JP2008272139A - Charged particle beam irradiation system and charged particle beam emission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charged particle beam irradiation system capable of securing high safety and highly accurately performing irradiation with charged particle beams, and a charged particle beam emission method. <P>SOLUTION: The charged particle beam emitted from a charged particle beam generator is supplied to a scanning magnet for performing scanning on an irradiation surface vertical to a beam advancing direction, and on the basis of the position and dose on the irradiation surface of the charged particle beam which passes through the scanning magnet, the emission amount of the charged particle beams from the charged particle beam generator is controlled. To put it concretely, the supply of the charged particle beam to a region wherein a target dose is reached among the plurality of regions formed by division on the irradiation surface is stopped and the charged particle beams are supplied to the other regions wherein the target dose is not reached. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charged particle beam irradiation system and an extraction method, and more particularly to irradiation of a charged particle beam suitable for application to a particle beam therapy apparatus that irradiates an affected area with an ion beam such as protons or carbon ions. The present invention relates to a system and an emission method.

  2. Description of the Related Art A treatment method is known in which a diseased part of a patient such as cancer is irradiated with a charged particle beam (ion beam) such as protons or carbon ions. The ion beam irradiation system used for this treatment includes an ion beam generator, a beam transport system, and an irradiation device. The ion beam generator includes an ion source, a front stage accelerator, a circular accelerator, and the like. As the irradiation device, for example, there is a rotary irradiation device including an irradiation field forming device. The circular accelerator emits an ion beam that circulates along a circular orbit after accelerating to a target energy, and transports the ion beam to an irradiation field forming apparatus through a beam transport system. The irradiation field forming device shapes the dose distribution of the ion beam according to the shape of the affected area of the patient and irradiates the affected area.

  As the circular accelerator, for example, the one described in Patent Document 1 is known. Patent Document 1 discloses a synchrotron having means for circulating an ion beam along a circular orbit, means for increasing the betatron oscillation amplitude of the ion beam within the resonance stability limit, and an extraction deflector for extracting the ion beam from the circular orbit. Is disclosed. By increasing the betatron oscillation amplitude of the ion beam, the ion beam is moved out of the stability limit and emitted from the synchrotron to the beam transport system.

  In the treatment using an ion beam, the energy that releases most of the energy immediately before the ion stops to form a dose distribution called Bragg curve, and the Bragg peak that is the peak of the Bragg curve in the depth direction. The position can be controlled by controlling the magnitude of the energy of the ion beam incident on the body, the ion beam energy is appropriately selected, the ion beam is stopped in the vicinity of the affected area, and most of the energy is absorbed by the affected area. To give to cells. The width of the Bragg peak in the depth direction (beam traveling direction) is several mm. Usually, the affected area has a greater thickness in the depth direction. In order to effectively irradiate such an affected area with an ion beam in the depth direction of the entire affected area, a wide and uniform dose distribution (Spread Out Bragg) It is necessary to control the energy and irradiation amount of the ion beam so as to form (Peak: hereinafter referred to as SOBP).

  In general, the beam emitted from the accelerator has a Gaussian distribution in a direction perpendicular to the traveling direction (hereinafter referred to as a lateral direction), and the beam size (1σ) is about 1 to 5 mm. Usually, the affected area has a larger size in the lateral direction, so in order to effectively irradiate the ion beam across the entire affected area, a wide and uniform dose distribution of the affected area in the lateral direction is required. Need to form.

  From this point of view, as a conventional ion beam irradiation system, there is known a method of forming a uniform dose region by scanning a beam having a Gaussian distribution shape in a lateral direction in a circular or zigzag manner with a scanning magnet ( Non-patent document 1). In the wobbler method, a uniform dose distribution is formed at the center by setting the beam size and the beam scanning radius to optimum values. Patent Document 2 describes a method of forming a uniform dose distribution by scanning a beam in a Lissajous shape.

Japanese Patent No. 2596292 JP 2006-208200 A REVIEW OF SCIENTIFIC INSTRUMENTS Vol.64 No.8 (August 1993, pp. 2084-2089)

  In the above prior art, the amount of beam emitted from the accelerator is not necessarily constant, and the beam emission amount may change with time while scanning the beam. For this reason, when an extreme change in beam intensity occurs, a situation where uniform irradiation cannot be performed within the planned irradiation dose may occur. In order to avoid this, it is necessary to make the beam scanning speed sufficiently faster than the time change of the beam intensity and to average the change of the beam emission amount temporally by scanning the irradiation region many times. is there. Therefore, the dose distribution is not necessarily uniform during the irradiation, and there is a problem that it is difficult to obtain a dose distribution with a desired uniformity at the end of the irradiation. In addition, since it is necessary to use a power source that can change the excitation current supplied to the scanning electromagnet at high speed, there is a problem that the cost increases.

  An object of the present invention is to provide a charged particle beam irradiation system and a charged particle beam extraction method capable of ensuring high safety and irradiating a charged particle beam with high accuracy.

  The present invention supplies a charged particle beam emitted from a charged particle beam generator to a scanning magnet that scans an irradiation surface perpendicular to the beam traveling direction, and on the irradiation surface of the charged particle beam that has passed through the scanning magnet. Based on the position and the dose, the emission amount of the charged particle beam from the charged particle beam generator is controlled. Specifically, among a plurality of regions formed by dividing on the irradiation surface, the supply of the charged particle beam to the region that has reached the target dose is stopped, and the charged particles are applied to other regions that have not reached the target dose. Supply the beam. The position on the irradiation surface of the charged particle beam can be controlled by the magnetic field strength of the scanning magnet.

  The present invention stops the supply of a charged particle beam to a region that has reached a target dose among a plurality of regions formed by being divided on the irradiation surface, and charged particle beams to other regions that have not reached the target dose , The irradiation dose for each position in the lateral direction within the irradiation target can be easily adjusted (controlled). That is, according to the present invention, the dose distribution in the lateral direction within the irradiation target can be easily adjusted to a desired dose distribution. For this reason, it is possible to remarkably reduce the probability of erroneous irradiation that causes excessive or insufficient irradiation dose at each position in the horizontal direction within the irradiation target. Further, since a power source that changes the current at a high speed as in the conventional case is not necessary, the cost of the apparatus can be reduced.

  According to the present invention, the dose distribution in a direction perpendicular to the traveling direction of the charged particle beam in the irradiation target can be easily adjusted to a desired dose distribution. For this reason, it is possible to remarkably reduce the probability of erroneous irradiation that causes excessive or insufficient irradiation dose at each position in the beam traveling direction within the irradiation target.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of a particle beam therapy system (ion beam irradiation system) according to the present invention. As shown in FIG. 1, the particle beam therapy system includes an ion beam generator (proton beam generator) 1, a central controller 100, an irradiation field forming device 200, and an irradiation control system 300. The particle beam treatment apparatus irradiates the affected part 216a of the patient 216 fixed to the treatment bed 217 with an ion beam (for example, a proton beam).

  The central controller 100 determines irradiation conditions (beam irradiation direction, SOBP width, irradiation dose, maximum irradiation depth, irradiation field size, etc.) determined by the treatment planning apparatus 102 for forming an appropriate irradiation field in the affected area 216a. , And select nozzle device parameters such as device type, installation position, and set values, and accelerator operation parameters such as beam energy and beam intensity pattern. The central controller 100 includes a memory 101 and stores information as shown in FIG. Based on the information recorded (saved) in the memory 101, each nozzle device parameter is set in the irradiation field forming device 200 through the irradiation control system 300, and the accelerator operation parameter is set in the ion beam generator 1.

  The ion beam generator 1 includes an ion source 2, a pre-stage accelerator 3, a low energy beam transport system 4, and a synchrotron 5, and generates an ion beam having a predetermined beam energy. The ion beam generated by the ion source 2 is accelerated by the upstream accelerator 3 and supplied to the synchrotron 5 through the low energy beam transport system 4.

  The synchrotron 5 includes an acceleration device 6, an extraction high-frequency application device 7, an extraction deflector 13, a quadrupole electromagnet (not shown), and a deflection electromagnet 15 on its orbit. The high-frequency application device 7 includes a high-frequency application electrode (not shown) for emission, and is connected to the high-frequency supply device 12 for emission. The high-frequency supply device 12 includes a high-frequency power supply 8 for output, a signal synthesis device 10, and switches (opening / closing devices) 9 and 11. The switch 9 is a switch for interlock and irradiation completion. The switch 11 is an ON / OFF switch for a beam being irradiated.

  The high-frequency applying device 7 is supplied with high-frequency power from a high-frequency power source 8 via the closed switches 9 and 11 and the signal synthesis device 10. The ion beam orbiting the orbit of the synchrotron 5 is accelerated by applying a high frequency to a high frequency acceleration cavity (not shown) provided in the acceleration device 6. After the ion beam is accelerated to a desired energy (for example, 70 to 250 MeV), when the high frequency power from the high frequency power supply 8 is applied to the ion beam circulating in the synchrotron 5 by the high frequency application electrode, Is emitted from the synchrotron 5.

  The high-energy beam transport system 16 communicates the synchrotron 5 and the irradiation field forming apparatus 200 and is partially installed in the rotating gantry 14. The ion beam extracted from the synchrotron 5 is guided to the irradiation field forming apparatus 200 installed in the rotating gantry 14 via the high energy beam transport system 16. By adjusting the rotation angle of the rotating gantry 14, the patient 216 is irradiated with an ion beam from a desired direction.

  The irradiation field forming apparatus 200 will be described with reference to FIG. FIG. 2 is a detailed explanatory diagram of the irradiation field forming apparatus 200. The irradiation field forming device 200 is a device that shapes the ion beam generated by the ion beam generator 1 according to the shape of the affected part 216a. The irradiation field forming apparatus 200 includes a beam scanning electromagnet 202 attached via a holding member 203, a scatterer 206 attached via a holding member 207, and a ridge filter attached via a holding member 209 in the casing 201. 208, a range shifter 210 attached through a holding member 211, a dose monitor 212 and a beam position monitor 218 attached through a holding member 213, a bolus 214, and a collimator 215.

  The scanning electromagnet 202 scans the beam temporally to form a uniform dose distribution in the lateral direction of the affected area 216a. The scanning electromagnet 202 is connected to a scanning electromagnet power supply 219, and the scanning electromagnet power supply 219 is connected to a scanning electromagnet power supply controller 220. The scanning electromagnet 202 is composed of a pair of electromagnets that scan the beam in two directions (for example, the X direction and the Y direction) orthogonal to each other in a plane perpendicular to the beam traveling direction. The pair of electromagnets includes 202a that scans the beam in the X direction and 202b that scans the beam in the Y direction.

  The scanning electromagnet power source 219 supplies a current to the pair of scanning electromagnets 202 to generate a magnetic field and deflect the beam. Since the amount of deflection of the beam is determined by this supply current, the beam can be irradiated to an arbitrary position in the lateral direction by adjusting the supply current. The current set by the scanning electromagnet power supply controller 220 is supplied from the scanning electromagnet power supply 219 to the scanning electromagnet 202. The relationship between the current value supplied to the scanning electromagnet and the beam irradiation position is stored in advance in the memory 101 of the central controller 100.

  The set current value by the scanning electromagnet power supply control device 220 is transmitted to an area determination device 301 (see FIG. 3) provided in the irradiation control system 300. A magnetic field strength measuring device 205 is provided in the magnetic field generation region of the scanning electromagnet 202. The magnetic field strength measuring device 205 detects the magnetic field strength of the scanning electromagnet 202, and the detected magnetic field strength is transmitted to the region determination device 301 provided in the irradiation control system 300. By confirming that the region determination device 301 has the intended magnetic field strength based on the set current value, the safety during beam irradiation is improved.

  In the present embodiment, the excitation region (irradiation region) is determined based on the set excitation current value of the scanning electromagnet 202, but the excitation region is determined based on the measurement result (measurement value) of the magnetic field strength detected by the magnetic field strength measuring device 205. May be determined. In addition, since the excitation area can be determined from the beam position detected by the beam position monitor 218, it is possible to determine whether the beam is scanned in the desired area with the set magnetic field strength, thereby stabilizing the beam irradiation. Will improve.

  The scatterer 206 is for expanding the lateral distribution of the beam by the phenomenon of ion scattering by the substance. The spatial intensity distribution of the scattered beam is almost Gaussian. The scatterer 206 is generally composed of a substance having a large atomic number, such as tungsten, which has little energy loss with respect to the amount of scattering. The scatterer 206 may be a mixture of a plurality of substances. The scatterer 206 may be formed by stacking a plurality of plate members having different thicknesses, and the total thickness of the plate members in the beam traveling direction can be changed. In this embodiment, the scatterer 206 is disposed on the downstream side of the scanning electromagnet 202, but may be disposed on the upstream side of the scanning electromagnet 202.

  The ridge filter 208 is for forming a wide and uniform dose distribution by forming a plurality of energy regions in the beam and superimposing a plurality of Bragg peaks formed in the depth direction of the affected part 216a. The ridge filter 208 includes a plurality of wedge-shaped structures 208a and support portions 208b thereof. Openings are formed between adjacent wedge-shaped structures 208a. The wedge-shaped structure 208a has a plurality of planar regions arranged stepwise, and the thickness from the bottom surface of the ridge filter 208 to each planar region in the beam axis direction (traveling direction) is different. The wedge-shaped structure 208a is formed so that the thickness in the beam axis direction increases stepwise from the openings located on both sides thereof toward the flat region at the highest position in the beam axis direction.

  That is, in the ridge filter 208, the thickness of the portion through which the beam passes changes according to the beam passing position. As a result, the beam energy after passing through the ridge filter 208 is changed, and a Bragg peak is formed at different depths corresponding to each beam energy, thereby uniformly irradiating a wide region of a desired depth in the affected area 216a. A field can be formed.

  The ridge filter 208 reduces the difference in energy distribution at the lateral position by reducing the width in the direction (lateral direction) in which the thickness of the wedge-shaped structure 208a is different and reducing the difference in beam energy depending on the passing position. . The ridge filter 208 according to the present embodiment includes a plurality of wedge-shaped structures 208a having a plurality of planar regions arranged in a step shape. In addition, in order to compensate for the amount of beam scattering due to the difference in thickness of the wedge-shaped structure 208a, a scattering compensator having different thicknesses may be provided in the direction in which the thickness of the wedge-shaped structure 208a is different (lateral direction).

  The range shifter 210 matches the maximum range of the ion beam with the maximum depth of the affected area 216a. The range shifter 210 is made of a material having a small atomic number such as a resin having a small beam scattering amount with respect to energy loss. Since the energy is lost when the ion beam passes through the range shifter 210, the maximum range of the ion beam can be reduced. Thereby, the maximum range of the ion beam can be matched with the affected part 216a. The range shifter 210 is formed by stacking a plurality of plate members having different thicknesses, and the total thickness in the beam traveling direction can be changed by combining the plate members. In order to make the maximum range of the ion beam coincide with the affected part 216a, the acceleration energy of the ion beam by the synchrotron 5 may be reduced without using the range shifter 210. Further, the energy of the beam may be lost by the high energy beam transport system 16.

  Through the above process, the ion beam scanned in the horizontal direction and expanded in the depth direction is incident on the dose monitor 212, and the amount of the beam that has passed through is measured. When the dose monitor 212 is arranged on the beam downstream side (downstream side of the range shifter 210), it can measure the passing amount of the ion beam immediately before irradiating the affected area 216a. When the dose monitor 212 is arranged on the upstream side of the beam (upstream side of the device that changes the energy of the ion beam such as the ridge filter 208 and the range shifter 210), the calculation of the output signal from the dose monitor 212 due to the difference in energy is performed. Save time and effort.

  The bolus 214 is formed by excavating a resin block body, for example, and the resin passage thickness of the beam changes according to the beam incident position in the lateral direction. Thereby, the energy of the ion beam after passing through the bolus 214 can be changed for each incident position, and the arrival depth of the ion beam can be matched with the shape of the affected part 216a in the depth direction.

  The collimator 215 is composed of a radiation shield and forms a through hole corresponding to the affected part 216a. The collimator 215 irradiates the affected part 216a only with the ion beam that has passed through the through-hole among the ion beams expanded in the horizontal direction.

  The bolus 214 and the collimator 215 are processed in accordance with the shape of the affected area 216a, and are exchanged for each affected area 216a. By using a multi-leaf collimator as the collimator 215 and moving the leaf to match the shape of the affected part 216a in the lateral direction, it is possible to save time and labor for collimator processing and replacement.

  The irradiation control system 300 will be described with reference to FIG. FIG. 3 is a detailed configuration diagram of the irradiation control system 300. The irradiation control system 300 manages the beam irradiation amount (absorbed dose) for each scanning region of the scanning electromagnet 202 in order to form a desired irradiation field. The scanning region can be expressed as one excitation region formed by being divided into a plurality of portions in the entire excitation range of the scanning electromagnet 202. The irradiation control system 300 includes an area determination device 301, a distribution device 303, an open / close signal generation device 307, an irradiation completion signal generation device 309, an interlock signal generation device 310, a memory (target value memory) 305, and a counter (multi-channel counter) 304. , A memory (irradiation area memory) 311 is provided.

The region determination device 301 includes a memory (region determination device memory) 302 and is connected to the central control device 100, the magnetic field strength measuring device 205, and the memory 311. The sorter 303 is connected to the memory 311, the dose monitor 212, and the counter 304, respectively. The open / close signal generator 307 is connected to the memory 311, the counter 304, the memory 305, and the switch 11. The irradiation completion signal generation device 309 is connected to the counter 304, the memory 305, and the central control device 100, respectively. The interlock signal generation device 310 is connected to the counter 304, the memory 305, and the central control device 100, respectively. Counter 304 includes a N ² pieces of counters from the counter 1 until the counter N ^2, the sum of the counter S a (N ² +1) pieces of counters. Each of the counter 1 to the counter N ² is connected to the dose monitor 212 via the distribution device 303. The counter S is connected to the dose monitor 212 without going through the sorting device 303.

  Hereinafter, the operation of the main components of the irradiation control system 300 will be described with reference to FIG. FIG. 4 is a schematic explanatory diagram of an irradiation control method by the irradiation control system 300. When the beam irradiation start signal is generated by the central control device 100, the synchrotron 5, the region determination device 301, the sorting device 303, the open / close signal generation device 307, the irradiation completion signal generation device 309, and the interlock signal generation device 310 are respectively connected. The operation starts and the extraction of the ion beam from the synchrotron 5 is started.

First, of the information stored in the memory 101 of the central controller 100, the information shown in FIG. 9 is taken into the memory 305 of the irradiation control system 300. The information in FIG. 9 is a target beam irradiation amount (target value) and its allowable value, a ratio (N _i / N _S ) of the target beam irradiation amount and its allowable value for each region number of the excitation region. In the memory areas 306-1 to 306-N ² and 306-S in the memory 305, related information (for example, a target beam irradiation amount and an allowable value thereof) for the corresponding area number is stored.

The role of the region determination device 301 is to convert the current value set by the scanning electromagnet power supply control device 220 into an excitation region. The area determination device memory 302 stores the number of excitation areas in which the set current value to the scanning electromagnet 202 and the corresponding excitation areas (the number of all excitation areas is N ² ) are related to each other ( (Region number) and information on the start current value and end current value of the excitation region are registered as a data table (see FIGS. 5 and 6). These pieces of information are fetched from the memory 101 of the central controller 100 by the area determination device 301.

As shown in FIG. 5, for example, if the excitation current range of the scanning electromagnet 202a that scans the beam in the X direction is I _{MIN to} I _MAX [A], the region number X ₁ has an excitation current value of I _MIN Excitation region (irradiation region) corresponding to ˜I ₁ , region number Xi is the excitation current value of the scanning electromagnet corresponding to I _{i−1 to} I _i , region number X _N is the excitation current value of the scanning electromagnet Are excitation regions corresponding to I _{N-1 to} I _MAX .

The above-described excitation region (irradiation region) is also set in the scanning electromagnet 202b that scans the beam in the Y direction. As shown in FIG. 6, for example, when the exciting current range of the scanning electromagnet 202b is to _{I 'MIN ~I' MAX [A} ], the region number Y ₁ is the excitation current value of the scanning electromagnet is I _'MIN ~I' ₁ Excitation area corresponding to, the area number Yi is the excitation current value of the scanning electromagnet corresponding to I ' _{i-1 to} I' _i , the area number Y _N is the excitation current value of the scanning electromagnet I ' _{N- 1 to} I ′ indicates an excitation region corresponding to _MAX .

As a whole, when the beam is scanned two-dimensionally, the number of all excitation regions (all irradiation regions) is N ² , and the region number on the two-dimensional plane (XY plane) and the X and Y directions The relationship with the area number is registered in the memory 101 of the central controller 100 as a data table as shown in FIG. Further, all the above data tables may be combined into one data table and registered in the memory 101 of the central control apparatus 100 as a data table as shown in FIG.

  The target value indicates the target value of the beam irradiation amount. That is, it is the target value (target dose value) of the absorbed dose at each region number (excitation region number) of the beam position monitor 218 selected for each patient. The allowable value of the target value is an allowable value of the target value of the absorbed dose in each area number of the beam position monitor 218. The target dose ratio indicates the ratio of the absorbed dose at each area number to the total absorbed dose. The tolerance for the target dose ratio is the tolerance for this ratio.

  Each piece of information shown in FIG. 7 stored in the memory 101 is information set (created) by a doctor using the treatment planning apparatus 102 when creating a treatment plan for a certain patient. Each set information is temporarily stored in the memory 103 and is taken into the memory 101 by the central control device 100 before treatment of a certain patient. The information shown in FIG. 7 does not have to be prepared for every patient. For example, the relationship between the area number and the excitation area can be set in advance as a common item.

  Next, the region determination device 301 uses the data table to transmit the excitation current of the scanning electromagnet 202 input from the scanning electromagnet power supply control device 220 while irradiating the affected part 216a with the ion beam. Convert to the excitation area. Specifically, it is converted into an area number (such as area number i) of the excitation area. The excitation region through which the ion beam passes is called an irradiation excitation region. The irradiation excitation area is stored in the memory 311. That is, the memory 311 stores an irradiation excitation area located in the beam path in the irradiation field forming apparatus 200. The process of converting the excitation current of the scanning electromagnet 202 into the irradiation excitation region and storing it in the memory 311 is repeatedly performed during the extraction of the ion beam. For this reason, the memory 311 always stores an irradiation excitation region located in the beam path.

  The irradiation position of the ion beam in the body of the patient 216 is determined by the excitation current of the scanning electromagnet 202 set by the scanning electromagnet power supply controller 220. Therefore, if a correspondence relationship is established between the irradiation region in the body of the patient 216 and the excitation current value set by the scanning electromagnet power supply control device 220, the ion beam irradiation amount in the lateral direction can be managed. However, this correspondence may not be necessary.

The distribution device 303 distributes the beam irradiation amount (absorbed dose) sequentially measured by the dose monitor 212 to each counter (counter of the counter 304) corresponding to the excitation region set by the scanning electromagnet power supply control device 220. First, the excitation area (area number i) stored in the memory 311 is read. The beam irradiation amount from the dose monitor 212 is output to the counter-k corresponding to the region number i. That is, in the counter k, the beam irradiation amount (absorbed dose) measured for the excitation region with the region number i is integrated and recorded. This allows counted independently of each beam dose in all the excitation region (region number 1 to N ^2). In addition, the signal of the beam irradiation amount measured by the dose monitor 212 is input to the counter S as it is, and the total irradiation dose of all regions is counted.

In the present embodiment, the total irradiation dose of the entire region is measured by another counter, but the total beam irradiation amount may be configured to sum the count values from the counter 1 to the counter N ² . In this case, the counter S can be saved. Further, as a method of recording the beam irradiation amount in each counter, when the beam irradiation amount signal is always input from the counter 1 to the counter N ² and it is determined that the region number is i, only the corresponding counter k is measured. The measurement of the counter 304 may be switched on / off so that the counter is turned on and the other counters are turned off.

  Further, the number of counters is not necessarily the same as the number of divided areas. For example, the number of counters is about several, and after counting the beam irradiation amount of each excitation region, the count amount is stored in a separate memory in association with the region number i, and then the counter is reset to the next region. Alternatively, the beam irradiation amount may be counted. At this time, when the excitation area of area number i is irradiated again, the area number i is irradiated by reading the count number so far from a separately provided memory into the counter and counting the beam irradiation amount. The integrated value of the beam amount can be obtained.

  The open / close signal generation device 307 compares the irradiated beam irradiation amount and the target dose (target value) in the excitation region (irradiation region) located in the beam path in the irradiation field forming device 200, and opens and closes the switch 11. Then, ON / OFF control of beam emission from the synchrotron 5 is performed. First, the target value for each excitation area is fetched from the memory 305. Next, the open / close signal generation device 307 takes in the information of the excitation region being irradiated from the memory 311 and compares the target value in the excitation region of the region number i with the irradiated beam irradiation amount.

  If the irradiated beam amount has reached the target value, the open / close signal generation device 307 generates a beam OFF signal and transmits it to the switch 11. Thereby, the switch 11 is opened, the application of the high frequency signal for extraction to the high frequency applying device 7 is stopped, and the extraction of the ion beam from the synchrotron 5 is stopped.

  If the irradiated beam amount is less than the target value, the open / close signal generation device 307 generates a beam ON signal and transmits it to the switch 11. As a result, the switch 11 is closed, and the high frequency signal for emission is applied to the high frequency applying device 7. Thereby, an ion beam is irradiated only to the excitation area | region which is less than a target value.

  In this embodiment, the area under irradiation is stored in the memory 311, but it is also possible to directly input the determination result of the excitation area by the area determination device 301 to the distribution device 303 and the open / close signal generation device 307. . In order to input the information of the excitation area located in the beam path to the sorting device 303 and the open / close signal generation device 307, it is necessary to match the operation timing with the region determination device 301, so that the control becomes complicated.

  As the ion beam irradiation progresses, a target value of the ion beam irradiation amount is irradiated to the affected area 216a through each excitation region. The role of the interlock signal generator 310 is to prevent the patient 216 from being irradiated with unwanted ion beams. First, the interlock signal generation device 310 takes in the target value for each excitation area and its allowable value, and the total target value for all areas and its allowable value from the memory 305. In addition to the target value for each excitation area and its allowable value acquired from the central controller 100, the memory 305 previously stores the total beam irradiation target value and its allowable value for all excitation areas. Next, the irradiated beam irradiation amount of each excitation region and all the excitation regions is taken in from the counter 304. Since the counter S counts the total amount of beam irradiation, when the ratio between the counter i and the count value of the counter S is taken, the ratio of the beam irradiation amount irradiated to the excitation region of the region number i to the total irradiation amount can be calculated.

  The interlock signal generation device 310 confirms that the count value of the counter S (the sum of the irradiated beam amounts in all excitation regions) is equal to or less than the value of (target value S + allowable value S). When the count value of the counter S exceeds the value of (target value S + allowable value S), this means that the ion beam is over-irradiated, so the interlock signal generation device 310 generates a beam irradiation stop signal, It transmits to the control apparatus 100. The interlock signal generation device 310 similarly confirms that the irradiated beam amount is equal to or less than (target value i + allowable value i) for each excitation region.

  It is also confirmed that the ratio of the beam irradiation amount of each excitation region obtained from the counter 304 is within (target ratio Ri ± allowable value ΔRi). If this ratio deviates from the allowable range, it means that the beam irradiation amount is biased between the excitation areas, and therefore the interlock signal generation device 310 generates a beam irradiation stop signal and transmits it to the central control device 100. To do. Receiving the beam irradiation stop signal, the central controller 100 generates a beam emission stop command and outputs it to the interlock switch 9 (signal line omitted). Thereby, the switch 9 is opened, the supply of the high frequency power from the high frequency power supply 8 to the high frequency application electrode is stopped, and the emission of the ion beam from the synchrotron 5 is stopped.

  In this way, the interlock signal generation device 310 repeatedly captures the current beam irradiation amount from the counter 304 and confirms that the beam irradiation amount and its ratio are within the allowable range, thereby causing unexpected ions. Beam irradiation can be prevented.

  The irradiation completion signal generation device 309 determines whether a target amount of ion beam has been irradiated in all excitation regions (all irradiation regions), and generates an irradiation completion signal when the irradiation is completed. First, the irradiation completion signal generation device 309 takes in a target value for each excitation area from the memory 305. Next, the beam irradiation amount for each excitation region is fetched from the counter 304, and the target value and the beam irradiation amount are compared for each excitation region. When the beam irradiation amount reaches the target value in the entire excitation region, the irradiation completion signal generation device 309 outputs the irradiation completion signal to the central control device 100. If there is at least one excitation region in which the beam irradiation amount is less than the target value, the irradiation completion signal generation device 309 performs again the process of taking the beam irradiation amount from the counter 304 and comparing it with the target value. Since the open / close signal generation device 307 irradiates the ion beam only to the excitation region where the beam irradiation amount is less than the target value, finally, the beam irradiation amount of the target value is irradiated over the entire region.

  When receiving the irradiation completion signal, the central control device 100 generates a beam extraction completion signal and transmits it to the irradiation (extraction) completion switch 9. Since the irradiation completion switch 9 is opened by the beam extraction completion signal, the supply of the high frequency power to the high frequency application electrode is stopped, and the extraction of the ion beam from the synchrotron 5 is stopped.

  The display device 308 displays the irradiated beam irradiation amount and target value for each excitation region of the scanning electromagnet 202 set from the scanning electromagnet power supply control device 220. The display device 308 is connected to the counter 304 and the central controller 100, and displays the dose counter value measured by the dose monitor 212 for each excitation region, the sum of the dose counter values for all the excitation regions, and the target value for each excitation region. Display sequentially during irradiation. This informs the driver of the progress of beam irradiation. Further, by displaying the irradiation parameters and the devices used on the display device 308, the driver can easily grasp the beam irradiation conditions. Further, the ratio between the beam irradiation amount for each excitation region and the total thereof may be displayed on the display device 308. As a result, the driver can be informed that the irradiation is proceeding evenly.

  A beam irradiation method for the affected area 216a using the particle beam therapy system of this embodiment will be described. The ion beam generated by the ion source 2 is accelerated by the upstream accelerator 3 and supplied to the synchrotron 5 through the low energy beam transport system 4. The ion beam is accelerated by a high-frequency accelerating cavity (not shown) while orbiting the synchrotron 5. After the ion beam is accelerated to a desired energy, the high-frequency power from the high-frequency power source 8 passes through the switches 9 and 11 to the ion beam circulating in the synchrotron 5 by the high-frequency application electrode of the high-frequency application device 7. Applied. As a result, the ion beam orbiting within the stability limit moves out of the stability limit and is emitted from the synchrotron 5. This ion beam is supplied to the irradiation field forming apparatus 200 through the extraction deflector 13 and the high energy beam transport system 16.

  In the irradiation field forming apparatus 200, the ion beam passes through a scanning electromagnet 202, a scatterer 206, a ridge filter 208, a range shifter 210, a dose monitor 212, a beam position monitor 218, a bolus 214, and a collimator 215 arranged on the beam path. Then, the affected part 216a of the patient 216 on the treatment bed 217 is irradiated. During beam irradiation, the excitation current set by the scanning electromagnet power supply controller 220 is supplied from the scanning electromagnet power supply 219 to the scanning electromagnet 202, and the beam is scanned so that the dose distribution in the affected area 216a is uniform.

  The dose monitor 212 measures the beam dose (absorbed dose) of the ion beam passing through the irradiation field forming apparatus 200. When the dose measured by the dose monitor 212 reaches the target value, the irradiation (extraction) completion switch 9 is opened, the extraction of the ion beam from the synchrotron 5 is stopped, and the irradiation of the ion beam to the affected area 216a is completed. .

  In this embodiment, the ridge filter 208 is used in order to make the dose distribution in the traveling direction (depth direction) of the ion beam in the affected area 216a uniform. In the ridge filter 208, the size in the depth direction of the region where the dose distribution is uniform is determined by the maximum thickness of the wedge-shaped structure 208a. Therefore, by preparing a plurality of ridge filters having different maximum thicknesses of the wedge-shaped structure 208a and replacing the plurality of ridge filters, the size in the depth direction of the region where the dose distribution is uniform is adjusted.

  The open / close signal generation device 307 determines whether or not the integrated value of the beam irradiation amount (absorbed dose) measured by the dose monitor 212 has reached the target value for each excitation region corresponding to each region number. The open / close signal generation device 307 generates a beam OFF signal for the excitation region whose integrated value has reached the target value. As a result, the switch 11 is opened as described above, and the supply of the ion beam to the excitation region is stopped. The open / close signal generation device 307 generates a beam ON signal for an excitation region where the integrated value of the beam irradiation amount does not reach the target value. Thereby, as described above, the ion beam is supplied to the excitation region with the switch 11 closed.

  In this embodiment, the ion beam extraction start and extraction stop (ON / OFF) are controlled so that the ion beam is not supplied to the excitation region that has reached the target value, and the ion beam is not supplied to the excitation region that has reached the target value. By supplying the beam, the irradiation dose for each position in the lateral direction of the ion beam in the affected area 216a can be easily adjusted. For this reason, the dose distribution in the lateral direction of the ion beam in the affected area 216a can be easily set to a desired dose distribution determined in the treatment plan, and the irradiation dose at each position in the lateral direction of the ion beam in the affected area 216a. The probability of mis-irradiation that causes excess or deficiency can be significantly reduced.

  In this embodiment, the beam is emitted from the synchrotron 5 so that the beam intensity (the amount of emission) set in the data table of FIG. 7 is obtained based on the excitation current of the scanning electromagnet 202 set by the scanning electromagnet power supply controller 220. The beam output amount (beam output intensity) of the ion beam is controlled. Specifically, a modulation signal that adjusts the amplitude of the high-frequency signal supplied to the high-frequency applying device 7 according to the beam intensity corresponding to the region number determined by the irradiation control system 300 is signal-synthesized from the central control device 100. Transmit to device 10. As a result, the amplitude modulation of the high-frequency signal as shown in FIG. 10 is performed, and the beam emission amount from the synchrotron 5 is adjusted to a desired intensity. In this way, the ion beam intensity can be controlled according to the amount (large or small) of the target irradiation amount for each excitation region, and a desired dose distribution can be formed in the lateral direction of the ion beam even before the irradiation is completed. Therefore, irradiation with higher safety can be realized.

  In the present embodiment, during irradiation of the ion beam, the irradiation integrated ion beam amount is compared with the target integrated ion beam amount in the excitation region group including at least one of the plurality of excitation regions by the scanning electromagnet 202. Means (interlock signal generation device 310) for stopping the irradiation of the ion beam when the ion beam exceeding the target value is irradiated in the excitation region. As a result, during irradiation of the ion beam, the irradiated integrated ion beam amount and the target integrated ion beam amount are sequentially compared, and an unexpected ion beam irradiation is performed (allowable value set in advance for the target value). In this case, the ion beam irradiation can be stopped immediately, so that the reliability can be further improved.

  In the present embodiment, at least the ion beam amount irradiated to the first excitation region group including at least one of the plurality of excitation regions by the scanning electromagnet 202 and the excitation region not included in the first excitation region group are at least. A means for stopping the irradiation of the ion beam is provided when the ratio of the amount of ion beam irradiated to the second excitation region group including one exceeds a preset allowable value range. Thereby, during the ion beam irradiation, the respective ratios of the irradiated accumulated ion beam amount and the target ion beam amount in the first excitation region group and the second excitation region group are sequentially compared, and a preset allowable value is obtained. When the ion beam irradiation is performed beyond that, the ion beam irradiation can be stopped immediately, so that the reliability can be further improved.

  In the present embodiment, the synchrotron 5 is described as an example of the circular accelerator, but the present invention can also be applied to a case where a cyclotron is used instead of the synchrotron 5. In the case of the cyclotron, the start and stop of extraction of the ion beam from the cyclotron to the irradiation field forming device are controlled by turning on / off the power source of the ion source that supplies the ion beam to the cyclotron. The particle beam therapy system using a cyclotron as an acceleration device has a configuration in which the synchrotron is replaced with a cyclotron in FIG. In the particle beam therapy system using the cyclotron, the beam ON signal and the beam OFF signal output from the switching signal generation device 307 are used for switching control of the switching device provided in the wiring connecting the power source and the ion source. By controlling the switchgear as described above, as in the embodiment of FIG. 1, the ion beam is not supplied to the excitation region of the scanning electromagnet 202 that has reached the target value, and the ion beam is applied to the excitation region that has not reached the target value. Can be supplied. For this reason, the irradiation dose with respect to each position in the lateral direction of the ion beam in the affected part 216a can be easily adjusted, and the probability of erroneous irradiation in which the irradiation dose is excessive or insufficient at each position in the ion beam traveling direction in the affected part 216a. Can be significantly reduced.

  INDUSTRIAL APPLICABILITY The present invention can be used in a charged particle beam irradiation system that treats an affected area by irradiating an ion beam of protons, carbon ions, or the like.

The schematic block diagram of one Example of the particle beam therapy apparatus by this invention. Detailed explanatory drawing of the irradiation field forming apparatus of FIG. The detailed block diagram of the irradiation control system of FIG. The schematic explanatory drawing of the irradiation control method by the irradiation control system of FIG. 6 is a data table showing the relationship between the region number of the excitation region in the X direction and the start current value and end current value of the excitation current of the scanning electromagnet. A data table showing the relationship between the area number of the excitation area in the Y direction and the start current value and end current value of the excitation current of the scanning electromagnet. The data table which shows the relationship between the area number on an XY plane, the area number of a X direction and a Y direction, the target value of beam irradiation amount, its allowable value, etc. The data table which shows the relationship between the area number on XY plane, and the area number of a X direction and a Y direction. The data table which shows the relationship between the area number of an excitation area | region, the target value of beam irradiation amount, its allowable value, etc. Schematic explanatory drawing of amplitude modulation of a high frequency signal for beam extraction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion beam generator 2 Ion source 3 Previous stage accelerator 4 Low energy beam transport system 5 Synchrotron 6 Accelerator 7 High frequency application device 8 High frequency power supply 10 Signal synthesis device 9, 11 Switch 14 Rotating gantry 16 High energy beam transport system 100 Central control Apparatus 101, 302, 305 Memory 200 Irradiation field forming apparatus 201 Casing 202 Scanning magnet 203 Scanning magnet holding member 205 Magnetic field strength measuring device 206 Scattering body 208 Ridge filter 210 Range shifter 212 Dose monitor 214 Bolus 215 Collimator 219 Scanning electromagnet power supply 220 Scanning electromagnet power supply Control device 300 Irradiation control system 301 Area determination device 303 Sorting device 304 Counter 307 Open / close signal generation device 308 Display device

Claims (18)

A charged particle beam generator that accelerates and emits a charged particle beam; and a scanning magnet that scans the charged particle beam emitted from the charged particle beam generator on an irradiation surface perpendicular to the beam traveling direction. In the charged particle beam irradiation system for irradiating the irradiation object with the charged particle beam that has passed through the scanning magnet,
A control device is provided that controls an amount of the charged particle beam emitted from the charged particle beam generator based on an irradiation position and a dose on the irradiation surface of the charged particle beam that has passed through the scanning magnet. Charged particle beam irradiation system.   In Claim 1, The said control apparatus calculates | requires the integrated value of the dose of the said charged particle beam which passed the several area | region on the said irradiation surface for every said area | region, Based on the integrated value for every said area | region, the said charged particle A charged particle beam irradiation system for controlling an emission amount of the charged particle beam from a beam generator.   3. The control device according to claim 2, wherein when the region where the integrated value has reached a target dose is located in a beam path, the control device stops emission of the charged particle beam from the charged particle beam generator, and performs the integration. A charged particle beam irradiation system that emits the charged particle beam from the charged particle beam generator when the region whose value does not reach the target dose is located in the beam path.   3. The apparatus according to claim 2, wherein when the integrated value of any one of the regions is equal to or greater than a tolerance set in the region, the charged particle beam generation device stops the emission of the charged particle beam. A charged particle beam irradiation system comprising:   3. The charged particle beam that has passed through the second irradiation region that is an irradiation region other than the first irradiation region, and the integrated value of the charged particle beam that has passed through the first irradiation region on the irradiation surface. A charged particle beam irradiation system comprising: a device that stops emission of the charged particle beam from the charged particle beam generator when a ratio with the integrated value exceeds a set allowable value.   The charged particle beam irradiation system according to claim 2, further comprising a display device that displays the integrated value for each region. The magnetic field strength control device for controlling the magnetic field strength of the scanning magnet according to claim 1, and a measuring device for measuring a dose of the charged particle beam that has passed through the scanning magnet,
The control device controls the emission amount of the charged particle beam from the charged particle beam generation device based on the magnetic field strength and the dose set by the magnetic field strength control device. system. In claim 1, comprising a magnetic field strength measuring device for detecting the magnetic field strength of the scanning magnet, and a measuring device for measuring the dose of the charged particle beam that has passed through the scanning magnet,
The control device controls an emission amount of the charged particle beam from the charged particle beam generation device based on the magnetic field strength and the dose detected by the magnetic field strength measuring device. Irradiation system. In Claim 1, It comprises a beam position measuring device for detecting the irradiation position of the charged particle beam scanned by the scanning magnet, and a measuring device for measuring the dose of the charged particle beam that has passed through the scanning magnet,
The control device controls an emission amount of the charged particle beam from the charged particle beam generator based on an irradiation position and the dose of the charged particle beam detected by the beam position measuring device. Charged particle beam irradiation system. A charged particle beam generator for accelerating and emitting a charged particle beam, and an irradiation surface perpendicular to the beam traveling direction, the charged particle beam emitted from the charged particle beam generator; A scanning magnet that scans up, and a beam irradiation device that irradiates the irradiation target with the charged particle beam;
A control device that controls the amplitude of a high-frequency signal supplied to the high-frequency application device based on the position of the charged particle beam that has passed through the scanning magnet on the irradiation surface and the dose of the charged particle beam that has passed through the scanning magnet A charged particle beam irradiation system comprising: An ion source for generating a charged particle beam;
A charged particle beam generator for accelerating and emitting the charged particle beam emitted from the ion source, and the charged particle beam emitted from the charged particle beam generator are scanned on an irradiation surface perpendicular to the beam traveling direction. A beam irradiation device for irradiating the irradiation target with the charged particle beam.
Control for controlling the emission amount of the charged particle beam from the ion source based on the position on the irradiation surface of the charged particle beam that has passed through the scanning magnet and the dose of the charged particle beam that has passed through the scanning magnet A charged particle beam irradiation system comprising an apparatus. A charged particle beam generator for accelerating and emitting a charged particle beam;
A scanning magnet for scanning the charged particle beam emitted from the charged particle beam generator on an irradiation surface perpendicular to a beam traveling direction, and a beam irradiation device for irradiating the irradiation target with the charged particle beam;
Out of a plurality of regions formed by division on the irradiation surface, supply of the charged particle beam to the region that has reached the target dose is stopped, and the other charged regions that have not reached the target dose are charged. A charged particle beam irradiation system comprising a controller for supplying a particle beam.   The control device according to claim 12, wherein the controller stops the supply of the charged particle beam to the region where the integrated value of the dose of the charged particle beam that has passed through the region has reached the target dose, and the integrated value is A charged particle beam irradiation system, characterized in that the charged particle beam is supplied to another region that has not reached a target dose. The magnetic field strength control device for controlling the magnetic field strength of the scanning magnet according to claim 12,
The charged particle beam irradiation system, wherein the control device supplies and stops supplying the charged particle beam based on a magnetic field strength set by the magnetic field strength control device. The magnetic field strength measuring device for detecting the magnetic field strength of the scanning magnet according to claim 12,
The charged particle beam irradiation system, wherein the control device supplies and stops supplying the charged particle beam based on the magnetic field strength detected by the magnetic field strength measuring device. The beam position measuring device according to claim 12, further comprising a beam position measuring device that detects an irradiation position of the charged particle beam scanned by the scanning magnet,
The charged particle beam irradiation system, wherein the control device supplies and stops the supply of the charged particle beam based on the irradiation position of the charged particle beam detected by the beam position measuring device. The charged particle beam emitted from the charged particle beam generator is scanned on the irradiation surface perpendicular to the beam traveling direction by a scanning magnet and supplied to the irradiation target.
A charged particle beam characterized by controlling an emission amount of the charged particle beam from the charged particle beam generator based on an irradiation position and a dose on the irradiation surface of the charged particle beam that has passed through the scanning magnet. Output method. Supply the charged particle beam emitted from the charged particle beam generator to a scanning magnet that scans the irradiation surface perpendicular to the beam traveling direction,
Of the plurality of regions formed by dividing the scanning range on the irradiation surface of the charged particle beam that has passed through the scanning magnet, stopping the supply of the charged particle beam to the region that has reached a target dose, A charged particle beam extraction method, characterized in that the charged particle beam is supplied to another region that has not reached the target dose.

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