WO2021152881A1

WO2021152881A1 - Treatment planning device, particle beam therapy system, and computer program

Info

Publication number: WO2021152881A1
Application number: PCT/JP2020/024758
Authority: WO
Inventors: 祐介藤井; 嘉彦長峯; 嵩祐平山; 徹梅川; 伸一郎藤高
Original assignee: 株式会社日立製作所
Priority date: 2020-01-31
Filing date: 2020-06-24
Publication date: 2021-08-05
Also published as: JP2021121273A

Abstract

The present invention makes it possible to recreate a treatment plan for adaptive radiation that is more similar to an original treatment plan. A treatment planning device 501 calculates the dose distribution of charged particle beams on the basis of a three-dimensional image for planning obtained by imaging a target, and determines the irradiation dose of charged particle beams to the target. The treatment planning device 501 deforms the three-dimensional image for planning on the basis of a preliminary three-dimensional image obtained by imaging the target after the three-dimensional image for planning, calculates the dose distribution of charged particle beams and the distribution of energy per distance on the basis of the deformed three-dimensional image for planning, and redetermines the irradiation dose of charged particle beams to the target on the basis of the dose distribution and the distribution of energy per distance.

Description

Treatment planning equipment, particle beam therapy system and computer program

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

Radiation therapy aimed at necrosis of tumor cells by irradiating various types of radiation has been widely used in recent years. Not only X-rays, which are the most widely used radiation, but also treatments using particle beams such as proton beams and carbon beams are spreading.

The use of scanning method is widespread in particle beam therapy. This is a method of applying a high dose only to the tumor area by irradiating a thin particle beam so as to fill the inside of the tumor. Various distributions can be formed without the need for patient-specific instruments such as a collimator for molding the distribution into a tumor shape.

For particle beam therapy, it is necessary to make a detailed treatment plan in advance (see, for example, Patent Document 1). The treatment planning device determines in advance the energy, irradiation amount, and irradiation position so that the desired dose distribution to the affected area and the surrounding area of the affected area can be obtained. X-ray CT images (hereinafter referred to as CT images) are the most common means for confirming the state of the patient's body at the time of planning in advance. The designation of the affected area and the calculation of the dose distribution in the body based on the position are often performed using CT images.

In particle beam therapy, irradiation once a day is repeated over multiple days. Conventionally, the treatment plan was basically made first, and the same irradiation position was irradiated with the same irradiation amount every day. With the widespread use of scanning irradiation methods that do not require patient-specific tools, the irradiation position and irradiation amount have begun to be changed according to changes in the state of the body. Irradiation with a modified treatment plan is called adaptive irradiation.

Non-Patent Document 1 discloses a method for determining the irradiation amount in adaptive irradiation. For adaptive irradiation, it is important to recreate the treatment plan so that the effect is equivalent to the original treatment plan originally planned. Non-Patent Document 1 discloses a method of deforming the dose distribution according to the image of the treatment day and determining the irradiation amount so as to reproduce the dose distribution as a target.

Japanese Unexamined Patent Publication No. 2013-248133

In the method of Non-Patent Document 1 described above, an index based on the dose, for example, the maximum dose and the minimum dose to the target and normal organs around the target can be replanned so as to be equivalent to the original treatment plan. On the other hand, it is known that the damage caused by particle beams to cells depends on both the dose and the amount called linear energy transfer (LET), but conventional adaptive irradiation has changed the treatment plan. Sometimes there was a problem that LET was not taken into consideration.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a treatment planning device, a particle beam therapy system, and a computer program capable of recreating a treatment plan closer to the original treatment plan in adaptive irradiation. ..

A treatment planning device according to one aspect of the present invention in order to solve the above problems is a treatment planning device applied to a particle beam therapy system that irradiates a target with a charged particle beam, and is a three-dimensional planning device that images the target. The dose distribution of the charged particle beam is calculated based on the image to determine the irradiation amount of the charged particle beam on the target, and the three-dimensional image at the time of planning is based on the pre-three-dimensional image obtained by imaging the target after the three-dimensional image at the time of planning. The image is deformed, the dose distribution of the charged particle beam and the energy distribution per distance are calculated based on the deformed three-dimensional image at the time of planning, and the charged particle beam to the target is calculated based on the dose distribution and the energy distribution per distance. Redetermine the dose of.

According to the present invention, it is possible to recreate a treatment plan that is closer to the original treatment plan in adaptive irradiation.

It is a schematic block diagram which shows the particle beam therapy system which concerns on Example. It is a figure which shows the structure of the irradiation field forming apparatus used in the particle beam therapy system which concerns on embodiment. It is a figure which shows the concept of the irradiation position in the particle beam scanning irradiation method. It is a figure which shows the concept of energy change in a particle beam scanning irradiation method. It is a figure which shows the treatment planning apparatus which concerns on Example. It is a flowchart for demonstrating the treatment plan creation operation of the treatment plan apparatus which concerns on Example. It is a flowchart for demonstrating the operation of recreating the treatment plan of the treatment planning apparatus which concerns on Example. It is a flowchart for demonstrating the operation of recreating the treatment plan of the treatment planning apparatus which concerns on Example. It is a figure which shows an example of the modification of the dose distribution and the LET distribution in the treatment planning apparatus which concerns on an Example. It is a flowchart for demonstrating the procedure of particle beam irradiation by the particle beam therapy system which concerns on Example. It is a figure which shows an example of the dose distribution and LET distribution for each irradiation direction in the treatment planning apparatus which concerns on Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the embodiments described below do not limit the invention according to the claims, and all of the elements and combinations thereof described in the embodiments are indispensable for the means for solving the invention. Is not always.

An embodiment of the present invention is a particle beam therapy system that irradiates a particle beam such as a proton beam or a carbon beam, and a treatment planning device that forms a part of this particle beam therapy system. The particle beam used in the particle beam therapy system of this embodiment is not limited as long as it is a particle beam that has already been put into practical use, such as the above-mentioned proton beam and carbon beam, and will be put into practical use in the future. ..

In the figure for explaining the embodiment, the same reference numerals are given to the parts having the same function, and the repeated description thereof will be omitted.

The position, size, shape, range, etc. of each component shown in the drawing 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 and the like disclosed in the drawings.

When there are multiple components having the same or similar functions, the same code may be described with different subscripts. However, when it is not necessary to distinguish between these plurality of components, the subscripts may be omitted for explanation.

A particle beam therapy system and a treatment planning apparatus, which are preferred embodiments of the present invention, will be described with reference to FIG. The target of this embodiment is a particle beam therapy system and a treatment planning device that irradiate particle beams such as proton beams and carbon beams.

FIG. 1 is a diagram showing the overall configuration of the particle beam therapy system. In FIG. 1, the particle beam therapy system includes a charged particle beam generator 301, a high energy beam transport system 310, a rotary irradiation device 311, a control device 314 equipped with a treatment planning program 312 and a memory 313, a display device 315, and an irradiation field formation. It includes an apparatus (irradiation apparatus) 400, a bed 407, a treatment planning apparatus 501, and a data server 502.

The charged particle beam generator 301 is composed of an ion source 302, a pre-stage 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 has a deflection electromagnet 305, an accelerator 306, a high frequency application device 307 for emission, a deflector 308 for emission, and a quadrupole electromagnet (FIG. Not shown).

FIG. 1 will explain the process from the particle beam generated from the charged particle beam generator 301 using the synchrotron type particle beam accelerator 304 to the emission toward the patient. The particles supplied from the ion source 302 are accelerated by the pre-stage accelerator 303 and sent to the synchrotron which is a beam accelerator. An accelerator 306 is installed in the synchrotron, and a high-frequency acceleration cavity (not shown) provided in the accelerator 306 is synchronized with the cycle in which the particle beam orbiting the synchrotron passes through the accelerator 306. A high frequency is applied to accelerate the particle beam. In this way, the particle beam is accelerated until it reaches a predetermined energy.

When the emission start signal is output from the control device 314 after the particle beam is accelerated to a predetermined energy (for example, 70 to 250 MeV), the high frequency power from the high frequency power supply 309 is transferred to the high frequency applied to the high frequency application device 307. The application electrode is applied to the particle beam orbiting in the synchrotron, and the particle beam is emitted from the synchrotron.

The high energy beam transport system 310 connects the synchrotron and the irradiation field forming device 400. The particle beam taken out from the synchrotron is guided to the irradiation field forming device 400 installed in the rotary irradiation device 311 via the high energy beam transport system 310. The rotary irradiation device 311 is for irradiating the beam from an arbitrary direction of the patient 406, and the rotation of the entire device can be rotated in any direction around the bed 407 in which the patient 406 is installed. The irradiation field forming device 400 rotates together with the rotary irradiation device.

X-ray detectors

420 and 421 are provided at the tip of the irradiation field forming device, and

X-ray generators

422 and 423 are provided on the opposite side of the patient 406.

The irradiation field forming device 400 is a device that shapes the shape of the particle beam that is finally irradiated to the patient 406, and its structure differs depending on the irradiation method. The scatterer method and the scanning method are typical irradiation methods, but this embodiment targets the scanning method. In the scanning method, a thin beam transported from the high-energy beam transport system 310 is irradiated to the target as it is, and the target is scanned three-dimensionally, so that a high-dose region can be finally formed only on the target.

FIG. 2 shows the configuration of the irradiation field forming device 400 corresponding to the scanning method. With reference to FIG. 2, the roles and functions of the devices in the irradiation field forming apparatus 400 will be briefly described. The irradiation field forming device 400 includes two scanning

electromagnets

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 has passed through the monitor. On the other hand, the beam position monitor 404 can measure the position where the particle beam has passed. Based on the information from the

monitors

403 and 404, the control device 314 can manage that the planned position is irradiated with the planned amount of the beam.

The thin particle beam transported from the charged particle beam generator 301 via the high energy beam transport system 310 is deflected in its traveling direction by the

scanning electromagnets

401 and 402. These scanning electromagnets 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 401 deflects the beam in the scanning direction 405, and the scanning electromagnet 402 deflects the beam. Deflection in the vertical direction. By using these two electromagnets, the beam can be moved to an arbitrary position in a plane perpendicular to the beam traveling direction, and the target 406a can be irradiated with the beam.

The control device 314 controls the amount of current flowing through the

scanning electromagnets

401 and 402 via the scanning electromagnet magnetic field strength 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 so that 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 control device 314, and the relationship is referred to.

There are two types of scanning beam scanning methods. One is discrete scanning irradiation in which the particle beam is irradiated only when 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 continuously changed without stopping the irradiation of the particle beam. Although discrete scanning irradiation is described in this embodiment, the present invention can also be applied to continuous scanning irradiation.

Fig. 3 shows a conceptual diagram of irradiation by discrete scanning irradiation.

FIG. 3 is an example of irradiating a cubic target 801. Since the particle beam stops at a certain position in the traveling direction and gives most of the energy to the stop position, the energy is adjusted so that the stopping depth of the beam is within the target region. In FIG. 3, a beam of energy that stops near the surface 802 irradiated with the same energy is selected. Irradiation positions (spots) are arranged on this surface at a spot interval of 803. The spot represents a combination of irradiation position and irradiation amount.

When the specified amount is irradiated at one spot, the irradiation is stopped once and the next spot is moved. When the movement is completed, the irradiation of the next spot is started, and when the specified amount is reached, the irradiation is stopped. After that, this is repeated.

The spot 804 is irradiated with a beam that passes through the locus 805 of the beam that irradiates the spot 804. When the spots of the same energy arranged in the target are sequentially irradiated, the depth at which the beam is stopped is changed in order to irradiate another depth position in the target. Here, it is assumed that a simple cubic target is irradiated with a constant irradiation amount, but in reality, since a dose distribution having a complicated shape is formed as the target, the irradiation amount for each spot is greatly different.

In the example of FIG. 3, energy was mainly applied to the region corresponding to the surface 802 irradiated with the same energy. By changing the energy, for example, the situation shown in FIG. 4 is obtained. In FIG. 4, a beam having an energy lower than the energy used in FIG. 3 is irradiated. Therefore, the beam stops at a shallower position. This surface is represented by the surface 901 irradiated with the same energy. The spot 902, which is one of the spots corresponding to the beam of this energy, is irradiated with a beam passing through the trajectory 903 of the beam irradiating the spot 902.

Another method of changing the beam energy is to insert a range modulator (not shown) into the irradiation field forming device 400. Select the thickness of the range modulator according to the energy you want to change. The thickness may be selected by using a plurality of range modulators having a plurality of thicknesses or by using opposing wedge-shaped range modulators.

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

In order to change the stopping depth of the beam, the energy of the beam irradiating the patient 406 is changed. One of the methods of changing the energy is to change the setting of the particle beam accelerator, that is, the synchrotron in this embodiment. The particles are accelerated to the set energy in the synchrotron, and the energy incident on the patient 406 can be changed by changing this setting value. In this case, since the energy extracted from the synchrotron changes, the energy when passing through the high-energy beam transport system 310 also changes, and it is necessary to change the setting of the high-energy beam transport system 310. In the case of a synchrotron, it takes about 1 second to change the energy.

Linear energy transfer (LET) is the amount of energy given per unit length. The larger the LET, the denser the ionization related to the damage to the living cells, so that the damage to the living cells differs depending on the size of the LET even at the same dose. The profile of the proton line in the LET depth direction reaches its maximum at the position where the proton line stops. Moreover, it is almost constant in the lateral direction. Focusing on the points in the target, proton beams of various energies are irradiated, and the LET value is different for each energy. Therefore, the dose average LET is often used as an index of the LET considering that particles of various energies are irradiated. The average dose LET is a value obtained by dividing the sum of the values obtained by multiplying the LET and the dose for each energy for the total energy to be irradiated for each position in the body by the total dose.

Until now, in proton therapy, damage to cells in the body has been represented by the physical dose or the equivalent dose obtained by multiplying the physical dose by a constant. On the other hand, although it is widely known that damage to cells has a dependence on LET, it has not been adopted so far because the dependence is uncertain.

In this example, regardless of the uncertain part that LET has on the cells, the LET distribution is the same as the original distribution, so that the effect of the particle beam on the body is the same as the original treatment plan. create.

FIG. 5 shows the configuration of the treatment planning device 501.

First, the treatment planning device 501 is connected to the data server 502 and the control device 314 via a network. As shown in FIG. 6, the treatment planning device 501 includes an input device 602 for inputting parameters for irradiating particle beams, a display device 603 for displaying the treatment plan, a memory 604, and an arithmetic process for performing dose distribution calculation. A device 605 (arithmetic unit) and a communication device 606 are provided. The arithmetic processing unit 605 is connected to the input device 602, the display device 603, the memory (storage device) 604, and the communication device 606.

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

The storage device 604 stores programs such as firmware. At the start of operation of the treatment planning device 501 (for example, when the power is turned on), a program such as firmware is read from this storage medium and executed to perform overall control of the treatment planning device 501. In addition to the program, the storage device 604 stores data and the like required 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. You may be.

From here, the flow of the operation using the treatment planning device 501 at the time of creating the treatment plan will be described with reference to FIG. Prior to treatment, an image for treatment planning is taken. The most commonly used image for treatment planning is a CT image. The CT image reconstructs three-dimensional data from fluoroscopic images acquired from a plurality of directions of the patient. The CT image captured by the CT device (not shown) is stored in the data server 502.

When the treatment planning is started (step 101), the engineer (or doctor) who is the operator of the treatment planning device becomes a target from the data server 502 using a device such as a mouse which is an input device 602. Read CT data. That is, the treatment planning device 501 copies the CT image from the data server 502 onto the memory 604 through the network connected to the communication device 606 by operating the input device 602 (step 102).

When the reading 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 confirms the 3D CT image displayed on the display device 603. , A device such as a mouse corresponding to the input device 602 is used to input a slice of a three-dimensional CT image, that is, an area to be designated as a target for each two-dimensional CT image. The target region to be input here is a region where it is determined that a sufficient amount of particle beam should be irradiated because the tumor cells are present or may be present. This is called the target area. If there are other areas that require evaluation and control, such as the presence of important organs whose irradiation dose should be suppressed as much as possible near the target area, the operator also specifies the areas such as those important organs. Alternatively, it may be executed on images of different modality represented by MRI (step 103).

When the input of the area is completed for all the 3D CT images, the operator instructs the registration of the input area. By registering, the area input by the operator is saved in the memory 604 as three-dimensional position information (step 104). The position information of the area can also be stored in the data server 502, and when reading the 3D CT image, the information input in the past can be read together with the 3D CT image.

Next, the operator creates a treatment plan that includes information on the position and energy of the beam to be irradiated to the registered target area. (Step 104). First, the operator sets the irradiation direction. In the particle beam therapy system to which this embodiment is applied, the beam can be irradiated from any direction of the patient by selecting the angle between the rotary irradiation device 311 and the bed 407. It is possible to set a plurality of irradiation directions for one target. Normally, positioning is performed so that the vicinity of the center of the target region 706 coincides with the isocenter (rotation center position of the rotation irradiation device 311).

Another parameter for irradiation that the operator should determine is the dose value (prescription dose) that should be irradiated 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 by important organs.

After the above parameters are determined, the treatment planning device 501 automatically calculates according to the instruction of the operator (step 106). The details of the contents related to the dose calculation performed by the treatment planning apparatus 501 will be described below.

Here, we will explain the creation of a treatment plan for an irradiation method called intensity-modulated proton beam therapy by robust optimization as an example. In normal irradiation, a uniform dose distribution is formed on the target in each irradiation direction. Therefore, even in the optimization of the irradiation amount, the irradiation amount is optimized for each irradiation direction. On the other hand, in intensity-modulated proton therapy, the irradiation doses from all irradiation directions are simultaneously optimized so that the target is irradiated with a sufficient dose. Intensity-modulated proton therapy provides more freedom than in the normal case of optimizing the dose for each irradiation direction, so reduce the dose at areas where irradiation should be avoided while ensuring a sufficient dose to the target. Can be done.

When creating a treatment plan, consider the position error of the patient and the error of the depth reached by the particle beam. That is, a treatment plan is created so that a sufficient dose is applied to the target even when these errors occur.

There are two main methods to consider the error. One is a method of setting a region larger than the target by the assumed error and optimizing the irradiation amount so that a sufficient dose is irradiated to that region. This is a suspense suitable for a normal irradiation method in which a uniform dose distribution is formed for each irradiation direction. The other is a method called robust optimization, which actually calculates the dose distribution when an error occurs and optimizes the irradiation dose so that the effect of the error on the dose distribution is minimized. This method is suitable for intensity-modulated proton beam therapy in which the dose distribution in each irradiation direction is not uniform.

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

When all the irradiation positions are determined, the treatment planning device 501 starts the optimization calculation of the irradiation amount.

First, the relationship between the irradiation dose and the dose distribution at each irradiation position is calculated for multiple cases. For example, if there is no error, the position of the target changes in a total of 6 directions in 3 directions orthogonal to each other and the opposite direction, and the arrival position of the proton line changes to the deep side and the shallow side, for a total of 9 cases. be.

Next, the irradiation amount to each irradiation position is determined. A method using an objective function that quantifies the deviation from the target dose with the irradiation amount for each irradiation position as a parameter is widely adopted. The objective function is defined so that the smaller the difference from the target prescription dose set in step 105, the smaller the dose in the total of 9 cases. The optimum irradiation amount is calculated by repeatedly searching for the irradiation amount that minimizes the target function. When the iterative calculation is completed, the irradiation amount required for each irradiation position is finally determined.

Next, the treatment planning device 501 calculates the dose distribution by the arithmetic processing device 605 using the obtained irradiation position and irradiation amount. If necessary, the calculated dose distribution result is displayed on the display device 603.

The operator evaluates the displayed dose distribution and determines whether or not this dose distribution satisfies the target conditions and the degree of agreement with the target dose distribution (steps 107 and 108).

As a result of evaluating the dose distribution, if the operator determines that the distribution is not desirable, the process returns to step 105 and the irradiation parameters are reset. The parameters to be changed include the irradiation direction and the prescribed dose. After obtaining the desired results, the treatment planning apparatus stores spot data including energy, irradiation dose, and irradiation position in the data server 502 through the network (step 109, step 110).

Next, using the flow of FIGS. 7 and 8, the procedure of recreating the treatment plan by adaptive irradiation and forming the dose distribution on the target will be described. The flowcharts shown in FIGS. 7 and 8 are performed prior to irradiation of the charged particle beam by the irradiation device 400. Usually, the re-creation of the treatment plan is performed on the day when the particle beam therapy is performed by irradiating the charged particle beam, and immediately before the irradiation of the charged particle beam.

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

In step 201, the control device 314 performs X-ray fluoroscopy while rotating the gantry, and acquires a cone beam CT image. In step 202, the position of the patient is adjusted by comparing the acquired cone beam image with the CT image at the time of treatment planning.

Replan (recreate) the treatment plan in step 203 and evaluate that the replanned plan is in line with the goal.

The details of the replanning in step 203 will be described according to the flow of FIG.

The treatment plan program of the control device 314 reads the acquired cone beam CT image in step 211, and recreates the treatment plan according to the patient's body shape at the time of irradiation in step 212. By comparing the CT image used in the prior treatment plan with the acquired cone beam CT image and performing deformation registration, the CT image at the time of the treatment plan is deformed according to the cone beam CT image. Here, the deformation registration is to accurately match those images in one coordinate system by finding the correspondence between each pixel between the images in which the deformation or movement has occurred. Since the registration method itself is known in image processing and image conversion technology, the description thereof is omitted here.

While the CT image used for treatment planning represents the electron density in the patient's body with high accuracy, the cone beam CT image has a large contribution of X-ray scattering, so it is difficult to accurately represent the electron density. This is because it is not suitable for accurately calculating the arrival position of the particle beam.

Recreate the treatment plan based on the deformed CT image and the similarly deformed contour information. In step 213, the spot position is arranged so as to cover the target based on the deformed contour information. When irradiating from a plurality of irradiation directions, spots are arranged so as to cover the target in each irradiation direction. Further, in step 214, the dose distribution and the LET distribution are deformed according to the deformation of the CT image as shown in FIG.

Here, the dose distribution and the LET distribution are the one for each irradiation angle and the total dose distribution and the LET distribution from all the irradiation angles. The total dose distribution from all irradiation angles is the sum of the doses from each irradiation angle, while the LET distribution is a distribution of values obtained by further averaging the LET distributions from each irradiation direction.

FIG. 11 shows the dose distribution and the LET distribution when irradiating the central target region from two left and right directions. The dotted line shows the distribution for each irradiation direction, and the solid line shows the total from all irradiation directions. The distribution in FIG. 11 is also deformed according to the deformation of the CT image in the same manner as in FIG.

Next, in step 215, dose evaluation points are set for the target and the organs around the target.

In step 216, the dose value and the LET value at each dose evaluation point are obtained from the deformed dose distribution and the LET distribution, and are set as the target value of each evaluation point. For the dose value and LET value set for each evaluation point, the one from each irradiation direction and the total from all irradiation directions are registered. That is, in the example of FIG. 11, a dose value and a total dose value for irradiation from the left and right directions, a LET value from the left and right directions and a total LET value, and a total of six values are set for one evaluation point. do.

In step 217, the relationship between the irradiation amount to be irradiated to the spot position, the dose value at the dose evaluation point, and the LET is calculated, and the dose value and the total from each irradiation direction and all irradiation directions at each dose evaluation point are calculated. The irradiation amount of each spot is optimized and adjusted so that the LET value approaches the target value.

Returning to FIG. 7, in step 204, the operator compares the treatment plan created in advance with the treatment plan created immediately before irradiation, and selects the preferred treatment plan. If a pre-prepared treatment plan is preferred, irradiation is initiated in step 207.

When the 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 the memory as the treatment plan to be irradiated and the irradiation in step 207 is started.

The control device 314 sets the exciting current values of the

scanning electromagnets

401 and 402 in the irradiation device 400 based on the energy, irradiation position, and irradiation amount information recorded in the memory 313.

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

The irradiation procedure will be described with reference to FIG.

In step 701, irradiation is started from energy number i = 1 and spot number j = 1. In step 702, controller 314 controls the synchrotron to accelerate the proton beam from controller 314 to the specified energy. The proton beam is incident on the synchrotron from the linac and is accelerated by the accelerator 306 while orbiting the synchrotron. Further, the control device 314 controls the beam transport system 310 and excites the electromagnet so that the proton beam can reach the irradiation device 400.

In step 703, the control device 314 excites the X-axis scanning electromagnet and the Y-axis scanning electromagnet, respectively, in order to irradiate the first irradiation position.

In step 704, when the excitation of the

scanning electromagnets

401 and 402 is completed, the control device 314 controls the high frequency applying device 307 to apply a high frequency to the proton beam. The proton beam to which the high frequency is applied is scanned by the irradiation device 400 via the beam transport system 310 and reaches the first irradiation position. The irradiation amount of the proton beam passing through the irradiation device is measured by the dose monitor 403, and when the amount reaches the irradiation amount specified for the spot, the control device 314 stops the high frequency application device 307 and emits the proton beam. To stop. After the emission of the proton beam is 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 electromagnet.

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 the next energy irradiation in step 702.

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

According to the present embodiment configured as described above, the treatment planning apparatus 501 calculates the dose distribution of the charged particle beam based on the three-dimensional image at the time of planning in which the target 406a is imaged, and the charged particle beam to the target 406a is calculated. The irradiation amount is determined, the planned three-dimensional image is deformed based on the pre-three-dimensional image obtained by capturing the target 406a after the planned three-dimensional image, and the dose of the charged particle beam is based on the deformed planned three-dimensional image. The distribution and the energy distribution per distance are calculated, and the irradiation amount of the charged particle beam to the target 406a is redetermined based on the dose distribution and the energy distribution per distance.

Therefore, according to this embodiment, it is possible to realize a treatment planning device 501, a particle beam therapy system, and a computer program capable of recreating a treatment plan closer to the original treatment plan in adaptive irradiation.

In other words, as in this example, both the dose distribution and the LET distribution are deformed according to the shape of the patient's body at the time of treatment, and the irradiation dose is determined using that value as the target value, thereby resulting in position error and range error. It is possible to re-plan a robust treatment plan in a short time. In addition, the replanned distribution can have the same effect on the tumor as compared to the original distribution.

An index called Relative Biological Effectiveness (RBE) is known as an index that is generally considered to be applicable in addition to the LET distribution. However, RBE is a relative value that varies from tissue to tissue and can vary from model to model. On the other hand, since LET is a physical quantity itself, it is possible to create an accurate treatment plan as a target value in the same manner as the dose distribution which is also a physical quantity.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

As an example, in this embodiment, the proton beam has been described as an example, but the calculation can be performed in the same manner when irradiating the carbon beam.

Further, in this embodiment, an example was used in which the optimization at the time of replanning was calculated using the dose distribution and the LET distribution integrated for each irradiation direction and in all directions. The reproducibility can be improved by calculating using both the irradiation direction and the omnidirectional integration. On the other hand, it is also possible to calculate using only omnidirectional integration. In this case, the calculation time can be shortened.

Further, in this embodiment, an example using a cone beam CT image is shown, but a CT image of a device called InRoomCT in which a normal CT device is placed indoors may be used, or an MRI image by an MRI device may be used. good.

Then, in this embodiment, the calculation was performed using LET as an example, but the amount of energy used for calculating the biological effect called microdosometry may be divided by the distance.

Further, each of the above configurations, functions, processing units, processing means, etc. may be realized by hardware by designing a part or all of them by, for example, an integrated circuit. Further, each of the above configurations, functions, and the like may be realized by software by the processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be placed 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 indicate those that are considered necessary for explanation, and not all control lines and information lines are necessarily indicated on the product. In practice, it can be considered that almost all configurations are interconnected.

301 ... Charged particle beam generator, 302 ... Ion source, 303 ... Pre-stage accelerator, 304 ... Particle beam accelerator, 305 ... Deflection electromagnet, 306 ... Accelerator, 307 ... High frequency application device for emission, 308 ... Deflector for emission, 309 ... High frequency supply device, 310 ... High energy beam transport system, 311 ... Rotational irradiation device, 314 ... Control device, 313, 604 ... Memory, 315, 603 ... Display device, 400 ... Irradiation field forming device, 401, 402 ... Scanning Electromagnet, 403 ... Dose monitor, 404 ... Beam position monitor, 405 ... Scanning direction, 406 ... Patient, 406a, 801 ... Target, 410 ... Scanning electromagnet power supply, 411 ... Scanning electromagnet magnetic field strength control device, 501 ... Treatment planning device, 502 ... Data server, 602 ... Input device, 605 ... Arithmetic processing device, 606 ... Communication device

Claims

A treatment planning device applied to a particle beam therapy system that irradiates a target with a charged particle beam.
The dose distribution of the charged particle beam is calculated based on the planned three-dimensional image of the target, and the irradiation amount of the charged particle beam on the target is determined.
The planning time 3D image is deformed based on the pre-three-dimensional image obtained by capturing the target after the planning time 3D image.
The dose distribution of the charged particle beam and the energy distribution per distance are calculated based on the deformed three-dimensional image at the time of planning.
A treatment planning apparatus comprising redetermining the irradiation amount of the charged particle beam to the target based on the dose distribution and the energy distribution per distance.
The treatment planning apparatus according to claim 1, wherein the pre-three-dimensional image is taken immediately before irradiation of the charged particle beam by the particle beam therapy system.
The treatment planning device
Dose evaluation points are set for the target and around the target, respectively.
The dose distribution and the energy per distance distribution at the dose evaluation point are calculated from the dose distribution and the energy per distance distribution of the charged particle beam based on the deformed three-dimensional image at the time of planning.
The treatment planning apparatus according to claim 1, wherein the irradiation amount of the charged particle beam to the target is determined by setting the dose distribution at the dose evaluation point and the energy distribution per distance as target values.
The treatment planning apparatus according to claim 1, wherein the energy distribution per distance is a LET distribution or a dose average LET distribution.
The treatment planning apparatus according to claim 1, wherein the energy distribution per distance is a variable distribution in microdosometry.
A particle beam therapy system that irradiates a target with a charged particle beam and has a treatment planning device.
The treatment planning device
The dose distribution of the charged particle beam is calculated based on the planned three-dimensional image of the target, and the irradiation amount of the charged particle beam on the target is determined.
The planning time 3D image is deformed based on the pre-three-dimensional image obtained by capturing the target after the planning time 3D image.
The dose distribution of the charged particle beam and the energy distribution per distance are calculated based on the deformed three-dimensional image at the time of planning.
A particle beam therapy system comprising redetermining the dose of the charged particle beam to the target based on the dose distribution and the energy distribution per distance.
The particle beam therapy system according to claim 6, wherein the particle beam therapy system divides the target into a plurality of small regions and sequentially irradiates these small regions with the charged particle beam.
A computer program executed by a computer applied to a particle beam therapy system that irradiates a target with charged particle beams.
A function of calculating the dose distribution of the charged particle beam based on the planned three-dimensional image of the target and determining the irradiation amount of the charged particle beam on the target.
A function of transforming the 3D image at the time of planning based on a pre-three-dimensional image obtained by capturing the target after the 3D image at the time of planning.
A function to calculate the dose distribution and the energy distribution per distance of the charged particle beam based on the deformed three-dimensional image at the time of planning, and
A computer program that realizes a function of redetermining the irradiation amount of the charged particle beam on the target based on the dose distribution and the energy distribution per distance.
A treatment planning device applied to a particle beam therapy system that irradiates a target with a charged particle beam.
Based on the three-dimensional image of the target, the dose distribution for each irradiation direction of the charged particle beam and the dose distribution from all irradiation directions of the charged particle beam are calculated to create a treatment plan. A featured treatment planning device.