JP6358948B2 - Particle beam irradiation apparatus and control method of particle beam irradiation apparatus - Google Patents

Description

  The present invention relates to a particle beam irradiation apparatus and a method for controlling the particle beam irradiation apparatus.

  As a beam extraction control method of a charged particle beam accelerator that can reduce the cost of an irradiation dose control system and reduce an irradiation dose error, for example, Patent Document 1 includes a charged particle beam accelerator, and this charged particle beam accelerator. In the charged particle beam irradiation system in which the charged particle beam emitted from the irradiation object is transported to the installation position of the irradiated object, and the transported charged particle beam is irradiated to a specific irradiation site of the irradiated object, at least 1 An invention in which the emission beam intensity of the charged particle beam emitted from the charged particle beam accelerator is changed in two or more stages within one irradiation corresponding to the irradiation of the planned dose set in advance for the irradiation site of Have been described.

JP 2007-31125 A

  2. Description of the Related Art A treatment method is known in which an affected area of a patient such as cancer is irradiated with a charged particle beam (also referred to as ion beam or particle beam) such as proton or carbon ion. The particle beam irradiation apparatus used for this treatment includes a charged particle beam generation apparatus, a beam transport system, and an irradiation apparatus.

  As an irradiation method of the irradiation device, a scatterer method in which a beam is expanded by a scatterer and then cut out according to the shape of the affected area, or a scanning method in which a fine beam is scanned in the affected area is known.

  In the particle beam irradiation apparatus using the scanning method, the charged particle beam accelerated by the accelerator of the charged particle beam generation apparatus reaches the irradiation apparatus through the beam transport system, and is scanned by the scanning electromagnet provided in the irradiation apparatus. Thereafter, the affected area of the patient is irradiated from the irradiation device.

  This scanning method includes a spot scanning method and a raster scanning method.

  The spot scanning method divides the irradiation plane of the affected area into dose management areas called spots, stops scanning for each spot, irradiates the beam until it reaches the set irradiation dose, stops the beam, and then performs the next irradiation Move to the spot position. Thus, the spot scanning method is an irradiation method in which the irradiation start position is updated for each spot.

  In the raster scanning method, a dose management region is set in the same manner as the spot scanning method, but the beam is irradiated while scanning the scanning path without stopping the beam scanning for each spot. Therefore, the uniformity of the irradiation dose is improved by lowering the irradiation dose per time and performing repaint irradiation that repeatedly irradiates a plurality of times. Thus, the raster scanning method is an irradiation method in which the irradiation start position is updated for each scanning path.

  In spot scanning irradiation using a charged particle beam accelerator, an irradiation dose error for each spot is required to be 1% or less, and a particle beam irradiation apparatus is constructed on the premise of this. Naturally, even in a particle beam irradiation apparatus using a raster scanning method or a scatterer method, it is required to reduce an irradiation dose error as much as possible.

  When a synchrotron is used as a charged particle beam accelerator, a method of controlling beam emission at high speed is used. Here, the beam blocking time considering the entire system is finite. For example, depending on the synchrotron, the time to stop the charged particle beam may be about 1 ms, which is longer than the time for irradiating the spot. In this case, there is a problem that the beam stop is long, which affects the dose count to the next layer.

  Further, as described in Patent Document 1, an emitted beam of a charged particle beam emitted from a charged particle beam accelerator within one irradiation corresponding to irradiation of a predetermined planned dose for at least one irradiation site. When the intensity is changed in two or more stages, since the timing of changing depends on the planned dose, very fine control is required.

  For example, when the spot scanning method is adopted in the technique described in Patent Document 1, it is necessary to change the beam intensity according to the planned dose for each spot, and very fine control is required. Very fine control is very difficult to implement.

  The present invention has been made to solve such problems, and provides a particle beam irradiation apparatus and a method for controlling the particle beam irradiation apparatus that can reduce an irradiation dose error by simple means. The purpose is to provide.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present invention includes a plurality of means for solving the above-described problems. For example, an accelerator for accelerating and emitting a charged particle beam, and a spot formed by dividing an irradiation target into a plurality of irradiation regions. comprising an irradiation unit for morphism irradiation of the charged particle beam in a planned order, and a control device for controlling the accelerator and the irradiation device, the controller, the spot immediately before moving to a remote spot and control point The control is performed to reduce the intensity of the charged particle beam from irradiation of a spot a predetermined number before the control point .

  According to the present invention, the irradiation dose error can be reduced by simple means.

It is a conceptual diagram which shows the whole structure of the heavy particle beam irradiation system which is one Embodiment of the particle beam irradiation apparatus of this invention. It is a conceptual diagram showing the detail of the scanning irradiation apparatus of the heavy particle beam irradiation system which is one Embodiment of the particle beam irradiation apparatus of this invention. It is a conceptual diagram showing an example of the dose distribution irradiated in each layer in order to ensure the uniformity of the dose distribution in an affected part area | region. It is a figure showing an example of the layering of the affected part area | region which is the irradiation object of the particle beam irradiation apparatus shown in FIG. It is a part of the treatment plan information planned with the treatment plan apparatus shown in FIG. 1, and is a figure which shows an example of the content of the command signal which implements the scanning irradiation of each layer at the time of irradiation. It is a figure showing an example of the affected part area | region which is the irradiation object of the particle beam irradiation apparatus shown in FIG. It is a time chart figure of control of the feedback current target value of the charged particle beam of one embodiment of the particle beam irradiation apparatus of the present invention. It is the flowchart figure which showed an example of control of one Embodiment of the particle beam irradiation apparatus of this invention. It is a time chart figure of control of the feedback current target value of a comparison charged particle beam.

  A particle beam irradiation apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, a heavy particle beam irradiation system such as carbon ions will be described as an example of the particle beam irradiation device.

  FIG. 1 is a schematic diagram of a heavy particle beam irradiation system that is a particle beam irradiation apparatus of the present embodiment, and FIG. 2 is a schematic diagram of a scanning irradiation apparatus that constitutes the particle beam irradiation apparatus of the present embodiment.

  In FIG. 1, a heavy particle beam irradiation system performs treatment by irradiating an affected area 31 of a patient 30 fixed to a treatment bed in a treatment room with a charged particle beam (heavy particle beam). 1, a beam transport system 4 connected to the downstream side of the charged particle beam generator 1, a scanning irradiation device 15 connected to the transport system 4 to irradiate the affected part 31 of the patient 30, and these charged particles A control system 90 is provided for controlling the beam generator, the beam transport system, and the scanning irradiation device 15 based on the treatment plan.

  The charged particle beam generator 1 includes an ion source (not shown), a pre-stage charged particle beam generator (linac) 11, and a synchrotron (accelerator) 12. The synchrotron 12 has a high-frequency application device 9 and an acceleration device 10. The high-frequency applying device 9 is configured by connecting a high-frequency applying electrode 93 and a high-frequency power source 91 arranged on the orbit of the synchrotron 12 by an open / close switch 92.

  The acceleration device (charged particle beam energy changing device) 10 includes a high-frequency accelerating cavity (not shown) arranged in its orbit and a high-frequency power source (not shown) for applying high-frequency power to the high-frequency accelerating cavity. .

  Heavy particle ions generated in the ion source are accelerated by a pre-stage charged particle beam generator 11 (for example, a linear charged particle beam generator).

  The ion beam (heavy particle ion beam) emitted from the previous charged particle beam generator 11 is incident on the synchrotron 12.

  The ion beam, which is a charged particle beam, is accelerated by the synchrotron 12 by being given energy by a high-frequency power applied to the ion beam from a high-frequency power source through a high-frequency acceleration cavity.

  After the energy of the ion beam that circulates in the synchrotron 12 is increased to a set energy (for example, 100 to 200 MeV), the high frequency for emission from the high frequency power supply 91 is applied to the high frequency via the closed open / close switch 92. It reaches the electrode 93 and is applied to the ion beam from the high-frequency applying electrode 93.

  The ion beam orbiting within the stability limit moves outside the stability limit by the application of this high frequency, and is emitted from the synchrotron 12 through the extraction deflector 8. When the ion beam is emitted, the current guided to the quadrupole electromagnet 13 and the deflection electromagnet 14 provided in the synchrotron 12 is held at the current set value, and the stability limit is also kept almost constant.

  By opening the open / close switch 92 and stopping the application of the high-frequency power to the high-frequency application electrode 93, the extraction of the ion beam from the synchrotron 12 is stopped.

  The ion beam emitted from the synchrotron 12 is transported downstream from the beam transport system 4. The beam transport system 4 includes a quadrupole electromagnet 21, a quadrupole electromagnet 22, a quadrupole electromagnet 21, a quadrupole electromagnet 22, a quadrupole electromagnet 21, a quadrupole electromagnet 22, and a quadrupole electromagnet 22, A deflection electromagnet 23 and a deflection electromagnet 24 are provided. The ion beam introduced into the beam transport system 4 is transported to the scanning irradiation device 15 through the beam path 62.

  A rotating gantry (not shown) is installed inside the treatment room, and the scanning irradiation device 15 is installed on a substantially cylindrical rotating drum (not shown) of the rotating gantry together with a part of the beam transport system. Yes. The rotating drum can be rotated by a motor (not shown), and a treatment gauge (not shown) is formed in the rotating drum.

  In the casing (not shown) of the scanning irradiation device 15, an incident position monitor (FIG. 1) detects the incident position of the beam from the upstream side in the beam traveling direction (the lower direction in FIGS. 1 and 2 and the Z direction in FIG. 2). Scanning electromagnets 5A and 5B for scanning the beam, a beam position monitor 6A for detecting the beam scanning position, a dose monitor 6B for detecting the irradiation dose at the beam scanning position, and the like are installed.

  The scanning electromagnets 5A and 5B are for, for example, deflecting the beam in directions orthogonal to each other (X direction and Y direction) on a plane perpendicular to the beam axis and moving the irradiation position in the X direction and the Y direction.

  As shown in FIG. 2, these scanning electromagnets 5A and 5B are connected to scanning electromagnet power supplies 7A and 7B, and power supply control for controlling the current supplied from the scanning electromagnet power supplies 7A and 7B to the scanning electromagnets 5A and 5B. A device 42 is provided. The power supply control device 42 controls the supply current to the scanning electromagnets 5A and 5B according to the control signal from the scanning controller 41, and controls the excitation magnetic fields of the scanning electromagnets 5A and 5B, respectively. The charged particle beams are deflected by the excitation magnetic fields of the scanning electromagnets 5A and 5B controlled in this way.

  The beam position monitor 6A detects whether or not the beam scanning position by the scanning electromagnets 5A and 5B is at the control position (set value), and the detection signal is output to the scanning position measuring device 11A to determine the beam scanning position. The calculation data is output to the scanning controller 41.

Dose monitor 6B is adapted to detect the radiation dose of the beam scanned by the beam position monitor 6A, the dose values are output to the detection signal is the dose measuring device 11 A is calculated, the operation data scanning controller 41 Is output. The scanning controller 41 compares the calculation data input from the dose monitor 6B with the set dose value in the treatment plan information stored in the memory, and outputs the high frequency signal for extraction so that the difference becomes zero. 91, so-called feedback control is performed.

  Returning to FIG. 1, the treatment bed 29 is moved by a bed driving device (not shown) and inserted into the treatment gauge before irradiating the ion beam from the scanning irradiation device 15, and is also attached to the scanning irradiation device 15. Positioning for irradiation is performed. The rotating drum is rotated by controlling the rotation of the motor by a gantry controller (not shown), so that the beam axis of the scanning irradiation device 15 faces the affected part 31 of the patient 30.

  The ion beam introduced into the scanning irradiation device 15 from the inverted U-shaped beam transport device via the beam path 62 is sequentially scanned at the irradiation position by the scanning electromagnets (charged particle beam scanning devices) 5A and 5B. The affected part (for example, cancer or tumor occurrence site) 31 is irradiated. The irradiated ion beam releases its energy at the affected area 31 to form a high dose region.

  Next, the control system 90 with which the particle beam irradiation apparatus of this embodiment is provided is demonstrated using FIG. 1 and FIG.

The control system 90 includes a database 110 for storing treatment planning data created by the treatment planning system 140, the charged particle sub-beam generator 1 and the beam transport system 4 accelerator and transport system controller 40 for controlling (hereinafter, referred to as the accelerator controller 40 ), A scanning controller 41 that controls the scanning irradiation device 15, and a central controller 100 that controls the accelerator controller 40 and the scanning controller 41 based on the treatment plan data read from the database 110.

  The treatment plan information (patient information) for each patient stored in the database is not particularly shown, but data such as patient ID number, dose (per dose), irradiation energy, irradiation direction, irradiation position, etc. Contains.

  The central control device 100 reads the treatment plan information related to the patient 30 to be treated from the database 110 in accordance with patient identification information input from an input device such as a keyboard or a mouse. The control pattern for supplying excitation power to each electromagnet already described is determined based on the irradiation energy value in the patient-specific treatment plan information.

  A power supply control table is stored in advance in the memory in the central controller 100, and charging including the synchrotron 12 is performed according to various values (70, 80, 90,... [Mev], etc.) of irradiation energy. A supply excitation power value or a pattern for the quadrupole electromagnet 13 and the deflection electromagnet 14 in the particle beam generator 1, the quadrupole electromagnet 18 in the beam transport system 4, the deflection electromagnet 17, the quadrupole electromagnets 21 and 22, and the deflection electromagnets 23 and 24 are set in advance. ing.

  Further, the CPU in the central controller 100 uses the treatment plan information and the power supply control table, and the charged particle beam generator 1 related to the patient who is about to receive treatment and the electromagnets arranged in each beam path. Control command data (control command information) for controlling the control is created. The control command data created in this way is output to the scanning controller 41 and the accelerator controller 40.

  In the heavy particle beam irradiation system according to the present embodiment, the central control device 100, the scanning controller 41, and the accelerator controller 40 perform control in cooperation with each other based on the treatment plan information created by the treatment plan device 140. These controls will be described.

  First, the relationship between the depth of the target and the energy of the ion beam will be described. The target is an ion beam irradiation target region including the affected part 31 and is somewhat larger than the affected part 31. FIG. 3 shows an example of the relationship between the depth inside the body and the dose due to the ion beam. The charged particle beam imparts extremely large energy to the surroundings when it loses energy and stops, so it has a dose peak at its depth of arrival. This dose peak is called the Bragg peak.

  The target is irradiated with the ion beam at the position of the Bragg peak. The position of the Bragg peak changes depending on the energy of the ion beam. Therefore, the target is divided into a plurality of layers (slices) in the depth direction (the direction in which the ion beam travels in the body), and the ion beam energy is changed in accordance with the depth (each layer), thereby increasing the thickness in the depth direction. It is possible to irradiate the ion beam uniformly over the entire target (target region) having Based on such a viewpoint, the treatment planning apparatus 140 determines the number of layers that divide the target region in the depth direction.

  FIG. 4 is a diagram illustrating an example of the layers determined as described above. In this example, the affected part 31 is divided into four layers of layers 1, 2, 3, 4 from the lowermost layer toward the body surface of the patient 30. Each layer is an example having a spread of 20 cm in the X direction and 10 cm in the Y direction. The dose distribution in FIG. 3 is a dose distribution in the depth direction in the section AA ′ in FIG. 4.

  After the number of layers is determined as described above, the treatment planning apparatus 140 determines the number of spots (irradiation positions) to be divided in the direction perpendicular to the depth direction within each layer (target cross section).

  In addition, in all spots, one spot may be divided and irradiated several times, and even if the variation in irradiation dose for each spot is within a certain range, the dose distribution is almost uniform throughout the target. The number of irradiations and the irradiation amount per target (target irradiation amount) are determined.

  The central control device 100 reads out the treatment plan information planned as described above and stored in the database 110 and stores it in the memory. Based on the treatment plan information stored in the memory, the CPU of the central control device 100 provides information related to ion beam irradiation (number of layers, number of irradiation positions (number of spots), irradiation position in each layer, and irradiation position in each irradiation position. Target irradiation amount (set irradiation amount), beam intensity at that time, beam size (size adjustment (whether scatterers are present)), and information such as current values of scanning electromagnets 5A and 5B regarding all spots of each layer) are generated. To the scanning controller 41.

  Part of the transmitted treatment plan information is shown in FIG. Information on the X-direction position (X position) and Y-direction position (Y position) of the irradiation position (spot) for each irradiation position in the layer, the target irradiation amount (set dose) at each irradiation position, and a layer change flag Information is included and spot numbers are assigned in the order of irradiation. In this embodiment, irradiation is performed in order from the deepest layer from the body surface. The target dose (set dose) at each irradiation position is an integrated dose (integrated dose) starting from the first irradiation start on the affected area 31, and the central controller 100 determines the target dose for each irradiation position. Information on the target dose to be transmitted to the scanning controller 41 is generated by sequentially integrating the set individual doses. The scanning controller 41 stores these treatment plan information in a memory.

  FIG. 5 shows an example of the case where the divided irradiation is not performed. When the divided irradiation is performed, the X-direction position (X position) and the Y-direction position (Y position) of the irradiation position (spot) are further increased by the number of the divided irradiation. ) And target irradiation dose (set dose) at each irradiation position are necessary, and the treatment plan information in FIG. 5 includes such information.

  Further, the CPU of the central controller 100 transmits all the acceleration parameters of the synchrotron 12 related to all layers in the treatment plan information to the accelerator controller 40. These acceleration parameter data transmitted here are classified in advance into a plurality of acceleration patterns.

  FIG. 6 is a diagram showing an example of the positional relationship between an irradiation target and an important organ on a slice having CT data. As shown in FIG. 6, for example, there is a case where the affected part 31 is adjacent to an important organ 32 such as a spine. Since the important organ 32 is a region where the irradiation dose should be suppressed as much as possible, it is required to sufficiently irradiate the affected part 31 located on both sides of the important organ 32 while reducing the exposure of the important organ 32. In such a case, it is necessary to move to a remote spot after the irradiation of the spot adjacent to the important organ 32 is completed. When the important organ 32 is adjacent to the affected part 31, the position of the important organ is also stored in the memory.

  If irradiation of the spot just before moving to such a remote spot is performed with the same beam intensity as usual, it takes time to stop the beam, so that the spot where you do not want to irradiate the beam is irradiated with the beam. In order to suppress this, there arises a problem that the scanning electromagnet cannot be scanned until the beam stop is confirmed, which may hinder further shortening of the irradiation time.

  In addition, when changing the layer, if the beam intensity is reduced from the point where the last spot irradiation of the layer is completed, the beam that leaks and exits before the beam is stopped is counted by the dose count of the next layer, which is accurate. Dose counting could be difficult.

  Therefore, in this embodiment, first, in the treatment planning apparatus 140, a control point (CP) that is an arbitrarily planned beam stop timing, such as a layer change or a spot immediately before moving to a remote spot, is newly defined. And stored in memory as part of the treatment plan information. Further, as shown in FIG. 7, the beam intensity is decreased from a point in time before reaching the control point several MU (monitor unit) before the predetermined timing, for example, the intensity is 1/10 of the planned value. Take control. FIG. 7 is a time chart for controlling the feedback current target value of the charged particle beam according to this embodiment.

  More specifically, the scanning controller 41 monitors the calculation data of the irradiation dose of the beam input from the dose monitor 6B, and reaches several MU units before a predetermined timing to reach the control point stored as the treatment plan information. When it is confirmed that the frequency reaches the feedback target value for outputting the high-frequency signal for extraction to the high-frequency power supply 91, the difference from the calculation data input from the dose monitor 6B becomes zero. Feedback control is performed.

Since the time Td required for stopping the charged particle beam is substantially constant (˜1 ms), the number MU for starting the beam intensity reduction control is determined from the intensity of the charged particle beam current and the time required for stopping the beam. The central control device 100 can calculate and set in advance the number of spots before the expiration of the dose of the control point to be lowered the feedback target value. The determination timing that the number of MUs has been reached may be any of the timing of starting irradiation of the spot before the number MU, during irradiation, and at the end of irradiation, and can be arbitrarily set.

  Next, each control of the central control apparatus 100, the scanning controller 41, and the accelerator controller 40 when performing spot scanning irradiation in this embodiment is demonstrated using FIG. FIG. 8 shows an example of a control flow for executing each control.

  First, when an irradiation start instructing device (not shown) in the treatment room is operated, the central control device 100 accordingly sets the operation i representing the layer number and the operator j representing the spot number to 1 in step 201. , And output them to the accelerator controller 40.

  The accelerator controller 40 makes initial settings accordingly. After completion of the initial setting, in step 202, the accelerator parameters for the i-th layer (i = 1 at this time) are read out and set from the acceleration parameters of a plurality of patterns stored in the memory.

  In step 203, these setting parameters are output to the synchrotron 12 and the beam transport system 4, and the power supply is controlled so that each electromagnet power supply is excited with a set predetermined current. In addition, a high frequency power source that applies high frequency power to the high frequency acceleration cavity is controlled to increase the high frequency power and frequency to a predetermined value.

  As described above, when the energy of the ion beam circulating in the synchrotron 12 is increased to a value determined in the treatment plan, the accelerator controller 40 proceeds to step 204 and scans via the central controller 100. An output preparation command is output to the controller 41.

  In response to this extraction preparation command, the scanning controller 41 determines in step 205 the current value data stored in the memory (data shown in the columns “X position” and “Y position” in FIG. 5) and the target irradiation amount. The current value data and target dose data of the j-th spot (j = 1 at this time) are read out from the data (data shown in the column “target dose” in FIG. 5) and set. Here, the scanning controller 41 controls the corresponding power supply so that the scanning electromagnets 5A and 5B are excited with the current value of the j-th spot.

  As described above, after the preparation for irradiation of the spot is completed, the scanning controller 41 outputs a beam extraction start signal to the accelerator controller 40 (third control device) via the central control device 100 in step 206. To do.

  Accordingly, the accelerator controller 40 controls the high frequency applying device 9 to emit an ion beam from the synchrotron 12 in step 207. That is, the open / close switch 92 is closed by the beam extraction start signal from the accelerator controller 40 and a high frequency is applied to the ion beam from the high frequency application electrode 93, so that the ion beam is emitted from the synchrotron 12.

  Since the scanning electromagnets 5A and 5B are excited so that the ion beam reaches the position of the j-th spot, the ion beam is irradiated to the j-th spot of the corresponding layer from the scanning irradiation device 15 in step 208A. Is done.

  The j-th spot (irradiation position) is detected by the beam position monitor 6A, and the beam scanning position is calculated by the scanning position measuring device 11A. The irradiation dose to the j-th spot is detected by the dose monitor 6B, the dose value is calculated by the dose measuring device 11B, and the calculation result is input to the scanning controller 41.

  In step 208B, the scanning controller 41 compares the set target irradiation amount with the input calculation result, and the number of control points whose current irradiation spot is an event flag such as a layer change or movement to a remote spot. Upon confirming that the MU has been reached, in step 208C, the scanning controller 41 goes through the central controller 100 and the accelerator controller 40 (third controller) to set the feedback beam intensity to 1/10 times. ) To output a beam emission intensity decrease start signal.

  Thereby, the accelerator controller 40 controls the high-frequency applying device 9 to reduce the intensity of the ion beam emitted from the synchrotron 12 to 1/10 and continues the emission in step 208D.

  Thereafter, in step 209, the scanning controller 41 continues to compare the set target irradiation amount with the input calculation result. When the irradiation dose to the j-th spot reaches the target irradiation amount, step 210 is performed. And a beam extraction stop command is output to the accelerator controller 40 via the central controller 100.

  Accordingly, in step 211, the open / close switch 92 is opened via the accelerator controller 40, and the extraction of the ion beam is stopped.

  As described above, when the irradiation with respect to the first spot is completed, in step 212A, it is determined whether or not the spot is adjacent to the important organ 32. If the determination is “Yes”, the process proceeds to step 213. 1 is added to the number (ie, the irradiation position is moved to the next spot (remote spot)). If the determination is “No”, the process proceeds to step 212B, and then in step 212B, it is determined whether or not the spot is the last spot in the layer. Since the determination is “No”, the process proceeds to step 213, and the spot number is set to 1. Added (ie, the irradiation position is moved to the next spot).

  And the process of steps 205-213 is performed repeatedly. That is, the scanning electromagnets 5A and 5B sequentially move the ion beam to adjacent spots until the irradiation of all the spots of the first layer is completed (while the irradiation of the ion beam is stopped during the movement). Then, ion beam irradiation is performed (spot scanning irradiation).

  When irradiation with respect to all the spots of the first layer is completed, the determination is “Yes” in step 212B, and the scanning controller 41 outputs a layer change command to the accelerator controller 40 via the central controller 100. .

  In addition, when performing divided irradiation, the following process is performed before outputting a layer change command in step 21B. That is, when the operator j representing the spot number is initially set to 1, it is determined whether the operator n representing the number of times of divided irradiation has reached a preset number of divisions, and the determination is “No” 1 is added to the number of times of irradiation n (that is, the divided irradiation is changed to the next number of times of irradiation), the processing of steps 205 to 213 is repeatedly performed, and the number of times of irradiation of divided irradiation is set in advance. When the number is reached, a layer change command is output to the accelerator controller 40 in step 212.

  When a layer change command is output from the scanning controller 41, the accelerator controller 40 receives it and adds 1 to the layer number i in step 214 (that is, the irradiation position is changed to the second layer). In step 215, a beam deceleration command is output to the synchrotron 12.

  The accelerator controller 40 controls the power source of each electromagnet of the synchrotron 12 according to the output of the beam deceleration command to gradually reduce the excitation current of each electromagnet. Finally, a predetermined value such as the next ion beam is used. Use an excitation current suitable for incidence. As a result, the ion beam circulating in the synchrotron 12 is decelerated.

  At this time, since the irradiation of the first layer is only completed and the determination in step 216 is “No”, the process returns to step 202 and the processing of steps 203 to 215 is repeated for the second layer. Done.

  Similarly, after the processing in steps 202 to 215 is executed for all layers, the determination in step 216 is “Yes”, and the predetermined irradiation to all spots in all layers in the affected area of the patient 30 is completed. To do. As a result, the accelerator controller 40 outputs an irradiation end signal to the CPU in step 217 to the central controller 100.

  Thus, a series of irradiation processes on the affected area of the patient 30 is completed.

  Next, the effect of this embodiment is demonstrated with reference to FIG. 7 and FIG. FIG. 9 is a time chart of control of a feedback current target value of a comparative charged particle beam.

  As shown in FIG. 9, as described in Patent Document 1, charged particles emitted from a charged particle beam accelerator within one irradiation corresponding to irradiation of a predetermined planned dose with respect to at least one irradiation site. When changing the output beam intensity of the beam in two or more stages, as described in paragraph (0023) of Patent Document 1, it is not limited to irradiation of a spot corresponding to the final spot reaching the control point in the present invention. Control is performed to decrease the beam intensity when the ratio of the irradiation dose to the planned irradiation dose of the final spot reaching the control point reaches a predetermined value. However, as described above, the beam blocking time is finite. Further, in the control for narrowing the separation parameters as described in Patent Document 1, it is very difficult to control the beam intensity in detail. For example, there is a problem that the separatrix is narrowed more than necessary and the beam current is greatly reduced, or the beam current is hardly changed without being almost narrowed. For this reason, the beam intensity does not decrease as set, the beam intensity decreases more than necessary, and it is very difficult to perform stable control. For this reason, it is impossible to change the layer or move to a remote spot until confirmation of beam stoppage, and it is difficult to shorten the irradiation time and suppress the occurrence of dose counts on the next spot. It was also difficult. In the first place, it took time to control the separatrix itself (on the order of several hundred microseconds), and it was difficult to shorten the irradiation time.

  On the other hand, in this embodiment, as shown in FIG. 7, before a predetermined timing to reach a control point that is an arbitrarily planned beam stop timing, such as a layer change or a spot immediately before moving to a remote spot. Control is performed to reduce the beam intensity from the point of time before reaching several MU units.

  As a result, even if the stop time of the charged particle beam is finite, the beam intensity can be reduced with a sufficient margin, and thus the absolute value of the beam intensity emitted during the finite stop time can be reduced. And the error of the irradiation dose can be reduced.

  In addition, by defining a control point that is an arbitrarily planned beam stop timing, and reducing the beam intensity before the number of control points MU, the beam intensity can be reduced at an arbitrary timing. Therefore, it is possible to flexibly cope with a case where it is desired to reduce the irradiation dose or change of the layer, and it is possible to further improve the irradiation accuracy and shorten the irradiation time by speeding up the change of the setting parameter.

<Other embodiments>
In the above-described embodiment, the spot scanning method for stopping the emission of the particle beam for each spot has been described as an example. However, the present invention can also be applied to a raster scanning method or a line scanning method that does not stop the emission of the particle beam.

  For example, in the raster scanning method, unlike the spot scanning method, the ion beam is moved by the scanning electromagnets 5A and 5B without stopping the ion beam irradiation until the irradiation of all the spots of the first layer is completed. While irradiating with an ion beam. In the line scanning method, the ion beam irradiation is performed while moving the ion beam by the scanning electromagnets 5A and 5B without stopping the ion beam irradiation on any of the XY planes, and the irradiation is stopped on the other side. .

  Other configurations and controls are substantially the same as those in the above-described embodiment, and thus description thereof is omitted.

  Also, not limited to the spot scanning method or raster scanning method described above, when irradiating a beam according to the shape of the affected area with an irradiation device, the beam diameter is enlarged with a scatterer, and then the periphery is shaved with a collimator to shape the beam It can also be applied to the scatterer method.

<Others>
In addition, this invention is not restricted to said embodiment, A various deformation | transformation and application are possible. The above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described.

  For example, in the above-described embodiment, the case where control is performed to reduce the feedback beam intensity to 1/10 when reaching the number MU before the control point has been described as an example, but the beam intensity setting value is decreased in the treatment planning stage. It can be a control.

  Further, the beam intensity reduction rate may be set arbitrarily.

  Furthermore, although the case where the feedback control is performed by the scanning controller 41 has been described, the feedback control can be performed by any controller in the central control apparatus 100, and the feedback control need not be performed in the first place.

  Further, although the case where a high frequency application electrode is used as the beam extraction device has been described as an example, the beam extraction device is not limited to the high frequency application electrode, and an emission quadrupole electromagnet, a betatron core, or the like may be used.

  Furthermore, although the synchrotron is shown as an example of the heavy particle beam accelerator, the accelerator may be a cyclotron or a linear accelerator.

  In addition, the heavy particle beam irradiation system that irradiates heavy particle ions such as carbon is shown as an example, but the charged particle beam irradiated to the irradiation target is not limited to heavy particle ions, protons that are lighter than heavy particles, or protons other than carbon It can be applied to heavier particles and neutrons.

1 ... charged particle beam generator,
4 ... Beam transport system,
5A, 5B ... scanning electromagnet (charged particle beam scanning device),
6A: Scanning position monitor (irradiation amount detection device),
6B ... Dose monitor (irradiation amount detection device),
7A: Scanning magnet power supply (X direction),
7B: Scanning magnet power supply (Y direction),
8 ... Deflector ,
9: High frequency application device (betatron vibration amplitude increasing device),
11A ... scanning position measuring device,
11B ... Dose measuring device,
12 ... Synchrotron (accelerator),
15 ... Scanning irradiation device,
40 ... Accelerator / transport controller,
41 ... Scanning controller,
42 ... power supply control device,
90 ... Control system (control device),
91 ... High frequency power supply,
92 ... Open / close switch,
93 ... High frequency application electrode (betatron vibration amplitude increasing device),
100: Central control unit,
140: Treatment planning device.

Claims (10)

An accelerator that accelerates and emits charged particle beams;
An irradiation device for morphism irradiation of the charged particle beam was designed spot formed by dividing the radiation into a plurality of irradiation regions order,
A controller for controlling the accelerator and the irradiation device;
The controller is
A particle beam irradiation apparatus characterized in that a control immediately before moving to a remote spot is used as a control point, and control is performed to reduce the intensity of the charged particle beam from irradiation to a spot a predetermined number of times before the control point . In the particle beam irradiation apparatus of Claim 1,
A planner for creating a plan for irradiating the charged particle beam;
The particle beam irradiation apparatus characterized in that the predetermined number of spots are planned from the planned beam stop dose and a preset time by the planning apparatus. In the particle beam irradiation apparatus of Claim 1,
A planner for creating a plan for irradiating the charged particle beam;
A particle beam irradiation apparatus characterized in that the planning apparatus plans the predetermined number of spots from a planned beam stop dose, a preset time, and a planned beam intensity. In the particle beam irradiation apparatus as described in any one of Claims 1 thru | or 3 ,
The accelerator has a betatron vibration amplitude increasing device,
The control device reduces the intensity of the charged particle beam from the predetermined number of times by controlling the output of the betatron vibration amplitude increasing device. In the particle beam irradiation apparatus as described in any one of Claims 1 thru | or 4 ,
The irradiation apparatus includes a beam monitor that measures the intensity of the charged particle beam emitted from the accelerator,
The control device performs feedback control so that the intensity of the charged particle beam measured by the beam monitor approaches a predetermined target beam intensity, and reduces the target beam intensity from the predetermined number before, thereby performing the charging. A particle beam irradiation apparatus characterized by reducing the intensity of a particle beam. In the particle beam irradiation apparatus as described in any one of Claims 1 thru | or 5 ,
Before SL control point, in addition to just before the spot moves to a remote spot, the particle beam irradiation apparatus which is a spot just before changing the layer to be irradiated. In the particle beam irradiation apparatus as described in any one of Claims 1 thru | or 5 ,
The control point, in addition to just before the spot moves to a remote spot, the particle beam irradiation apparatus which is a spot just before changing the energy of the charged particle beam emitted by the accelerator. In the particle beam irradiation apparatus as described in any one of Claims 1 thru | or 7 ,
The control device changes at least one setting parameter of the accelerator and the irradiation device after reaching the control point. In the particle beam irradiation apparatus according to claim 8,
The particle beam irradiation apparatus, wherein the setting parameter to be changed after reaching the control point is any one of beam energy, beam intensity, and a beam size changing scatterer. An accelerator for accelerating / extracting a charged particle beam, an irradiation device for irradiating the charged particle beam in an order planned for each spot formed by dividing an irradiation target into a plurality of irradiation regions, the accelerator, and the irradiation device A control method for a particle beam irradiation apparatus comprising a control device for controlling
A control method for a particle beam irradiation apparatus , wherein a spot immediately before moving to a remote spot is used as a control point, and the intensity of the charged particle beam is reduced from irradiation to a spot a predetermined number of times before the control point .

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