JP5002612B2 - Charged particle beam irradiation equipment - Google Patents

Description

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

  There is known a treatment method (particle beam treatment) in which an affected part of a patient such as cancer is irradiated with a charged particle beam (ion beam) such as protons and carbon ions.

  An ion beam irradiation system used for particle beam therapy includes, for example, an ion beam generator provided with a circular accelerator, a beam transport system, and an irradiation device provided with an irradiation field forming device. A circular accelerator accelerates an ion beam (circular beam) that circulates along a circular orbit to a target energy and then emits the ion beam. The emitted ion beam (exit beam) is transported to an irradiation field forming device via a beam transport system. Is done. 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 a circular accelerator, for example, a synchrotron provided with a means for increasing the betatron oscillation amplitude of an orbiting beam and an extraction deflector for extracting the ion beam from the orbit is known. By increasing the betatron oscillation amplitude of the orbiting beam, the ion beam is moved out of the stability limit of resonance and is emitted from the synchrotron to the beam transport system by the extraction deflector. The synchrotron repeats a periodic operation with a set of ion beam incidence, circular beam acceleration, and beam extraction until a desired dose distribution is formed in the affected area.

  Usually, 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 of the Gaussian distribution) is about 1 to 5 mm. Usually, the affected area is larger than the beam size in the lateral direction. Therefore, in order to effectively irradiate the ion beam over the entire lateral direction of the affected area, the dose is large in the lateral direction and has a high degree of uniformity. A distribution needs to be formed. In order to form a uniform dose distribution in the horizontal direction, a method of scanning the beam with a scanning electromagnet and moving the irradiation position of the beam discretely or continuously to form a uniform dose distribution (scanning irradiation method) It is known (Non-Patent Document 1).

  The ion beam incident on the patient's body emits most of the energy immediately before the ions stop, and forms a dose distribution called a Bragg curve in the depth direction (beam traveling direction). Since the position of the Bragg peak, which is the maximum of the Bragg curve, depends on the energy of the ion beam incident on the body, the ion beam is stopped near the affected area by appropriately selecting the energy of the ion beam in particle beam therapy. To give most of the energy to the affected cancer cells. Here, the width of the Bragg peak in the depth direction is about several millimeters, but the affected part usually has a thickness greater than the Bragg peak width in the depth direction. In such a case, in order to effectively irradiate the ion beam over the entire depth direction of the affected area, the dose distribution (Spread Out Bragg Peak, hereinafter referred to as SOBP) having a large uniformity in the affected area in the depth direction. Need to form. The SOBP is formed, for example, by appropriately controlling the ion beam energy (beam energy) and the irradiation amount.

  Non-Patent Document 2 discloses a technique for changing the energy of an ion beam (irradiation beam) irradiated to an affected area stepwise during one cycle of synchrotron operation to shorten the time required for beam irradiation. The energy of the irradiation beam is changed by changing the thickness of the range shifter installed in the transport system while keeping the output beam energy of the synchrotron constant or by changing the output beam energy during one cycle of the synchrotron. The range shifter is installed in the beam transport system, and changes the energy of the beam passing through the range shifter by changing the thickness of the plate inserted into the beam trajectory.

Japanese Patent No. 2596292

REVIEW OF SCIENTIFIC INSTRUMENTS Vol.64 No.8 (August 1993; P2084-2089) Proceedings of EPAC08 (European Particle Accelerator Conference 2008) (June 2008; P1800-1802)

  The above prior art for changing the energy of the irradiation beam during one cycle of synchrotron operation has the following problems.

  In the scanning irradiation method, if the charge amount of the circulating beam decreases so that it is difficult to continue irradiation during scanning at a certain energy, the beam emission from the synchrotron is stopped, the beam is incident and accelerated again, Irradiation at the same energy needs to be resumed. Normally, the affected area moves with the patient's body movement and breathing. Therefore, the affected area moves and changes the irradiation position of the beam between the stop of the beam extraction and the restart of the extraction in the next cycle. The uniformity of dose distribution in the direction (dose uniformity) may be deteriorated.

  In general synchrotrons for particle beam therapy, a time for extraction preparation (extraction preparation period) is provided between the end of acceleration of an orbiting beam or change of energy and the start of beam extraction. When changing the energy of the irradiated beam by changing the energy of the emitted beam during one cycle of the synchrotron, if irradiation at a certain energy is performed over two periods, two preparation periods are required for that energy, and irradiation is performed. There is a possibility that the time required for completion (irradiation time) may increase.

  The first object of the present invention is to change the irradiation dose energy during one cycle of synchrotron operation. It is an object of the present invention to provide a particle beam therapy system capable of preventing the deterioration of the above. The second object of the present invention is to change the irradiation beam energy during one cycle of the synchrotron to change the irradiation beam energy, and the irradiation time by performing irradiation at a certain energy over two operation cycles. It is an object of the present invention to provide a particle beam therapy system capable of preventing an increase in the number of particles.

The feature of the present invention to achieve the above object is to measure the amount of charge of the orbiting beam at the time when scanning of the entire irradiation region at a certain irradiation depth is completed or when irradiation at a certain energy is completed in the scanning irradiation method. The operation pattern of the synchrotron is changed based on the measurement result. Furthermore, the feature of the present invention is that the amount of circular beam charge at the time when the scanning of the entire irradiation region at a certain irradiation depth is completed or the irradiation at a certain energy is completed is the next scanning or the next energy. It is determined whether it is sufficient to complete the irradiation in the case, and if the amount of circular beam charge is sufficient, the next scanning or irradiation at the next energy is started within the same operation period of the synchrotron. If the amount of the orbiting beam charge is not sufficient, the operation cycle is shifted to the next operation cycle.

  The present invention starts the next scan during the synchrotron operation cycle only when the amount of round beam charge is sufficient to complete one scan. There is no shortage of quantity. As a result, the lateral dose uniformity is prevented from deteriorating due to the fact that the lateral dose distribution is formed over two operation periods of the synchrotron. In addition, the present invention is such that when the irradiation beam energy is changed by changing the emission beam energy of the synchrotron within the same operation period of the synchrotron, the amount of circulating beam charge is insufficient during irradiation at a certain irradiation energy. Therefore, it is possible to prevent an increase in irradiation time caused by performing preparation for extraction twice with the irradiation energy.

  According to the present invention, the amount of circular beam charge is not deficient in the course of scanning the beam in the horizontal direction, and the dose uniformity in the horizontal direction is improved.

It is a conceptual diagram showing the whole structure of the particle beam therapy apparatus which is a 1st Example of this invention. It is a conceptual diagram showing the detail of the irradiation field forming apparatus with which the particle beam therapy system which is a 1st Example of this invention is equipped. It is a conceptual diagram showing the structure of the irradiation control system with which the particle beam therapy system which is a 1st Example of this invention is equipped. In the 1st Example of this invention, it is a conceptual diagram of the data preserve | saved at the memory with which an irradiation control apparatus is provided. In the 1st Example of this invention, it is a conceptual diagram of the data regarding the thickness of the range shifter preserve | saved at the memory with which an irradiation control apparatus is provided. In the 1st Example of this invention, it is a conceptual diagram of the data preserve | saved at the target value memory of an irradiation control system. In 1st embodiment of this invention, it is a conceptual diagram showing the driving | operation pattern of a bending electromagnet. In 1st embodiment of this invention, it is a conceptual diagram showing the horizontal direction beam irradiation position at the time of scanning an affected part continuously. In the 2nd Example of this invention, it is a conceptual diagram showing the driving | operation pattern of a bending electromagnet. In the 2nd Example of this invention, it is a conceptual diagram showing the driving | operation pattern of a bending electromagnet. It is a conceptual diagram showing the whole structure of the particle beam therapy apparatus which is the 2nd Example of this invention. It is a flowchart figure showing the control method of the synchrotron in the 2nd Example of this invention. In the 3rd Example of this invention, it is a conceptual diagram showing the driving | operation pattern of a bending electromagnet. It is a flowchart figure showing the control method of the synchrotron in the 3rd Example of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the particle beam therapy system (ion beam irradiation system) of this embodiment irradiates an affected part 216a of a patient 216 fixed to a treatment bed 217 with an ion beam (for example, a proton beam). And an ion beam generator 1, a high-energy beam transport system 14, an irradiation field forming device 200, a central controller 100, and an irradiation control system 300.

  The central controller 100 determines the irradiation conditions (beam irradiation direction, SOBP width, irradiation dose, maximum irradiation depth, irradiation field size, etc.) for forming an appropriate irradiation field on the affected area 216a of the patient 216 determined by the treatment planning apparatus 102. ) To select nozzle device parameters such as device type, installation position, and set value, and to select accelerator operation parameters such as beam energy and beam intensity pattern. The central controller 100 includes a memory 101 and stores information necessary for treatment (irradiation beam energy, irradiation angle (gantry rotation angle), scanning electromagnet pattern, range shifter insertion amount, etc.) in the memory 101. The irradiation control system 300 sets parameters of each device constituting the irradiation field forming apparatus 200 based on the information recorded in the memory 101. Parameters of each device constituting the ion beam generator 1 are set by a control device (not shown) of each device based on information recorded in the memory 101.

  The ion beam generator 1 is an apparatus for generating an ion beam having a predetermined beam energy, and includes an ion source 4, a front stage accelerator 5, a low energy beam transport system 6, and a synchrotron 2. The synchrotron 2 is connected to the synchrotron control device 3. The ion beam generated by the ion source 4 is accelerated to the incident energy of the synchrotron 2 by the pre-stage accelerator 5 and is incident on the synchrotron 2 via the low energy beam transport system 6.

  As shown in FIG. 1, the synchrotron 2 includes a deflecting electromagnet 7 that deflects the beam trajectory to form a circular orbit, a quadrupole electromagnet 8 that converges and diverges an ion beam that circulates in the synchrotron, and a high frequency An accelerating cavity 9, a high-frequency application device 10 for extraction, a monitor 12 for measuring the charge amount of a circular beam (circular beam charge amount), and an output deflector 13 are provided. The high-frequency application device 10 includes a high-frequency application electrode (not shown), and the high-frequency application electrode receives a high-frequency voltage from the high-frequency supply device 11 for emission. The monitor 12 is connected to the irradiation control system 300 via the control device 16 of the monitor 12.

  The ion beam incident on the synchrotron 2 is accelerated to a desired energy (for example, 70 to 250 MeV) by the high frequency voltage applied to the high frequency acceleration cavity 9. When the high frequency voltage from the high frequency supply device 11 is applied to the circular beam by the high frequency application electrode after the acceleration is completed, the circular beam exceeds the resonance stability limit and is emitted from the synchrotron 2 via the extraction deflector 13. The

  The high energy beam transport system 14 communicates the synchrotron 2 and the irradiation field forming apparatus 200, and a part thereof is installed in the rotating gantry 15. The ion beam emitted from the synchrotron 2 is transported to the irradiation field forming apparatus 200 installed in the rotating gantry 15 via the high energy beam transport system 14. By adjusting the rotation angle of the rotating gantry 15, the patient 216 can be irradiated with an ion beam from a desired direction.

  The details of the irradiation field forming apparatus 200 will be described with reference to FIG. The irradiation field forming device 200 is a device that shapes the ion beam generated by the ion beam generating device 1 in accordance with the shape of the affected part 216a of the patient 216. The irradiation field forming apparatus 200 includes a casing 201, and includes a beam scanning electromagnet 202, a scatterer 203, a ridge filter 204, a range shifter 205, a dose monitor 206, a beam position monitor 207, and a collimator 208 in the casing 201.

  The scanning electromagnet 202 forms a uniform dose distribution in the lateral direction of the affected area 216a by scanning the irradiation position of the beam. A scanning electromagnet power supply 220 is connected to the scanning electromagnet 202, and the scanning electromagnet power supply 220 is connected to the scanning electromagnet power supply controller 221. The scanning electromagnet 202 is composed of, for example, a pair of bipolar electromagnets that deflect the beam in the transverse direction perpendicular to each other so that the beam can be scanned in two directions orthogonal to each other in a plane perpendicular to the beam traveling direction. The scanning electromagnet power supply 220 supplies a current to the scanning electromagnet 202 to generate a deflection magnetic field. Since the intensity of the deflection magnetic field, that is, the amount of deflection of the beam is determined by the excitation current supplied to the scanning electromagnet 202, it is possible to irradiate the beam at any point in the lateral direction by adjusting the excitation current. The scanning electromagnet 202 is supplied with the current set by the scanning electromagnet power supply controller 221 by the scanning electromagnet power supply 220. The operation pattern of the scanning electromagnet 202 is stored in advance in a memory 222 provided in the scanning electromagnet power supply control device 221. The excitation current value of the scanning electromagnet 202 is transmitted to the irradiation control device 301 (FIG. 3) provided in the irradiation control system 300.

  The scatterer 203 is for expanding the lateral distribution of the ion beam by the phenomenon of ion scattering by the substance. The beam is broadened in a Gaussian distribution by the scatterer 203. The scatterer 203 is generally made of a substance having a large atomic number, such as tungsten, which has a small energy loss with respect to the amount of scattering. If the distribution of the ion beam (outgoing beam) emitted from the synchrotron 2 does not cause a problem in forming a lateral dose distribution, the scatterer 203 may be omitted.

  The ridge filter 204 is for expanding the Bragg peak of the ion beam by superimposing a plurality of Bragg curves having different peak positions. The ridge filter 204 is composed of a plurality of wedge-shaped structures, and the thickness changes according to the position in the lateral direction. As a result, the energy of the beam particles passing through the ridge filter 204 changes according to the position in the lateral direction, and Bragg peaks are formed at different depths corresponding to the respective beam energies. In this embodiment, the SOBP is formed by changing the energy of the outgoing beam and the thickness of the range shifter 205. By using the ridge filter 204 together, the dose distribution is uniform in the depth direction even if the Bragg peak is separated. Therefore, the number of operating conditions is reduced, and the time required for adjusting the synchrotron 2 and the high energy beam transport system 14 (beam adjustment) is shortened. The ridge filter 204 may be omitted, and the SOBP may be formed only by changing the energy of the outgoing beam and the thickness of the range shifter 205.

  The range shifter 205 is for adjusting the range of the ion beam. The range shifter 205 includes a pair of plates 205a having different thicknesses depending on the position in the horizontal direction and a range shifter driving device 205b. The range shifter driving device 205b is connected to the irradiation control system 300. The plate 205a is generally 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 205, the range of the ion beam can be reduced. The range shifter driving device 205b changes the thickness of the plate 210a on the beam trajectory by changing the insertion amount of the plate 210a, and forms Bragg peaks at different positions in the affected area 216a. By irradiating the ion beam while changing the thickness of the range shifter, an SOBP having a large affected area 216a is formed in the depth direction. Further, the energy of the ion beam may be lost while transporting the high energy beam transport system 14 without using the range shifter 210.

  The dose monitor 206 measures the amount of beam that has passed, and the beam position monitor 207 measures the beam position in the lateral direction. The collimator 208 is composed of a radiation shield and forms a through hole corresponding to the affected part 216a. The collimator 208 irradiates the affected part 216a only with the ion beam that has passed through the through-hole among the beams expanded in the horizontal direction. The collimator 208 is usually processed in accordance with the shape of the affected area 216a, and is replaced for each affected area 216a. By using a multi-leaf collimator as the collimator 208 and moving the leaf to match the shape of the affected part 216a in the lateral direction, the labor of processing and replacement may be saved.

  Details of the irradiation control system 300 will be described with reference to FIG.

  The irradiation control system 300 controls the beam irradiation position in the lateral direction, the timing of beam emission from the synchrotron 2, and the thickness of the range shifter 205 in order to form a desired irradiation field. In this embodiment, the irradiation position of the beam is scanned discretely, and the horizontal beam position is expressed as a lattice point when the entire irradiation region in the horizontal direction is divided into a lattice shape. At this time, since one irradiation position corresponds to one combination of excitation amounts of the scanning electromagnet 202, controlling the irradiation position is equivalent to controlling the excitation amount of the scanning electromagnet 202.

  The irradiation control system 300 includes an irradiation control device 301, an irradiation control device memory 302, a counter 303, an irradiation completion signal generation device 304, an interlock signal generation device 305, and a target value memory 306. The irradiation control device 301 includes a central control device 100, an accelerator control device 3, a beam charge amount monitor control device 16, a high frequency supply device 11, a scanning electromagnet power supply control device 221, a range shifter driving device 205b, an irradiation completion signal generation device 304, an interlock. The signal generator 305 and the target value memory 306 are connected to each other.

  The irradiation completion signal generation device 304 is connected to the irradiation control device 301, the counter 303, the target value memory 306, and the high frequency supply device 11, respectively. The interlock signal generation device is connected to the irradiation control device 301, the counter 303, the target value memory 306, the high-frequency supply device 11, and the central control device 100, respectively.

  The irradiation control device 301 reads the operation pattern of the scanning electromagnet 202 and the set value of the thickness of the range shifter 205 created by the treatment planning device 102 from the central control device 100 and registers them in the memory 302 provided in the irradiation control device. As shown in FIG. 4, the operation pattern of the scanning electromagnet 202 is a set value of the irradiation order set for each irradiation position, the excitation amount of the scanning electromagnet 202, and the excitation current of the scanning electromagnet 202. As shown in FIG. 5, the set value of the thickness of the range shifter 205 is a combination of the irradiation depth for forming a desired SOBP, the corresponding set value of the thickness of the range shifter 205 and the order of irradiation. is there.

  Further, the irradiation control device 301 reads the information shown in FIG. 6 from the central control device 100, the irradiation depth and the target value (target dose) of the irradiation dose for each irradiation position in the lateral direction, and the allowable range (allowable dose). Save in the target value memory 305. Further, the memory 305 stores a target value (target value S) and an allowable value (allowable value S) of an irradiation dose for the entire irradiation field.

  The operation pattern of the scanning electromagnet 202 is registered in advance in the memory 222 provided in the scanning electromagnet power supply control device 221. The operation pattern of the scanning electromagnet 202 may be read from the irradiation controller 301 by the scanning electromagnet power supply controller 221 or directly from the central controller 100.

  The target value and allowable value of the irradiation dose, the operating pattern of the scanning electromagnet 202, and the set value of the thickness of the range shifter 205 are previously created by the treatment planning device 102 based on the type and shape of the affected area 216a, and the central control device 100 treats the treatment. These pieces of information created by the planning device 102 are read and stored in the memory 101. The irradiation controller 301 reads these pieces of information from the central controller 100 before starting treatment.

  When the treatment starts, the ion beam is accelerated to a predetermined energy by the synchrotron 2, and after the acceleration is completed and preparation for emitting the beam is completed, an extraction preparation completion signal is transmitted from the accelerator controller 3 to the irradiation controller 301. Is done. Upon receiving the emission preparation completion signal, the emission control device 301 outputs the first set value (the order is 1) of the thickness of the range shifter 205 to the range shifter driving device 205b, and issues a command to change the thickness of the range shifter. Upon receiving the command, the range shifter driving device 205b changes the thickness of the range shifter 205 to match the initial set value, and indicates that the adjustment of the range shifter 205 is completed when the change of the thickness of the range shifter 205 is completed. (Range shifter adjustment completion signal) is output to the irradiation control device 301.

  Upon receiving the range shifter adjustment completion signal, the irradiation control device 301 issues a command to the scanning electromagnet power supply control device 221 to excite the scanning electromagnet 202. Upon receiving the command, the scanning electromagnet power supply control device 221 excites the two scanning electromagnets 202 based on the excitation current setting value stored in the memory 222 at the position of the first irradiation (the order is 1). When the excitation current reaches the set value, the scanning electromagnet power supply controller 221 outputs a signal (scanning magnet excitation completion signal) indicating that the excitation of the scanning electromagnet 202 is completed to the irradiation controller 301.

  Upon receiving the scanning magnet excitation completion signal, the irradiation control device 301 stores the irradiation position corresponding to the current excitation current setting value in the memory 302 as the current irradiation position, and outputs an emission start signal (beam ON signal) as the high frequency supply device 11. Output to. The high-frequency supply device 11 that has received the emission start signal applies a high-frequency voltage for emission to the high-frequency application device 10, and a beam is emitted from the synchrotron 2.

  The ion beam emitted from the synchrotron 2 is transported to the irradiation field forming apparatus 200 via the high energy transport system 14. The ion beam passing through the irradiation field forming apparatus 200 is deflected by the scanning electromagnet 202, and then the range is adjusted by the range shifter 205 and irradiated to the position set in the treatment plan. The current irradiation depth and lateral irradiation position are stored in the memory 302. The dose monitor 206 sequentially measures the beam irradiation amount (irradiation dose), and the counter 304 connected to the dose monitor 206 records the beam irradiation amount at the current irradiation position.

  The irradiation completion signal generation device 304 reads the current irradiation depth and the horizontal irradiation position number from the irradiation control device 301. The irradiation completion signal generation device 304 reads the irradiation dose at the current irradiation position from the counter 303 and sequentially compares it with the target dose at the current irradiation position stored in the memory 306. If the irradiation dose has reached the target dose, the irradiation completion signal generation device 304 outputs a beam OFF signal to the high-frequency supply device 11. The high-frequency supply device 11 that has received the beam OFF signal stops the application of the high-frequency voltage to the high-frequency application device 10, so that the beam emission from the synchrotron 2 is stopped. If the irradiation dose is less than the target dose, the irradiation completion signal generation device 304 does not generate the beam OFF signal, so the supply of the high frequency voltage to the high frequency application device 7 is continued and the beam is continuously emitted.

  The role of the irradiation completion signal generation device 304 is to continue the beam emission until the irradiation dose reaches the target dose at each irradiation position, and to stop the beam emission when the irradiation dose reaches the target dose. is there. The irradiation completion signal generation device 304 that has output the beam OFF signal outputs a signal indicating that irradiation at the current irradiation position is completed to the irradiation control device 301. Further, the irradiation completion signal generation device 304 outputs the irradiation dose at the current irradiation position to the irradiation control device 301, and resets the counter 303 in preparation for irradiation to the next irradiation position. Instead of resetting the counter 303, the integrated value of the irradiation dose from the start of treatment to the completion of irradiation is recorded, and the irradiation dose is obtained from the difference between the reading of the counter 303 and the integrated value at the next irradiation position. May be.

  The irradiation dose input to the irradiation controller 301 is recorded in the memory 101 of the central controller 100 together with the current irradiation depth and lateral irradiation position. Upon receiving the irradiation completion signal, the irradiation control device 301 changes the lateral irradiation position (excitation current setting value) based on the operation pattern of the scanning electromagnet 202 stored in the memory 302, and sends an excitation current to the scanning electromagnet power supply control device 220. Instruct to change. The scanning electromagnet power supply control device 221 sets the excitation current of the scanning electromagnet 202 based on the operation pattern stored in the memory 222, and thereby the ion beam is irradiated to a new lateral irradiation position. In this way, by repeating the change of the excitation amount of the scanning electromagnet 202 and the beam irradiation, a beam of a desired dose is irradiated to all the irradiation positions in the lateral direction at the current irradiation depth.

  When irradiation at the current irradiation depth is completed, the irradiation control device 301 outputs the next set value of the thickness of the range shifter 205 to the range shifter driving device 205b, and instructs to change the thickness of the range shifter 205. At this time, beam emission from the synchrotron 2 is stopped, and the energy of the circulating beam of the synchrotron 2 is kept constant. When the change of the thickness of the range shifter 205 is completed, the range shifter driving device 205b outputs a range shifter adjustment completion signal to the irradiation control device 301, and irradiation at a new irradiation depth is started similarly to the initial irradiation depth. In this way, by changing the thickness of the range shifter 205 and repeating the irradiation at each irradiation depth, a beam with a desired dose is applied to all the irradiation directions in all the irradiation depths set by the treatment planning apparatus 101. Is irradiated.

  The display device 320 is connected to the central control device 100 and sequentially displays the irradiation dose for each irradiation position in the lateral direction at each irradiation depth stored in the memory 101. Since the irradiation dose stored in the memory 101 is updated every time irradiation to a certain irradiation position is completed, the driver can know the progress of treatment by the display device 320. Further, the display device 320 displays the operation parameters of the synchrotron 2, the parameters of the irradiation field forming device 200, and information on the treatment plan, so that the driver can easily grasp the operation conditions of the particle beam treatment system.

  The interlock signal generation device 305 reads the current irradiation depth and the horizontal irradiation position number from the irradiation control device 301. The interlock signal generation device 305 reads the irradiation dose at the current irradiation position from the counter 303 and sequentially compares it with the allowable dose at the current irradiation position stored in the memory 306. The interlock signal generation device 305 confirms that the irradiation dose is less than the allowable dose, and outputs an interlock signal to the high-frequency supply device 11 and the central control device 100 if the irradiation dose exceeds the allowable dose. Thereby, the procedure of stopping beam extraction and interrupting treatment is performed. Further, the interlock signal generation device 305 calculates the total (total dose) of the irradiation dose at each irradiation position, and the allowable value (allowable value S) of the irradiation dose for the entire irradiation field stored in the memory 305. Compare with When the total dose exceeds the allowable value, the interlock signal generation device 305 outputs an interlock signal and the beam emission stops. The interlock signal generation device 305 sequentially compares the irradiation dose and its allowable value, and outputs an interlock signal when the allowable value is exceeded. Therefore, in the unlikely event that the accelerator or its control device operates unexpectedly Irradiation of an unnecessary ion beam to the patient 216 can be prevented.

  A method for changing the operation pattern of the synchrotron 2 on the basis of the amount of circular beam charge at the time when irradiation is completed at a certain irradiation depth will be described in detail.

  The operation pattern of the synchrotron 2 will be described using the operation pattern of the deflection electromagnet 7 of the synchrotron 2 shown in FIG. FIG. 7 is a graph in which time is plotted on the horizontal axis and the amount of excitation of the deflecting electromagnet 7 is plotted on the vertical axis, and a broken line 400 represents an operation pattern of the deflecting electromagnet 7. The operation pattern of the deflecting electromagnet 7 (the operation pattern of the synchrotron 2) is composed of an incident period, an acceleration period, an extraction preparation period, an extraction period, a deceleration preparation period, and a deceleration period, and one cycle from the start of the beam incident period to the end of the deceleration period. Periodic operation is performed. The ion beam from the front accelerator 5 is incident on the orbit of the synchrotron 2 during the incident period, and is accelerated to the target energy during the acceleration period. The excitation amount of the deflecting electromagnet 7 is constant during the emission preparation period, but the excitation amount of the quadrupole electromagnet 8 and the hexapole electromagnet (not shown) is changed to form an unstable region (separatory) of the betatron oscillation of the circular beam. Is done. During the emission period, the thickness of the range shifter 205 is changed and beam scanning is performed at each irradiation depth, and the circulating beam remaining without being emitted from the synchrotron 2 has the same energy (incident as the incident beam of the synchrotron 2 in the deceleration period). Energy). In the deceleration preparation period, the excitation amounts of the quadrupole electromagnet 8 and the hexapole electromagnet are changed, and the separatrix formed during the extraction preparation period is released.

  If the total amount of ion beam to be irradiated to the irradiation field is larger than the maximum value of the circulating beam charge of the synchrotron 2, the circulating beam is insufficient at any point in the extraction period, and it is difficult to continue the irradiation. Become. When the round beam charge amount is extremely reduced, the emission beam current is reduced and the irradiation time is increased. Therefore, when the round beam charge amount is less than a certain threshold (for example, 5% of the maximum value of the round beam charge amount). Irradiation must be stopped, the circulating beam that has not been emitted must be decelerated, and then incident again on the synchrotron 2. Such a threshold value of the amount of the orbiting beam charge is stored in advance in the irradiation control device memory 302, and the irradiation control device 301 controls the stop of extraction of the ion beam from the synchrotron 2 based on this threshold value. Further, the irradiation control layer device 301 controls each device so that the ion beam enters the synchrotron 2 from the pre-stage accelerator 5 after decelerating the ion beam that circulates in the synchrotron 2 without being emitted. At this time, if the amount of circular beam charge is insufficient before irradiation at a certain irradiation depth is completed, beam emission stops while scanning the beam in the horizontal direction, and a dose distribution in the horizontal direction is formed over two periods. Will be. Since it takes about 1 second from the start of the deceleration preparation period of the synchrotron 2 to the start of the extraction period of the next cycle, the dose uniformity in the lateral direction deteriorates due to the movement of the affected part 216a accompanying the breathing or body movement of the patient 216. There is a fear.

  Therefore, in the present embodiment, the operation pattern of the synchrotron 2 is changed based on the measurement result of the orbiting beam charge at the time when irradiation at a certain irradiation depth is completed, and the orbiting beam is in the middle of scanning the beam in the horizontal direction. Preventing a shortage of charge.

  When the irradiation with respect to a certain irradiation depth in the emission period of the synchrotron 2 is completed, the irradiation control device 301 of the irradiation control system 300 informs the accelerator control device 3 and the beam charge amount monitor control device 16 in the lateral direction at the current irradiation depth. A signal (scan completion signal) indicating that scanning and irradiation have been completed is output. Upon receiving the scanning completion signal, the accelerator controller 3 keeps the energy of the circulating beam constant, and the beam charge monitor controller 16 measures the circulating beam charge amount of the synchrotron 2 with the beam charge monitor 12, and the measurement result. Is output to the irradiation control device 301. In this embodiment, the dedicated monitor 12 is provided on the orbit of the ion beam of the synchrotron 2 for measuring the amount of the orbiting beam charge, but the signal of the beam position monitor (not shown) in the synchrotron 2 is used. May be used to calculate the circulating beam charge amount, and the beam charge monitor 12 may be omitted.

  The memory 302 of the irradiation control device 301 stores the value of the amount of orbital beam charge that is read from the treatment planning device 101 and is necessary for completing irradiation at each irradiation depth. The value of the orbital beam charge necessary for completing irradiation at each irradiation depth is calculated by the treatment planning apparatus 101 based on the target value of the irradiation dose for each irradiation depth. The correlation between the target value of the irradiation dose at each irradiation depth and the circulating beam charge amount necessary for completion of irradiation can be obtained in advance by simulation or experiment. The amount of circular beam charge required to complete irradiation for a certain irradiation depth is the amount of circular beam charge emitted while irradiating the beam to the depth and the above-mentioned irradiation. This is a value obtained by adding the necessary amount of circulating beam charges. In order to prevent the amount of circular beam charge from running short while scanning the beam in the horizontal direction, the value of the circular beam charge necessary for completion of irradiation is obtained by adding a margin to the above-mentioned value. May be.

  The irradiation control device 301 compares the current amount of the orbiting beam charge with the amount of the orbiting beam charge necessary for completing the irradiation for the next irradiation depth. It is determined that the amount of charge is sufficient to complete irradiation for the next irradiation depth. When it is determined that the circulating beam charge amount is sufficient, the irradiation control device 301 waits for the range shifter adjustment completion signal from the range shifter driving device 205b, and the next irradiation depth during the same operation cycle (outgoing period) of the synchrotron 2 Irradiation is performed. When it is determined that the amount of the orbiting beam charge is insufficient, the irradiation control device 301 instructs the accelerator control device 3 to decelerate the orbiting beam and move to the next cycle. Receiving the instruction, the accelerator control device 3 decelerates the circulating beam that has not been emitted from the synchrotron 2, and again enters the beam from the pre-accelerator 5 to prepare for acceleration and extraction of the circulating beam. As a result, it is guaranteed that a sufficient amount of beam is always circulating around the synchrotron 2 at the time of starting irradiation at a certain irradiation depth. There is no shortage of circulating beam charge during the formation of the irradiation field.

  In this embodiment, the orbiting beam charge amount is measured immediately after the irradiation to a certain irradiation depth is completed. However, the timing for measuring the orbiting beam charge amount is the next irradiation after the irradiation to a certain irradiation depth is completed. It can be arbitrarily set until irradiation with respect to the depth is started.

  In this embodiment, the irradiation depth is changed within the same period of the synchrotron 2 only when the circulation beam charge amount of the synchrotron 2 is sufficient to complete the irradiation at the next irradiation depth, and the circulation beam charge amount is changed. Is not sufficient, the next cycle of the synchrotron 2 is entered, so that the amount of circular beam charge does not become deficient during the scanning of the beam in the horizontal direction, and the dose distribution in the horizontal direction is Deterioration of the lateral dose uniformity due to being formed over two operating cycles can be prevented.

  If the target value of the irradiation dose for a certain irradiation depth is larger than the maximum value of the circulating beam charge of the synchrotron 2, it is always necessary to make a round trip in the middle of the scan if the horizontal dose distribution is formed by only one scan. The beam charge amount is insufficient, and a lateral dose distribution is formed over two or more operating cycles of the synchrotron 2. Since the amount of ion beam necessary to irradiate the affected area 216 with a dose increases as the position becomes deeper, the amount of the circulating beam charge tends to be insufficient particularly at a deep position. In the present embodiment, the dose distribution formation in the horizontal direction is divided into a plurality of times, and the affected part 216a is repeatedly scanned to prevent the amount of circulating beam charge from becoming insufficient during the scanning. Specifically, the irradiation control device 300 and the target value memory 306 record the target value of the irradiation dose at each irradiation position per scan, and during the beam irradiation, the irradiated dose and the current irradiation position are recorded. Compare target doses per dose. When the irradiated dose reaches the target value per time, the beam emission from the synchrotron 2 is stopped, the excitation amount of the scanning electromagnet 202 is changed, and the irradiation position in the horizontal direction is scanned. When one irradiation at the current irradiation depth is completed, the irradiation control device 301 instructs the beam charge amount monitor control device 16 to measure the round beam charge amount, and the measurement result of the round beam charge amount is the irradiation control device 301. Is input. The irradiation control device 301 compares the current amount of circular beam charge with the amount of circular beam charge required to complete one scan at the current irradiation depth, and the current amount of circular beam charge is larger. Only if the scan at the current irradiation depth is repeated within the same operating period of the synchrotron 2. When the current amount of the orbital beam charge is not sufficient to complete one scan, the irradiation control device 301 instructs the accelerator control device 3 to shift to the next operation cycle. The target value of the irradiation dose per scan at each irradiation position and the amount of circulating beam charge necessary to complete one scan are calculated in advance by the treatment planning device 101, and the irradiation control device 301 is sent from the treatment planning device 101. It is read and saved in the memory 302. Further, the irradiation control device 301 reads the setting value of the number of scans at each irradiation depth from the treatment planning device 101 and stores it in the memory 302.

  The irradiation controller 301 counts the number of scans at the current irradiation depth, and completes ion beam irradiation at the current irradiation depth when the number of scans reaches a set value. The irradiation control device 301 acquires the amount of circular beam charge at the time when irradiation at the current irradiation depth is completed, and performs one scanning at the next irradiation depth, as in the case where one scanning is completed. Compare with the amount of circular beam charge required to complete. If the set value of the number of scans at the next irradiation depth is one, the amount of circular beam charge required to complete one scan is the amount of circular beam charge required to complete irradiation at the next irradiation depth. Matches.

  Even when the maximum value of the circulating beam charge of the synchrotron 2 is sufficient for completion of irradiation at a certain irradiation depth, the formation of the lateral dose distribution at the depth is divided into a plurality of times, and the affected area 216a is repeatedly scanned. You may do it. Thereby, since the time required for one scan is shortened, the influence on the lateral dose distribution due to the movement of the affected part 216a is further reduced. In addition, since the amount of circular beam charge required for one scan is reduced by the division, the amount of circular beam charge at the time when irradiation at a certain irradiation depth is completed is not sufficient for completion of irradiation at the next irradiation depth. In both cases, if it is sufficient to complete one scan at the next irradiation depth, it is possible to shift to irradiation at the next irradiation depth within the same operation cycle of the synchrotron 2. Thereby, the utilization efficiency of the circulating beam is improved and the irradiation time is shortened.

  In this embodiment, the scanning is started within the same period of the synchrotron 2 only when the amount of the circular beam charge of the synchrotron 2 is sufficient to complete one scan of the lateral irradiation position. Even when scanning is repeatedly performed, it is possible to prevent deterioration of the lateral dose uniformity due to the fact that the lateral dose distribution is formed over two periods of the synchrotron 2.

  In this embodiment, the horizontal beam position is discretely scanned. However, the excitation amount of the scanning electromagnet 202 may be changed during beam irradiation to continuously scan the horizontal beam irradiation position. . When the beam is continuously scanned, the irradiation position in the horizontal direction continuously moves on the trajectory set by the treatment planning apparatus 101 as shown in FIG. FIG. 8 is a schematic diagram showing a horizontal irradiation position when scanning is performed in two directions (X direction and Y direction) perpendicularly intersecting a certain irradiation depth of the affected part 216a, and a curve 500 indicates the irradiation position in the horizontal direction. A trajectory to be traced, a black circle 501 is a scanning start position, and a black circle 502 is a scanning end position. The scanning start position 501 and end position 502 may be the same place. Since the intensity of the outgoing beam from the synchrotron 2 is not constant in time, the scanning with respect to a certain irradiation depth is performed a plurality of times in continuous scanning, and the temporal change in the outgoing beam intensity is averaged. At this time, a process in which the irradiation position moves from the start position 501 to the end position 502 is defined as one scan. When the start position 501 and the end position 502 are different, the beam emission from the synchrotron 2 is stopped when the irradiation position reaches the end position 502, and the excitation amount of the scanning electromagnet 202 is changed to move the irradiation position to the start position 501. After moving, the next scan is started. When the start position 501 and the end position 502 are the same, even if the irradiation position reaches the end position 502 (start position 501), the beam emission does not stop, and the next scanning is immediately started.

  Similar to the case where the irradiation position is scanned discretely, also in the case where the irradiation position is continuously scanned in the horizontal direction, based on the measurement result of the circulating beam charge amount of the synchrotron 2 at the time when one scan is completed. By changing the operation pattern of the synchrotron 2, it is possible to prevent the deterioration of the lateral dose uniformity due to the shortage of the circulating beam charge during the scanning.

  The irradiation controller 301 acquires the measurement result of the circular beam charge amount at the time when one irradiation is completed, and the circular beam charge amount is compared with the circular beam charge amount necessary for one scan. Determine if it is sufficient for completion. If the round beam charge amount is sufficient for the completion of the next scan, the irradiation control device 301 starts the next scan within the same operation cycle of the synchrotron 2, and if the round beam charge amount is not sufficient, the irradiation control device. 301 instructs the control device 3 of the synchrotron 2 to shift to the next operation cycle.

  When the scan start position 501 and the end position 502 are different, the measurement of the circulating beam charge and the determination of whether or not to move to the next scan within the same operation cycle of the synchrotron 2 are performed by setting the lateral irradiation position to the end position 502. This is performed while moving from to the start position 501, that is, while stopping the beam emission. When the start position 501 and the end position 502 are the same, the next scan is started immediately after the end of one scan, so that the lateral irradiation position is more than the end position 502 (start position 501). The orbiting beam charge amount is measured at the previous timing, and the determination as to whether or not the orbiting beam charge amount is sufficient for the completion of the next scan is completed until the lateral irradiation position reaches the end position 502. At this time, the amount of circular beam charge necessary for completion of the next scan is the amount of circular beam charge emitted from the synchrotron 2 during one scan, the amount of circular beam charge necessary for continuing the emission, This is the total amount of the circulating beam charge emitted from the measurement of the circulating beam charge amount until the lateral irradiation position reaches the end point 502. When the round beam charge amount is sufficient, even when the lateral irradiation position reaches the end point 502, the beam emission from the synchrotron 2 is not stopped, and the next scanning is immediately started. When the amount of rounding beam charge is not sufficient, beam emission stops when the lateral irradiation position reaches the end point 502, and the irradiation control device 301 instructs the accelerator control device 3 to shift to the next operation cycle.

  When the lateral irradiation position is continuously scanned, the irradiation area is scanned repeatedly until a desired lateral dose distribution is formed, as in the case of discrete scanning. When irradiation at a certain irradiation depth is completed, the irradiation control device 301 acquires a measurement result of the circulating beam charge amount of the synchrotron 2 and whether or not it is sufficient to complete one scan at the next irradiation depth. Determine. If the circulating beam charge amount is sufficient, the irradiation control device 301 instructs to change the thickness of the range shifter 205 and starts scanning at the next irradiation depth within the same operation cycle of the synchrotron 2. If the circulating beam charge amount is not sufficient, the irradiation control device 301 instructs the accelerator control device 3 to shift to the next operation cycle. Since the change of the thickness of the range shifter requires a finite time, the measurement of the circulating beam charge and the next within the same operation cycle of the synchrotron 2 are performed regardless of whether the start point 501 and the end point 502 are the same. Whether or not to shift to scanning at the irradiation depth is determined in a state where beam emission from the synchrotron 2 is stopped.

(Embodiment 2)
As in the first embodiment, the particle beam therapy system according to the present embodiment irradiates the affected area 216a of the patient 216 with an ion beam. The configuration of the particle beam therapy system of this embodiment is shown in FIG. The particle beam therapy system according to the present embodiment has the same configuration as that of Example 1 shown in FIG. 1, but changes the energy of the outgoing beam from the synchrotron 2 instead of changing the thickness of the range shifter 205. Thus, the irradiation depth is changed within the operation cycle of the synchrotron 2. In the particle beam therapy system of this embodiment, the range shifter 205 in the irradiation field forming apparatus 200 is omitted in order to adjust the irradiation depth by changing the emitted beam energy of the synchrotron 2. As a result, the ion beam passing through the irradiation field forming apparatus 200 is not scattered in the lateral direction by the range shifter, so that the lateral size of the irradiation beam is reduced and a more accurate lateral dose distribution is formed. It is possible.

  As in the first embodiment, in this embodiment, the amount of circular beam charge at the time when irradiation at a certain irradiation depth is completed, or at the time when one scan of the lateral irradiation position is completed is measured, and based on the measurement result. By changing the operation pattern of the synchrotron 2, it is possible to prevent the deterioration of the lateral dose uniformity due to the shortage of the circulating beam charge of the synchrotron 2 during the scan.

  When the beam is scanned a plurality of times at a certain irradiation depth and there is no change in the irradiation depth between the scans, it is possible to prevent the shortage of the round beam charge during the scanning in the same manner as in the first embodiment. . Only when the amount of orbiting beam charge at the time when one scan is completed is sufficient to complete the next scan, the next scan is shifted within the same operation cycle of the synchrotron 2, and the amount of orbiting beam charge is insufficient during the scan. Therefore, the deterioration of the lateral dose uniformity due to the formation of the lateral dose distribution over the two periods of the synchrotron 2 is prevented.

  FIG. 12 shows a method for preventing the deterioration of the lateral dose uniformity due to the shortage of the circulating beam charge during the beam scanning when the irradiation depth is changed within the same operation cycle of the synchrotron 2. This will be described with reference to a flowchart.

  When irradiation at a certain irradiation depth is completed, the irradiation control device 301 acquires the amount of circular beam charge of the synchrotron 2 at the time of completion of irradiation as in the first embodiment, and completes one scan at the next irradiation depth. Compare with the required round beam charge. Here, when the irradiation at the next irradiation depth is completed in one scan, the amount of circular beam charge required for one scan at the next irradiation depth and the irradiation at the next irradiation depth are completed. The necessary amount of the round beam charge is the same. The irradiation control device 301 instructs the accelerator control device 3 to change the emitted beam energy when the round beam charge amount is sufficient to complete one scan at the next irradiation depth, and the round beam charge amount is not sufficient. Instructs the accelerator controller 3 to decelerate the orbiting beam and shift to the next operation cycle. The accelerator control device 3 that has received the instruction to change the outgoing beam energy changes the energy of the orbiting beam to a value corresponding to the next irradiation depth within the same operation cycle of the synchrotron 2, and prepares for outgoing with the changed energy. Is completed, an output preparation completion signal is output to the irradiation control device 301. The accelerator control device 3 that has been instructed to shift to the next operation cycle decelerates the orbiting beam to the incident energy of the synchrotron 2, injects the beam from the previous stage accelerator 5 into the synchrotron 2, After completing the preparation for extraction by accelerating to the energy corresponding to the irradiation depth, an extraction preparation completion signal is output to the irradiation control device 301.

  When changing the energy of the outgoing beam within the same operation cycle of the synchrotron 2, the irradiation control device 301 gives an instruction to the high-energy beam transport system 14 and the electromagnet control device (not shown) installed in the gantry 15, The amount of excitation of these electromagnets is changed to a value corresponding to the energy of the outgoing beam after the change.

  The operation pattern of the synchrotron 2 when instructed to change the emitted beam energy or shift to the next operation cycle will be described with reference to FIG. FIG. 9 is a graph in which time is plotted on the horizontal axis and the amount of excitation of the deflection electromagnet 7 of the synchrotron 2 is plotted on the vertical axis, and the operation pattern of the deflection electromagnet 7 when irradiating an ion beam at two irradiation depths is shown. To express. In addition, the irradiation with respect to each irradiation depth shall be completed by one scan. A broken line 410 is an excitation pattern of the deflection electromagnet 7 when instructed to change the emitted beam energy within the same operation cycle, and a broken line 411 is an excitation pattern of the deflection electromagnet 7 when instructed to shift to the next cycle. A black circle 414 represents a point in time when the amount of circular beam charge is measured. Since the momentum of the circular beam (outgoing beam) is proportional to the excitation amount of the deflection electromagnet 7, as indicated by the broken line 411, it is possible to emit beams with different energies by providing a plurality of outgoing periods within the same operation cycle. .

  In this way, the orbit within the same operation cycle of the synchrotron 2 only when the amount of orbital beam charge at the time when the irradiation to the first irradiation depth is completed is sufficient for the completion of one scanning at the second irradiation depth. Since the beam energy is changed, there is no shortage of the circulating beam charge in the middle of scanning, and the deterioration of dose uniformity due to the formation of the lateral dose distribution over two operating cycles is prevented. In FIG. 9, it is assumed that the number of irradiation depths is two and the beam is irradiated from the lower irradiation beam energy of the synchrotron 2, that is, from the irradiation depth close to the body surface, but the number of irradiation depths and the synchrotron 2 The number of irradiation depths irradiated within the same operation cycle may be two or more, and the beams may be irradiated in order from the irradiation beam with the higher energy of the circulating beam, that is, the irradiation depth far from the body surface. Further, in order to reduce the influence of hysteresis and improve the reproducibility of the excitation amount of the electromagnet including the deflection electromagnet 7, the orbiting beam is set to the maximum energy before the irradiation start at the first irradiation depth or before the deceleration preparation. You may make it accelerate to.

  In this embodiment, the orbiting beam charge amount is measured immediately after the irradiation to a certain irradiation depth is completed. However, the measurement timing of the orbiting beam charge amount is the irradiation depth after the irradiation to a certain irradiation depth is completed. It is possible to arbitrarily set the period until the start of the change of the energy of the orbiting beam for the subsequent change to the next operation cycle.

  When the irradiation with respect to each irradiation depth is completed by one scan, the present invention further has the following effects. FIG. 10 is a diagram showing the operation pattern of the deflecting electromagnet 7 as in FIG. 9. However, when the broken line 411 completes irradiation with respect to the first irradiation depth, the circulating beam charge amount is measured. The operation pattern of the deflecting electromagnet 8 when moving to the next operation cycle because it is not sufficient for completion of the irradiation for the second irradiation depth, and the broken line 412 is irradiated at the second irradiation depth without measuring the circulating beam charge amount. The operation pattern of the deflecting electromagnet 7 when the circular beam charge amount becomes insufficient during the scanning, and the black circle 413 represents the time point when the insufficient circular beam charge amount occurs. As is apparent from the drawing, the polygonal line 412 needs to accelerate the circulating beam to the same energy again after the amount of circulating beam charge is insufficient. Therefore, it is necessary to perform the preparation for extraction and the preparation for deceleration twice at the second irradiation depth. is there. Since the preparation for extraction and preparation for deceleration may occupy 10% or more of the entire operation cycle, the time required for irradiation increases as the number of preparations for extraction and preparation for deceleration increases. The present invention has the effect of shortening the irradiation time by reducing the number of preparations for extraction and deceleration preparation at each irradiation depth in order to prevent the amount of circulating beam charge from being insufficient before the irradiation for a certain energy is completed. .

(Embodiment 3)
As in the second embodiment, the particle beam therapy system according to the present embodiment irradiates the affected area 216a of the patient 216 with an ion beam. The particle beam therapy system of the present embodiment has the same configuration as that of the second embodiment shown in FIG. 11, and irradiation is performed within the operation cycle of the synchrotron 2 by changing the energy of the emitted beam from the synchrotron 2. It has a configuration for changing the depth.

  When the beam is scanned a plurality of times at a certain irradiation depth and there is no change in the irradiation depth between the scans, it is possible to prevent the shortage of the round beam charge during the scanning in the same manner as in the second embodiment. . Since the circular beam charge amount of the synchrotron 2 is measured every time one scan is completed, and only when the measurement result is sufficient for the completion of the next scan, the next scan is performed within the same operation cycle of the synchrotron 2, The amount of circular beam charge does not become insufficient in the middle of scanning, and deterioration of the lateral dose uniformity due to the formation of the lateral dose distribution over the two periods of the synchrotron 2 is prevented.

  When irradiating two or more irradiation depths within the same operation cycle of the synchrotron 2, in this embodiment, after the irradiation with respect to a certain irradiation depth is completed, the energy of the circulating beam of the synchrotron 2 is After changing to a value corresponding to the irradiation depth, measure the amount of circular beam charge and perform irradiation at the changed irradiation depth only when the measurement result is sufficient for one scan at the changed irradiation depth. Start.

  Since it takes a certain amount of time (for example, 100 to 300 ms) to change the energy of the circulating beam of the synchrotron 2 after the irradiation at a certain irradiation depth is completed, the energy of the circulating beam of the synchrotron 2 is changed. In the meantime, it may be slightly lost due to scattering with residual gas in the vacuum duct. In Embodiment 2, the circulating beam charge is measured before changing the energy of the circulating beam, so that the circulating beam is not lost at the next irradiation depth due to loss of the circulating beam during the energy change. In addition, it is necessary to add a margin when obtaining the amount of circular beam charge necessary for completing one scan at the next irradiation depth. In this embodiment, since the amount of circular beam charge is measured after changing the energy of the circular beam, is it necessary to add a margin when calculating the amount of circular beam charge necessary for completing one scan at the irradiation depth after the change? The margin can be made smaller than that in the second embodiment. This reduces the amount of orbital beam charge necessary for completing one scan at the irradiation depth after the change, and increases the probability that the measurement result of the amount of orbital beam charge is determined to be sufficient for one scan completion. The utilization efficiency of the circulating beam particles is increased, and the time required for irradiation can be shortened.

  When the beam is irradiated to two or more irradiation depths in the same operation cycle of the synchrotron 2, the deterioration of the lateral dose uniformity due to the shortage of the circulating beam charge amount during the beam scanning is prevented. The method will be described with reference to the flowchart shown in FIG.

  When irradiation at a certain irradiation depth is completed, the irradiation control device 301 instructs the accelerator control device 3 to change the output beam energy. The accelerator control device 3 that has received the instruction to change the outgoing beam energy changes the energy of the orbiting beam to a value corresponding to the next irradiation depth within the same operation cycle of the synchrotron 2, and prepares for outgoing with the changed energy. Is completed, an output preparation completion signal is output to the irradiation control device 301. Further, the irradiation control device 301 gives instructions to the electromagnet control device (not shown) installed in the high energy beam transport system 14 and the gantry 15 and corresponds to the energy of the emitted beam after changing the excitation amount of these electromagnets. Change to a value. The irradiation control device 301 that has received the emission preparation completion signal acquires the amount of circular beam charge of the synchrotron 2 in the same manner as in the second embodiment, and performs one scanning at the irradiation depth after the change (current irradiation depth). Compare with the amount of circular beam charge required for completion. The irradiation control device 301 starts beam emission from the synchrotron 2 in the same manner as in the second embodiment when the amount of circular beam charge is sufficient for one scan at the current irradiation depth, and the amount of circular beam charge is If not enough, the accelerator controller 3 is instructed to decelerate the orbiting beam and shift to the next operation cycle. In the present embodiment, the irradiation control device acquires the circular beam charge amount of the synchrotron 2 after receiving the extraction preparation completion signal. However, in order to start irradiation immediately after receiving the extraction preparation completion signal, the irradiation preparation period It is also possible to acquire the amount of orbital beam charge and determine whether to start irradiation with respect to the second irradiation depth or to shift to the next operation cycle.

  The operation pattern of the synchrotron 2 in the present embodiment will be described with reference to FIG. FIG. 13 is a graph in which time is plotted on the horizontal axis and the amount of excitation of the deflecting electromagnet 7 of the synchrotron 2 is plotted on the vertical axis, and the operation pattern of the deflecting electromagnet 7 when irradiating an ion beam at two irradiation depths is shown. To express. As in the second embodiment, irradiation with respect to each irradiation depth is completed in one scan. A polygonal line 410 is an excitation pattern of the deflection electromagnet 7 when instructed to irradiate a beam with a second irradiation depth within the same operation period of the synchrotron 2, and a polygonal line 420 is an instruction to shift to the next period. This is an operation pattern of the deflection electromagnet 7. A black circle 421 represents a time point at which the circulating beam charge amount of the synchrotron 2 is measured.

  In the present embodiment, the circulating beam charge amount is measured after the energy of the circulating beam of the synchrotron 2 is changed to a value corresponding to the second irradiation depth until the irradiation with respect to the second irradiation depth is started. However, since the irradiation to the second irradiation depth is started within the same operation cycle of the synchrotron 2 only when the measurement result is sufficient to complete one scanning at the second irradiation depth, The amount of beam charge is not insufficient, and deterioration of dose uniformity due to the formation of a lateral dose distribution over two operating cycles is prevented. Further, in this embodiment, the energy of the orbiting beam of the synchrotron 2 is changed to a value corresponding to the second irradiation depth and then the amount of the orbiting beam charge is measured, so that the beam utilization efficiency is improved and the irradiation is completed. Can be shortened. In FIG. 13, it is assumed that the number of irradiation depths is two and the beam is irradiated from the lower irradiation beam energy of the synchrotron 2, that is, the irradiation depth close to the body surface. The number of irradiation depths irradiated within the same operation cycle may be two or more, and the beams may be irradiated in order from the irradiation beam with the higher energy of the circulating beam, that is, the irradiation depth far from the body surface. Further, in order to reduce the influence of hysteresis and improve the reproducibility of the excitation amount of the electromagnet including the deflection electromagnet 7, the orbiting beam is set to the maximum energy before the irradiation start at the first irradiation depth or before the deceleration preparation. You may make it accelerate to.

  In the first to third embodiments, the operation pattern of the synchrotron that accelerates and emits the ion beam is controlled based on the amount of circular beam charge at the time when one scan is completed or when irradiation to a certain irradiation depth is completed. . Specifically, the next scan or next irradiation within the same operation cycle of the synchrotron is only performed when the amount of the circular beam charge is sufficient to complete the next one scan or the irradiation for the next irradiation depth. Transition to scanning in depth. When the amount of charge of the orbiting beam is not sufficient, the orbiting beam is decelerated and the next operation cycle of the synchrotron is started. This prevents the amount of circular beam charge from becoming insufficient in the middle of scanning, thus preventing deterioration in lateral dose uniformity due to the formation of a lateral dose distribution over two or more operating cycles of the synchrotron. can do.

DESCRIPTION OF SYMBOLS 1 Ion beam generator 2 Synchrotron 3 Accelerator controller 4 Ion source 5 Previous stage accelerator 6 Low energy beam transport system 7 Deflection magnet 8 Quadrupole electromagnet 9 High frequency acceleration cavity 10 High frequency application device for extraction 11 High frequency supply device 12 Beam charge monitor 13 Deflector for extraction 14 High energy beam transport system 15 Rotating gantry 16 Beam charge monitor control device 100 Central control device 101 Central control device memory 102 Treatment planning device 103 Treatment planning device memory 200 Irradiation field forming device 201 Casing 202 Scanning electromagnet 203 Scattering body 204 Ridge filter 205 Range shifter 205a Plate 205b Range shifter driving device 206 Dose monitor 207 Beam position monitor 208 Collimator 216 Patient 216a Affected part 220 Scanning electromagnet power supply 221 Scanning electromagnet power supply Control device 222 Scanning electromagnet power supply control device memory 300 Irradiation control system 301 Irradiation control device 302 Irradiation control device memory 303 Counter 304 Irradiation completion signal generation device 305 Interlock signal generation device 306 Target value memory 320 Display device 400, 401, 410, 411 , 412, 420 Excitation pattern 413 of the deflecting magnet Time point 414, 421 Time point when the amount of the round beam charge is measured Time point 500 for measuring the round beam charge amount Trajectory 501 of the lateral beam irradiation position Starting point 502 of the lateral beam scanning Lateral direction End point of beam scanning

Claims (12)

A synchrotron that accelerates and emits a charged particle beam;
An irradiation field forming apparatus for irradiating an irradiation target with the charged particle beam that has passed through the scanning electromagnet, and having a scanning electromagnet that scans the charged particle beam emitted from the synchrotron in a direction perpendicular to a beam traveling direction;
The amount of circular beam charge of the synchrotron in the period from the completion of the scanning of the charged particle beam to the entire irradiation region at the irradiation depth of the charged particle beam by the scanning electromagnet until the start of the next scanning Is provided with a control device that determines whether or not it is sufficient to complete the scanning of the entire irradiation region that is the target of the next scan, and changes the operation pattern of the synchrotron. Charged particle beam irradiation device. The charged particle beam irradiation apparatus according to claim 1,
The control device includes a measurement result of the orbiting beam charge amount in the period from the scanning of the charged particle beam to the entire irradiation region in the irradiation depth the is completed to start scanning the next round, the Compare the synchrotron's orbital beam charge required to complete the scanning of the irradiation position to the entire irradiation area at the irradiation depth that is the object of the next scan, and if the measurement result is greater The charged particle beam, wherein the next scan is started within the same operation cycle of the synchrotron and the synchrotron is controlled to shift to the next operation cycle when the measurement result is smaller Irradiation device. The charged particle beam irradiation apparatus according to claim 1,
The scanning electromagnet continuously scans the irradiation position in the lateral direction of the charged particle beam,
The control device includes a measurement result of a round beam charge amount before completion of scanning of the charged particle beam over the entire irradiation region at the certain irradiation depth, and an irradiation depth that is a target of the next scanning. Compare the amount of circular beam charge of the synchrotron required to complete the scanning of the entire irradiation area in the case of the above, and if the measurement result is larger, the next scan is performed within the same operation cycle of the synchrotron. The charged particle beam irradiation apparatus is characterized by starting and controlling the synchrotron to shift to the next operation cycle when the measurement result is smaller. The charged particle beam irradiation apparatus according to claim 1,
The irradiation device, a charged particle beam irradiation to the irradiation entire region definitive to the irradiation depth the is based on the orbiting beam charge amount of the synchrotron at the time of completion, and changes the operation pattern of the synchrotron Irradiation device. The charged particle beam irradiation apparatus according to claim 4,
The irradiation device includes: the orbiting beam charge amount measurement results during the period from when the irradiation of the charged particle beam with respect to the whole definitive irradiation region to the irradiation depth the is completed to start the change of the irradiation depth, the following Compared with the circulating beam charge amount of the synchrotron required for the completion of scanning of the entire irradiation area at the irradiation depth of the next, if the measurement result is larger, the next irradiation within the same operation cycle of the synchrotron A charged particle beam irradiation apparatus characterized by starting irradiation at a depth and controlling the synchrotron to shift to the next operation cycle when the measurement result is smaller. The charged particle beam irradiation apparatus according to claim 4,
The irradiation device includes: the orbiting beam charge amount measurement results during the period from when the irradiation of the charged particle beam with respect to the whole definitive irradiation region to the irradiation depth the is completed to start the change of the irradiation depth, the following When the number of the measurement results is larger, the same operation period of the synchrotron is compared with the amount of the circular beam charge of the synchrotron required to complete the irradiation of the charged particle beam with respect to the entire irradiation region at the irradiation depth of The charged particle beam irradiation apparatus is characterized in that the irradiation at the next irradiation depth is started and the synchrotron is controlled to shift to the next operation cycle when the measurement result is smaller. The charged particle beam irradiation apparatus according to claim 5,
The irradiation depth is changed by changing the thickness of the range shifter installed on the trajectory of the charged particle beam from the synchrotron until it reaches the irradiation target within the same operation cycle of the synchrotron. A charged particle beam irradiation apparatus characterized in that The charged particle beam irradiation apparatus according to claim 6,
The irradiation depth is changed by changing the energy of the circulating beam of the synchrotron within the same operation cycle of the synchrotron. The charged particle beam irradiation apparatus according to claim 4,
The irradiation apparatus, in the period between the completion of the change of the irradiation depth after irradiation of the charged particle beam with respect to the entire irradiation region definitive to the irradiation depth the have been completed to the start of the irradiation of the next irradiation depth wherein the orbiting beam charge amount measurement results, compared with the orbiting beam charge amount of the synchrotron required to complete the scanning of the entire the next irradiation region definitive the irradiation depth, when towards the measurement results is large Charging characterized by starting irradiation at the next irradiation depth within the same operation cycle of the synchrotron and controlling the synchrotron to move to the next operation cycle when the measurement result is smaller Particle beam irradiation device. The charged particle beam irradiation apparatus according to claim 4,
The irradiation apparatus, in the period between the completion of the change of the irradiation depth after irradiation of the charged particle beam with respect to the entire irradiation region definitive to the irradiation depth the have been completed to the start of the irradiation of the next irradiation depth comparing the measurement result of the orbiting beam charge amount, the orbiting beam charge amount of the synchrotron required for completion of the irradiation of the charged particle beam to the whole definitive irradiation region to the next irradiation depth, the measurements If there are more, start the irradiation at the next irradiation depth within the same operation cycle of the synchrotron, and control to move the synchrotron to the next operation cycle when the measurement result is less A charged particle beam irradiation apparatus characterized by the above. The charged particle beam irradiation apparatus according to claim 10,
The irradiation depth is changed by changing the energy of the circulating beam of the synchrotron within the same operation cycle of the synchrotron. The charged particle beam irradiation apparatus according to any one of claims 1 to 11,
A charged particle beam irradiation apparatus, wherein a beam monitor for measuring the amount of the orbiting beam charge is installed on an orbit of the charged particle beam of the synchrotron.

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