as an X-ray detection element that has not received X-rays.

[0108] Next, the correction function 446 refers to the rigging rotation balance misalignment data in memory 41 and identifies the received signal that would have been associated with the X-ray detection element identified as not receiving X-rays if there had been no misalignment in the rigging rotation balance. The reconstruction processing function 443 replaces the missing data with projection data based on the received signal identified above and performs the reconstruction process again.

[0109] According to this modified method, by identifying the received signal that would have been associated with the X-ray detection element corresponding to the missing data caused by the misalignment of the rigging rotation balance, and replacing the missing data with projection data based on the identified received signal, the influence of rigging vibration on the reconstructed image can be suppressed. In other words, since it is not necessary to correct the position of all X-ray detection elements, the influence of rigging vibration on the reconstructed image can be suppressed more efficiently.

[0110] (Modification 2) In the above-described embodiment, a measurement phantom consisting of multiple spherical phantoms arranged spirally in the opening of the support structure 10 was used to measure the deviation in the rotational balance of the support structure. In this modified example, a measurement phantom consisting of a number of spherical phantoms randomly arranged in the opening of the support structure 10 is used to measure the deviation in the rotational balance of the support structure.

[0111] In this modified example, when measuring the deviation in the rotational balance of the rigging, X-rays are irradiated onto a measurement phantom F3, which consists of a number of spherical phantoms randomly placed in the opening of the rigging device 10, to collect raw data.

[0112] Here, Figure 15 is a perspective view showing an example of the positional relationship between the mounting device 10 and the measuring phantom F3, which is composed of multiple spherical phantoms, according to Modification 2. As shown in Figure 15, in this modification, the measuring phantom F3 is composed of multiple spherical phantoms and is randomly arranged in the opening of the mounting device 10.

[0113] Furthermore, each of the multiple spherical phantoms constituting the measurement phantom F3 has pre-existing information representing its distance from other spherical phantoms and the angular difference in the viewing direction from other spherical phantoms. This information is stored, for example, in memory 41. This clarifies the positional relationship of the multiple spherical phantoms on the mounting device 10. As a result, it becomes easier to estimate which spherical phantom is projected by which X-ray detection element and how, assuming there is no deviation in the mounting device's rotational balance.

[0114] According to this modified version, it is possible to measure the deviation in the rotational balance of the mounting base over a wide range of channels and rows without having to arrange multiple spherical phantoms in a regular pattern.

[0115] (Variation 3) In the above-described embodiment, a measurement phantom consisting of multiple spherical phantoms arranged spirally in the opening of the support device 10 was used to measure the deviation of the support device's rotational balance. In this modified example, a measurement phantom consisting of multiple spherical phantoms arranged spirally inside the top plate 33 of the bed device 30 is used to measure the deviation of the support device's rotational balance.

[0116] In this modified example, when measuring the deviation of the frame rotation balance, X-rays are irradiated onto a measurement phantom F4, which consists of multiple spherical phantoms arranged (embedded) in a spiral pattern inside the top plate 33 of the bed apparatus 30, to collect raw data.

[0117] Here, Figure 16 is a perspective view showing an example of the positional relationship between the top plate 33 and the measuring phantom F4, which is composed of multiple spherical phantoms, according to Modification 3.

[0118] As shown in Figure 16, in this modified example, the measuring phantom F4 is composed of multiple spherical phantoms, which are embedded inside the top plate 33 in a spiral arrangement.

[0119] Furthermore, the measurement phantom F4 is embedded in the Z-axis direction within the range of the top plate 33 that can actually be scanned. Specifically, the spherical phantom constituting the measurement phantom F4 is embedded in the range from the Z-axis position of the top plate 33 corresponding to the position of the imaging cross-section when the top plate 33 is extended to its maximum extent into the opening of the mount device 10, to the Z-axis tip position of the top plate 33 on the opening side of the mount device 10.

[0120] Furthermore, the measurement phantom F4 is positioned in a location that does not overlap with the subject P in the X-axis, Y-axis, and Z-axis directions when the subject P is placed on the top plate 33.

[0121] As a result, in this modified example, even when scanning the measurement phantom F4 at the same time as scanning the subject P, the image of the measurement phantom F4 can be easily separated from the reconstructed image. In other words, in this modified example, the deviation of the rigging rotation balance can be measured in conjunction with the scanning of the subject P.

[0122] Furthermore, as shown in Figure 16, multiple spherical phantoms are embedded inside the top plate 33 in a spiral arrangement. In this modified example, the deflection (sagging) of the top plate 33 can be measured from the scan results of the multiple spherical phantoms. In this modified example, by measuring the sagging of the top plate 33, it is possible to estimate what state the subject P would be in if the top plate 33 were not sagging, and it is also possible to perform a process to correct the sagging of the top plate 33.

[0123] According to this modified method, the deviation in the rotational balance of the rig can be measured in conjunction with the scanning of the subject P, and the influence of rig vibration on the reconstructed image can be suppressed more efficiently.

[0124] (Modification 4) In the above-described embodiment, the X-ray CT apparatus described was an X-ray CT apparatus that images a subject P in a supine position (hereinafter referred to as a supine CT apparatus). In this modified example, the X-ray CT apparatus described is an X-ray CT apparatus that images a subject P in an upright position (an upright CT apparatus).

[0125] Here, Figure 17 shows an example of the configuration of the X-ray CT apparatus 100a according to Modification 4. As shown in Figure 17, the X-ray CT apparatus 100a is an upright CT apparatus. The X-ray CT apparatus 100a has a gantry device 10a.

[0126] As shown in Figure 17, the mounting device 10a comprises a mounting body 101, a support column 103, and a beam 104. The mounting body 101 is a substantially cylindrical structure with an opening that forms the field of view. As shown in Figure 17, the mounting body 101 houses the X-ray tube 11 and the X-ray detector 12, which are arranged opposite each other across the opening.

[0127] More specifically, the frame body 101 further comprises a main frame (not shown) made of a metal such as aluminum, and a rotating frame 131 that is rotatably supported by the main frame around a central axis R1 via bearings or the like.

[0128] An annular electrode (not shown) is provided at the contact point between the main frame and the rotating frame 131. A conductive slider (not shown) is attached to the contact point of the main frame so as to make sliding contact with the annular electrode.

[0129] The rotating frame 131 is a metal frame formed in an annular shape from a metal such as aluminum, and for example, the X-ray tube 11 and the X-ray detector 12 are mounted on it. The X-ray tube 11 and the X-ray detector 12 may be fitted into recesses formed in the rotating frame 131, or they may be fastened together with fasteners such as screws.

[0130] The rotating frame 131 rotates around its central axis R1 at a constant angular velocity, receiving power from a rotary drive unit (not shown). The rotary drive unit generates power to rotate the rotating frame 131 according to the control from the control device 15.

[0131] The rotary drive unit generates power by driving at a rotational speed corresponding to the duty cycle of the drive signal from the control device 15. The rotary drive unit is implemented by a motor such as a direct drive motor or a servo motor. The rotary drive unit is housed in, for example, the frame body 101.

[0132] Furthermore, as shown in Figure 17, the support column 103 is a base that supports the frame body 101 away from the floor surface. Specifically, the support column 103 supports the frame body 101 so that it can slide freely in the direction perpendicular to the floor surface. The support column 103 also supports the frame body 101 so that it can rotate freely around a horizontal axis.

[0133] The support columns 103 are made of metal, reinforced plastic, or the like. A beam 104 is erected on top of the pair of support columns 103. The beam 104 is made of metal, reinforced plastic, or the like. Typically, the beam 104 is made of the same material as the support columns 103. The support columns 103 and the beam 104 may be a single unit.

[0134] Typically, the support columns 103 are provided in pairs. One support column 103 is connected to one side of the frame body 101 in the Y-axis direction, and the other support column 103 is connected to the other side of the frame body 101 in the Y-axis direction.

[0135] However, this embodiment is not limited thereto. For example, one support column 103 may be connected to only one of the two sides of the frame body 101. Also, although the support column 103 is described as having a columnar shape, this embodiment is not limited thereto. For example, the support column 103 may have any shape, such as a U-shape, as long as it can support at least one side of the frame body 101.

[0136] Furthermore, the support column 103 does not need to fix the frame body 101 so that its central axis R1 is oriented in the direction of the vertical Z-axis. In other words, the support column 103 may be configured to support the frame body 101 so that it can rotate around the horizontal axis R2.

[0137] Specifically, the support column 103 and the frame body 101 may be connected via bearings or the like so that the frame body 101 can rotate around the horizontal axis R2. Hereinafter, the support column 103 will be assumed to support the frame body 101 so that it can slide in the longitudinal direction and can rotate (tilt) around the horizontal axis R2.

[0138] The support column 103 has a structure that supports the frame body 101 around the horizontal axis R2, so that X-ray CT imaging can be performed in both a standing position and a supine position using a single frame device 10a, as shown in Figure 17.

[0139] Furthermore, the support column 103 is not only capable of supporting the frame body 101 in a position where the central axis R1 maintains the Z-axis direction or the X-axis direction, but may also be stationary with the central axis R1 facing any angle around the horizontal axis R2.

[0140] The two columnar bodies 293 are fixed by retaining fixtures (upper fixture 271 and lower fixture 273). Specifically, the upper ends of the two columnar bodies 293 are fixed by the upper fixture 271, and the lower ends of the two columnar bodies 293 are fixed by the lower fixture 273.

[0141] The two columnar bodies 293 may be positioned at any location within the passage path RT of the opening. For example, as shown in Figure 17, the two columnar bodies 293 may be fixed by the upper fixing device 271 and the lower fixing device 273 so that they are located on both sides of the subject P.

[0142] As shown in Figure 17, in order to more firmly fix the subject P to the two columnar bodies 293, auxiliary fixing devices 294 such as bands may be detachably attached to the two columnar bodies 293. The subject P can be fixed to the two columnar bodies 293 using these auxiliary fixing devices 294.

[0143] In this modified example, the subject P is fixed to two columnar bodies, but the subject P may also be fixed to a single columnar body.

[0144] In this context, standing CT scanners require the measurement of raft vibration in the standing position in addition to the deviation of raft rotation balance in the supine position. The same methods as those used for measuring and correcting deviation of raft rotation balance in the above-described embodiment can be applied to the measurement and correction of raft vibration in the standing position. Furthermore, the same methods as those used for measuring and correcting deviation of raft rotation balance in the above-described embodiment can be applied to raft tilt.

[0145] In this modified example, in order to measure the vibration of the support structure in an upright position, a standing measurement phantom (not shown), consisting of multiple spherical phantoms, is embedded inside the two columnar bodies 293, with the multiple spherical phantoms arranged in a spiral pattern. Alternatively, the standing measurement phantom may be randomly arranged inside the two columnar bodies 293.

[0146] By positioning the standing measurement phantom inside the two columnar bodies 293, the standing measurement phantom and the subject P do not overlap in the X-axis, Y-axis, and Z-axis directions when imaging the subject P.

[0147] As a result, in this modified example, even when scanning the standing measurement phantom at the same time as scanning the subject P, the image of the standing measurement phantom can be easily separated from the reconstructed image. In other words, in this modified example, the vibration of the stand in a standing position can be measured simultaneously with the scanning of the subject P.

[0148] Furthermore, the standing measurement phantom is embedded in the Z-axis direction within the range that can actually be scanned by the two columnar bodies 293. Specifically, the spherical phantom constituting the standing measurement phantom is embedded in the two columnar bodies 293 in the range from the position corresponding to the imaging cross-section when the mount body 101 is at the upper limit position in the Z-axis direction to the position corresponding to the imaging cross-section when it is at the lower limit position.

[0149] According to this modified version, the effect of vibrations in the gantry of the standing CT scanner on the reconstructed image can be efficiently suppressed.

[0150] Furthermore, although the above embodiment was described as realizing each processing function with a single processing circuit, it is also possible to configure a processing circuit by combining multiple independent processors, and each processor can realize the function by executing a program.

[0151] In the above explanation, the term "processor" refers to circuits such as CPUs (Central Processing Units), GPUs (Graphics Processing Units), Application Specific Integrated Circuits (ASICs), and Programmable Logic Devices (e.g., Simple Programmable Logic Devices (SPLDs), Complex Programmable Logic Devices (CPLDs), and Field Programmable Gate Arrays (FPGAs)). A processor performs its functions by reading and executing programs stored in its memory circuits.

[0152] Alternatively, instead of storing the program in a memory circuit, the program can be directly embedded within the processor's circuitry. In this case, the processor performs its functions by reading and executing the program embedded within the circuitry.

[0153] Furthermore, each processor in this embodiment is not limited to being configured as a single circuit; multiple independent circuits may be combined to form a single processor and realize its functions. In addition, multiple components shown in each figure may be integrated into a single processor to realize its functions.

[0154] Furthermore, for example, each component of each illustrated device is a functional concept and does not necessarily have to be physically configured as shown. In other words, the specific forms of distribution and integration of each device are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads and usage conditions. Moreover, each processing function performed by each device can be implemented, all or any part of it, by a CPU and the program that is analyzed and executed by that CPU, or by hardware using wired logic.

[0155] Furthermore, among the processes described in the embodiments described above, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically by known methods. In addition, the processing procedures, control procedures, specific names, and information including various data and parameters shown in the above document and drawings can be changed at will unless otherwise specified.

[0156] Furthermore, the method described in this embodiment can be implemented by executing a pre-prepared program on a computer such as a personal computer or workstation. This program can be distributed via a network such as the Internet. Alternatively, this program can be recorded on a computer-readable non-temporary recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and executed by reading it from the recording medium by a computer.

[0157] According to at least one embodiment described above, the effect of vibrations of the mounting structure on the reconstructed image can be efficiently suppressed.

[0158] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0159] 10. Mounting device 12 X-ray detectors 18 DAS 30 Bed equipment 40 Console device 41 memory 44 Processing Circuits 100 X-ray CT device 441 System control function 442 Pre-processing function 443 Reconstruction Processing Function 444 Image processing functions 445 Measurement function 446 Correction function

Claims

1. A collection unit that collects first detection data based on a first scan of the subject, An acquisition unit that acquires correction data to correct the rotational balance of the mounting frame, A correction unit corrects the position of the X-ray detection element that actually received X-rays in the first scan to the position of the X-ray detection element that is predicted to have received X-rays if there were no vibrations, based on the correction data. A reconstruction processing unit generates a reconstructed image based on the first detection data and the corrected position of the X-ray detection element. An X-ray CT scanner equipped with [a specific feature].

2. The collection unit collects second detection data based on a second scan of the measurement phantom, A generation unit that generates the correction data based on the second detection data, The system further comprises a storage control unit that stores the generated correction data in a storage unit, The acquisition unit acquires the correction data stored in the storage unit. The X-ray CT apparatus according to claim 1.

3. The measuring phantom is composed of multiple spherical phantoms and is placed within the opening of the mounting frame. The X-ray CT apparatus according to claim 2.

4. The plurality of spherical phantoms are arranged spirally within the opening. The X-ray CT apparatus according to claim 3.

5. The plurality of spherical phantoms are randomly arranged within the opening. Each of the aforementioned spherical phantoms is further provided with a memory unit that stores information representing its positional relationship with other spherical phantoms. The X-ray CT apparatus according to claim 3.

6. The system further includes a top plate on which the subject, who is in a supine position during imaging, is placed. The aforementioned multiple spherical phantoms are arranged inside the top plate. The X-ray CT apparatus according to claim 3.

7. The system further includes a columnar subject holder that supports the subject in an upright position during imaging, The plurality of spherical phantoms are arranged inside the subject holder. The X-ray CT apparatus according to claim 3.

8. The collection unit performs the second scan at each executable scan speed and collects the second detection data. The generation unit generates the correction data for each executable scan speed based on the second detection data corresponding to the executable scan speed, The memory control unit causes each of the correction data to be stored in the memory unit in association with each of the executable scan speeds. The acquisition unit acquires the correction data corresponding to the scan speed at which the subject was scanned. The X-ray CT apparatus according to claim 2.

9. The collection unit performs the second scan for only two arbitrary scan speeds and collects the second detection data. The generation unit generates the correction data for each executable scan speed based on the second detection data corresponding to any two scan speeds. The memory control unit causes each of the correction data to be stored in the memory unit in association with each of the executable scan speeds. The acquisition unit acquires the correction data corresponding to the scan speed at which the subject was scanned. The X-ray CT apparatus according to claim 2.

10. A method for correcting the effect of rotational balance deviations of the gantry of an X-ray CT scanner, Based on the first scan of the subject, initial detection data is collected. We obtain correction data to correct the rotational balance of the mounting frame. In the first scan, the position of the X-ray detection element that actually received the X-rays is corrected based on the correction data to the position of the X-ray detection element that is predicted to have received the X-rays if there were no vibrations. Based on the first detection data and the corrected position of the X-ray detection element, a reconstructed image is generated. method.

11. A phantom used to correct the effect of rotational balance deviations of the pedestal of an X-ray CT scanner, which comprises at least one of a top plate on which a subject in a supine position is placed during imaging and a columnar subject holder that supports the subject in an upright position during imaging, Composed of multiple spherical phantoms, The plurality of spherical phantoms are arranged in at least one of the interior of the top plate and the interior of the subject holder. phantom.

12. The plurality of spherical phantoms are arranged spirally inside at least one of the top plate and the inside of the subject holder. The phantom according to claim 11.

13. The plurality of spherical phantoms are positioned in locations that do not overlap with the subject. The phantom according to claim 11 or 12.

Images