Positioning device, radiotherapy system including positioning device, and positioning method

Abstract

To provide a positioning device in which a time required for positioning of a patient is enabled to be reduced, a radiotherapy system including the positioning device, and a positioning method.SOLUTION: A positioning device for positioning, at a predetermined position, a patient Pa on a therapy table 7 comprises: a CBCT imaging device 12 that rotates around the patient on the therapy table to image at least one perspective X-ray picture and creates a CBCT reconstruction picture from the imaged perspective X-ray picture; and a picture collation unit 240 that executes first positioning calculation for the patient using the perspective X-ray picture of the patient acquired by the CBCT imaging device and a pseudo perspective X-ray picture created by performing projection processing on a CT picture of the patient acquired before the imaging by the CBCT imaging device. The picture collation unit starts the first positioning calculation before completion of the creation of the CBCT reconstruction picture.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a positioning device, a radiation therapy system having the positioning device, and a positioning method.

Background Art

[0002] As one of the cancer treatment methods, radiation therapy that irradiates a patient with radiation is known. The radiation used in radiation therapy is roughly classified into non-charged particle beams such as X-rays or gamma rays, and charged particle beams such as proton beams or carbon beams. Radiation therapy using the latter charged particle beam is generally called particle beam therapy.

[0003] In the case of non-charged particle beams, the dose decreases at a constant rate from a shallow position to a deep position in the body. On the other hand, in the case of charged particle beams, a dose distribution (black curve) having a peak of energy loss at a specific depth can be formed. Therefore, by adjusting the peak of the energy loss of the charged particle beam to the position of the tumor, it is possible to significantly reduce the dose of the charged particle beam irradiated to normal tissues located deeper than the tumor.

[0004] Therefore, in radiation therapy, it is important for improving the treatment effect to accurately irradiate a tumor as a target with radiation of a desired dose. In order to achieve accurate irradiation of the tumor with radiation, it is necessary to align the position of the patient with the planned position determined by a pre-created treatment plan. Aligning the position of this patient is called patient positioning.

[0005] As methods for positioning a patient in radiotherapy, the following two methods are mainly used. The first positioning method is a three-dimensional to two-dimensional (3D-2D) registration in which a patient lying on a couch (treatment table) on the treatment day is imaged from two different directions by two sets of X-ray tubes and a flat panel detector (FPD), and the fluoroscopic X-ray image (Digital Radiography: DR) thus obtained is compared with a digitally reconstructed radiograph (DRR) created from the treatment planning CT image to position the patient so that the positions of positioning target structures such as bones match between the fluoroscopic X-ray image and the digitally reconstructed radiograph. The second positioning method is a three-dimensional to three-dimensional (3D-3D) registration in which the CT image used to create the treatment plan, the CT image taken with a CT device in the treatment room on the treatment day, or the cone beam CT (CBCT) image taken using an X-ray imaging device mounted on the rotating gantry of the treatment room is aligned with the treatment planning CT image.

[0006] Generally, in the former 3D-2D registration, structures other than the positioning target structures such as the patient's fixtures and soft tissues may be superimposed on the fluoroscopic X-ray image, or the arrangement of the bones, which are the positioning target structures, may change from the treatment planning time. In such a situation, the structures shown in the fluoroscopic X-ray image and the digitally reconstructed radiograph do not match throughout the entire image. In this case, in the three-dimensional to two-dimensional (3D-2D) registration, a region of interest (ROI) is set in advance as the region where the positioning target structure exists on the digitally reconstructed radiograph, and the patient is positioned using only the ROI. Similarly, in the three-dimensional to three-dimensional (3D-3D) registration, image matching is performed only within a volume of interest (VOI) that is set in advance as the target region for registration, using the three-dimensional region where the positioning target structure exists on the three-dimensional image. The setting of the region of interest is usually performed by a user who is a medical professional by drawing or numerically setting the region of interest on the image.

[0007] In the automatic alignment for positioning a patient, the translation amount and rotation amount of the hospital bed on which the patient lies are used as parameters, and the optimal values of these parameters are calculated by optimization calculation. Usually, the translation amount has three components along three axes (x, y, z) orthogonal to each other. The rotation amount has three components (Pitch, Roll, Yaw) with these three axes as the rotation axes. Therefore, in the optimization calculation, the optimal values of the parameters are calculated by repeatedly performing the optimization process for each of the six components. The three axes defining the translation amount coincide with the moving axes of the hospital bed for placing the patient at the planned position. The x-axis is the direction from right to left (Right-Left direction: RL direction) as seen from the patient lying on the back on the hospital bed. The y-axis is the direction from the patient's feet to the head (Superior-Inferior direction: SI direction). The z-axis is the direction from the patient's back to the abdomen (Anterior-Posterior: AP direction).

[0008] Patent Document 1 discloses a technique for obtaining the amount of deformation in which a virtual fluoroscopic X-ray image created by changing the deformation control point information set in the CT image most matches the virtual fluoroscopic X-ray image created using a plurality of fluoroscopic X-ray images and the virtual fluoroscopic X-ray image created from the CT image and the fluoroscopic X-ray.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] In the technique described in Patent Document 1, since it is necessary to calculate the parameters required for deformation for each deformation control point, the amount of calculation is large, the time required for patient positioning becomes long, and the convenience for the user using the radiation therapy system decreases.

[0011] An object of the present disclosure is to provide a positioning device, a radiation therapy system having the positioning device, and a positioning method that can shorten the time required for positioning a patient.

Means for Solving the Problems

[0012] To solve the above problems, a positioning device according to the present disclosure is a positioning device that positions a patient on a treatment table at a predetermined position, and rotates around the patient on the treatment table to take at least one fluoroscopic X-ray image, and creates a CBCT reconstructed image from the taken fluoroscopic X-ray image. A CBCT imaging device, a fluoroscopic X-ray image of the patient acquired by the CBCT imaging device, and a virtual fluoroscopic X-ray image created by projecting and processing a CT image of the patient acquired before imaging by the CBCT imaging device. An image matching unit that performs a first positioning calculation for the patient, and the image matching unit starts the first positioning calculation before the creation of the CBCT reconstructed image is completed.

Advantages of the Invention

[0013] Therefore, according to the present invention, the time required for positioning a patient can be shortened.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

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Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The positioning device of the present disclosure enables highly accurate patient positioning while reducing the calculation time. In the present disclosure, since the first positioning calculation (3D2D automatic positioning calculation) can be completed earlier, the patient position when optimizing the patient positioning can be brought closer to the patient position when creating a treatment plan.

[0016] Therefore, the positioning device of the present disclosure can reduce, for example, the change in the similarity value of the pseudo-fluoroscopic X-ray image with respect to the fluoroscopic X-ray image in the calculation for optimizing the positioning, and can perform processing so that the similarity serving as a judgment index becomes higher toward the original correct position (the patient position when creating a treatment plan). Therefore, the positioning device of the present disclosure can reduce the number of repeated calculation times and reduce the calculation amount in the optimization calculation for obtaining parameters for controlling the position of the treatment table on which the patient is placed, and as a result, can optimize the parameters in a shorter time.

[0017] Furthermore, in order to improve the positioning accuracy, the present disclosure takes fluoroscopic X-ray images of a patient from a plurality of preset angles so as to obtain high-precision images. For example, in 3D automatic positioning calculation (alignment) as "second positioning calculation", when a metal structure is included around the VOI in the CBCT, a metal artifact is mixed into the VOI. Due to the metal artifact, the amount of information of the structure to be positioned may decrease, which may have an adverse effect on the positioning accuracy. Furthermore, in 3D positioning calculation, since the similarity calculation between three-dimensional information is repeated, the amount of calculation increases, and thus the processing time becomes long.

[0018] The positioning device of the present disclosure controls the position of a treatment table (bed) on which a patient is mounted. The positioning device of the present disclosure uses a fluoroscopic X-ray image obtained during CBCT imaging of a patient and a pseudo-fluoroscopic X-ray image created by performing projection processing on a CT image in a virtual space in the same imaging system, and calculates a three-dimensional movement amount for controlling the position of the treatment table so that the fluoroscopic X-ray image and the pseudo-fluoroscopic X-ray image match.

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0020] Note that the following description and drawings are examples for explaining the present invention, and for the sake of clarity of explanation, omissions and simplifications are made as appropriate. The present invention can be implemented in various other forms. Unless otherwise limited, each component may be singular or plural. Also, in the drawings for explaining the embodiments, the same reference numerals are given to portions having the same function, and the repeated explanation thereof may be omitted. Also, the positions, sizes, shapes, ranges, etc. of the components shown in the drawings may not represent the actual positions, sizes, shapes, ranges, etc. for the sake of facilitating understanding of the invention. For this reason, the present invention is not limited to the positions, sizes, shapes, ranges, etc. disclosed in the drawings. Also, when there are a plurality of identical or similar components, different subscripts may be attached to the same reference numeral for explanation. However, when it is not necessary to distinguish these plurality of components, the subscripts may be omitted for explanation.

Example

[0021] Figure 1 shows the overall configuration of a radiation therapy system (particle beam therapy system) 100. The radiation therapy system 100 shown in Figure 1 has a group of devices for irradiating a patient Pa, who is a subject, with a particle beam. The radiation therapy system 100 includes, for example, an accelerator 1, a beam transport device 2, a rotating gantry 3, an irradiation nozzle 4, FPDs 5A and 5B, X-ray tubes 6A and 6B, a treatment table (bed) 7, a robotic arm 8, a communication device 9, a data server 10, a treatment planning device 11, a fluoroscopic X-ray imaging device 12, a treatment table control device 13, an overall control device 14, and a patient positioning device 20.

[0022] The accelerator 1 is a particle beam generator that generates a particle beam to be irradiated to the patient Pa, and accelerates and outputs the particle beam until it reaches an energy suitable for the treatment of the patient Pa. The beam transport device 2 transports the particle beam output from the accelerator 1 to the rotating gantry 3. The type of the particle beam is not particularly limited, and for example, it is a proton beam or a carbon beam.

[0023] The rotating gantry 3 and the irradiation nozzle 4 are irradiation devices that irradiate the patient Pa with the particle beam transported from the accelerator 1. The rotating gantry 3 adjusts the irradiation angle for irradiating the patient Pa with the particle beam transported from the accelerator 1. For example, the rotating gantry 3 has a rotating mechanism (not shown) that can rotate 360 degrees around the patient Pa, and adjusts the irradiation angle by rotating. The irradiation nozzle 4 is provided on the rotating gantry 3 and irradiates the patient Pa with the particle beam transported to the rotating gantry 3. The irradiation nozzle 4 may incorporate a mechanism for adjusting the shape of the particle beam to match the shape of the affected part of the patient.

[0024] The FPDs 5A and 5B and the X-ray tubes 6A and 6B constitute an imaging system for performing fluoroscopic imaging of the patient Pa. The FPDs 5A and 5B are planar detectors that detect X-rays and image the patient Pa. The X-ray tubes 6A and 6B output X-rays. The FPD 5A and the X-ray tube 6A are arranged to face each other such that the X-rays output from the X-ray tube 6A are detected by the FPD 5A, and the FPD 5B and the X-ray tube 6B are arranged to face each other such that the X-rays output from the X-ray tube 6B are detected by the FPD 5B. The axis connecting the center of the FPD 5A and the X-ray tube 6A and the axis connecting the center of the FPD 5B and the X-ray tube 6B are two imaging axes for imaging the patient. These two imaging axes are preferably orthogonal to each other, but may not be orthogonal to each other. The radiation therapy system 100 may include three or more FPDs and X-ray tubes respectively. In this case, there are also three or more imaging axes.

[0025] In addition, when the FPDs 5A and 5B and the X-ray tubes 6A and 6B are fixed to the rotating gantry 3, a CBCT image can be obtained by reconstructing the fluoroscopic X-ray image taken as the rotating gantry 3 rotates. By comparing the obtained CBCT image with the CT image when creating the treatment plan, the patient Pa can be positioned.

[0026] The treatment table 7 is a table on which the patient Pa is placed when irradiating the patient Pa with particle beams. The robotic arm 8 is a treatment table moving device that moves the treatment table 7. For example, the robotic arm 8 performs translational movement of the treatment table 7 in a plurality of translational directions along each of a plurality of moving axes and rotational movement in a plurality of rotational directions about a plurality of rotational axes. In this embodiment, the moving axes and the rotational axes are the same, and there are three moving axes (rotational axes). Each moving axis is a direction from right to left (RL direction) as viewed from the patient Pa lying supine on the treatment table 7, a direction from the feet to the head of the patient Pa (SI direction), and a direction from the back to the abdomen of the patient Pa (AP direction).

[0027] The communication device 9 communicably connects the data server 10, the treatment planning device 11, the overall control device 14, and the patient positioning device 20 to each other.

[0028] The data server 10 is an information storage device that stores various information related to the particle beam treatment of patient Pa. The data server 10 stores, for example, the three-dimensional fluoroscopic image information of patient Pa and the treatment plan information indicating the treatment plan of patient Pa.

[0029] The three-dimensional fluoroscopic image includes information indicating the shape and electron density of the patient in voxel units. The three-dimensional fluoroscopic image is, for example, a Computed Tomography (CT) image, and is generated in advance (before creating the treatment plan information of patient Pa. Also referred to as "when creating the treatment plan").

[0030] The treatment plan information is generated based on the three-dimensional fluoroscopic image. The treatment plan information includes the planned placement information indicating the planned placement, which is the placement of patient Pa during treatment. The placement of patient Pa indicates the position and angle (posture) of patient Pa, and is determined by the position and angle of the treatment table 7. In the present disclosure, as will be described later, the placement of patient Pa on the treatment day is brought close to the planned placement at the time of creating the treatment plan in a short time.

[0031] The treatment planning device 11 creates a treatment plan for patient Pa based on the three-dimensional fluoroscopic image information stored in the data server 10, and stores the treatment plan information indicating the treatment plan in the data server 10.

[0032] The fluoroscopic X-ray imaging device 12 is an example of a "CBCT imaging device". The fluoroscopic X-ray imaging device 12 acquires a plurality of fluoroscopic X-ray images of patient Pa taken from different angles by controlling the FPD 5A and the X-ray tube 6A, and the FPD 5B and the X-ray tube 6B, respectively, and transmits the acquired fluoroscopic X-ray images to the positioning device 20. In this embodiment, there are two fluoroscopic X-ray images.

[0033] The treatment table control device 13 adjusts the placement of patient Pa by controlling the robot arm 8 to adjust the placement of the treatment table 7.

[0034] The patient positioning device 20 executes a positioning process for the patient Pa based on the three-dimensional fluoroscopic image information and treatment plan information stored in the data server 10 and the fluoroscopic X-ray image acquired by the fluoroscopic X-ray imaging device 12.

[0035] The positioning process for the patient Pa is a process of placing the patient Pa placed on the treatment table 7 in the same arrangement as the planned arrangement indicated by the treatment plan information before the start of the particle beam treatment of the patient Pa. The patient positioning device 20 controls the robotic arm 8 via the treatment table control device 13 and adjusts the position and angle of the treatment table 7 to place the patient Pa in the same arrangement as the planned arrangement.

[0036] When the positioning process is completed, the particle beam treatment of the patient Pa is performed by the overall control device 14. For example, the overall control device 14 transports the particle beam accelerated to an energy suitable for treatment by the accelerator 1 to the rotating gantry 3 via the beam transport device 2. The overall control device 14 deflects the particle beam in an appropriate direction by the rotating gantry 3 and irradiates the affected part of the patient Pa through the irradiation nozzle 4.

[0037] Hereinafter, the positioning device 20 will be described in more detail. As shown in FIG. 1, the positioning device 20 includes an image acquisition unit 210, a pseudo-fluoroscopic X-ray image creation unit 220, an ROI drawing unit 230, an image matching unit 240, an image display unit 250, and a control unit 260.

[0038] The image acquisition unit 210 acquires three-dimensional image information from the data server 10 via the communication device 9 and acquires a fluoroscopic X-ray image from the fluoroscopic X-ray imaging device 12.

[0039] The pseudo-fluoroscopic X-ray image creation unit 220 assumes the same imaging system as the fluoroscopic X-ray images of a plurality of imaging axes acquired by the image acquisition unit 210 in a virtual space, arranges the three-dimensional image of the patient Pa, and performs projection processing to create a pseudo-fluoroscopic X-ray image of a plane corresponding to the imaging axis. The plane corresponding to the imaging axis is, for example, a plane orthogonal to the imaging axis.

[0040] The ROI (Region of Interest) drawing unit 230 identifies the region of interest in the virtual fluoroscopic X-ray image used for patient positioning. For example, the virtual fluoroscopic X-ray image is displayed on the software screen, and the user is allowed to draw the region of interest on the virtual fluoroscopic X-ray image to identify the region. The region of interest is drawn to include, for example, the positioning target structure such as a bone.

[0041] The image matching unit 240 is a calculation processing unit that calculates the movement amount of the treatment table 7 such that the fluoroscopic X-ray image and the virtual fluoroscopic X-ray image match most closely. When the region of interest is specified by the ROI drawing unit 230, the movement amount of the treatment table 7 is calculated such that the fluoroscopic X-ray image and the virtual fluoroscopic X-ray image match most closely based only on the information within the region of interest.

[0042] The image display unit 250 is a display unit that displays various information and images. For example, the image display unit 250 displays the fluoroscopic X-ray image, the virtual fluoroscopic X-ray image, and the region of interest image indicating the region of interest, etc.

[0043] The control unit 260 controls the treatment table control device 13 to adjust the arrangement of the treatment table 7, thereby adjusting the arrangement of the patient Pa.

[0044] The positioning device 20 having the above functions can be realized by an information processing device such as a computer. The information processing device in which the positioning device 20 is realized includes, for example, a processor (arithmetic unit) 271, a memory (storage unit) 272, a communication interface unit 273, and a user interface unit 274. In the figure, the communication interface unit is displayed as "C-IF", and the user interface unit is displayed as "UI".

[0045] The processor 271 is an arithmetic circuit such as a CPU (Central Processing Unit) and an FPGA (Field-Programmable Gate Array), for example. The memory 272 includes a main storage device and an auxiliary storage device. The memory 272 is, for example, a magnetic storage medium such as an HDD (Hard Disk Drive), a semiconductor storage medium such as a RAM (Random Access Memory), a ROM (Read Only Memory), and an SSD (Solid State Drive). As the memory 272, a combination of an optical disk such as a DVD (Digital Versatile Disk) and an optical disk drive may be used. As the memory 272, a storage medium such as a magnetic tape medium may be used.

[0046] The memory 272 stores a computer program such as firmware in advance. When the positioning device 20 starts operating (for example, when power is turned on), the processor 271 reads the computer program from the memory 272 and executes it, whereby each functional unit 210 to 260 of the positioning device 20 is realized and a series of controls is executed. In addition to the computer program, data and the like necessary for each process of the positioning device 20 are stored in the memory 272.

[0047] The communication interface unit 273 is a device that communicates with the communication device 9, the fluoroscopic X-ray imaging device 12, and the treatment table control device 13. The user interface unit 274 is a device that exchanges information with a user (medical staff) who operates the radiation therapy system 100. The user interface unit 274 includes, for example, a monitor display, a keyboard, a touch panel, a printer, and the like.

[0048] Note that the positioning device 20 may be configured by a single computer, or may be configured by so-called cloud computing by cooperation of a plurality of computers.

[0049] The patient positioning device 20 can be connected to a storage medium MM. The storage medium MM can be configured, for example, as a memory device, a hard disk device, an optical disk device, a magneto-optical disk device, a magnetic tape device, etc., and stores a computer program and data non-temporarily. The storage medium MM can transfer and store the computer program and data to the memory 272 of the patient positioning device 20. It is also possible to transfer and store the computer program and data from the memory 272 to the storage medium MM. By storing a computer program that realizes the functions of the patient positioning device 20 in the storage medium MM, connecting the storage medium MM to another computer, and installing the computer program stored in the storage medium MM on the other computer, the other computer can be made to function as the patient positioning device 20.

[0050] Hereinafter, the patient positioning process by the patient positioning device 20 will be described in more detail with reference to FIGS. 2 to 5.

[0051] FIG. 2 is a flowchart showing an example of the process of determining the position of a patient. It is assumed that the patient Pa is placed at the setup position of the treatment table 7. The setup position is a position for placing the patient Pa in the same arrangement as the planned arrangement. For example, the position of the body surface of the patient Pa on the treatment table 7 is measured using an infrared laser installed in the treatment room, and based on that position, the patient Pa is placed at the setup position of the treatment table 7.

[0052] The control unit 260 acquires treatment plan information from the data server 10. Based on the planned arrangement information included in the treatment plan information, the control unit 260 controls the robot arm 8 via the treatment table control device 13, and moves the treatment table 7 with the patient Pa placed thereon so that the arrangement of the patient Pa becomes the planned arrangement indicated by the planned arrangement information (S10).

[0053] At this time, the positioning target structure of the patient Pa placed on the treatment table 7 is included in the X-ray irradiation area formed by the FPDs 5A and 5B and the X-ray tubes 6A and 6B.

[0054] The image acquisition unit 210 starts CBCT imaging (S11) by outputting a predetermined signal via the fluoroscopic X-ray imaging device 12. That is, the image acquisition unit 210 starts CBCT imaging (S11) by transmitting a signal for rotating the rotating gantry 3 and a signal for capturing a fluoroscopic X-ray image to the rotating gantry 3 and the FPDs 5A and 5B and the X-ray tubes 6A and 6B. Thereafter, the image acquisition unit 210 starts acquiring fluoroscopic X-ray image information from a plurality of directions of the patient Pa (S12).

[0055] The pseudo-fluoroscopic X-ray image creation unit 220 acquires three-dimensional image information from the data server 10, and creates a pseudo-fluoroscopic X-ray image by projecting the three-dimensional fluoroscopic image information onto a plane assuming the same imaging system as the imaging system of the fluoroscopic X-ray image information. Further, the image matching unit 240 uses the fluoroscopic X-ray image and the pseudo-fluoroscopic X-ray image to obtain the movement amount of the treatment table 7 at which the two images match most closely by an optimization calculation process in the same manner as the 3D-2D automatic positioning calculation (S13).

[0056] The optimization calculation used here uses an optimization calculation method for multivariate variables to change six variables in total, namely, three translational components (x, y, z) and three rotational components (pitch, roll, yaw), to search for a value that maximizes the similarity between the images. Generally, methods such as the BFGS method and the Powell method based on the quasi-Newton method are used.

[0057] As shown in FIG. 3, when a region of interest (VOI) is set on the three-dimensional image information, a region that appears on the pseudo-fluoroscopic X-ray image when the VOI is projected is set as a region of interest (ROI), and the optimization calculation is performed using only the images within the ROI.

[0058] When the optimization calculation ends, if CBCT imaging is in progress (S14: YES), steps S12 to S14 are repeated (S14). If CBCT imaging has ended (S14: NO), the most reliable result among the obtained optimization calculation results is determined as the movement amount parameter of the treatment table 7 (S15). Here, as the reliability determination information, a numerical value used as an index of similarity may be used, or a value showing the most identical values among the results of multiple executions may be adopted.

[0059] The image matching unit 240 calculates the similarity between the fluoroscopic X-ray image and the pseudo-fluoroscopic X-ray image. Examples of similarity indexes include the zero-mean normalized cross correlation (ZNCC) coefficient shown by formula (1) in step S13. Here, g(i, j) is the DR image, f(i, j) is the DRR image, μg is the average luminance value of the DR image, and μf is the average luminance value of the DRR image.

[0060] The image matching unit 240 sends the movement amount of the treatment table 7 obtained by the above optimization calculation to the control unit 260 as the movement amount of the treatment table 7 required to align the patient Pa with the treatment plan position. The control unit 260 may move the treatment table 7 by the amount of movement via the treatment table control device 13, or may perform 3D automatic positioning calculation with the result as the initial position.

[0061] During the optimization calculation in step S13, a similarity index calculated using only a partial region of interest among the fluoroscopic X-ray image and the pseudo-fluoroscopic X-ray image may be used. FIG. 3 shows an example of the region of interest setting method. In FIG. 3, virtual FPDs 200A and 200B and virtual X-ray tubes 201A and 201B that are the same as the layout of each device in the actual treatment room are assumed in the virtual space, and a state where the planning CT 205 is arranged at the treatment plan position is shown. When a three-dimensional volume region including the positioning target bone preset by the user in the planning CT 205 is set as the three-dimensional region of interest (Volume of Interest: VOI) 204, a two-dimensional region obtained by projecting the VOI onto the virtual FPDs 200A and 200B is set as the two-dimensional region of interest (Region of Interest: ROI) and used in the calculation.

[0062] What has been described above is just an example, and the following processing can also be performed to achieve higher-precision positioning. Hereinafter, a modified example will be described with reference to FIGS. 4 and 5. FIG. 4 shows a CBCT imaging system. FIG. 5 shows the timing of obtaining a fluoroscopic image and the timing of the automatic positioning calculation process.

[0063] The imaging signal of the image taken at the first imaging angle 300 in FIG. 4 corresponds to signal 300A on the timing diagram of FIG. 5. The imaging signal of the image taken at the second imaging angle 301 in FIG. 4 corresponds to signal 301A on the timing diagram of FIG. 5. The imaging signal of the image taken at the third imaging angle 302 corresponds to signal 302A on the timing diagram of FIG. 5. Each of the imaging angles 300, 301, and 302 is arranged clockwise in FIG. 4.

[0064] In FIG. 5, the times for performing 3D-2D automatic positioning calculation using the fluoroscopic X-ray images obtained at each of the imaging angles 300, 301, and 302 are shown as the first automatic positioning calculation 303, the second automatic positioning calculation 304, and the third automatic positioning calculation 305.

[0065] For the imaging angles of the fluoroscopic X-ray images for performing 3D-2D calculation, as shown by the white rectangular signals of "fluoroscopic X-ray image imaging signals during gantry rotation" in FIG. 5, images obtained by taking pictures at regular intervals may be used. Not limited to this, for the imaging angles of the fluoroscopic X-ray images for performing 3D-2D calculation, only the fluoroscopic X-ray images taken at preset angles, as shown by the black rectangular signals, may be used.

[0066] For example, on a fluoroscopic X-ray image, an image taken at an angle where the bone to be positioned overlaps with a high-density structure may be considered an inappropriate image for positioning and thus may not be used for 3D-2D automatic positioning calculation. Thereby, automatic positioning calculation can be performed without degrading the accuracy.

[0067] During CBCT imaging, the results of multiple 3D-2D automatic positioning calculations can be compared with the previously calculated results at any time, and the most appropriate result can be adopted as the correct answer. As shown in Fig. 5, after obtaining the results of the second automatic positioning calculation and then after obtaining the results of the third automatic positioning calculation, as shown as the consistency verification timings 306 and 307, the consistency with the past data can also be verified.

[0068] As a method for determining the most appropriate result as the correct answer, for example, a virtual fluoroscopic X-ray image of the imaging angle calculated in the past is created using the calculation results obtained this time, the similarity with the fluoroscopic X-ray image at the same angle is calculated, and if the similarity is higher than that of the past calculation results, the calculation results of this time may be adopted.

[0069] That is, the image matching unit 240 can execute the first positioning calculation for a plurality of angles and continuously compete their calculation results to select one optimal calculation result for patient positioning. Alternatively, the image matching unit 240 can execute the first positioning calculation for a plurality of angles and select one optimal calculation result for patient positioning from among their calculation results. Continuously competing the calculation results means that, like a so-called knockout battle, if the current calculation result is more suitable for patient positioning than the previous calculation result, it means adopting the current calculation result.

[0070] <Modification example> The modification example will be described with reference to Figs. 6 and 7. The timing for performing the 3D-2D automatic positioning calculation between the fluoroscopic X-ray image and the virtual fluoroscopic X-ray image may not be during CBCT imaging or may be during CBCT reconstruction. Fig. 6 shows a flowchart in the case of performing the 3D-2D automatic positioning calculation after CBCT imaging. Fig. 7 shows a timing chart.

[0071] In this modification example, similar to the first embodiment, first, the patient is placed on the treatment table and the treatment table is moved (S20), and CBCT imaging is started (S21). During CBCT imaging, fluoroscopic X-ray images at a plurality of angles are acquired while the gantry is rotating (S22, S23). The image matching unit 240 uses a plurality of pseudo-fluoroscopic X-ray images and fluoroscopic X-ray images acquired at arbitrary angles to obtain, by optimization calculation processing, the movement amount of the treatment table 7 at which the two images most closely match through 3D-2D automatic positioning calculation (S24). The image matching unit 240 determines, as the movement amount parameter of the treatment table 7, the result with the highest reliability among the results obtained by the above optimization calculation (S25).

[0072] In the timing chart of FIG. 7, the matching score is recalculated (313, 314) before the completion of the 3D-2D automatic positioning calculation.

[0073] As described above, according to this embodiment, since 3D-2D alignment as the "first positioning calculation" is performed before the completion of CBCT imaging, the 3D-2D alignment can be terminated early. As a result, the time until the start of the patient's treatment can be shortened, the treatment can be completed earlier to reduce the burden on the patient, and the convenience for the patient is improved. Furthermore, according to this embodiment, since the treatment time per patient can be shortened, the number of patients who can be treated by the radiation treatment system 100 can be increased.

[0074] Furthermore, according to this embodiment, the 3D-3D positioning calculation, which is the "second positioning calculation", can be performed with the result of the 3D-2D positioning calculation, which is the "first positioning calculation", as the initial position. Therefore, according to this embodiment, not only can the time required for patient positioning be shortened, but also the patient can be positioned with high precision.

[0075] In 3D-3D positioning (alignment), when there are metal structures around the VOI in the CBCT, metal artifacts will be mixed into the VOI. As a result, the information of the structure to be positioned will be reduced by the amount of the mixture, which may affect the positioning accuracy. However, in this embodiment, since 3D-2D alignment is performed first, image matching that is not affected by the metal artifacts in the CBCT image becomes possible. Furthermore, when performing 3D-3D alignment later, since the result of the previous 3D-2D alignment is utilized, the optimization calculation can be started in a state close to the correct position. Thereby, it is possible to prevent getting stuck in a local solution and perform high-precision positioning calculation in a short time.

[0076] Furthermore, in this embodiment, as shown by reference numeral 309 in FIG. 5, the result of 3D-2D alignment can also be used as the final result as it is. In this case, the 3D-3D positioning process can be omitted, and the time until the start of treatment can be further shortened. For example, in adaptive radiotherapy where treatment is appropriately adjusted to the patient's condition on the treatment day using the information in the patient's body on the treatment day, the process of creating a high-quality synthesized CT image on the treatment day by non-rigidly deforming (non-rigid registration) the CBCT image on the treatment day to the planned CT image can be advanced. In that case, as shown in FIG. 5, the conventional non-rigid registration timing 310 can be advanced and performed immediately after the CBCT reconstruction process (308) like the timing 311.

Example

[0077] Example 2 will be described with reference to FIGS. 8 to 10. Hereinafter, the description will focus on the differences from Example 1. FIG. 8 shows the CBCT imaging system. FIG. 9 shows the timing of acquiring the fluoroscopic image, the timing of creating the synthesized image, and the timing of the automatic positioning calculation process. FIG. 10 shows the process of positioning the patient.

[0078] In this embodiment, instead of using the fluoroscopic X-ray image taken at a specific angle and the pseudo-fluoroscopic X-ray image created in the same system as in Embodiment 1, 3D-2D registration, which is the first positioning calculation, is performed using tomosynthesis images. That is, in this embodiment, using the tomosynthesis composite image created from a plurality of fluoroscopic X-ray images taken within a specific angle range and the tomosynthesis composite image created from a plurality of pseudo-fluoroscopic X-ray images created in the same system, the optimization calculation of 3D-2D registration is performed to obtain the movement amount of the treatment table 7.

[0079] Thereby, in this embodiment, even when the bone to be positioned overlaps other structures on the fluoroscopic X-ray image and is difficult to visually recognize, positioning focusing on the target bone can be performed.

[0080] As shown in FIG. 10, in this embodiment, as in Embodiment 1, first, the patient is placed on the treatment table 7 and the treatment table 7 is moved (S30), and CBCT imaging is started (S31). During CBCT imaging (S35: YES), fluoroscopic X-ray images at a plurality of angles are acquired during gantry rotation (S33), and a synthetic fluoroscopic X-ray image is created using the plurality of fluoroscopic X-ray images acquired within an arbitrary angle range. In FIG. 8, the angle ranges are, for example, the first angle range 400, the second angle range 401, and the third angle range 402. The fluoroscopic X-ray image imaging signals taken in those angle ranges 400, 401, 402 are imaging signals 400A, 401A, 402A. Thereafter, the image matching unit 240 creates a synthetic DRR from a plurality of pseudo-fluoroscopic X-ray images (DRRs) created in the same system (S33).

[0081] Composite images of the plurality of images respectively acquired by the fluoroscopic X-ray image imaging signals 400A, 401A, 402A are created at the timings 403, 404, 405 shown in FIG. 9. As an example of the composite image creation method, for example, a composite image creation method using the shift addition method, an analytical reconstruction method such as the filtered back projection method, or a statistical reconstruction method such as the successive approximation reconstruction method can be used.

[0082] Thereafter, as shown by the 3D-2D automatic positioning calculation timings 406, 407, and 408 in FIG. 9, the image matching unit 240 uses the created synthetic fluoroscopic X-ray image and the synthetic pseudo-fluoroscopic X-ray image to obtain, through an optimization calculation process, the amount of movement of the treatment table 7 at which the two images most closely match by 3D-2D automatic positioning calculation (S34). During CBCT imaging, the processes of S32 to S34 are repeated (S35: YES). When the CBCT imaging is completed (S35: NO), the image matching unit 240 determines, as the movement amount parameter of the treatment table 7, the result with the highest reliability among the results obtained by the above optimization calculation (S36).

[0083] This embodiment configured as described above also exhibits the same operational effects as those of the first embodiment. In this embodiment, since a synthetic fluoroscopic X-ray image is obtained by a tomosynthesis technique that integrates images taken multiple times from a plurality of directions within a predetermined angle for each of a plurality of angles, the patient can be positioned more accurately.

[0084] In this embodiment, since 3D-2D automatic positioning calculation can be performed with high precision using the tomosynthesis technique, parameters for accurately positioning the patient can be calculated without performing 3D-3D automatic positioning calculation.

[0085] Note that the present invention is not limited to the above-described embodiments and includes various modifications. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

[0086] It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations for a part of the configuration of each embodiment.

[0087] The present disclosure includes at least the following expressions 1-12.

[0088] (Expression 1) A positioning device for positioning a patient on a treatment table at a predetermined position, A positioning device comprising: a CBCT imaging device that rotates around the patient on the treatment table to capture at least one fluoroscopic X-ray image and creates a CBCT reconstructed image from the captured fluoroscopic X-ray image; an image matching unit that performs a first positioning calculation for the patient using the fluoroscopic X-ray image of the patient acquired by the CBCT imaging device and a pseudo-fluoroscopic X-ray image created by performing a projection process on a CT image acquired before imaging by the CT imaging device, wherein the image matching unit starts the first positioning calculation before the creation of the CBCT reconstructed image is completed.

[0089] (Expression 2) The positioning device according to Expression 1, wherein the image matching unit performs the first positioning calculation a plurality of times using the fluoroscopic X-ray images of the patient acquired from a plurality of angles by the CBCT imaging device and the X-ray image of the patient acquired before imaging by the CBCT imaging device, and selects the most probable calculation result from among the results of the first positioning calculations performed a plurality of times.

[0090] (Expression 3) The positioning device according to any one of Expressions 1 and 2, wherein the image matching unit performs the first positioning calculation using the fluoroscopic X-ray image of the patient and the pseudo-fluoroscopic X-ray image for a region of interest set in the pseudo-fluoroscopic X-ray image created by performing a projection process on a CT image acquired before imaging by the CBCT imaging device.

[0091] (Expression 4) The positioning device according to any one of Expressions 1 to 3, wherein the image matching unit performs a second positioning calculation for the patient using the CBCT reconstructed image and a planned CT image acquired when creating a treatment plan.

[0092] (Expression 5) The positioning device according to any one of Expressions 1 to 4, wherein the result of the first positioning calculation is used as an initial value for the second positioning calculation.

[0093] (Expression 6) The positioning device according to any one of Expressions 1 to 5, wherein the plurality of angles are set in advance as angles suitable for imaging.

[0094] (Expression 7) The positioning device according to any one of Expressions 1-6, wherein the image matching unit executes the first positioning calculation for the plurality of angles and continuously competes the calculation results thereof to select one calculation result that is optimal for the positioning of the patient.

[0095] (Expression 8) The positioning device according to any one of Expressions 1-6, wherein the image matching unit executes the first positioning calculation for the plurality of angles and selects one calculation result that is optimal for the positioning of the patient from among the calculation results.

[0096] (Expression 9) The positioning device according to any one of Expressions 1-8, wherein the CBCT imaging device obtains an image by a tomosynthesis technique that integrates images taken a plurality of times from a plurality of directions for each of the plurality of angles.

[0097] (Expression 10) The positioning device according to any one of Expressions 1-9, wherein the CBCT imaging device uses a radiation generator and a radiation detector provided on a rotating gantry of a radiation therapy device to take a fluoroscopic X-ray image and create the CBCT reconstructed image from the taken fluoroscopic X-ray image.

[0098] (Expression 11) A radiation therapy device comprising: the positioning device according to any one of Expressions 1-10; an irradiation device provided on a rotating gantry that rotates around the treatment table and irradiates radiation to a patient on the treatment table; and a control device that controls the irradiation device and a robot that adjusts the positions of the irradiation device and the treatment table.

[0099] (Expression 12) A method for positioning a patient on a treatment table, comprising the steps of rotating around the patient on the treatment table by a CBCT imaging device to capture at least one fluoroscopic X-ray image, and creating a CBCT reconstructed image from the captured fluoroscopic X-ray image; and performing a first positioning calculation for the patient using the acquired fluoroscopic X-ray image of the patient and the X-ray image of the patient acquired before imaging by the CBCT imaging device. In the step of performing the first positioning calculation, the first positioning calculation is started before the creation of the CBCT reconstructed image is completed. Positioning method.

Explanation of symbols

[0100] 1: Accelerator, 2: Beam transport device, 3: Rotating gantry, 4: Irradiation nozzle, 5A, 5B: FPD, 6A, 6B: X-ray tube, 7: Treatment table, 8: Robot arm, 9: Communication device, 10: Data server, 11: Treatment planning device, 12: Fluoroscopic X-ray imaging device, 13: Treatment table control device, 14: Overall control device, 20: Patient positioning device, 100: Radiation therapy system, 210: Image acquisition unit, 220: Virtual fluoroscopic X-ray image creation unit, 230: Region of interest drawing unit, 240: Image matching unit, 250: Image display unit, 260: Control unit

Claims

1. A positioning device for positioning a patient on a treatment table at a predetermined position, comprising: a CBCT imaging device that rotates around the patient on the treatment table to capture at least one fluoroscopic X-ray image and creates a CBCT reconstructed image from the captured fluoroscopic X-ray image; an image matching unit that performs a first positioning calculation for the patient using the fluoroscopic X-ray image of the patient acquired by the CBCT imaging device and a virtual fluoroscopic X-ray image created by projecting a CT image of the patient acquired before imaging by the CBCT imaging device; The image matching unit starts the first positioning calculation before the creation of the CBCT reconstructed image is completed. Positioning device.

2. The image matching unit performs the first positioning calculation multiple times using the fluoroscopic X-ray images of the patient acquired at multiple angles by the CBCT imaging device and the virtual fluoroscopic X-ray image created by projecting the CT image of the patient acquired before imaging by the CBCT imaging device, and selects the most probable calculation result from among the results of the first positioning calculations performed multiple times. The positioning device according to claim 1.

3. The image matching unit performs the first positioning calculation using the fluoroscopic X-ray image of the patient and the virtual fluoroscopic X-ray image for a region of interest set in the virtual fluoroscopic X-ray image created by projecting the CT image of the patient acquired before imaging by the CBCT imaging device. The positioning device according to claim 2.

4. The image matching unit performs a second positioning calculation for the patient using the CBCT reconstructed image and a planned CT image acquired when creating a treatment plan. The positioning device according to claim 3.

5. The result of the first positioning calculation is used as an initial value for the second positioning calculation. The positioning device according to claim 4.

6. The multiple angles are preset as angles suitable for imaging. The positioning device according to claim 5.

7. The image matching unit performs the first positioning calculation for the multiple angles and continuously competes their calculation results to select one calculation result that is optimal for positioning the patient. The positioning device according to claim 6.

8. The image matching unit performs the first positioning calculation for the multiple angles and selects one calculation result that is optimal for positioning the patient from among their calculation results. The positioning device according to claim 6.

9. The CBCT imaging device obtains an image by a tomosynthesis technique that integrates fluoroscopic X-ray images taken multiple times from multiple directions for each of the plurality of angles. The positioning device according to claim 8.

10. The CBCT imaging device uses a radiation generator and a radiation detector provided on a rotating gantry of a radiation therapy device to take the fluoroscopic X-ray image, and creates the CBCT reconstructed image from the taken fluoroscopic X-ray image. The positioning device according to claim 9.

11. The positioning device according to any one of claims 1 to 10, An irradiation device provided on a rotating gantry that rotates around the treatment table and irradiates radiation to a patient on the treatment table, A radiation therapy system comprising a control device that controls the irradiation device and a robot that adjusts the positions of the irradiation device and the treatment table.

12. A method for positioning a patient on a treatment table, A step of rotating around the patient on the treatment table by a CBCT imaging device to take at least one fluoroscopic X-ray image, and creating a CBCT reconstructed image from the taken fluoroscopic X-ray image; Performing a first positioning calculation for the patient using the obtained fluoroscopic X-ray image of the patient and a pseudo-fluoroscopic X-ray image created by performing a projection process on a CT image of the patient obtained before imaging by the CBCT imaging device. In the step of performing the first positioning calculation, the first positioning calculation is started before the creation of the CBCT reconstructed image is completed. Positioning method.

Images