JP2020146334A - Particle-beam radiation therapy system, measured particle-beam ct image generation method, and ct image generation program - Google Patents

Abstract

To provide a particle-beam radiation therapy system capable of measuring a stopping power ratio distribution with a high degree of accuracy without upsizing therapy equipment, a measured particle-beam CT image generation method, and a CT image generation program.SOLUTION: A particle-beam radiation therapy system comprises: a remaining range measuring device 81 which can apply a proton beam and a helium line as charged particle beams and which measures energy of the proton beam transmitted through a patient 5; and a particle-beam CT image generation device 80 which determines a stopping power ratio distribution with respect to the proton beam through the patient 5, measured by the remaining range measuring device 81, and which calculates the stopping power ratio distribution with respect to the helium line on the basis of the determined stopping power ratio distribution.SELECTED DRAWING: Figure 1

Description

The present invention relates to a particle beam therapy system for performing cancer treatment by irradiating a cancer affected area with a particle beam, and a method or program for generating a measured particle beam CT image used for performing particle beam therapy. ..

As an example of techniques related to proton computed tomography, Patent Document 1 states that detection of a proton can provide track information before and after the object for each proton, thereby for each proton within the object. It is stated that it will be possible to find a route with a high probability.

Patent No. 5726910

In particle beam therapy, treatment plan data that saves set values such as particle beam irradiation direction, energy, and irradiation amount is created for each patient based on an X-ray CT image. At that time, the CT value of the X-ray CT image is converted into a water equivalent thickness to determine the irradiation method of the particle beam, but it is known that an error occurs in the depth direction of the particle beam due to the conversion.

In order to secure this error, it is conceivable to increase the margin of the irradiation area, but this may not provide a good dose distribution. Further, Patent Document 1 discloses a method of directly measuring the stopping power ratio distribution using a particle beam used for treatment. In the present invention, the stopping power ratio means the ratio of the stopping power of the measurement target to the stopping power of water.

Here, when measuring the stopping power ratio distribution with a particle beam used for treatment (hereinafter referred to as a treatment beam), a beam of energy transmitted through the measurement target is required. However, for this purpose, an accelerator capable of accelerating energy larger than the particle beam required for the treatment beam is required, and there is a problem that the device becomes large.

Further, in a device using a carbon beam as a treatment beam, when CT imaging is performed with a proton beam (hereinafter referred to as a measurement beam) which is an ion species lighter than the treatment beam, a beam of energy transmitted through the measurement target is transmitted without enlarging the device. Although it can be accelerated, there may be an error in converting the stopping power distribution for the measurement beam to the stopping power distribution for the treatment beam.

To solve such problems, the present invention provides a particle beam therapy system capable of measuring a highly accurate stopping power distribution without increasing the size of the treatment device, a measurement particle beam CT image generation method, and a CT image generation. The purpose is to provide a program.

The present invention includes a plurality of means for solving the above problems. For example, a particle beam therapy system that irradiates an irradiated object of an irradiated object with a charged particle beam, and the charged particles As a line, it is possible to irradiate a first charged particle beam and a second charged particle beam having a particle type different from that of the first charged particle beam, and accelerate the first charged particle beam and the second charged particle beam. The accelerator and the irradiation device that irradiates the irradiation target with the first charged particle beam or the second charged particle beam accelerated by the accelerator are arranged at positions facing each other with the irradiated body interposed therebetween. Based on the monitor that measures the energy of the one charged particle beam and the energy measured by the monitor, the first blocking ability ratio distribution of the irradiated object with respect to the first charged particle beam is obtained, and the first blocking ability ratio distribution is obtained. A particle beam CT image generator for calculating a second blocking ability ratio distribution with respect to the second charged particle beam based on the above, and a combination of the first charged particle beam and the second charged particle beam is the first. Either the 1-charged particle beam is a proton beam and the second charged particle beam is a helium beam, or the first charged particle beam is a helium beam and the second charged particle beam is a carbon beam. , Characterized by.

According to the present invention, it is possible to measure the stopping power ratio distribution with high accuracy without increasing the size of the treatment device. Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a figure which shows the whole structure of the particle beam therapy system of Embodiment 1 of this invention. It is a figure which shows the outline of the irradiation nozzle of the particle beam therapy system of Embodiment 1. It is a figure which shows the flowchart of the measurement particle beam CT image for making the treatment plan by the particle beam therapy system of Embodiment 1. FIG. It is a schematic diagram which shows the outline of the measuring method of the stopping power ratio distribution in the particle beam therapy system of Embodiment 2 of this invention.

Hereinafter, embodiments of the particle beam therapy system, the measured particle beam CT image generation method, and the CT image generation program of the present invention will be described with reference to the drawings.

<Embodiment 1>
The particle beam therapy system of the present invention, the measurement particle beam CT image generation method, and the first embodiment of the CT image generation program will be described with reference to FIGS. 1 to 3.

First, the overall configuration of the particle beam therapy system will be described with reference to FIG. FIG. 1 is a diagram showing an overall configuration of the particle beam therapy system of the present embodiment.

The particle beam therapy system 100 is a system for irradiating the affected portion 51 of the patient 5 with a charged particle beam (hereinafter, beam 90, treatment beam 90A (see FIG. 2), measurement beam 90B (see FIG. 2)). Yes, as shown in FIG. 1, the accelerator 20, the beam transport system 30, the irradiation nozzle 40, the treatment table 50, the overall control device 11, the accelerator / beam transport system control device 12, and the irradiation nozzle control device 13 The remaining distance measuring device 81 and the measuring particle beam CT image creating device 80 are provided.

The accelerator 20 is a device that generates and accelerates the beam 90, and includes an injector 21, a synchrotron accelerator 22, and ion sources 23A and 23B.

The ion source 23A produces the ions that are the source of the therapeutic beam 90A used for treatment. On the other hand, the ion source 23B generates ions that are the source of the measurement beam 90B used for measurement.

Specifically, in the present invention, the ion source 23A produces helium ions as the source of the therapeutic beam 90A. In this case, the ion source 23B produces protons as the source of the measurement beam 90B. Alternatively, the ion source 23A produces carbon ions as the source of the therapeutic beam 90A. In this case, the ion source 23B generates helium ions as the source of the measurement beam 90B.

The beam transport system 30 is a group of devices that transports the beam 90 accelerated by the accelerator 20 to the irradiation nozzle 40 that irradiates the affected portion 51 with the beam 90, and connects the accelerator 20 and the irradiation nozzle 40.

The beam 90 accelerated to the required energy by the accelerator 20 is transported to the irradiation nozzle 40 while being bent by a magnetic field in a vacuum by a deflection electromagnet 31 arranged in the beam transport system 30.

The beam 90 is shaped by the irradiation nozzle 40 so as to match the shape of the irradiation region, and the irradiation target is irradiated. The irradiation target is, for example, the affected part 51 (see FIG. 2) of the patient 5 lying on the treatment table 50.

Here, in the present invention, the measurement beam 90B is irradiated when creating a measurement particle beam CT image used when creating a treatment plan for determining various parameters such as irradiation energy and irradiation angle of the treatment beam 90A. When irradiating the measurement beam 90B to be irradiated, the remaining range of the measurement beam 90B after passing through the irradiation target is measured by the remaining range measuring device 81.

The remaining range measuring device 81 is a device that measures the energy of the proton beam or the energy of the helium beam as the measuring beam 90B transmitted through the patient 5. For example, a detector having a known configuration such as a stacked radiation measuring device or a scintillator can be applied.

The measurement particle beam CT image creating device 80 has a function of creating a measurement particle beam CT image from the energy of the proton beam of the patient 5 measured by the residual range measuring device 81. Furthermore, a stopping power ratio conversion function that obtains the stopping power ratio distribution for the proton beam of patient 5 from the created measured particle beam CT image and calculates the stopping power ratio distribution for the helium beam based on the obtained stopping power ratio distribution is provided. Have.

Alternatively, the measurement particle beam CT image creating device 80 has a function of creating a measurement particle beam CT image from the energy of the helium ray of the patient 5 measured by the residual range measuring device 81. Furthermore, a stopping power ratio conversion function that obtains the stopping power ratio distribution for helium rays of patient 5 from the created measured particle beam CT image and calculates the stopping power ratio distribution for carbon rays based on the obtained stopping power ratio distribution is provided. Have.

The treatment planning device 110 utilizes the measurement particle beam CT image created by the measurement particle beam CT image creation device 80 and the information on the blocking ability ratio distribution with respect to the treatment beam obtained from the measurement particle beam CT image. The position of the irradiation spot for irradiating the affected area with a uniform dose and the target irradiation amount for each irradiation spot are calculated.

The overall control device 11 is connected to a treatment planning device 110, an accelerator / beam transport system control device 12, an irradiation nozzle control device 13, a treatment table 50, a measurement particle beam CT image creation device 80, and the like, and is connected to the particle beam therapy system 100. Control the overall operation.

The accelerator / beam transport system control device 12 controls the operation of each device constituting the accelerator 20 and the beam transport system 30.

The irradiation nozzle control device 13 controls the operation of each device constituting the irradiation nozzle 40.

The overall control device 11, the accelerator / beam transport system control device 12, the irradiation nozzle control device 13, the measurement particle beam CT image creation device 80, and the treatment planning device 110 have a central processing unit (CPU) and a memory connected to the CPU. Have.

The overall control device 11 reads various operation control programs related to irradiation of each device constituting the particle beam therapy system 100 from the treatment plan created by the treatment planning device 110, executes the read programs, and executes the accelerator. By outputting a command via the beam transport system control device 12 and the irradiation nozzle control device 13, the operation of each device in the particle beam therapy system 100 is controlled.

The measurement particle beam CT image creation device 80 and the treatment planning device 110 are installed with the measurement particle beam CT image creation program and the treatment planning program, respectively, and execute these programs to create a CT image and a treatment plan.

The operation control process to be executed may be integrated into one program, may be divided into a plurality of programs, or may be a combination thereof.

Further, a part or all of the program may be realized by dedicated hardware or may be modularized. Further, various programs may be installed in each device by a program distribution server or an external storage medium.

Further, each device may be an independent device connected by a wired or wireless network, or two or more may be integrated.

The treatment table 50 is a bed on which the patient 5 is placed. The treatment table 50 can be moved in the directions of three orthogonal axes based on the instruction from the overall control device 11, and can be further moved in the so-called six-axis direction, which is rotated around each axis. By these movements and rotations, the position of the affected portion 51 of the patient 5 can be moved to a desired position.

Next, the details of the irradiation nozzle 40 will be described with reference to FIG. FIG. 2 is a diagram showing an outline of the irradiation nozzle 40.

As shown in FIG. 2, scanning electromagnets 41A and 41B, a dose monitor 42, a position monitor 43, a ridge filter 44, and a range shifter 45 are arranged in the irradiation nozzle 40.

Further, as shown in FIG. 2, the irradiation nozzle control device 13 is connected to the dose monitor control device 72, the position monitor control device 73, and the scanning electromagnet power supply control device 71.

The irradiation nozzle 40 is a device that scans the beam 90 in a two-dimensional plane by scanning electromagnets 41A and 41B in order to scan the beam 90 in a plane perpendicular to the passing direction of the beam 90. The beam 90 scanned by the scanning electromagnets 41A and 41B irradiates the affected area 51.

The dose monitor 42 is a monitor for collecting electrons generated by the passage of the beam 90 in order to calculate the dose of the beam 90 applied to each spot. The detection signal (pulse signal obtained by collecting electrons) of the dose monitor 42 is input to the dose monitor control device 72.

The dose monitor control device 72 calculates the irradiation amount to be irradiated to each irradiation spot 53 based on the detection signal input from the dose monitor 42, and outputs the calculated irradiation amount to the irradiation nozzle control device 13.

The position monitor 43 is a monitor for collecting electrons generated by the passage of the beam 90 in order to calculate the position of each irradiation spot 53 (for example, the position of the center of gravity). The detection signal (pulse signal obtained by collecting electrons) of the position monitor 43 is input to the position monitor control device 73.

The position monitor control device 73 counts the dose at each irradiation spot 53 based on the detection signal input from the position monitor 43, and outputs the calculated count value to the irradiation nozzle control device 13.

The irradiation nozzle control device 13 obtains the passing position of the beam 90 based on the signal input to the position monitor control device 73, calculates the position and width of the irradiation spot 53 from the obtained passing position data, and irradiates the beam 90. Check the position. Further, the irradiation nozzle control device 13 advances the control of irradiation of the beam 90 according to the irradiation dose input to the dose monitor control device 72.

The ridge filter 44 can be used when it is necessary to thicken the Bragg peak. Further, the range shifter 45 can be inserted when adjusting the arrival position of the beam 90.

In scanning irradiation as in the present embodiment, as described above, the position of the irradiation spot 53 for irradiating the affected area 51 with a uniform dose and the target irradiation amount for each irradiation spot 53 are calculated in advance by the treatment planning device 110. ..

Next, a method of generating a measurement particle beam CT image for creating a treatment plan and an operation at the time of measuring the stopping power ratio distribution will be described with reference to FIG. FIG. 3 is a diagram showing a flowchart at the time of generating the measurement particle beam CT image and at the time of measuring the stopping power ratio distribution.

Before starting the measurement using the measurement beam 90B, the change pitch of the irradiation angle, the energy, the position and the irradiation amount of the irradiation spots installed for each irradiation angle are determined in advance and saved as irradiation plan data in the overall control device 11. Has been done. Here, the irradiation angle means a gantry angle when the beam transport system 30 is a rotating gantry, and means an installation angle of an irradiation target when the beam transport system 30 is a fixed irradiation system.

First, the start of measurement is instructed by the operator (step S101).

Next, based on the irradiation plan data, the overall control device 11 sets the parameters of the treatment table 50, the accelerator / beam transport system control device 12, and the irradiation nozzle control device 13 (step S102). Further, the overall control device 11 sends a set value of energy for each spot to the measurement particle beam CT image creating device 80. The coordinate values of the irradiation spot 53 are converted into exciting current values of the scanning electromagnets 41A and 41B by the irradiation nozzle control device 13, and sent to the scanning electromagnet power supply control device 71 shown in FIG.

After the parameter settings and the like are completed, irradiation is started by the operator's operation (step S103).

When the irradiation is started, the overall control device 11 outputs an energy change, an emission signal of the beam 90, an emission stop signal, or the like to the accelerator / beam transport system control device 12. According to the order recorded in the treatment plan data, the irradiation spots 53 sequentially from N = 1 are irradiated with the beam 90 of the predetermined irradiation amount (step S104). At this time, when it is determined that the irradiation to the irradiation spot 53 is completed based on the signal from the dose monitor 42, the remaining range measuring device 81 measures the measured value and measures the particle beam CT image creating device 80. Send to.

Next, the overall control device 11 determines whether or not a certain irradiation spot 53 that has been irradiated first is the last spot to be irradiated within the same energy (step S105). When it is determined that the spot is the final spot in the energy, the process proceeds to step S106. On the other hand, when it is determined that the spot is not the final spot in the energy, the process proceeds to step S104 in order to execute the irradiation of the next irradiation spot 53.

Next, the overall control device 11 determines whether or not the energy to which the irradiation spot 53, which has been irradiated first, belongs is the energy to be irradiated last (step S106). When it is determined that the energy is the last energy, the process proceeds to step S107, and when it is determined that the energy is not the last energy, the process proceeds to step S104 in order to change the energy and irradiate the next energy.

Next, the overall control device 11 determines whether or not the irradiation angle to which the irradiation spot 53 whose irradiation has been completed belongs is the irradiation angle to be irradiated last (step S107). When it is determined that the irradiation angle is the last, the process proceeds to step S108, and when it is determined that the irradiation angle is not the last, the irradiation angle is changed and the irradiation is performed at the next irradiation angle. Proceed to step S103.

From step S101 to step S107, the irradiation step of irradiating the patient 5 having the affected part 51 with the proton beam or the helium beam, and the proton beam transmitted through the patient 5 among the proton beam or the helium beam irradiated in the irradiation step. Or, it corresponds to a measurement step in which the energy of the helium beam is measured by the residual range measuring device 81.

When the irradiation is completed, the measurement particle beam CT image creating device 80 loses energy based on the remaining range measured by the remaining range measuring device 81 and the set value of the energy for each spot sent from the overall control device 11. The amount distribution is calculated for each irradiation angle (step S108). Further, the measurement particle beam CT image creation device 80 generates a proton beam or helium beam CT image by the measurement particle beam CT image creation function, and uses these CT images based on the calculated energy loss distribution. Reconstruct the three-dimensional stopping power distribution for the measurement beam. Subsequently, the measurement particle beam CT image creating device 80 converts the stopping power ratio distribution for the measurement beam into the stopping power ratio distribution for the treatment beam by using the stopping power ratio conversion function.

This step 108 is a measurement stopping power ratio distribution calculation step for obtaining the stopping power ratio distribution of the patient 5 with respect to the proton wire or the helium wire based on the energy measured by the residual range measuring device 81, and the measuring stopping power. The stopping power distribution of patient 5 to helium rays based on the stopping power distribution to proton rays obtained by the ratio distribution calculation step, or the stopping power ratio of patient 5 to carbon rays based on the stopping power distribution to helium rays obtained. Corresponds to the therapeutic stopping power distribution calculation step for calculating the distribution.

Finally, the stopping power distribution for the created treatment beam and the measured particle beam CT image are sent to the treatment planning device 110, and the treatment planning device 110 creates a treatment plan (step 109). As a method for creating a treatment plan, a known method can be used. After that, the process ends.

Next, the effect of this embodiment will be described.

In the particle beam therapy system 100 of the first embodiment of the present invention described above, it is possible to irradiate a proton beam and a helium beam as charged particle beams, and the residual distance measuring device 81 that measures the energy of the proton beam that has passed through the patient 5 A particle beam CT image generator that obtains the stopping power distribution for the proton beam of patient 5 measured by the residual flight measuring device 81 and calculates the stopping power distribution for the helium beam based on the obtained stopping power distribution. It has 80 and. Alternatively, a residual range measuring device 81 that can irradiate a helium beam and a carbon beam as charged particle beams and measures the energy of the helium wire that has passed through the patient 5 and a patient 5 measured by the residual range measuring device 81. The particle beam CT image generator 80 is provided, which obtains the stopping power distribution for helium beam and calculates the stopping power distribution for carbon beam based on the obtained stopping power distribution.

First, the effect of the combination of the helium beam and the proton beam will be described. Comparing the helium beam and the proton beam, according to ICRU REPORT 49, the speed of light ratio β of the velocities is almost the same for the beams having the same remaining range.

On the other hand, according to the Bethe-Bloch formula, the stopping power S is represented by the formula (1) shown below.

Here, in the formula (1), K, z, Z, A, m, c, I, and δ are constants, valences of incident particles, valences of target nuclei, atomic weights, electron mass, speed of light, and average, respectively. It means ionization potential and density effect.

As shown in equation (1), the term that depends on the beam, the value is determined by β except z ^2. Therefore, the more Zanhi compares the same proton and helium line, term difference dependent terms β is small, determines the stopping power for protons is stopping power for helium lines except the section z ² Almost matches with. From this, it can be seen that when a helium beam is used for the treatment beam 90A and a proton beam is used for the measurement beam 90B, the error generated at the time of conversion of the stopping power ratio can be reduced.

The magnetic rigidity of a helium wire having a maximum residual range of 30 cm, which is typical for a therapeutic beam 90A, is about 4.5 m. On the other hand, the remaining range of a proton beam having a magnetic rigidity of 4.5 m is about 199 cm, and when the measurement target is a human body, it has a remaining range that can be sufficiently transmitted. That is, in an accelerator capable of accelerating the helium beam as the treatment beam 90A, it is possible to generate the measurement beam 90B using the proton beam without increasing the size of the accelerator.

From these two facts, it can be seen that the stopping power ratio distribution can be measured with high accuracy without increasing the size of the treatment device. By utilizing this, it is possible to suppress the occurrence of an error in the depth direction of the particle beam, realize the creation of a treatment plan with higher accuracy than before, and realize highly accurate particle beam irradiation. It becomes possible.

Next, the combination of carbon wire and helium wire will be described.

Even for carbon wire and helium wire having the same magnetic rigidity, β is almost the same. The typical magnetic rigidity of carbon wire used for treatment is about 3.5-6.6 m, and the maximum remaining range of helium wire having a magnetic rigidity in this range is 93 cm. Therefore, when the measurement target is the human body, it can be seen that it has a remaining range that can be sufficiently transmitted.

That is, when a carbon wire is used for the treatment beam 90A and a helium wire is used for the measurement beam 90B, the stopping power ratio distribution can be measured with the measurement beam 90B close to the β value of the treatment beam 90A, and the difference in terms depending on β. It is possible to reduce the conversion error of the stopping power ratio by reducing the value of.

Therefore, as in the case of the combination of the helium beam and the proton beam, it is possible to measure the stopping power ratio distribution with high accuracy without increasing the size of the treatment device.

<Embodiment 2>
The particle beam therapy system, the measured particle beam CT image generation method, and the CT image generation program according to the second embodiment of the present invention will be described with reference to FIG. The same reference numerals are given to the same configurations as those in the first embodiment, and the description thereof will be omitted. The same shall apply in the following embodiments.

In this embodiment, when creating the irradiation plan data for measurement, the measurement in the irradiation direction 2 is performed regardless of the irradiation position, even if the measurement beam 90B in the irradiation direction 1 is used, for example, as shown in FIG. Even with the beam 90B, the energy of the measurement beam 90B is changed according to the irradiation position so that the remaining range becomes constant with a small value.

Here, the remaining range of a small value is, for example, about 1 cm. The energy of the measurement beam 90B is determined based on the thickness of each irradiation position of the measurement target calculated from the X-ray CT image measured in advance.

Then, in the present embodiment, as shown in FIG. 4, the collimator 82 is installed on the upstream side of the remaining range measuring device 81.

The collimator 82 suppresses the measurement beam 90B scattered in the measurement target from reaching the remaining range measuring device 81. As a result, it becomes possible to measure the remaining range of only the measurement beam 90B that has passed through the planned irradiation direction, and the accuracy of the distribution of the energy loss amount is improved. Therefore, the accuracy of the measured particle beam CT image and the accuracy of the stopping power ratio can be further improved.

Further, by keeping the remaining range constant at a small value, the upper limit of the energy measured by the remaining range measuring device 81 can be reduced, and as a result, the remaining range measuring device 81 can be miniaturized. Become.

Further, as the remaining range becomes smaller, the collimator 82 can be similarly miniaturized. In particular, if a grid for removing scattered X-rays is used, it is possible to reduce the size and cost as compared with the movable leaf type collimator.

Furthermore, since the accuracy of the stopping power distribution is improved, it is possible to further suppress the occurrence of an error in the depth direction of the particle beam, and it is possible to create a more accurate treatment plan with high accuracy. It is possible to realize particle beam irradiation.

Other configurations / operations are substantially the same as those of the particle beam therapy system of the first embodiment, the measurement particle beam CT image generation method, and the CT image generation program described above, and details thereof will be omitted.

In the particle beam therapy system of the second embodiment of the present invention, the measurement particle beam CT image generation method, and the CT image generation program, almost the same effects as those of the above-described first embodiment can be obtained, and the remaining range measuring device The size of 81 can be reduced and the accuracy of the stopping power distribution can be improved.

The above-mentioned effects peculiar to the present embodiment can be obtained even when the same particle beam is used as the treatment beam 90A and the measurement beam 90B. That is, in the particle beam therapy system, when the measurement particle beam CT image is generated, the measurement beam and the treatment beam can be separated by installing the collimeter 82 on the upstream side of the residual range measurement device 81 as in this embodiment. Even if the ion species are the same, the accuracy of the energy loss distribution can be improved, and the accuracy of generating the measured particle beam CT image can be improved. Therefore, the accuracy of the treatment plan and the accuracy of particle beam irradiation can be improved.

<Others>
The present invention is not limited to the above embodiment, and includes various modifications. 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 those having all the described configurations.

For example, as an irradiation method of the measurement beam 90B, a discrete spot irradiation method in which the current is stopped between spots has been described as an example, but the same can be applied to a continuous spot irradiation method in which the beam current is not stopped between spots. In addition to this, the present invention is also applied to an irradiation method such as a wobbler method or a double scatterer method in which the distribution of particle beams is expanded and then a dose distribution that matches the shape of the target is formed using a collimator or a bolus. be able to. Similarly, the irradiation method of the treatment beam 90A is not particularly limited.

Further, as the accelerator 20, in addition to the synchrotron accelerator 22 described in the embodiment, various known accelerators such as a cyclotron accelerator and a synchrotron accelerator can be used.

Further, although the case where the stopping power ratio is used for the physical quantity to be measured and obtained by the measurement beam 90B has been described, it is also possible to use the stopping power or the water equivalent thickness instead of the stopping power ratio.

5 ... Patient (irradiated body)
11 ... Overall control device 12 ... Accelerator / beam transport system control device 13 ... Irradiation nozzle control device 20 ... Accelerator 21 ... Injector 22 ... Synchrotron accelerators 23A, 23B ... Ion source 30 ... Beam transport system 31 ... Deflection electromagnet 40 ... Irradiation Nozzles 41A, 41B ... Scanning electromagnet 42 ... Dose monitor 43 ... Position monitor 44 ... Ridge filter 45 ... Range shifter 50 ... Treatment table 51 ... Affected area (irradiation target)
61A, 61B ... Scanning electromagnet power supply 71 ... Scanning electromagnet power supply control device 72 ... Dose monitor control device 73 ... Position monitor control device 80 ... Measurement particle beam CT image creation device 81 ... Remaining range measurement device (monitor)
82 ... Collimator 90 ... Beam 90A ... Treatment beam 90B ... Measurement beam

Claims (6)

A particle beam therapy system that irradiates an irradiated object of an irradiated body with a charged particle beam.
As the charged particle beam, a first charged particle beam and a second charged particle beam having a different particle type from the first charged particle beam can be irradiated.
An accelerator that accelerates the first charged particle beam and the second charged particle beam,
An irradiation device that irradiates the irradiation target with the first charged particle beam or the second charged particle beam accelerated by the accelerator.
A monitor arranged at positions facing each other across the irradiated body and measuring the energy of the first charged particle beam,
The first stopping power distribution of the irradiated body with respect to the first charged particle beam is obtained based on the energy measured by the monitor, and the second stopping power distribution with respect to the second charged particle beam is obtained based on the first stopping power distribution. It is equipped with a particle beam CT image generator that calculates the stopping power distribution.
In the combination of the first charged particle beam and the second charged particle beam, the first charged particle beam is a proton beam and the second charged particle beam is a helium beam, or the first charged particle beam is helium. A particle beam therapy system characterized in that the second charged particle beam is one of a combination of carbon beams. In the particle beam therapy system according to claim 1,
The monitor is a particle beam therapy system characterized in that a collimator is provided on the upstream side with respect to the traveling direction of the first charged particle beam. In the particle beam therapy system according to claim 1 or 2.
The monitor is a particle beam therapy system characterized in that the energy loss distribution of the first charged particle beam can be measured. An irradiation step of irradiating an irradiated body having an irradiation target with a proton beam or a helium beam,
Among the proton beam or helium beam irradiated in the irradiation step, a measurement step of measuring the energy of the proton beam or helium beam transmitted through the irradiated body with a monitor.
A measurement blocking power ratio distribution calculation step for obtaining a stopping power ratio distribution of the irradiated body with respect to the proton beam or the helium beam based on the energy measured by the monitor.
Based on the stopping power distribution for the proton beam obtained by the measurement step, the stopping power distribution for the irradiated object to the helium beam, or the stopping power distribution for the helium beam obtained. A method for generating a measurement particle beam CT image, which comprises a therapeutic stopping power distribution calculation step for calculating the stopping power distribution of the irradiated body with respect to carbon rays. In the measurement particle beam CT image generation method according to claim 4.
In the measurement step, a measurement particle beam CT image generation method characterized in that a collimator is arranged on the upstream side of the monitor. A step of calculating the distribution of the amount of energy loss for each irradiation angle based on the energy of the first charged particle beam irradiated to the irradiated body and the remaining range of the first charged particle beam transmitted through the irradiated body. ,
A step of generating a CT image of the irradiated body based on the energy loss amount, and
A step of calculating the first stopping power ratio distribution, which is the stopping power ratio distribution with respect to the first charged particle beam, based on the energy loss amount and the CT image.
It has a step of converting the first stopping power ratio distribution into a second stopping power distribution which is a stopping power ratio distribution for a second charged particle beam having a particle type different from that of the first charged particle beam.
In the combination of the first charged particle beam and the second charged particle beam, the first charged particle beam is a proton beam and the second charged particle beam is a helium beam, or the first charged particle beam is helium. A CT image generation program characterized in that the second charged particle beam is one of a combination of carbon beams.

Images