WO2019077936A1

WO2019077936A1 - Radiation therapy apparatus

Info

Publication number: WO2019077936A1
Application number: PCT/JP2018/034976
Authority: WO
Inventors: 祐介藤井
Original assignee: 株式会社日立製作所
Priority date: 2017-10-19
Filing date: 2018-09-21
Publication date: 2019-04-25
Also published as: JP2019072393A

Abstract

A particle beam therapy apparatus 1 is provided with: a calculation unit 316B which calculates the positional relation between the position of a marker 61 in a therapeutic planning CT image captured when preparing a therapeutic plan and the position of the marker 61 in a CT image captured immediately prior to irradiation with particle beams, and the positional relation between the position of a target 47 in the therapeutic planning CT image and the position of the target 47 in the CT image captured immediately prior to irradiation; and a display device 315 which displays the respective positional relations, as calculated by the calculation device 316B, of the target 47 and the marker 61 in the therapeutic planning CT image and the CT image captured immediately prior to irradiation. This configuration provides a radiation therapy apparatus that enables, in a therapy employing a marker, more efficient determination, as compared to conventional methods, of the structure inside the body of a patient immediately prior to treatment, and that is capable of reducing the time required to place a patient in a planned position.

Description

Radiation therapy equipment

The present invention relates to a radiotherapy apparatus for irradiating a diseased part with radiation such as particle beam such as proton beam or carbon beam or X-ray.

As an example of a radiotherapy system capable of acquiring an image capable of grasping a positional relationship between a target and a radiation passing area in a therapeutic radiation irradiation state and a dangerous organ, which is required in patient positioning of radiotherapy, The X-ray imaging apparatus performs X-ray imaging by irradiating X-rays to the subject from a plurality of directions while rotating, and recognizes the three-dimensional position of the target in the subject from the X-ray image acquired by the X-ray imaging apparatus Select an image from the target recognition device to be detected and the X-ray image acquired by the X-ray imaging device, and the position of the target recognized by the target recognition device satisfies the treatment radiation irradiation condition for moving body tracking treatment A radiation treatment system is described, comprising: a CT imaging device for generating a cone-beam CT image.

JP, 2015-29793, A

There is known a treatment method of irradiating the affected part of a patient such as cancer with radiation such as proton beam. In the case of a proton beam, for example, a radiation treatment apparatus used for this treatment method is provided with a beam generator comprising an accelerator and a beam transport system, an irradiation field forming device, and a positioning device comprising an X-ray fluoroscope and a patient bed.

The particle beam accelerated by the accelerator passes through the beam transport system to the radiation field forming device, is monitored by the radiation field forming device, and is shaped to fit the patient's affected area.

A particle beam such as a proton beam or a carbon beam has a characteristic of releasing most of the energy immediately before stopping, and the resulting shape of the dose distribution is called a Bragg peak. The particle beam treatment apparatus utilizes this characteristic and selects the energy of the particle beam to stop the particle beam at the irradiation target and release most of the energy to the affected area.

In order to irradiate a proton beam toward the affected area of a patient using a radiation treatment apparatus and form a dose distribution conforming to the affected area, it is important to place the patient at a planned position.

As a method of confirming the position and shape of the target immediately before the treatment and the surroundings of the target in order to accurately set the position of the patient at the planned position, three-dimensional X-ray by cone beam CT apparatus as described in Patent Document 1 mentioned above. There is a method of acquiring a line CT image (hereinafter referred to as a cone beam CT image).

This is because on the three-dimensional X-ray CT image (hereinafter referred to as a planned CT image) acquired for planning, an irradiation reference point called an isocenter is designated, and the cone beam CT image and the planned CT image coincide. By moving the position of the patient in such a way, the patient can be positioned with high accuracy.

In radiation therapy, when irradiating a moving organ by respiration etc., the target is focused on irradiating the proton beam, so the marker placed in the vicinity of the target such as the affected part only irradiates the proton beam when coming to the planned position There is a way.

In taking a cone-beam CT image, the fluoroscope rotates around the patient at a speed of about 1 rpm. Since reconstruction of a CT image requires an X-ray image from a direction of 180 degrees or more, an imaging time of 30 seconds or more is required.

In particular, in imaging of moving organs by respiration etc., since the target moves during imaging, in Patent Document 1, an X-ray image is acquired while measuring the position of the target or marker, and the target or marker is at the planned position. A method is disclosed for creating CT images using only x-ray images.

The cone beam CT image acquired as described above is used to determine the installation position of the patient by displaying it in comparison with the planned CT image.

If the marker placed near the target illuminates only when the planned position is reached, cone beam CT images can be used to confirm both the position of the marker and the position of the target.

Here, the comparison and confirmation of the position of the marker and target in the planned CT image and the position of the marker and target in the cone beam CT are conventionally performed by superimposing and displaying the cone beam CT image and the planned CT image. Had visually confirmed the difference.

The present invention is a treatment that uses markers, in which the structure in the patient's body immediately before treatment can be confirmed more efficiently than in the past, and radiation that can shorten the time required to place the patient in a planned position Provide a therapeutic device.

The present invention includes a plurality of means for solving the above problems, and an example thereof is a radiotherapy apparatus for irradiating a target with radiation, and a treatment plan CT image captured at the time of preparation of a treatment plan. The positional relationship between the position of the marker in the and the position of the marker in the CT image immediately before the irradiation of radiation, the position of the target in the treatment plan CT image, and the position of the target in the CT image immediately before the irradiation And a display device for displaying a positional relationship between a target and a marker in the treatment plan CT image calculated by the calculation device and the CT image immediately before the irradiation. .

According to the present invention, the amount of operation of the operator in the confirmation of the positions of the marker and the target can be reduced as compared with the conventional case, so the structure in the patient's body immediately before the treatment can be efficiently confirmed as compared with the conventional. The time required to place the patient in the planned position can be reduced.

It is a figure showing an outline of the whole composition of particle beam therapy equipment of one example of the present invention. It is a figure showing an outline of an irradiation field formation device in a particle beam therapy system of this example. It is a figure which shows the spot arrangement | positioning of the maximum energy by particle beam irradiation by the particle beam therapy apparatus of a present Example. It is a figure which shows the spot arrangement | positioning of the 2nd energy by particle beam irradiation by the particle beam therapy apparatus of a present Example. It is a figure showing an outline of a positioning system in a particle beam therapy system of this example. It is a flowchart explaining the flow which draws up the treatment plan by the particle beam treatment apparatus of a present Example. It is a flowchart explaining the flow which irradiates the particle beam by the particle beam therapy system of a present Example. It is a flowchart explaining the flow of positioning in the particle beam therapy system of a present Example. It is a figure which shows an example of the display screen of the vector in the particle beam therapy apparatus of a present Example. It is a figure which shows an example of the display screen which piles up and displays the plan CT and the target in a cone beam image in the particle beam therapy apparatus of a present Example. It is a figure which shows an example of the display screen which highlights the difference with the target in planned CT and a cone beam image in the particle beam therapy apparatus of a present Example. It is a figure which shows an example of the display screen which displays the water equivalent thickness in the particle beam therapy apparatus of a present Example.

A particle beam treatment apparatus according to a preferred embodiment of the present invention will be described with reference to FIGS.

In this embodiment, a particle beam therapy system using particle beams such as proton beam and carbon beam as one type of radiation therapy system is described as an example, but the present invention is also applied to an X-ray therapy system using X-rays. The same effect can be obtained.

First, the entire configuration of the particle beam therapy system will be described with reference to FIG. FIG. 1 is a view schematically showing the entire configuration of a particle beam therapy system.

In FIG. 1, a particle beam therapy system 1 for irradiating a particle beam to a target 47 includes a charged particle beam generator 11, a high energy beam transport system 20, a rotator 21, a central controller 312, a memory 313, and an irradiation control system. 314, a display device 315, a positioning control system 316, an irradiation field forming device (irradiation device) 40, a bed 50, a fluoroscopic device 51, and a treatment planning device 501.

The charged particle beam generator 11 comprises an ion source 12, a pre-stage accelerator 13 and a particle beam accelerator 14. In the present embodiment, a synchrotron-type particle beam accelerator is assumed as the particle beam accelerator 14, but various other particle beam accelerators such as a cyclotron can be used as the particle beam accelerator 14.

As shown in FIG. 1, the synchrotron type particle beam accelerating device 14 has a deflection electromagnet 15, an accelerating device 16, a high frequency applying device 17 for extraction, an extraction deflector 18 and a quadrupole electromagnet (shown in FIG. Omission).

A process until a particle beam is generated from a charged particle beam generator 11 using a synchrotron-type particle beam accelerator 14 and emitted toward a patient will be described using FIG.

The particles supplied from the ion source 12 are accelerated by the pre-stage accelerator 13 and sent to the beam accelerator synchrotron. The particle beam circulating in the synchrotron is accelerated by applying a high frequency from a high frequency accelerating cavity (not shown) provided in the accelerating device 16 in synchronization with a cycle of passing through the accelerating device 16. In this way, the particle beam is accelerated until it reaches a predetermined energy.

After the particle beam is accelerated to a predetermined energy (for example, 70 to 250 MeV), when the emission start signal is output from the central control unit 312 via the irradiation control system 314, the high frequency application installed in the high frequency application unit 17 The high frequency power from the high frequency power source 19 is applied to the particle beam circulating in the synchrotron from the electrode, and the particle beam is emitted from the synchrotron.

The high energy beam transport system 20 communicates the synchrotron with the irradiation field forming apparatus 40, and the extracted particle beam is installed in the rotating apparatus 21 via the high energy beam transport system 20. It is led up to 40.

The rotation device 21 is for irradiating a beam from any direction of the patient 30, and is mounted on a tubular structure called a gantry, and the bed 50 on which the patient 30 is placed by rotating the entire device. Can rotate in any direction around the.

The irradiation field forming device 40 is a device for shaping the shape of the particle beam to be finally irradiated to the patient 30, and the structure differs depending on the irradiation method. The scatterer method and the scanning method are representative irradiation methods, and the present invention is effective for both irradiation methods. The present embodiment will be described using a scanning method.

In the scanning method, a thin beam transported from the high energy beam transport system 20 is directly irradiated to a target, and this can be three-dimensionally scanned to finally form a high dose area only on the target.

The fluoroscope 51 and the bed 50 are connected to the display 315 and the central control 312 via a positioning control system 316.

The X-ray fluoroscope 51 is composed of two X-ray generators and two X-ray detectors, and can capture X-ray fluoroscopic images seen through the inside of the patient 30 from two orthogonal directions. The X-ray fluoroscopic image is an X-ray imaging of the marker 61 and the target 47 (see FIG. 2) from a plurality of directions in order to detect the position of the marker 61 (see FIG. 2) in the patient 30. It is used for positioning before line irradiation and measurement of the target position during particle beam irradiation.

The positioning control system 316 is a system that executes processing for determining the position of the bed 50 at the time of particle beam irradiation from the X-ray fluoroscopic image captured by the X-ray fluoroscope 51, and includes a recognition device 316A and a calculation device 316B. Is equipped.

The recognition device 316A recognizes the three-dimensional position of the target 47 in the patient 30 from the X-ray image acquired by the fluoroscope 51.

The calculation device 316 B is imaged by the three-dimensional imaging device 700 at the time of creation of the treatment plan, and the position of the marker 61 in the treatment plan CT image stored in the data server 600 and the marker in the CT image just before irradiation of particle beam. The positional relationship with the position of 61 is calculated. In addition, the calculation device 316B calculates a positional relationship between the position of the target 47 in the treatment plan CT image and the position of the target 47 in the CT image immediately before the irradiation. At this time, the positional relationship of the center of gravity of the target 47 is calculated with reference to the position of the marker 61.

The calculating device 316B calculates the amount of movement of the bed 50 on which the patient 30 having the target 47 is placed, based on the calculated positional relationship.

In order to calculate the positional relationship of the marker 61 and the positional relationship of the target 47, the calculation device 316B performs image reconstruction from the X-ray image acquired by the X-ray fluoroscope 51, and uses a cone beam CT image as a CT image just before irradiation. Generate At this time, the calculating device 316B is configured to keep the position of the target 47 recognized by the recognizing device 316A out of the predetermined range from the X-ray image acquired by the X-ray fluoroscope 51 (irradiation permission region, therapeutic particle beam for moving object tracking treatment Image reconstruction is performed from the X-ray image captured when the irradiation conditions are satisfied.

Furthermore, the calculation device 316B matches the positions of the marker 61 in the treatment plan CT image and the CT image immediately before irradiation, and the irradiation direction of the target 47 and the normal organ in each of the treatment plan CT image and the CT image immediately before irradiation Determine the water equivalent thickness and its difference up to the front and / or back side boundary.

The display device 315 displays the positional relationship between the target 47 and the marker 61 in the treatment plan CT image calculated by the calculation device 316 B of the positioning control system 316 and the CT image just before irradiation. In this display device 315, when the water equivalent thickness to the front side and / or the back side boundary of the irradiation direction of the target 47 or the normal organ and the difference thereof are calculated by the calculation device 316B, the water equivalent thickness and the difference It is possible to display

Details of the processes of the recognition device 316A and the calculation device 316B described above and details of the display screen displayed on the display device 315 will be described later.

The respective roles and functions of the devices in the irradiation field forming apparatus 40 will be briefly described using FIG. FIG. 2 is a view showing the arrangement of an irradiation field forming apparatus 40 corresponding to the scanning method.

The irradiation field forming apparatus 40 includes two

scanning electromagnets

41 and 42, a dose monitor 43, and a beam position monitor 44 from the upstream side. The dose monitor 43 measures the amount of particle beam that has passed through the monitor. The beam position monitor 44 can measure the position where the particle beam has passed. The information from the dose monitor 43 and the beam position monitor 44 enables the irradiation control system 314 to manage that the planned amount of the beam is irradiated at the planned position.

The traveling direction of the thin particle beam transported from the charged particle beam generator 11 through the high energy beam transport system 20 is deflected by the

scanning electromagnets

41 and 42. The

scanning electromagnets

41 and 42 are provided so that magnetic lines of force are generated in a direction perpendicular to the beam traveling direction. For example, in FIG. 2, the scanning electromagnet 41 deflects the beam in the scanning direction 45 The beam deflects the beam in a direction perpendicular to the scanning direction 45. By using these two electromagnets, the beam can be moved to any position in a plane perpendicular to the beam traveling direction, and the beam irradiation to the target 47 becomes possible.

Here, the irradiation control system 314 executes control to irradiate the particle beam to the target 47 when the position of the target 47 in the patient 30 is present in the irradiation permission area, so-called moving object tracking control. The irradiation control system 314 can change the irradiation permission area from the positional relationship between the marker 61 and the target 47.

The irradiation control system 314 also controls the amount of current supplied to the

scanning electromagnets

41 and 42 via the scanning electromagnet magnetic field strength control unit 49. The

scanning electromagnets

41 and 42 are supplied with current from the scanning electromagnet power supply 48, and the magnetic field corresponding to the amount of current is excited, whereby the amount of deflection of the beam can be freely set. The relationship between the amount of deflection of the particle beam and the amount of current is previously stored as a table in the memory 313 in the central control unit 312, and is referred to.

There are two beam scanning methods of the scanning method. One is a discrete method in which movement and stop of the irradiation position is repeated, and the other is a method in which the irradiation position is changed continuously.

In the discrete method, first, a specified amount of beam is irradiated while the irradiation position is kept at a certain point. This point is called a spot. When the beam is irradiated to the spot by the specified amount, the beam irradiation is temporarily stopped, and then the current amount of the scanning electromagnet is changed so that the irradiation can be performed to the next position. The amount of current is changed, and after moving to the next irradiation position, the beam is irradiated again.

The method of moving the irradiation position continuously changes the irradiation position while irradiating the beam. That is, while continuously changing the amount of excitation of the electromagnet, the beam is moved while passing through the entire irradiation field. In this method, the change of the irradiation amount for each irradiation position is realized by modulating the scanning speed and / or the amount of current of the beam.

A conceptual view of the discrete scheme of illumination is shown in FIG. FIG. 3 shows an example of irradiating a cubic target 47. The particle beam is stopped at a certain position in the traveling direction, and the energy is adjusted so that the stopping depth of the beam is within or near the target 47 in order to apply most of the energy to the stopping position. In FIG. 3, a beam of energy stopping near the surface 82 illuminated with the same energy is selected. Discrete beam irradiation positions (spots) are arranged at spot intervals 83 on this surface. Irradiating a specified amount with one spot moves to the next spot. The spot 84 is illuminated with a beam that passes through the trajectory 85 of the beam that illuminates the spot 84. Once the same energy spots located in the target 47 have been sequentially irradiated, the depth at which the beam is stopped is changed in order to irradiate another depth position in the target 47.

In order to change the stopping depth of the beam, the energy of the beam irradiated to the patient 30 is changed. One way to change the energy is to change the setting of the particle beam accelerator, ie, the synchrotron in this example. The particles are accelerated to the energy set in the synchrotron, but changing this setting allows the energy incident on the patient 30 to be changed. In this case, since the energy extracted from the synchrotron changes, the energy when passing through the high energy beam transport system 20 also changes, and the setting change of the high energy beam transport system 20 also becomes necessary.

In the example of FIG. 3, energy is mainly applied to a region corresponding to the surface 82 irradiated with the same energy. By changing the energy, for example, the situation as shown in FIG. 4 is obtained. In FIG. 4, a beam of energy lower than the energy used in FIG. 3 is irradiated. Therefore, the beam stops at a shallower position. This surface is represented by a surface 91 irradiated with the same energy. A spot 92, which is one of the spots corresponding to this beam of energy, is illuminated with the beam passing through the trajectory 93 of the beam illuminating the spot 92.

As described above, when the information of the energy for each spot, the irradiation position, and the irradiation amount is input, the particle beam therapy system 1 irradiates the particle beam toward the target 47 and forms a dose distribution. The treatment planning device 501 determines information such as the energy for each spot, the irradiation position, and the irradiation amount.

As shown in FIG. 5, two X-ray detectors 53 are disposed at the tip of the irradiation apparatus. In addition, two X-ray generators 52 are disposed in the rotating device. The X-rays from the X-ray generator 52 can be viewed in two orthogonal directions in the patient's body. The X-rays in the two directions do not have to be orthogonal.

By using the X-ray fluoroscope 51 composed of the two sets of X-ray generator 52 and X-ray detector 53, a cone beam CT image can be taken before particle beam irradiation, and near the target 47 during particle beam irradiation It is possible to measure the position of the marker 61 placed in the

Next, the flow of treatment planning by the operator and the flow of the operation of the treatment planning device 501 will be described with reference to FIG. FIG. 6 shows the flow of calculation contents of the treatment planning device 501.

Prior to treatment, planned CT images for treatment planning are taken. Three-dimensional X-ray CT images are most commonly used as planned CT images for treatment planning. A three-dimensional X-ray CT image is generated by reconstructing three-dimensional data from fluoroscopic images acquired from a plurality of directions of a patient by a three-dimensional imaging apparatus 700 such as a CT apparatus. The captured planned CT image is stored in the data server 600. The treatment planning device 501 uses this planned CT image.

In FIG. 6, when the treatment planning apparatus 501 first recognizes that the planning of the treatment plan has been started (step S101), the technician (or doctor) who is the operator of the treatment planning apparatus 501 is an input device such as a mouse. The target planned CT data is read from the data server 600 using The treatment planning device 501 copies the CT image from the data server 600 onto the memory by the operation of the input device (step S102).

When the reading of the planned CT image from the data server 600 to the memory is completed, and the planned CT image is displayed on the display device 315, the operator confirms the planned CT image displayed on the display device 315 and inputs the input device. Using the slice of the planned CT image, that is, the region to be designated as the target 47 for each two-dimensional CT image is input (step S103). The target 47 to be input here is a region determined to be irradiated with a sufficient amount of radiation because a tumor cell is present or may be present. This is called target 47. If there is another area requiring evaluation and control, such as when there is a normal tissue in the vicinity of the target 47 for which the irradiation dose should be minimized, the operator designates the regions such as those normal tissues as well.

In the area drawing in step S103, the treatment planning apparatus 501 may automatically specify the area based on the area drawing data drawn in the past. In addition, the operator can correct and designate the drawing automatically drawn by the treatment planning apparatus 501 based on the area drawing data. Alternatively, it may be performed on images of different modalities represented by MRI.

Next, the operator sets necessary irradiation parameters to create a treatment plan including information on the position and energy of the beam to be irradiated to the registered target 47 (step S104). The operator first sets the irradiation direction. In the particle beam therapy system to which the present embodiment is applied, beam irradiation can be performed from any direction of the patient by selecting the angle between the rotating device 21 and the bed 50. A plurality of irradiation directions can be set for one target 47. When the beam is irradiated from a certain direction, it is assumed that the center of gravity of the target 47 is positioned so as to coincide with the isocenter (the rotation center position of the rotation device 21) at the time of irradiation.

Other parameters for irradiation that the operator should determine include the dose value (prescription dose) to be irradiated and the number of times of irradiation in the area registered in step S103. The prescribed dose includes the dose to be irradiated to the target 47 and the maximum dose allowed for normal tissue.

After the above parameters are determined, the treatment planning device 501 automatically calculates according to the instruction of the operator (step S105). In the following, details of contents related to dose calculation performed by the treatment planning device 501 will be described.

First, the treatment planning device 501 determines the beam irradiation position. In the case of the above-described discrete scanning method dealt with in this embodiment, discrete spot positions are calculated. The irradiation position is set to cover the target 47. When a plurality of directions are designated as the irradiation direction (the angle between the rotating device 21 and the bed 50), the same operation is performed in each direction.

When all irradiation positions are determined, the treatment planning device 501 starts optimization calculation of the irradiation dose. The dose to each spot is determined to approach the target prescribed dose set in step S104. In this calculation, a method using an objective function that numerically represents a deviation from a target dose with the irradiation amount for each spot as a parameter is widely adopted. Since the objective function is defined so that the dose distribution has a smaller value as the target dose is met, the optimal irradiation can be obtained by iteratively calculating the dose that minimizes the target function. Calculate the quantity.

When the iterative calculation is completed, the required dose for each spot is finally determined. The irradiation order of a plurality of spots is also determined at this stage. Usually, a zigzag route is set as shown by the scan route 86 in FIG. 3, but it is also possible to rearrange the irradiation order according to a standard in consideration of the scan time and the scan direction.

Next, the treatment planning device 501 calculates a dose distribution using the spot position and the spot irradiation amount finally obtained by the arithmetic processing unit. The calculated dose distribution result is displayed on the display unit 315 (step S106).

The operator confirms the dose distribution displayed on the display device 315. If the dose distribution does not meet the target dose distribution, the operator returns to step S104 and changes settings such as adding a dose constraint to a new region. Then, steps S104 to S107 are repeated until a target dose distribution is obtained (step S107).

When the target dose distribution is obtained in step S107, the operation is completed (step S108).

Next, the entire flow of particle beam irradiation will be described using the flow chart of FIG. FIG. 7 shows a flow chart for explaining the flow of irradiating particle beams by the particle beam therapy system.

In FIG. 7, first, the patient 30 enters the treatment room (step S201).

Next, the patient 30 lies on the bed 50 and performs the positioning that is the feature of the present invention (step S202).

In the present step S202, the central control device 312 reads the information determined by the treatment planning device 501. Information necessary for positioning is sent from central controller 312 to positioning control system 316. The detailed flow of positioning will be described later with reference to FIG.

Next, the central control unit 312 sets the angle of the rotating device that emits the particle beam (step S203). In addition, information such as the energy for each spot and the dose required for irradiation is transmitted from the central control unit 312 to the irradiation control system 314.

Next, the central control unit 312 controls the charged particle beam generator 11, the high energy beam transport system 20 and the irradiation field forming unit 40 together with the irradiation control system 314 to irradiate particle beams toward the patient (step S204).

During the irradiation of the particle beam in the present step S204, the position of the marker 61 placed in the vicinity of the target 47 is continuously measured. For measurement of the marker 61, X-ray fluoroscopic images in two directions are used. The measurement position of the marker 61 is a point where two straight lines connecting the X-ray generating position of the two X-ray fluoroscopes 51 and the position of the marker 61 captured on the X-ray fluoroscopic image intersect or the closest point I assume.

In this step, the particle beam is directed to the target 47 only when the measurement position of the marker 61 is within the irradiation permission area. The irradiation permission area is set as, for example, an area of ± 2 mm with respect to the planned position of the marker 61. The planned position of the marker 61 is the position of the marker 61 in the planned CT image.

When the irradiation of the particle beam is completed, in step S105, the gantry is rotated to irradiate the particle beam.

Next, the central control unit 312 determines whether or not the irradiation from all planned irradiation directions has been completed (step S205), and when it is determined that the irradiation has been completed, the process proceeds to step S206, and the patient 30 The patient gets off the bed 50 and exits the treatment room (step S206). On the other hand, if it is determined that the process has not been completed, the process returns to step S203 to complete the irradiation from all the irradiation directions.

Next, the details of the positioning process in step S202 of FIG. 7 will be described using the flowchart of FIG. FIG. 8 is a flow diagram for explaining the flow of positioning in the particle beam therapy system of this embodiment.

In FIG. 8, the patient 30 lies on the bed 50, and the same posture as when capturing the reference CT image is reproduced (step S301). The support tool is used to reproduce the positions of both arms and the angle at which the knee is bent. The bed 50 is moved to an approximate position such that the position of the target 47 coincides with the isocenter.

After moving the bed 50 to the approximate position, for example, while the patient 30 exhales, fluoroscopic images in two directions are acquired using the two fluoroscopic devices 51 (step S302). The acquired X-ray fluoroscopic image and the projection image obtained by calculation from the planned CT image are compared, and the bed 50 is moved so that the position of the patient is set at the planned position.

After movement of the bed 50 in step S302, X-ray imaging is continuously performed by the two X-ray fluoroscopes 51 to confirm that the marker 61 in the vicinity of the target 47 is in the vicinity of the planned position (step S303). For example, since the particle beam is irradiated when the marker 61 is in an area of ± 2 mm around the planned position, the area is called an irradiation permitted area. Here, it is confirmed that the time for the marker 61 to pass through the irradiation permission area is sufficiently long.

Next, a cone beam CT image is captured using two X-ray fluoroscopes 51 (step S304). In order to acquire cone-beam CT images, the gantry is rotated while acquiring x-ray fluoroscopic images in two directions. The gantry needs to be rotated by at least 90 degrees, and the larger the rotation angle, the better the cone-beam CT image can be acquired.

A fluoroscopic image records what was acquired from two directions as a pair. The recognition device 316A recognizes the position where the marker 61 is shown in each of the two images by template matching or the like. A position at which the two straight lines connecting the position at which the X-ray generator 52 generates X-rays and the position on the image where the marker 61 is imaged intersects or approaches the position is taken as the position of the marker 61. Thus, the position of the marker 61 can be recorded for each X-ray fluoroscopic image recorded in pairs. The recognition device 316A extracts only the X-ray fluoroscopic image in which the position of the marker 61 is in the irradiation permission area, and the calculation device 316B reconstructs a cone beam CT image from the extracted X-ray fluoroscopic image.

Next, the information of the target 47 or organ designated on the planned CT is transcribed on the acquired cone beam CT image by the calculation device 316B (step S305). In this transcription, an operator can designate a target 47 and an organ on a cone beam CT image on the screen, but a technique called non-rigid registration can also be used. In the method using non-rigid registration, a strain vector from planned CT to cone beam CT is calculated, and the target 47 on planned CT and the organ are distorted according to the strain vector. And organs are designated.

Next, the calculation device 316B calculates the coordinates of the marker 61 and the barycentric coordinates of the target 47 on the planned CT and the cone beam CT respectively, and calculates the vector to the target barycentric coordinates starting from the coordinates of the marker 61 (Step S306).

Next, the components of x, y, z of the vector calculated by the calculation device 316 B are divided into the planned CT and the cone beam CT and displayed on the operation screen (step S 307).

In step S307, the vector calculated in step S306 is displayed on the display screen 315A of the display device 315. An example of this display screen 315A is shown in FIG. FIG. 9 is a diagram showing an example of a display screen of vectors.

In the display screen 315A shown in FIG. 9, the calculated barycentric coordinates of the target 47 are displayed in the area 315A1 described as the current value, and X, Y, and Z are displayed. In addition, in the area 315A2 below that, a planned value of barycentric coordinates of the target 47 at the time of planning on the planned CT is displayed. The differences for each axis are displayed in the third row area 315A3.

The operator determines that the positioning is completed after confirming that the values displayed in the regions 315A1, 315A2, and 315A3 of the display screen 315A as shown in FIG. 9 are within the allowable range and that there is no problem. The central controller 312 is instructed to start the irradiation of the line. In response to the input of this instruction, as shown in step S204 of FIG. 7, the central control unit 312 starts the irradiation of the particle beam.

On the other hand, when it is determined that the user wants to more closely match the planned position, the bed 50 is moved again in step S302, and the positioning process is performed again.

Note that what is calculated in step S306 does not have to be the barycentric coordinates, and may be, for example, the midpoint of each of the three axes of the target 47 or the like.

Also, the information of the target 47 used in step S306 does not have to be a point.

Further, in step S307, after matching the position of the marker 61 on the cone beam CT image or the planned CT image, the entire shape of the target 47 can be overlapped and drawn to highlight the difference. Hereinafter, the display screen 315B will be described with reference to FIGS. 10 and 11. FIG. 10 shows an example of overlapping and displaying the target 47 in the planned CT and cone beam image. FIG. 11 shows an example of a screen when highlighting a difference.

To that end, in step S306, the calculation device 316B matches the three-dimensional position of the marker 61 in the treatment plan CT image and the CT image immediately before irradiation, and the target 47 corresponding to each of the treatment plan CT image and the CT immediately before irradiation Calculate the three-dimensional coordinate position of the shape of.

As shown in FIG. 10, as a result of arithmetic processing by the calculation device 316B, the display device 315 displays the marker 61 and the target contour 62 immediately before or during treatment on the cone beam CT image. Also, the target contour 60 on the planned CT image is displayed with the relative position between the position of the marker 61 and the target contour being transferred so that the position of the marker 61 matches the position of the marker 61 of the cone beam CT image Be done.

Furthermore, on the display screen 315B, the non-overlapping difference 64 between the target contour 62 in the cone beam CT and the target contour 60 in the plan CT is highlighted as a filled portion in FIG.

In addition, the shapes of normal organs other than the target 47 are also displayed repeatedly, and the difference is displayed, so that it can be confirmed that the normal organ is at the same position as that at the time of planning.

Furthermore, a plurality of threshold values are provided in advance for the difference between the values of the planned CT image and the cone beam CT image, and when the calculated difference exceeds the threshold, as shown in FIG. It can be displayed that the difference is large. For example, on the display screen 315C, a portion where the difference is below the threshold is displayed as the difference 64A, and a portion above the threshold is displayed as the difference 64B, and a warning display 65 is displayed. It is preferable to use different characters and colors for each threshold.

In step S307, when matched with the position of the marker 61, a cone beam CT image and a plan for the water equivalent thickness up to the front or back boundary of the target 47 or normal organ seen from the irradiation direction It is also possible to display the difference of CT images. In particle beam, the amount of change in water equivalent thickness is particularly important.

The example displayed about the difference of water equivalent thickness in FIG. 12 is shown. FIG. 12 shows an example of irradiating a particle beam toward the target 47 from the front side of the drawing. FIG. 12 is a diagram showing an example of a display screen for displaying the water equivalent thickness.

To that end, in step S306, the calculation device 316B converts the difference between the target contour in cone beam CT and the target contour in planned CT into water equivalent in the direction of particle beam irradiation. Then, in step S307, of the converted water equivalents, if the difference is large, it is painted in a dark color and displayed as area 315D1, and if the difference is small, it is painted in a light color and area 315D2 It displays on display screen 315D like this. Also, if there is no difference, do not paint. This is calculated for both the near side (shallow side) and the far side (deep side) with respect to the irradiation direction, and the respective are switched and displayed.

Further, if it is calculated in step S306 that the position of the target 47 has largely changed, the calculation device 316B calculates, for example, the movement amount of the bed 50 such that the target 47 matches, and the bed 50 is calculated based on that value. You can also move the When the bed 50 is moved, if the position of the irradiation permission area and the position of the marker 61 are separated, the position of the irradiation permission area can also be moved according to the movement amount of the bed 50.

In step S304, the recognition device 316A divides the locus of the marker 61 into a plurality of areas using the locus of the marker 61 obtained when acquiring a cone beam CT image, and the calculation apparatus 316B divides the locus of the marker 61. A cone beam CT image can be reconstructed for each region.

In addition, the calculation device 316 B calculates the relationship between the marker 61 and the target 47 for each divided area by calculating the position of the target 47 based on the marker 61 in step S 307 using the image divided for each of the plurality of areas. Is possible. According to this, it is possible to display the position of the divided area where the relationship between the marker 61 and the target 47 is closest to that at the time of planning based on the calculated result. Also, the movement amount of the bed 50 can be calculated so that the center of the divided area overlaps the center of the irradiation permission area, and the bed can be moved.

Next, the effects of this embodiment will be described.

In the particle beam therapy system 1 of the present embodiment described above, the positional relationship between the position of the marker 61 in the treatment plan CT image captured at the time of preparation of the treatment plan and the position of the marker 61 in the CT image just before irradiation of particle beam. And a calculation device 316B for calculating the positional relationship between the position of the target 47 in the treatment plan CT image and the position of the target 47 in the CT image immediately before irradiation, the treatment plan CT image calculated by the calculation device 316B and the irradiation And a display device 315 for displaying the positional relationship between the target 47 and the marker 61 in the immediately preceding CT image.

As a result, meaningful information can be provided in a form that allows the operator to easily grasp whether the position of the marker 61 and the position of the target 47 coincide with the planned time. For this reason, the time required to make the position of the target 47 equal to that at the time of planning can be reduced compared to the conventional case. In particular, the preparation time for irradiating the moving target 47 can be reduced. Accordingly, when irradiating the target 47 with the particle beam, it is possible to irradiate the target 47 with the particle beam in a short time with higher accuracy than in the prior art.

In addition, since the calculation device 316B calculates the positional relationship of the center of gravity of the target 47 based on the marker 61, it can be more accurately determined whether or not the position of the target 47 at the time of planning and immediately before irradiation match. It is possible to more accurately match the position of the target 47 with the planned time.

Furthermore, in the display of the positional relationship, the positions of the marker 61 in the treatment plan CT image and the CT image immediately before the irradiation are matched, and the shapes of the target 47 corresponding to each of the treatment plan CT image and the CT image just before the irradiation are displayed Therefore, if there is a region of the target 47 which does not match the planned time, the deviation can be easily confirmed, and the time required for making the position of the target 47 equal to the planned time can be further shortened. Can.

Further, in the display of the positional relationship, by highlighting the difference in the shape of the target 47, it is possible to more clearly grasp the positional relationship shift between the target 47 at the time of treatment planning and immediately before the treatment.

Furthermore, in the display of the positional relationship, the difference in the shape of the target 47 is compared with a predetermined threshold, and when it is determined that the difference exceeds the threshold, the difference during the threshold is highlighted to display the treatment plan. Deviations in the positional relationship of the target 47 immediately before and after the treatment can be more clearly grasped.

Further, in highlighting, displaying the characters on the screen and changing the color also makes it possible to more clearly grasp the positional relationship between the target 47 at the time of treatment planning and immediately before treatment.

Furthermore, the calculation device 316B matches the positions of the marker 61 in the treatment plan CT image and the CT image immediately before irradiation, and the near side of the irradiation direction of the target 47 and the normal organ in each of the treatment plan CT image and the CT image immediately before irradiation The water equivalent thickness up to the boundary on the back side and its difference are obtained, and the display device 315 irradiates the particle beam as radiation by displaying the difference between the water equivalent thickness of the treatment plan CT image and the CT image just before irradiation. It is possible to easily grasp the deviation immediately before the irradiation with respect to the treatment plan of the water equivalent thickness, which is an important index in the case. That is, whether or not the position of the marker 61 and the position of the target 47 coincide with the planned time can also be determined according to the deviation of the water equivalent thickness. For example, even if the position of the target 47 slightly deviates from the planned time, if it is determined that the water equivalent thickness is the same, it can be determined that the position of the target 47 is equivalent to the planned time. Therefore, it is possible to provide more information for determining whether or not the position of the target 47 matches the planned time, and the preparation time for irradiating the target 47 can be further shortened.

In addition, the calculating device 316B calculates the movement amount of the bed 50 on which the patient 30 having the target 47 is placed based on the positional relationship between the marker 61 and the target 47, thereby making the position of the target 47 equal to the planned time. And the preparation time for irradiating the target 47 can be further shortened.

Furthermore, the X-ray fluoroscope 51 for imaging the marker 61 and the target 47 from a plurality of directions by X-rays is further provided, and the calculation device 316 B performs image reconstruction from the X-ray image acquired by the X-ray fluoroscope 51 By generating a cone beam CT image as an immediately preceding CT image, it can be determined whether the position of the marker 61 and the position of the target 47 match the planned time using a device used for so-called moving object tracking. It is possible to shorten the preparation time for irradiating the target 47 without adding a new device.

The computer further includes a recognition device 316A that recognizes the three-dimensional position of the target 47 in the patient 30 from the X-ray image acquired by the X-ray fluoroscope 51, and the calculation device 316B detects the X-ray image acquired by the X-ray fluoroscope 51 The cone that reflects the internal structure at the timing of particle beam irradiation by performing image reconstruction from the image in which the position of the target 47 recognized by the recognition device 316A satisfies the treatment particle beam irradiation condition of the motion tracking treatment from among them. Beam CT images can be acquired. As a result, three-dimensional CT imaging (visualization) of a state closer to the patient 30 in the state of irradiation with the treatment particle beam can be performed (target 47 in the treatment irradiation state, etc. required for patient positioning of radiation treatment) An image capable of grasping the positional relationship of As a result, precise patient positioning according to the treatment plan is possible.

Furthermore, a treatment particle beam for the target 47 is further provided by further comprising an irradiation control system 314 that controls the target 47 to irradiate the particle beam when the position of the target 47 in the patient 30 fills the irradiation permission region of the motion tracking treatment. The irradiation accuracy of can be further improved.

Further, the irradiation control system 314 can set the irradiation permission area according to the position of the target 47 immediately before irradiation by changing the irradiation permission area based on the positional relationship between the marker 61 and the target 47. The irradiation accuracy of the therapeutic particle beam to the target 47 can be further improved.

<Others>
The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. The embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described.

For example, in the above-described embodiment, an example in which the cone beam CT image is captured after moving the bed using the X-ray fluoroscopic image in step S302 is first shown, but the cone is obtained without aligning the fluoroscopic image. Beam CT images can also be acquired.

In this case, from the locus of the marker 61 obtained at the time of cone beam CT image acquisition, the position to be the irradiation permission area is selected, and the selected position is used as the reference marker 61 position during planning, the marker 61 and the target Compare the positional relationship of 47. As a result of comparison, if the position of the target 47 matches, the moving amount of the bed 50 is calculated so that the selected position matches the irradiation permission area, and the bed 50 can be moved based on the calculated result. .

In addition, although a method using cone beam CT images has been described as means for acquiring an X-ray CT image immediately before treatment, an X-ray CT apparatus is separately placed in a treatment room, and data captured by the apparatus is a cone beam CT image It can be used instead.

Furthermore, the size of the irradiation permission area does not have to match the size of the area of the marker 61 for reconstructing a cone beam CT image. It is effective to appropriately adjust the area of the marker 61 for reconstructing a cone beam CT image from the magnitude of movement of the marker 61 and the image quality of the required cone beam CT image.

1 ... particle beam treatment apparatus 312 ... central control unit 314 ... irradiation control system (treatment particle beam control apparatus)
315:

Display device

315A, 315B, 315C, 315D: Display screen 316: Positioning control system 316A: Recognition device 316B: Calculation device 40: Radiation field forming device 46: Patient 47: Target 51: X-ray fluoroscopy device 52: X-ray generation 53: X-ray detector 61: marker 62:

target contour

64, 64A, 64B: difference 65: warning display 501: treatment planning device 700: three-dimensional imaging device

Claims

A radiation treatment apparatus for irradiating a target with radiation,
The positional relationship between the position of the marker in the treatment plan CT image imaged at the time of creation of the treatment plan and the position of the marker in the CT image immediately before the radiation irradiation, and the position of the target in the treatment plan CT image and the above A calculation device for calculating the positional relationship with the position of the target in the CT image immediately before irradiation;
A radiotherapy apparatus comprising: a display device for displaying the positional relationship between a target and a marker in the treatment plan CT image calculated by the calculation device and the CT image immediately before the irradiation.
In the radiation treatment apparatus according to claim 1,
The radiotherapy apparatus, wherein the calculation device calculates the positional relationship of the center of gravity of the target with reference to the marker.
In the radiation treatment apparatus according to claim 1,
In the display of the positional relationship, the positions of the markers in the treatment plan CT image and the CT image immediately before the irradiation are matched, and the shapes of the targets corresponding to the treatment plan CT image and the CT image just before the irradiation are overlapped. A radiation treatment apparatus characterized by displaying.
In the radiation treatment apparatus according to claim 3,
In the display of the positional relationship, a difference in the shape of the target is highlighted.
In the radiation treatment apparatus according to claim 3,
In the display of the positional relationship, the difference in the shape of the target is compared with a predetermined threshold, and when it is determined that the difference exceeds the threshold, the difference exceeding the threshold is highlighted. Radiation therapy equipment.
In the radiation treatment apparatus according to claim 4 or 5,
In the highlighted display, characters are displayed on the screen, and the color is changed and displayed.
In the radiation treatment apparatus according to claim 1,
The calculation device matches the positions of the markers in the treatment plan CT image and the CT image immediately before the irradiation, and the near side of the irradiation direction of the target and the normal organ in each of the treatment plan CT image and the CT image immediately before the irradiation Find the water equivalent thickness and its difference up to the boundary on the back side and / or
The display apparatus displays a difference between the water equivalent thickness of the treatment plan CT image and the CT image immediately before the irradiation.
In the radiation treatment apparatus according to claim 1,
The radiotherapy apparatus, wherein the calculation device calculates a movement amount of a bed on which a patient having the target is placed, based on a positional relationship between the marker and the target.
In the radiation treatment apparatus according to claim 1,
It further comprises a fluoroscope for imaging the marker and the target from a plurality of directions by X-rays,
The radiotherapy apparatus, wherein the calculation device reconstructs an image from an X-ray image acquired by the X-ray fluoroscope, and generates a cone beam CT image as the CT image immediately before the irradiation.
In the radiation treatment apparatus according to claim 9,
The apparatus further comprises a recognition device that recognizes a three-dimensional position of the target in a patient from an X-ray image acquired by the fluoroscope.
The calculation device performs image reconstruction from an image in which the position of the target recognized by the recognition device satisfies the treatment radiation irradiation condition of the motion tracking treatment from among the X-ray images acquired by the X-ray fluoroscope. Radiation therapy equipment.
In the radiation treatment apparatus according to claim 9,
A radiation treatment apparatus characterized by further comprising a treatment radiation control device for performing control to irradiate the target with radiation when the position of the target in the patient satisfies the treatment radiation irradiation condition of the movement tracking treatment.
In the radiation treatment apparatus according to claim 11,
A radiation treatment apparatus, wherein the treatment radiation control device changes the treatment radiation irradiation condition based on a positional relationship between the marker and the target.