JP7692282B2 - Treatment planning device, particle beam therapy system, treatment plan generation method, and computer program - Google Patents

Description

The present invention relates to a treatment planning device, a particle beam therapy system, a treatment plan generation method, and a computer program.

The present invention relates to a treatment planning device, and in particular to a radiation therapy system that treats an affected area by irradiating the affected area with radiation, primarily charged particle beams such as proton beams and carbon beams, and a treatment planning device used therein.

Radiation therapy, which aims to necrotize tumor cells by irradiating them with various types of radiation, has become widespread in recent years. In addition to X-rays, which are the most widely used radiation, treatments using particle beams such as proton beams and carbon beams are also becoming more widespread.

Radiation therapy delivers a high dose only to the tumor area, so a detailed treatment plan must be prepared in advance. For example, in particle beam therapy, the energy, dose, and irradiation position are determined in advance using a treatment planning device to obtain the desired dose distribution to the affected area and surrounding area.

The most common method for checking the state of the patient's body during advance planning is to use X-ray CT images (hereafter referred to as planning CT images). CT images are often used to specify the location of the affected area and to calculate the internal dose distribution based on that.

In radiation therapy, irradiation is repeated once a day for several days. Traditionally, a treatment plan was basically made at the beginning, and the same amount of radiation was irradiated at the same irradiation location every day, but in recent years, it has become common to change the irradiation location and amount of radiation in response to changes in the condition inside the body. Replanning the treatment plan and irradiating it is called adaptive irradiation.

A type of adaptive irradiation in which the affected area is imaged, replanned, and irradiated while the patient is lying on a bed is called online adaptive irradiation. In online adaptive irradiation, after replanning, the original treatment plan that was planned in advance is compared with the new treatment plan resulting from the replanning, and radiation is irradiated based on the more preferable treatment plan, as disclosed in Patent Document 1.

US Patent Application Publication No. 2020/0121951

In the method of Patent Document 1, the original treatment plan or the new treatment plan is selected based on a dose-based index, such as the maximum and minimum doses to the target and normal organs around the target. On the other hand, in online adaptive treatment, replanning may be performed based on images from Cone Beam CT (hereinafter, CBCT). Although CBCT has a simple configuration, its image quality is inferior to that of the planning CT image taken for the advance treatment plan. For this reason, there is a method in which the planning CT image is deformed to match the CBCT image taken on the day of treatment, and replanning is performed based on that image. This method involves errors not present in the advance treatment plan, such as deformation errors in the planning CT image. When comparing the original treatment plan with the new treatment plan, there is a problem in that a decision must be made taking into account the effects of these errors.

The present invention has been made in consideration of the above problems, and aims to provide a treatment planning device, particle beam therapy system, treatment plan generation method, and computer program that are capable of comparing an original treatment plan with a new treatment plan while taking into account the effects of errors.

In order to solve the above problems, a treatment planning device according to one aspect of the present invention is applied to a particle beam therapy system that irradiates a target with a particle beam, and is characterized in that it calculates a first dose distribution of the particle beam based on a planning X-ray image of the target, calculates a second dose distribution of the particle beam based on a preliminary X-ray image of the target that is captured after the planning X-ray image, calculates first and second dose indices related to the first and second dose distributions, and displays the variance of the first and second dose indices.

The present invention makes it possible to compare the original treatment plan with the new treatment plan while taking into account the effects of error.

1 is an explanatory diagram showing the overall configuration of a particle beam therapy system having a treatment planning device according to an embodiment; 1 is an explanatory diagram showing a configuration of an irradiation field forming device used in a particle beam therapy system according to an embodiment; FIG. 2 is a diagram showing the concept of an irradiation position in a particle beam scanning irradiation method. FIG. 1 is a diagram showing a concept of energy change in particle beam scanning irradiation method. FIG. 1 is an explanatory diagram showing the configuration of a treatment planning system according to an embodiment. 4 is a flowchart showing a procedure until a treatment plan is made in the particle beam therapy system according to the embodiment. 1 is a flowchart showing an irradiation procedure including replanning in a particle beam therapy system according to an embodiment. 1 is a flowchart showing a re-planning procedure in a treatment planning system according to an embodiment. FIG. 13 is a diagram showing a display screen that displays indices calculated by a treatment planning system according to an embodiment. 1 is a diagram showing a flow of particle beam irradiation in a particle beam therapy system according to an embodiment.

The following describes an embodiment of the present invention with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some parts have been omitted or simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

In addition, in the figures explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanations are omitted.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

When there are multiple components with the same or similar functions, they may be described using the same reference numerals with different subscripts. However, when there is no need to distinguish between these multiple components, the subscripts may be omitted.

A particle beam therapy system to which a radiation therapy planning device according to an embodiment (hereinafter simply referred to as a "treatment planning device") is applied will be described with reference to Figures 1 to 10. In this embodiment, a treatment planning device that creates a treatment plan for proton beam therapy using a scanning irradiation method, which is a type of radiation therapy, will be described, but the present invention can also be applied to a treatment planning device that creates a treatment plan for proton beam therapy using a scatterer irradiation method, or for heavy particle beam therapy using carbon beams or the like. The present invention can also be applied to a treatment planning device for X-ray therapy.

Figure 1 is a schematic diagram showing a particle beam therapy system to which a treatment planning device according to an embodiment of the present invention is applied.

Figure 1 shows the overall configuration of a particle beam therapy system. In Figure 1, the particle beam therapy system includes a charged particle beam generator 301, a high-energy beam transport system 310, a rotating irradiation device 311, a control device 314 equipped with a treatment planning program 312 and memory 313, a display device 315, an irradiation field forming device (irradiation device) 400, a bed 407, a treatment planning device 501, and a data server 502.

The charged particle beam generator 301 is composed of an ion source 302, a pre-accelerator 303, and a particle beam accelerator 304. In this embodiment, a synchrotron type particle beam accelerator is assumed as the particle beam accelerator 304, but any other particle beam accelerator such as a cyclotron may be used as the particle beam accelerator 304. As shown in FIG. 1, the synchrotron type particle beam accelerator 304 includes a deflection electromagnet 305, an accelerator 306, a high frequency application device 307 for extraction, an extraction deflector 308, and a quadrupole electromagnet (not shown) on its orbit.

Using Figure 1, we will explain the process by which a particle beam is generated from a charged particle beam generator 301 that uses a synchrotron-type particle beam accelerator 304 and is emitted toward a patient.

Particles supplied from the ion source 302 are accelerated by the pre-accelerator 303 and sent to the synchrotron, which is a beam acceleration device. The synchrotron is equipped with an accelerator 306, which applies radio frequency to a radio frequency acceleration cavity (not shown) provided in the accelerator 306 in synchronization with the period at which the particle beam circulating inside the synchrotron passes through the accelerator 306, accelerating the particle beam. In this way, the particle beam is accelerated until it reaches a predetermined energy.

After the particle beam has been accelerated to a predetermined energy (e.g., 70 to 250 MeV), the control device 314 outputs an extraction start signal, and high-frequency power from the high-frequency power supply 309 is applied to the particle beam circulating inside the synchrotron by the high-frequency application electrode installed in the high-frequency application device 307, and the particle beam is extracted from the synchrotron.

The high-energy beam transport system 310 connects the synchrotron and the irradiation nozzle 400. The particle beam extracted from the synchrotron is guided via the high-energy beam transport system 310 to the irradiation nozzle 400 installed in the rotating irradiation device 311. The rotating irradiation device 311 is designed to irradiate the patient 406 with the beam from any direction, and the entire device can rotate in any direction around the bed 407 on which the patient 406 is placed.

The irradiation field forming device 400 rotates together with the rotating irradiation device. The tip of the irradiation field forming device is equipped with X-ray detectors 420, 421, and on the opposite side of the patient 406, X-ray generators 422, 423 are provided. By acquiring X-ray fluoroscopic images of the patient 406 while the X-ray generators 422, 423 and the X-ray detectors 420, 421 rotate together with the rotating irradiation device, a cone beam CT image can be reconstructed from the fluoroscopic images.

The irradiation field forming device 400 is a device that shapes the particle beam that is ultimately irradiated onto the patient 406. The scanning method that is the subject of this embodiment irradiates the target directly with a thin beam transported from the high-energy beam transport system 310, and scans this in three dimensions, ultimately forming a high-dose area only on the target.

Figure 2 shows the configuration of an irradiation field forming device 400 that supports the scanning method.

The role and function of each piece of equipment in the irradiation nozzle 400 will be briefly described using Figure 2. The irradiation nozzle 400 is equipped with two scanning magnets 401 and 402, a dose monitor 403, and a beam position monitor 404 from the upstream side. The dose monitor 403 measures the amount of particle beam that passes through the monitor. Meanwhile, the beam position monitor 404 can measure the position through which the particle beam passes. Information from these monitors 403 and 404 allows the control device 314 to manage whether the planned amount of beam is being irradiated at the planned position.

The thin particle beam transported from the charged particle beam generator 301 via the high energy beam transport system 310 has its direction of travel deflected by the scanning electromagnets 401 and 402. These scanning electromagnets are arranged to generate magnetic field lines perpendicular to the beam direction of travel; for example, in FIG. 2, the scanning electromagnet 401 deflects the beam in the scanning direction 405, and the scanning electromagnet 402 deflects it in a direction perpendicular to this. By using these two electromagnets, the beam can be moved to any position within a plane perpendicular to the beam direction of travel, making it possible to irradiate the beam onto the target 406a.

The control device 314 controls the amount of current flowing through the scanning electromagnets 401 and 402 via the scanning electromagnet magnetic field intensity control device 411. A current is supplied to the scanning electromagnets 401 and 402 from the scanning electromagnet power supply 410, and a magnetic field corresponding to the amount of current is excited, allowing the amount of beam deflection to be freely set. The relationship between the amount of deflection of the particle beam and the amount of current is stored in advance as a table in the memory 313 in the control device 314, and this is referenced.

There are two types of beam scanning methods in the scanning method. One is discrete scanning irradiation, in which the particle beam is irradiated only while the irradiation position is stopped, and the irradiation of the particle beam is stopped while the irradiation position is changed. The other is continuous scanning irradiation, in which the irradiation position is changed continuously without stopping the irradiation of the particle beam. In this embodiment, discrete scanning irradiation is described, but the present invention can also be applied to continuous scanning irradiation.

A conceptual diagram of irradiation using discrete scanning irradiation is shown in Figure 3.

Figure 3 shows an example of irradiating a cubic target 801. The particle beam stops at a certain position in the direction of travel and imparts most of its energy at that stopping position, so the energy is adjusted so that the depth at which the beam stops is within the target area. In Figure 3, a beam of energy is selected that stops near a surface 802 that is irradiated with the same energy. Irradiation positions (spots) are arranged on this surface with a spot spacing of 803.

A spot represents a combination of irradiation position and irradiation amount. When a specified amount is irradiated at one spot, irradiation stops and the device moves to the next spot. Once the movement is complete, irradiation of the next spot begins, and irradiation stops when the specified amount is reached. This process is then repeated.

Spot 804 is irradiated with a beam that follows a beam trajectory 805 that irradiates spot 804. After sequentially irradiating spots of the same energy located within the target, the depth at which the beam stops is changed to irradiate other depth positions within the target. Here, it is assumed that a constant dose is irradiated onto a simple cubic target, but in reality, a complex dose distribution is formed on the target, and the dose for each spot varies greatly.

In the example of Figure 3, energy is mainly applied to the area corresponding to surface 802 that is irradiated with the same energy. By changing the energy, the situation becomes as shown in Figure 4, for example.

In FIG. 4, a beam of lower energy is applied than that used in FIG. 3. Therefore, the beam stops at a shallower position. This surface is represented as surface 901 irradiated with the same energy. One of the spots corresponding to the beam of this energy, spot 902, is irradiated with a beam that follows the trajectory 903 of the beam irradiating spot 902.

Another method for changing the beam energy is to insert a range modulator (not shown) into the irradiation field forming device 400. The thickness of the range modulator is selected according to the energy to be changed. The thickness can be selected by using multiple range modulators with multiple thicknesses, or by using opposing wedge-shaped range modulators.

In this embodiment, a collection of irradiation positions irradiated with the same energy is called a layer.

To change the depth at which the beam stops, the energy of the beam irradiated to the patient 406 is changed. One method for changing the energy is to change the settings of the particle beam accelerator, or in this embodiment, the synchrotron. Particles are accelerated in the synchrotron until they reach a set energy level, and by changing this setting, the energy incident on the patient 406 can be changed. In this case, the energy extracted from the synchrotron changes, and so the energy when passing through the high-energy beam transport system 310 also changes, making it necessary to change the settings of the high-energy beam transport system 310. In the case of a synchrotron, it takes about one second to change the energy.

Figure 5 shows the configuration of the treatment planning device 501. The treatment planning device 501 is connected to the data server 502 and the control device 314 via a network.

5, the treatment planning device 501 includes an input device 602 for inputting parameters for irradiating a particle beam, a display device 603 for displaying the treatment plan, a memory 604, a calculation processing device 605 (calculation device) for performing dose distribution calculations, and a communication device 606. The calculation processing device 605 is connected to the input device 602, the display device 603, the memory (storage device) 604, and the communication device 606.

The treatment planning device 501 is composed of a device capable of various information processing, for example an information processing device such as a computer. The information processing device has a calculation device 605, a storage device 604, and a communication interface which is a communication device 607, and further has an input device 602 such as a mouse and a keyboard, and a display device 603 such as a display.

The arithmetic device 605 is, for example, a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), or an FPGA (Field-Programmable Gate Array). The storage device 604 includes, for example, a magnetic storage medium such as a HDD (Hard Disk Drive), a RAM (Random Access Memory), a ROM (Read Only Memory), or a semiconductor storage medium such as an SSD (Solid State Drive). In addition, a combination of an optical disk such as a DVD (Digital Versatile Disk) and an optical disk drive is also used as the storage device 604. Other well-known storage media such as magnetic tape media are also used as the storage device 604.

The storage device 604 stores programs such as firmware. When the treatment planning device 501 starts operating (e.g., when the power is turned on), the programs such as firmware are read from the storage device 604 and executed to control the entire treatment planning device 501. In addition to the programs, the storage device 604 also stores data necessary for each process of the treatment planning device 501.

Alternatively, some of the components constituting the treatment planning device 501 may be connected to each other via a LAN (Local Area Network), or may be connected to each other via a WAN (Wide Area Network) such as the Internet.

From here, the operation flow using the treatment planning device 501 will be explained with reference to Figure 6.

Prior to treatment, images are taken for treatment planning. CT images are most commonly used for treatment planning. CT images reconstruct three-dimensional data from fluoroscopic images taken of the patient from multiple angles.

CT images taken by a CT device (not shown) are stored in the data server 502. In this embodiment, this CT image is called the original planning CT image (planning X-ray image). The CT image holds electron density information, and in dose distribution calculations, this electron density information is converted into a water equivalent thickness to calculate the penetration depth of the particle beam. The relationship between the pixel values of the CT image and the water equivalent thickness is provided in advance as a table.

When the creation of a treatment plan begins (step 101), the technician (or doctor) who is the operator of this treatment planning device 501 reads the target CT data from the data server 502 using an input device 602 such as a mouse. That is, by operating the input device 602, the treatment planning device 501 copies the CT images from the data server 502 to the memory 604 via a network connected to the communication device 606 (step 102).

When the loading of the 3D CT image from the data server 502 to the memory 604 is completed and the 3D CT image is displayed on the display device 603, the operator, while checking the 3D CT image displayed on the display device 603, inputs the area to be specified as the target for each slice of the 3D CT image, i.e., each 2D CT image, using an instrument such as a mouse equivalent to the input device 602. The target area to be input here is an area that is determined to be irradiated with a sufficient amount of particle beam because tumor cells exist or may exist. This is called the target area. If there are other areas that require evaluation and control, such as important organs that should have the lowest possible radiation dose near the target area, the operator similarly specifies the areas of those important organs, etc. Alternatively, the process may be performed on images of a different modality, such as MRI (step 103).

When the input of areas for all 3D CT images is completed, the operator instructs registration of the input areas. By registering, the areas input by the operator are saved in memory 604 as 3D position information (step 104). The position information of the areas can also be saved in data server 502, and when loading a 3D CT image, previously entered information can also be loaded together with the 3D CT image.

The operator then creates a treatment plan (original treatment plan) that includes information on the position and energy of the beam to be irradiated to the registered target region (step 104). First, the operator sets the irradiation direction. The particle beam therapy system to which this embodiment is applied can irradiate the patient with the beam from any direction by selecting the angle of the rotating irradiation device 311 and the bed 407. It is possible to set multiple irradiation directions for one target. Normally, the target region 706 is positioned so that the vicinity of the center coincides with the isocenter (the rotational center position of the rotating irradiation device 311).

Other parameters for irradiation that the operator must determine include the dose value (prescribed dose) to be applied to the area registered in step 104. The prescribed dose includes the dose to be applied to the target and the maximum dose to be avoided for critical organs.

After the above parameters have been determined, the treatment planning system 501 automatically performs calculations according to the operator's instructions (step 106). The details of the dose calculations performed by the treatment planning system 501 are explained below.

Here, we will use robust optimization to create an example of a treatment plan for an irradiation method called intensity-modulated proton therapy. In normal irradiation, a uniform dose distribution is formed at the target for each irradiation direction. Therefore, when optimizing the dose, the dose is also optimized for each irradiation direction. On the other hand, in intensity-modulated proton therapy, the dose from all irradiation directions is optimized simultaneously so that a sufficient dose is irradiated to the target. Intensity-modulated proton therapy allows for greater freedom than normal cases where the dose is optimized for each irradiation direction, making it possible to reduce the dose in areas that should not be irradiated while still ensuring a sufficient dose to the target.

When creating a treatment plan, errors in the patient's position and the depth to which the particle beam reaches are taken into consideration. In other words, a treatment plan is created so that a sufficient dose is delivered to the target even if these errors occur.

There are two main methods for taking errors into account. One is to set an area larger than the target by the amount of the expected error, and optimize the irradiation dose so that a sufficient dose is irradiated to that area. This method is suitable for normal irradiation methods that form a uniform dose distribution for each irradiation direction. The other is a method called robust optimization, which actually calculates the dose distribution when errors occur, and optimizes the irradiation dose to minimize the effect of the errors on the dose distribution. This method is suitable for intensity-modulated proton therapy, where the dose distribution for each irradiation direction is not uniform.

First, the treatment planning device 501 determines the beam irradiation position. The irradiation position is set to cover the target area. The same operation is performed for each of multiple irradiation directions (angles between the rotating irradiation device 311 and the bed 407).

Once all irradiation positions have been determined, the treatment planning device 501 begins optimizing the irradiation dose.

First, the relationship between the dose at each irradiation position and the dose distribution is calculated for multiple cases. For example, this is done for a total of nine cases: when there is no error, when the target position changes in three mutually orthogonal directions and their opposite directions, for a total of six directions, and when the proton beam arrival position changes to the deeper and shallower sides.

Next, the dose for each irradiation position is determined. A widely adopted method uses an objective function that quantifies the deviation from the target dose using the dose for each irradiation position as a parameter. The objective function is defined to have a smaller value as the largest difference from the target prescription dose set in step 105 among a total of nine cases of dose decreases. The optimal dose is calculated by searching for the dose that minimizes the objective function by iterative calculation. When the iterative calculation is completed, the dose required for each irradiation position is finally determined.

Next, the treatment planning device 501 uses the obtained irradiation positions and irradiation doses to calculate a dose distribution (first dose distribution) using the calculation processing device 605. If necessary, the calculated dose distribution result is displayed on the display device 603.

The operator evaluates the displayed dose distribution and determines whether this dose distribution meets the target conditions and its degree of agreement with the target dose distribution (steps 107, 108).

If, as a result of evaluating the dose distribution, the operator determines that the distribution is undesirable, the operator returns to step 105 and resets the irradiation parameters. Parameters that may need to be changed include the irradiation direction and the prescribed dose. After the desired result is obtained, the treatment planning device stores the spot data, including the energy, irradiation dose, and irradiation position, in the data server 502 via the network (steps 109 and 110).

Next, the procedure for forming a dose distribution at the target by performing replanning using the control device 314 will be described using the flows in Figures 7 and 8.

Before starting irradiation, the operator places the irradiation target 51 on the couch 32 and moves it to the planned position. The control device 314 reads out the information on energy, irradiation position, and irradiation amount registered in the data server 502 and registers it in memory.

In step 201, the control device 314 performs X-ray fluoroscopy while rotating the gantry and acquires a cone beam CT image (preliminary X-ray image). In step 202, the control device 314 compares the acquired cone beam image with the CT image at the time of treatment planning and adjusts the patient position.

In step 203, the treatment planning program 312 of the control device 314 replans the treatment plan and evaluates whether the replanned plan is as desired.

Details of the replanning in step 203 are explained according to the flow diagram in Figure 8.

In step 211, the treatment planning program 312 of the control device 314 reads the cone beam CT image acquired in step 201, and in step 212, recreates an image for the treatment plan to match the patient's body shape at the time of irradiation. The original planning CT image used in the prior treatment plan is compared with the acquired cone beam CT image. By performing deformation registration, the original planning CT image at the time of treatment planning is deformed to match the cone beam CT image.

The original planning CT images used for advance treatment planning show the electron density inside the patient's body with high accuracy, whereas cone beam CT images have a large contribution from X-ray scattering, making it difficult to show the electron density with high accuracy. The accuracy of the electron density contributes to the accuracy of the calculation of the arrival position of the particle beam. Therefore, a new planning CT image is created by transforming the original planning CT image, which measures the electron density inside the patient's body with high accuracy, to match it with the cone beam CT image, which measures the internal shape of the patient on the day of irradiation with high accuracy. Along with the original planning CT image, the contour information drawn on the original planning CT image is also transformed.

A treatment plan is recreated based on the new planning CT image and the deformed contour information. In step 213, spot positions are positioned to cover the target based on the deformed contour information. When irradiating from multiple irradiation directions, spots are positioned to cover the target for each irradiation direction. In addition, in step 214, dose evaluation points are set for the target and organs around the target. In step 215, target values are set for each dose evaluation point. The target values for each dose evaluation point can be determined in the same way as in step 105, which is the preliminary treatment plan, or can be determined by deforming the dose distribution obtained in the preliminary treatment plan in the same way as in step 203.

In step 216, the relationship between the dose applied to the spot position and the dose value at the dose evaluation point is calculated, and the dose of each spot is optimized and adjusted so that the dose value at each dose evaluation point approaches the target value. The optimized result is registered as a new treatment plan (retreatment plan).

In step 204, the operator compares the original treatment plan created in advance with the new treatment plan created immediately before irradiation, and selects the more preferable treatment plan. The dose distribution formed by the original treatment plan and the new treatment plan is calculated using the planning CT image created in step 212. Furthermore, a dose calculation that takes error into account, which is a feature of this embodiment, is performed.

The errors mainly occur when creating the planning CT images. We will explain the calculations that take specific errors into account.

The first method takes density errors into account. The water equivalent thickness obtained from the planning CT image is increased or decreased by a fixed ratio, and the dose distribution is calculated based on this value. Increasing the water equivalent thickness indicates that the particle beam reaches a shallow position, and decreasing it indicates that the particle beam reaches a deep position.

The second method takes into account positional errors. The relative positions of the planning CT image and the irradiation device are moved in multiple directions, and the dose distribution is calculated based on those positions.

The third method considers errors in non-rigid registration, which deforms a CT image to match a cone beam CT image. Non-rigid registration can be performed using pixel values as a basis for deformation, using the contours of organs as a reference, or considering both. There are also parameters such as values that indicate how easily the deformation bends and resolution. By changing these methods and parameters, it is possible to obtain results using different non-rigid registrations. For each of the multiple planned CT images obtained using non-rigid registrations in this way, the dose distributions of the original treatment plan and the new treatment plan are calculated.

From the dose distributions (first dose distribution, second dose distribution) calculated in this manner, dose indices (first dose index, second dose index) are calculated and displayed with the variations indicated by error bars as shown in FIG. 9. The screen shown in FIG. 9 may be displayed on either the display device 603 of the treatment planning device 501 or the display device 315 of the particle beam therapy system.

The dose index is the maximum dose, minimum dose, or value expressed by the dose volume histogram (DVH) in the target or normal organs. It may also be the dose uniformity in the target calculated from the dose distribution, the degree of match between the dose and the target, the tumor control probability (TCP), or the normal tissue damage probability (NTCP).

The treatment planning device 501 calculates and displays the values of these dose indices from the dose distributions calculated in multiple error cases. In the example of FIG. 9, the dose indices at the time of planning are shown as a reference, and the dose indices values from the original treatment plan and the new treatment plan are displayed along with their variations. In the example of FIG. 9(a), the new treatment plan shows a better value including the variations, so the adoption of the new treatment plan is encouraged. On the other hand, in the example of FIG. 9(b), although the new treatment plan is better in terms of values without errors, the new treatment plan has a larger variation, and in the worst case, the old plan has a better value, so the adoption of the original treatment plan is encouraged. Multiple of these indices are displayed, and the plan to be used for irradiation is selected from the original treatment plan and the new treatment plan by taking them into consideration comprehensively.

Note that here we have shown that there are many methods for adding error. By calculating all of them, it is possible to display the variation with high precision. However, since calculating the dose distribution takes time, it is also effective to select the main calculations from those listed here and calculate the dose distribution.

If the original treatment plan prepared in advance is preferable, irradiation begins in step 207.

On the other hand, if a new treatment plan created immediately before irradiation is selected, the treatment plan is verified in step 205, and if approved in step 206, it is registered in memory as the treatment plan to be irradiated, and irradiation begins in step 207.

The control device 314 sets the excitation current value of the scanning electromagnet in the irradiation device based on the energy, irradiation position, and irradiation amount information recorded in the memory.

The operator starts a series of irradiations by pressing the irradiation start button on the console connected to the control device 314.

The irradiation procedure is explained using Figure 10.

In step 701, irradiation begins with energy number i=1 and spot number j=1.

In step 702, the control device 314 controls the synchrotron to accelerate the proton beam to the energy specified by the control device. The proton beam is injected into the synchrotron from the linac and accelerated by the accelerator 306 while circulating inside the synchrotron. The control device 314 also controls the beam transport system 310 to excite the electromagnets so that the proton beam can reach the irradiation device 400.

In step 703, the control device 314 excites the X-axis scanning magnet and the Y-axis scanning magnet to irradiate the initial irradiation position. In step 704, when the excitation of the scanning magnets is completed, the control device 314 controls the high frequency application device 307 to apply high frequency to the proton beam. The proton beam to which high frequency has been applied passes through the beam transport system 310, is scanned by the irradiation device 400, and reaches the initial irradiation position.

The dose of the proton beam passing through the irradiation device is measured by the dose monitor 403, and when that amount reaches the dose specified for the spot, the control device 314 stops the high frequency application device 307 and stops the emission of the proton beam. After the emission of the proton beam has stopped, the process returns to step 703 to irradiate the next irradiation position, and the control device 314 changes the excitation amount of the scanning electromagnets 401 and 402.

When j = ns (ns is the number of spots contained in the energy) is satisfied in step 705, the control device 314 controls the synchrotron to decelerate in step 706, and prepares for irradiation of the next energy in step 702.

When i = nr (nr is the number of energies) is reached in step 707, irradiation is completed in step 708.

By displaying the variation alongside the dose index value as in this embodiment, it is possible to determine the selection of a treatment plan taking into account the error. Visualizing the variation allows for quicker decisions. In adaptive treatment, it is necessary to evaluate the dose distribution taking into account errors due to non-rigid registration. Non-rigid registration errors do not need to be considered in advance treatment plans and are unique to adaptive treatment. The present invention assists in making decisions by visualizing errors that are not usually taken into account.

The present invention is not limited to the above-mentioned examples, but includes various modified examples. The above-mentioned examples have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one example with the configuration of another example, and it is also possible to add the configuration of another example to the configuration of one example. It is also possible to add, delete, or replace part of the configuration of each example with other configurations.

As an example, in this embodiment, a proton beam is used, but the same calculations can be performed when irradiating carbon beams or X-rays.

In addition, although this embodiment shows an example using a cone beam CT, it is also possible to use CT images from a device called InRoomCT, which is a normal CT device placed inside a room, or MRI images from an MRI device.

In addition, in this embodiment, the processing in Figures 7 and 8 was performed by the treatment planning program 312 of the control device 314, but this processing may also be performed by a treatment planning device 501 external to the control device 314.

Furthermore, the above-mentioned configurations, functions, processing units, processing means, etc. may be realized in part or in whole in hardware, for example by designing them as integrated circuits. Furthermore, the above-mentioned configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. Information on the programs, tables, files, etc. that realize each function can be stored in a memory, a recording device such as a hard disk or SSD, or a recording medium such as an IC card, SD card, or DVD.

In addition, the control lines and information lines shown are those considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be assumed that almost all components are interconnected.

501: Treatment planning device 602: Input device 603: Display device 604: Memory 605: Database 606: Processing unit 607: Communication device

Claims (11)

A treatment planning device applied to a particle beam therapy system that irradiates a target with a particle beam, comprising:
calculating a first dose distribution of the particle beam based on a planning X-ray image of the target;
calculating a second dose distribution of the particle beam based on a preliminary X-ray image of the target captured after the planning X-ray image;
A treatment planning apparatus which calculates first and second dose indices relating to the first and second dose distributions and displays the variation of the first and second dose indices. The treatment planning device according to claim 1, characterized in that the variation is obtained by calculating the first and second dose distributions by adding an error in the density of the target. The treatment planning device according to claim 1, characterized in that the variation is obtained by calculating the first and second dose distributions by adding an overlay error between the planning X-ray image and the preliminary X-ray image. The treatment planning device according to claim 1, characterized in that the variation is obtained by calculating the first and second dose distributions by transforming the planning X-ray image based on the preliminary X-ray image. A treatment planning device according to claim 1, which displays the first and second dose indices when there is no variation, and displays the variation for the first and second dose indices as error bars. Calculating the dose of the particle beam based on the first dose distribution to generate an original treatment plan;
Calculating the dose of the particle beam based on the second dose distribution to create a retreatment plan;
2. The treatment planning device according to claim 1, further comprising: a display unit that displays the variations in the first and second dose indices, and then allows the user to select whether to use the original treatment plan or the retreatment plan for irradiating the particle beam. The treatment planning device according to claim 1, characterized in that the preliminary X-ray image is taken immediately before irradiation of the particle beam by the particle beam therapy system. A particle beam therapy system for irradiating a target with a particle beam and having a treatment planning device, comprising:
The treatment planning system includes:
calculating a first dose distribution of the particle beam based on a planning X-ray image of the target;
calculating a second dose distribution of the particle beam based on a preliminary X-ray image of the target captured after the planning X-ray image;
A particle beam therapy system that calculates first and second dose indices relating to the first and second dose distributions and displays the variation between the first and second dose indices. The particle beam therapy system according to claim 8, characterized in that the particle beam therapy system irradiates the target with X-rays. A method for generating a treatment plan by a treatment planning device applied to a particle beam therapy system that irradiates a target with a particle beam, comprising:
calculating a first dose distribution of the particle beam based on a planning X-ray image of the target;
calculating a second dose distribution of the particle beam based on a preliminary X-ray image of the target captured after the planning X-ray image;
A treatment plan generating method comprising the steps of: calculating first and second dose indices relating to the first and second dose distributions; and displaying the variations in the first and second dose indices. A computer program executed by a computer to be applied to a particle beam therapy system that irradiates a target with a particle beam,
a function of calculating a first dose distribution of the particle beam based on a planning X-ray image of the target;
a function of calculating a second dose distribution of the particle beam based on a preliminary X-ray image of the target captured after the planning X-ray image;
and a computer program that causes the computer to realize a function of calculating first and second dose indices relating to the first and second dose distributions and displaying the variations of the first and second dose indices.

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