JP2013094313A - Particle beam irradiation system and method for correcting charged particle beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle beam irradiation system capable of improving beam utilization efficiency without deteriorating the uniformity of irradiation dose.SOLUTION: The particle beam irradiation system has a synchrotron 13 for accelerating an ion beam 10 and emitting it, and an irradiation device 30 for irradiating a target with the ion beam 10 emitted from the synchrotron 13. The system causes the irradiation device 30 to execute a plurality of times of one-unit irradiation. The system includes: an accumulated beam charge quantity measuring means 15 for measuring the accumulated beam charge quantity (Qmeas) in the synchrotron 13; a target current setting means for setting a target beam current value (Ifb) to be emitted from the synchrotron 13 on the basis of the accumulated beam charge quantity (Qmeas) measured by the accumulated beam charge quantity measuring means 15; and an emitted beam current correction control means for controlling a beam current on the basis of the target value (Ifb) of the emitted beam current obtained by the target current setting means.

Description

  The present invention relates to a particle beam irradiation system and a charged particle beam correction method, and more particularly to a particle beam therapy apparatus that irradiates a diseased site with a charged particle beam (ion beam) such as protons or heavy ions to treat cancer. The present invention relates to a particle beam irradiation system and a charged particle beam extraction method suitable for the above.

  As radiotherapy for cancer, particle beam therapy is known in which an ion beam of protons, heavy ions, or the like is irradiated to a cancerous part of a patient for treatment. As an ion beam irradiation method, there is a uniform scanning irradiation method as disclosed in Patent Documents 1 to 3 and Non-Patent Documents 1 and 2.

Japanese Patent No. 2596292 JP 2009-28500 A Japanese Patent No. 4158931 JP 2010-238463 A Japanese Patent No. 4691583

Medical Physics Vol.36 No.8 (August 2009), 3560-3567 (MEDICAL PHYSICS VOLUME 36 NUMBER 8 (AUGUST 2009) P3560-3567) Review of Scientific Instruments Vol. 64 No. 8 (August 1993), 2074-2093 (REVIEW OF SCIENTIFIC INSTRUMENTS VOLUME 64 NUMBER 8 (AUGUST 1993) P2074-2093)

  In the uniform scanning irradiation method, in order to maintain the uniformity of the irradiation dose, it is necessary to prevent the beam from being depleted during the irradiation of one unit of a predetermined region. On the other hand, the charge amount of the ion beam accumulated in the synchrotron is not constant, and varies according to the current variation of the ion beam supplied from the pre-stage accelerator.

  If the amount of accumulated charge is less than one unit of irradiation, the beam will be depleted when irradiated as it is, and the uniformity of irradiation dose will be reduced. Conversely, unless an accumulated beam that is less than one unit of irradiation is used, it is disadvantageous in terms of beam utilization efficiency.

  An object of the present invention is to provide a particle beam irradiation system capable of increasing the beam utilization efficiency without reducing the uniformity of irradiation dose.

  In a particle beam irradiation system that includes a synchrotron that accelerates and emits an ion beam and an irradiation device that irradiates the ion beam emitted from the synchrotron, and performs irradiation of one unit multiple times from the irradiation device. Accumulated beam charge amount measuring means for measuring the accumulated beam charge amount (Qmeas) in the synchrotron, and a target emitted from the synchrotron based on the accumulated beam charge amount (Qmeas) measured by the accumulated beam charge amount measuring means. Target current setting means for setting a beam current value (Ifb), and output beam current correction control means for controlling the beam current based on the target value (Ifb) of the output beam current obtained from the target current setting means. A featured particle beam irradiation system.

  ADVANTAGE OF THE INVENTION According to this invention, the particle beam irradiation system which can improve beam utilization efficiency, without reducing irradiation dose uniformity can be provided.

The structure of the particle beam irradiation system which is an Example of this invention is shown. The change of the energy of an orbiting beam and the change of the amount of stored beam charges in the operation cycle of the synchrotron according to the embodiment of the present invention are shown. The structure of the irradiation apparatus which is an Example of this invention is shown. 2 shows a beam scanning path in a uniform scanning irradiation method according to an embodiment of the present invention. The control preparation flow before the start of irradiation control which is the Example of this invention is shown. The flow at the time of beam irradiation control which is the Example of this invention is shown. FIG. 6 shows a target beam current value during beam irradiation control according to a beam irradiation control flow according to an embodiment of the present invention and a change over time in the amount of accumulated beam charge associated therewith. 1 shows a configuration of a feedback control system for an outgoing beam current according to an embodiment of the present invention. The beam irradiation control flow which added the advance irradiation control which is the Example of this invention is shown. The target beam current value at the time of the beam irradiation control by the beam irradiation control flow to which the advance irradiation control according to the embodiment of the present invention is added and the time change of the accumulated beam charge amount associated therewith are shown.

  A particle beam irradiation apparatus used for particle beam therapy includes an ion beam generator, a beam transport system, and an irradiation apparatus. The ion beam generator includes a synchrotron and a cyclotron that accelerates an ion beam that circulates along a circular orbit to a desired energy.

  A synchrotron is a high-frequency accelerator (acceleration cavity) that accelerates to a target energy by applying a high-frequency voltage to an ion beam that circulates along a circular orbit, and an emission that increases the betatron oscillation amplitude of the circulating ion beam. A high-frequency electrode for extraction, and a deflector for extraction that extracts the ion beam from the orbit (see Patent Document 1). When an ion beam accelerated to the target energy is emitted from the synchrotron to the beam transport system, a high-frequency magnetic field or a high-frequency electric field (hereinafter referred to as a high-frequency signal) is applied to the extraction high-frequency electrode, and the characteristic of the circulating ion beam Increase the betatron oscillation amplitude, which is the oscillation. The ion beam having an increased betatron oscillation amplitude moves outside the stability limit, is emitted from the synchrotron to the beam transport system, and is transported to the irradiation device.

  The irradiation device shapes the ion beam guided from the ion beam generator according to the depth from the patient's body surface and the shape of the affected part, and irradiates the affected part of the patient on the treatment bed. As an irradiation method, there is a uniform scanning irradiation method (page 3561 of Non-Patent Document 1, FIG. 1).

  The uniform scanning irradiation method scans the ion beam on the irradiation plane with a scanning electromagnet, so there is less energy loss than the double scatterer irradiation system that spreads the beam over the entire irradiation surface with two types of scatterers, so double scattering The ion beam has a longer range than the body irradiation method.

  The uniform scanning irradiation device has two scanning electromagnets (horizontal scanning electromagnet and vertical scanning electromagnet) that scan the beam on the irradiation plane, and an absorbed dose range in which the ion beam scanned by the scanning magnet is matched to the depth of the affected area. It is composed of an energy absorber that forms an extended black peak (hereinafter referred to as SOBP), a bolus that forms an irradiation field in accordance with the shape of the affected part, and a collimator. In the uniform scanning irradiation apparatus, a ridge filter (page 2078 of Non-Patent Document 2, FIG. 31) is used as an energy absorber for forming SOBP. The ridge filter is a structure in which a plurality of wedge-shaped energy absorbers with different thicknesses in the region through which the ion beam passes are arranged on a plane. The beam that has passed through the ridge filter depends on the thickness of the passage part of the ridge filter. Energy is attenuated. The SOBP is formed by superimposing ion beams with attenuated energy.

  In the uniform scanning irradiation method, as described in Non-Patent Document 2, the ion current is repeatedly irradiated (hereinafter repainted) many times on the irradiation plane while keeping the beam current value low. Achieve a degree. Therefore, by controlling the beam current value at a constant value, deterioration of dose uniformity on the irradiation plane can be suppressed, so that the number of repaints can be reduced and the dose rate can be improved.

  A beam scanning method in the uniform scanning irradiation method will be described with reference to FIG. The uniform scanning irradiation method includes a single-circle wobbler method (for example, described in Patent Document 2), a spiral wobbler method (for example, described in Patent Document 3), a raster scanning method (Non-Patent Document 1, page 3564, FIG. 7), a line A scanning method is considered. In the single circle wobbler method, as shown in FIG. 4A, the irradiation beam is scanned in a single circle by a scanning electromagnet, thereby forming a flat uniformity by superimposing Gaussian distributions of the scanned beams. The spiral wobbler method (not shown) is a scanning method devised to improve the beam utilization efficiency while securing a range more than the single-circle wobbler method, and superimposes the scanning trajectory with the initial phase changed. Thus, the irradiation plane is scanned. Unlike the wobbler method described above, the raster scanning method is a method in which a beam is continuously scanned linearly as shown in FIG. 4B. In the line scanning method, as shown in FIG. 4C, the beam irradiation is stopped during the scanning in the short scanning direction, which was irradiated in the raster scanning method, and the effective use efficiency of the beam is increased. Is the method.

  Here, the beam scanning necessary for one unit of irradiation will be described. First, the beam scanning range necessary for one unit of irradiation is a trajectory scanned from the scanning start point to the end point. As shown in FIG. 4, in the single circle wobbler method and the spiral wobbler method (not shown), the scanning start point and the end point are the same point. Further, the raster scanning method and the line scanning method have different scanning start points and end points. The scanning time required for irradiation of one unit is several tens of milliseconds to 100 milliseconds per scanning, and is sufficiently short with respect to the synchrotron emission control time (about 0.5 seconds to several seconds).

  Next, items that need to be studied will be described using descriptions in each document. In the uniform scanning irradiation method, in order to maintain the uniformity of the irradiation dose, it is desired that the irradiation is performed without depleting the beam until irradiation of a predetermined region is completed during the emission control. In Non-Patent Document 1, a cyclotron is used as an ion beam generator. In the case of a cyclotron, the ion beam supplied to the irradiation device is a direct current beam. However, when a synchrotron is employed in the ion beam generator, the ion beam accumulated in the synchrotron is supplied to the irradiation device in accordance with the operation cycle of the synchrotron. Therefore, there is a possibility that the ion beam accumulated in the synchrotron is exhausted by continuing the extraction control. Therefore, when the synchrotron accumulated beam is depleted, the extraction control is stopped and the beam scanning control of the scanning magnet is stopped, and then the ion beam accumulation and extraction control and the beam scanning control of the scanning magnet are performed again from the next operation cycle. Need to continue.

  The ion beam current supplied from the synchrotron to the irradiation device is set low so that the dose uniformity is not affected even when the beam irradiation is stopped due to the depletion of the accumulated beam charge, and repainting is performed about 100 times. As a result, the deterioration of the dose uniformity at the beam irradiation stop position was suppressed (described on page 3562 of Non-Patent Document 1). Therefore, since it takes time to irradiate a predetermined dose, there is a problem that treatment time becomes long.

  In addition, as a means for suppressing the time fluctuation of the ion beam supplied from the synchrotron, the outgoing beam current feedback control has been devised. The outgoing beam current feedback control converts the ionized charge amount detected by a dose monitor or the like provided in the irradiation device into the current value of the ion beam, and the deviation between the detected current value and the target current value is the amplitude of the outgoing high frequency voltage. By correcting the value, it is corrected to a desired beam current value. When the outgoing beam current feedback control is applied to the uniform scanning irradiation method, the target beam current value is controlled at a constant value. However, it has been found that the amount of charge of the ion beam accumulated in the synchrotron varies due to the current variation of the ion beam supplied from the pre-accelerator of the synchrotron. Therefore, when the emission beam current feedback control is performed, the ion beam charge amount accumulated in the synchrotron with respect to the emission beam charge amount indicated by the product of the time required for one unit of irradiation and the target current value of the emission beam. As the accumulated beam charge amount is depleted, the beam current waveform in the latter half of the emission control may be deficient in spite of the emission beam current feedback control, which may deteriorate the dose uniformity. there were.

  In Patent Document 4, as a measure for suppressing beam depletion during the emission control, the accumulated beam charge amount is measured after the emission control of the beam from the synchrotron, and the accumulated beam charge amount is less than the charge amount necessary for one unit of irradiation. In this case, it is described that transition to deceleration control is performed. By carrying out such control, there is a problem that although beam depletion does not occur during one unit of irradiation, the utilization efficiency of the amount of beam charge accumulated in the synchrotron is lowered.

  Patent Document 5 describes that the accumulated beam charge amount is measured before the emission control and the target value of the emission beam current feedback control is corrected. In correcting the target value of feedback control, a standard value of the accumulated charge amount of the ion beam that circulates around the synchrotron is set in advance, and the accumulated beam charge amount and the standard value of the accumulated charge amount measured immediately before the synchrotron emission control are set. It is described that the output beam current value is corrected based on the comparison result. In Patent Document 5, since it is assumed that the accumulated ion beam charge amount is efficiently emitted by one extraction control, the current value of the ion beam supplied to the irradiation apparatus is set low as in the uniform scanning irradiation method, An irradiation method that scans and irradiates a plurality of times is not assumed.

  In each embodiment of the present invention described below, even if fluctuations in the accumulated beam charge amount in the synchrotron occur, beam depletion does not occur during one unit of irradiation, and the flatness of the irradiation dose can be ensured. it can. Further, by efficiently using the accumulated beam charge amount in the synchrotron, the time required for irradiation with a predetermined dose can be shortened and the treatment time can be shortened.

  In addition, each Example demonstrated below is related with the uniform scanning irradiation method which performs irradiation of 1 unit several times from an irradiation apparatus. Performing one unit of irradiation a plurality of times, that is, repainting, typically means repeating irradiation of one surface to a certain irradiation plane a plurality of times. In each example, “irradiation of one surface” in the uniform scanning irradiation method is expressed as “irradiation of one unit”. However, as in Patent Document 5, the irradiation of one surface of the ion beam accumulated in the synchrotron is completely controlled. This is to clarify the difference from what is done only once.

  A particle beam irradiation system according to a preferred embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. As shown in FIG. 1, the particle beam irradiation system 1 of the present embodiment includes an ion beam generator 11, a beam transport device 14, and an irradiation field forming device (charged particle beam irradiation device, hereinafter referred to as an irradiation device) 30. The beam transport device 14 communicates the ion beam generator 11 and the irradiation device 30 disposed in the treatment room.

  The control system of the particle beam irradiation system 1 includes an accelerator control device 40 that controls the ion beam generator 11 and the beam transport device 14, an overall control device 41 that controls the entire particle beam irradiation system 1, and a beam to a patient. The treatment planning device 43 for planning the irradiation conditions, the storage device 42 for storing the information planned by the treatment planning device 43, the control information of the synchrotron 13 which is an ion beam generator and the beam transport device 14, and the synchrotron 13 are configured. A timing system 50 that realizes synchronous control of devices, and an interlock system 60 that is independent of the overall control device 41 in order to ensure patient safety. Moreover, the high frequency voltage used when the beam from the ion beam generator 11 to the beam transport device 14 is emitted is controlled by the emission control device 20.

  The ion beam generator 11 includes an ion source (not shown), a pre-accelerator 12 and a synchrotron 13. The ion source is connected to the front stage accelerator 12, and the front stage accelerator 12 is connected to the synchrotron 13. The front-stage accelerator 12 accelerates the ion beam 10 generated by the ion source to energy that can be incident on the synchrotron 13. The ion beam 10 a accelerated by the front stage accelerator 12 is incident on the synchrotron 13.

  FIG. 2A shows a change in the energy of the circulating beam in the operation cycle of the synchrotron 13, and FIG. 2B shows a change in the accumulated beam charge amount. The synchrotron 13 performs a series of operation control of incidence, acceleration, emission, and deceleration at a cycle of 2 to 3 seconds. In addition, in preparation for emission control, emission preparation control is performed in advance.

  The beam 10b incident on the synchrotron 13 is accelerated to a desired energy by being given energy by a high frequency voltage applied to an acceleration cavity (not shown). At this time, the magnetic field strength of the deflecting electromagnet 18 and the quadrupole electromagnet (not shown) and the like is increased in accordance with the increase of the orbital energy of the ion beam 10b so that the orbit of the ion beam 10b orbiting in the synchrotron 13 is constant. Increase the frequency of the high frequency voltage applied to the acceleration cavity.

  The ion beam 10b accelerated to a desired energy establishes a condition (orbital beam stability limit condition) under which the orbiting beam 10b can be emitted by the excitation amount of a quadrupole electromagnet and a hexapole electromagnet (not shown) by extraction preparation control. . After the extraction preparation control is completed, a high frequency voltage is applied from the extraction control device 20 to the high frequency electrode 16 for extraction, and the betatron oscillation amplitude of the beam 10b circulating in the synchrotron 13 is increased. Due to the increase of the betatron oscillation amplitude, the circulating beam 10 b exceeding the stability limit condition is emitted from the synchrotron 13 to the beam transport device 14 and transported to the irradiation device 30. The beam extraction control from the synchrotron 13 can be realized at high speed by controlling the ON / OFF of the high-frequency voltage applied to the high-frequency electrode 16 for emission by the emission control device 20.

  The accumulated beam charge amount 70 in the synchrotron 13 changes as shown in FIG. 2B in accordance with the operation sequence of the synchrotron 13 (FIG. 2A). When the ion beam 10a is incident on the synchrotron 13, the amount of accumulated beam charge is gradually increased. In the early stage of acceleration control, the ion beam is lost due to the space charge effect or the like, so that the accumulated beam charge amount is attenuated, but is almost constant from the middle stage of acceleration to the late stage of acceleration. The synchrotron 13 emits the ion beam 10b from the synchrotron 13 for each charge amount (Qscan) necessary for one unit of irradiation. When one unit of irradiation is completed, the beam emission is stopped in preparation for moving the scanning electromagnet 32 of the irradiation device 30 to be described later to the irradiation start point. Such beam emission and stop are repeated, and the beam charge amount (Qloss) remaining in the synchrotron 13 without being emitted in the emission control section is decelerated to a low energy and disappears by the subsequent deceleration control.

  FIG. 3 shows the configuration of the irradiation apparatus. In the irradiation device 30, the dose intensity of the beam 10d to be irradiated is measured by a dose monitor 31 or a beam shape monitor (not shown) that scans the irradiation plane with the scanning electromagnet 32 and measures the irradiation dose of the beam 10d irradiated to the patient. Check the beam shape one after another. The beam 10d scanned by the scanning electromagnet 32 passes through the energy absorber 33 to form an SOBP that matches the thickness in the affected part depth direction. An irradiation field in which the beam on which the SOBP is formed is matched to the shape of the affected area is formed by a unique jig such as a collimator 34 or a bolus 35 that matches the shape of the affected area 37 of the patient 36.

  A method for controlling the output high-frequency voltage in the output control device 20 will be described with reference to FIG. The high frequency oscillator 21 outputs a high frequency signal having a center frequency Fc of the high frequency voltage for emission controlled according to energy. The high frequency signal output from the high frequency oscillator 21 is mixed with the band limited high frequency signal output from the band limited high frequency signal generator 22 by the high frequency mixer 221. As a result, a band-limited high-frequency signal having a center frequency of Fc and a frequency width of 2Fw is obtained. The mixed band-limited high-frequency signal is amplified by the beam current feedback control circuit 24 so that the beam current intensity waveform (target value of the beam current intensity) obtained by the target beam current correction calculation unit 29 is realized. Control the value. The beam current feedback control circuit 24 includes an amplitude modulator 23, a feedback loop gain adjuster 241, a feedback loop gain adjuster 242, an addition operation circuit 243, and a high frequency switch 25. First, the feedback loop gain adjuster 241 calculates the deviation between the dose monitor detection signal 311 detected by the dose monitor 31 and the target beam current value (Ifb) set from the target beam current correction calculation unit 29. Based on the feedback gain, the feedback loop gain adjuster 241 calculates the feedback correction signal. The addition operation circuit 243 adds the amplitude modulation signal (Am) and the feedback correction signal to correct the amplitude modulation signal. By setting this addition result in the amplitude modulator 23, beam current feedback control is realized.

  The high frequency signal whose amplitude value is controlled by the beam current feedback control circuit 24 is transmitted to the high frequency power amplifier 17 via the high frequency switch 26 controlled by the interlock system 60. The band limited high frequency signal amplified by the high frequency power amplifier 17 is applied to the high frequency electrode 16 for emission. The betatron oscillation amplitude of the beam 10 b that circulates in the synchrotron 13 is increased by the high-frequency signal applied to the emission high-frequency electrode 16, and is emitted from the synchrotron 13 to the beam transport device 14.

  A target beam current calculation processing method in the target beam current correction calculation unit 29 constituting the emission control device 20, which is a feature of the present embodiment, will be described with reference to FIGS. 5, 6, 7, and 8. . FIG. 5 shows a control preparation flow before the start of irradiation control, and FIG. 6 shows a flow at the time of beam irradiation control. FIG. 7 shows the change over time of the target beam current value during the beam irradiation control according to the control flow during the beam irradiation shown in FIG. 6 and the accompanying accumulated beam charge amount. FIG. 8 shows the configuration of the feedback control system for the outgoing beam current.

  The calculation setting flow of the target beam current value used for the outgoing beam current feedback control before irradiation will be described with reference to FIG. First, a method for setting an initial value of a target beam current value (Ifb) used for outgoing beam current feedback control before starting irradiation treatment for a patient will be described. The treatment planning device 43 calculates the total irradiation dose of the patient 47 to the patient 36 and registers it in the storage device 42. In the storage device 42, conversion table data of the irradiation charge amount with respect to the irradiation dose is prepared in advance. The overall control device 41 reads the total irradiation dose calculated by the treatment planning device 43 based on the irradiation conditions from the treatment scheduler (not shown) and obtains the total irradiation dose required by the treatment planning device 43. The irradiation charge amount (Qtarget) is calculated from conversion table data prepared in advance in the overall control device 41. The overall control device 41 transmits the total irradiation charge amount (Qtarget) and the setting conditions of the irradiation device to the irradiation control device 44, and the irradiation control device receives information such as the total irradiation charge amount (Qtarget) by the receiving means. Receive.

  The irradiation controller 44 calculates a reference beam current value (Iscan) for one unit of irradiation based on the beam current control range that can be emitted by the synchrotron, and performs one unit of irradiation based on the scanning speed of the scanning electromagnet 32. A necessary scanning time (Tscan) is set (801).

  Next, the amount of charge (Qscan) required for one unit of irradiation and the number of repaints (Nr) are calculated (802). As shown in (Equation 1), the charge amount (Qscan) required for one unit of irradiation is obtained by calculating a reference beam current value (Iscan) for one unit of irradiation and a scanning time (Tscan) required for one unit of irradiation. It is calculated by multiplying. Further, as shown in (Equation 2), the number of repaints (Nr) can be calculated by dividing the total irradiation charge amount (Qtarget) by the charge amount (Qscan) necessary for one unit of irradiation.

  Initialization is performed by setting the total irradiation charge amount (Qtarget) to the remaining irradiation charge amount (Qrest) to the irradiation region (803). The residual irradiation charge amount (Qrest) is obtained by subtracting a cumulative value (cumulative irradiation charge amount (Qsum)) of the charge amount irradiated to the affected area from the total irradiation charge amount (Qtarget). Also, initialization is performed by setting the accumulated irradiation charge amount (Qsum) to 0 (804).

  As an initial value of the target beam current value (Ifb) of the outgoing beam current feedback control, a reference beam current value (Iscan) for one unit of irradiation is set in the outgoing control device 20 (805). The control flow (801 to 805) is performed by the irradiation control device 44. Note that the irradiation preparation control shown in FIG. 5 is performed only in the operation cycle at the start of irradiation to the patient, and is not performed in the second and subsequent operation cycles.

  A beam irradiation control flow will be described with reference to FIG. The synchrotron 13 accelerates the beam incident from the front accelerator 12 to a predetermined energy (811). After the beam acceleration control is completed, the accumulated beam charge amount (Qmeas) accumulated in the synchrotron is measured (812). The accumulated beam charge amount (Qmeas) is measured by using accumulated beam charge amount detection means 15 such as DCCT provided in the synchrotron 13. The measurement result of the accumulated beam charge amount (Qmeas) is taken into the extraction control device 20, and the target beam current correction calculation unit 29 constituting the extraction control device 20 performs the processing shown in the following control flow.

  The target beam current correction calculation unit 29 first determines whether the accumulated beam charge amount (Qmeas) in the synchrotron 13 is exhausted (813). When the accumulated beam charge amount is depleted (Qmeas ≦ 0), the process proceeds to beam deceleration control (814).

  If the accumulated beam charge amount is not depleted (Qmeas> 0), the remaining irradiation charge amount (Qrest) is compared with the accumulated beam charge amount (Qmeas) to determine the charge amount to be set as the comparison charge amount (Qcomp) ( 815). The comparative charge amount (Qcomp) is a reference charge amount at the time of correction control of a reference beam current value (Iscan) in one unit irradiation described later. When the remaining irradiation charge amount (Qrest) is larger than the accumulated beam charge amount (Qmeas), the accumulated beam charge amount (Qmeas) is set in the comparison charge amount (Qcomp) (816), and the accumulated beam charge amount (Qmeas) If the remaining irradiation charge amount (Qrest) is small, the remaining irradiation charge amount (Qrest) is set as the comparison charge amount (Qcomp) (817). That is, the smaller of the remaining irradiation charge amount (Qrest) and the accumulated beam charge amount (Qmeas) is set as the comparison charge amount (Qcomp).

  Next, the comparison charge amount (Qcomp) is compared with the charge amount (Qscan) necessary for one unit irradiation (818). When the comparison charge amount (Qcomp) is larger than the charge amount (Qscan) required for one unit of irradiation (Qcomp ≧ Qscan), the target beam current value (Ifb) is corrected as a target value for the output beam current feedback control. Is not implemented (819). When the comparison charge amount (Qcomp) is smaller than the charge amount (Qscan) required for one unit of irradiation (Qcomp <Qscan), the target beam current value (Ifb) is set to the reference beam current value for one unit of irradiation. Correction is made so as to be smaller than (Iscan) (820).

  In this way, the target beam current correction calculation unit 29, which is a target current setting means, determines the target value (Ifb) of the beam current by correction based on the reference beam current value (Iscan) in one unit of irradiation, and thus the previous stage. It is possible to control the beam current fluctuation caused by the accelerator appropriately adjusted by correction. In this example, before carrying out one unit of irradiation, it is sequentially confirmed whether the amount of charge necessary for one unit of irradiation is accumulated in the synchrotron, and when the accumulated beam charge amount in the synchrotron is small By correcting and controlling the output beam current value, it is possible to suppress the beam depletion during one unit irradiation, thereby ensuring the irradiation dose uniformity.

  As shown in (Equation 3), the target beam current value (Ifb) is obtained by comparing the reference beam current value (Iscan) for one unit of irradiation with the charge amount (Qcomp) for the charge amount (Qscan) required for one unit of irradiation. ) Is corrected by the ratio of

  In this way, the comparative charge amount (Qcomp) is used for the determination of the target value (Ifb) of the target beam current by the target beam current correction calculation unit 29 serving as target current setting means. As a result, the beam current can be appropriately set so as to increase the beam utilization efficiency without causing beam depletion during irradiation of one surface. By efficiently using the accumulated beam charge amount in the synchrotron, the time required for irradiation with a predetermined dose can be shortened and the treatment time can be shortened. If beam depletion can be suppressed during one unit of irradiation, the beam current value during one unit of irradiation can be increased and the number of repaints can be reduced. Can be shortened.

  Based on the target beam current value (Ifb), the beam current feedback control circuit 24 which is a part of the emission control device 20 performs the emission beam current feedback control, and the beam from the synchrotron 13 to the irradiation device 30 is performed. The emission control is performed (821). When irradiation of one unit is completed, the amount of charge irradiated is added to the cumulative amount of charge (Qsum) (822). At this time, as shown in (Equation 4), the cumulative irradiation charge amount (Qsum) is obtained by multiplying the target beam current value (Ifb) by one unit of scanning time (Tscan). Is obtained by adding to Together with this, the remaining irradiation charge amount (Qrest) is updated (823). The remaining irradiation charge amount (Qrest) is obtained by subtracting the cumulative irradiation charge amount (Qsum) from the total irradiation charge amount (Qtarget) as shown in (Formula 5).

  Finally, the cumulative irradiation charge amount (Qsum) and the total irradiation charge amount (Qtarget) are compared (824). When the cumulative irradiation charge amount (Qsum) reaches the total irradiation charge amount (Qtarget) (Qsum ≧ Qtarget), the beam irradiation control is terminated, and the cumulative irradiation charge amount (Qsum) does not reach the total irradiation charge amount (Qtarget). In the case (Qsum <Qtarget), the process returns to the control flow (812) and the beam irradiation control is continued.

  Here, the reason for comparing the remaining irradiation charge amount (Qrest) and the accumulated beam charge amount (Qmeas) shown in the control flow (815), which is a feature of the present embodiment, will be described below.

  First, in the latter half of the synchrotron emission control time (Text), the accumulated beam charge amount (Qmeas) becomes smaller than the charge amount (Qscan) required for one unit of irradiation. If the emission control is continued in a state where the accumulated beam charge amount (Qmeas) is smaller than the charge amount (Qscan) required for one unit of irradiation, the beam will be depleted before completing the irradiation of one unit, and within the irradiation region. The uniformity of dose will deteriorate. For this reason, conventionally, the beam current value when irradiating one unit is lowered, and the number of repaints (Nr) is sufficiently large, thereby reducing the influence of non-uniform dose uniformity that occurs when the beam is depleted. As a result, the dose rate could not be increased and treatment time was required.

  Further, at the end of the beam irradiation control, the remaining irradiation charge amount (Qrest) becomes small. That is, it approaches the total irradiation dose (Qtarget) that satisfies the necessary irradiation dose. In this state, the amount of charge (Qscan) required for one unit of irradiation approaches, and the amount of remaining irradiation charge (Qrest) becomes smaller than the amount of charge (Qscan) required for one unit of irradiation due to the progress of irradiation control. In the prior art, as shown in Patent Document 4, when the accumulated beam charge amount (Qmeas) becomes smaller than the charge amount (Qscan) required for one unit of irradiation, the process shifts to deceleration control. The accumulated beam charge amount (Qmeas) smaller than the charge amount (Qscan) required for one unit of irradiation is decelerated without being used for irradiation, so that the beam utilization efficiency cannot be increased.

  Depending on these two situations, when the target beam current value (Ifb) is corrected during the emission beam current feedback control (820), either the remaining irradiation charge amount (Qrest) or the accumulated beam charge amount (Qmeas) is selected. By correcting the smaller one as the comparative charge amount (Qcomp), the dose rate can be improved along with the improvement of the beam utilization efficiency while satisfying the dose uniformity, so that the treatment time can be shortened.

  A target beam current value at the time of beam irradiation control according to the control flow at the time of beam irradiation and a temporal change in the amount of accumulated beam charge associated therewith will be described using FIG. In this embodiment, a case is shown in which the accumulated beam charge amount (Qmeas) is measured five times within the extraction control time (Text) and the extraction control is performed, and it is assumed that the remaining irradiation charge amount (Qrest) is sufficiently large. .

  After the acceleration control of the synchrotron 13 is finished, the accumulated beam charge amount (FIG. 7A) is installed in the synchrotron 13 based on the accumulated beam charge confirmation signal 501 (FIG. 7B). It is measured by the charge amount detection means 15. At this time, the accumulated beam charge amount is Qmeas1. Since the accumulated beam charge amount is larger than the charge amount (Qscan) required for one unit of irradiation, the comparison charge amount (Qcomp) is set to Qmeas1, and the target beam current value (Ifb) is not corrected. Therefore, the target beam current value (FIG. 7C) is set as a reference beam current value (Iscan) for one unit of irradiation which is an initial setting value.

  Based on the beam extraction control signal (FIG. 7D), the extraction control based on the emission beam current feedback control is started. As a result, a beam 10d having a constant current is supplied to the irradiation device 30, and the beam current value (Idose) converted from the detection signal from the dose monitor 31 is confirmed (FIG. 7 (e)). After the beam irradiation in one unit scanning time (Tscan) is completed, the beam emission control is stopped and the accumulated beam charge amount is measured. In the present embodiment, similarly, the beam measurement to the emission control are repeated three times (Qmeas2 to 4).

  Based on the fifth accumulated beam charge amount confirmation signal, the accumulated beam charge amount (Qmeas) is measured. The accumulated beam charge amount at this time is Qmeas5, which is smaller than the charge amount (Qscan) required for one unit of irradiation, so the comparison charge amount (Qcomp) is Qmeas5 and the target beam current value (Ifb) needs to be corrected. It is. Therefore, the target beam current value (Ifb) is corrected based on (Equation 3), and the target beam current value (Ifb) is set lower than the reference beam current value (Iscan) in one unit of irradiation. To do. By performing emission control by emission beam current feedback control based on the target beam current value (Ifb), a beam current value (Idose) converted from the dose monitor detection signal is emitted.

  Next, an operation method of the particle beam irradiation apparatus to which this embodiment is applied will be described with reference to FIG. The doctor inputs patient information (position and size of affected area, beam irradiation direction, and maximum irradiation depth) to the treatment planning apparatus 43. The treatment planning device 43 uses treatment planning software to calculate the SOBP width, irradiation field size, target dose for the affected area, and the like necessary for treatment based on the input patient information.

  The result calculated by the treatment planning device 43 is recorded in the storage device 42. The overall control device 41 transmits the total irradiation charge amount (Qtarget) and the irradiation conditions to the irradiation control device 44 based on the irradiation conditions from the treatment scheduler (not shown). The irradiation control device 44 selects the setting conditions of the devices that constitute the irradiation device, and together with this, the irradiation control device 20 gives a total irradiation charge amount (Qtarget) and a reference beam current value (in one unit of irradiation) ( Iscan), scanning time (Tscan) required for one unit of irradiation, charge amount (Qscan) required for one unit of irradiation, number of repaints (Nr), etc. are transmitted. The calculation of the charge amount (Qscan) necessary for one unit of irradiation, which is a feature of the present embodiment, is performed by the irradiation control device 44 based on information from the treatment planning device 43.

  The treatment plan information is displayed on a display device (not shown) arranged in the control room of the treatment room that is preparing for treatment. The radiologist confirms the display screen and places the energy absorber 33 designated by the display in the irradiation apparatus 30.

  The treatment bed control device (not shown) moves the treatment bed where the radiologist fixes the patient in accordance with an instruction from the overall control device 41, and the affected part (irradiation target) of the patient is positioned on the extended line of the beam axis. Position to do.

  The accelerator control device 40 determines the irradiation beam energy from the treatment plan information from the overall control device 41, and sets the operation control parameters of the devices constituting the synchrotron 13 and the beam transport device 14. For the emission control device 20, the center frequency Fc, frequency width Fw, amplitude modulation data Am, and feedback gain Gfb, which are operation control parameters of the emission high-frequency signal, are set corresponding to the energy of the emission beam.

  The doctor instructs the overall control device 41 to provide an irradiation start signal from the operation panel in the control room. Based on the irradiation start instruction, the pre-stage accelerator 12 accelerates the ion beam (for example, protons (or heavy particles such as carbon ions)) generated from the ion source and supplies the accelerated ion beam to the synchrotron 13.

  The synchrotron 13 accelerates the ion beam 10a incident from the front stage accelerator while circulating around the synchrotron 13 to a desired energy. After the ion beam 10 b is accelerated to the target beam energy, the accumulated beam charge amount detection means 15 measures the accumulated beam charge amount (Qmeas) based on the accumulated beam charge amount confirmation signal 501 output from the timing system 50. To do. Based on the accumulated beam charge amount (Qmeas), the target beam current correction calculation unit 29 sets the target beam current value (Ifb) of the outgoing beam current feedback control circuit 24. After that, the beam controlled based on the target beam current value (Ifb) is obtained by applying the extraction high-frequency signal to the extraction high-frequency electrode 16 by the beam extraction control signal 502 output from the timing system 50. 13 is emitted.

  In this embodiment, the accumulated beam charge amount is detected by detecting the accumulated beam charge amount corresponding to the first unit of irradiation based on the accumulated beam charge amount confirmation signal 501 output from the timing system 50, The accumulated beam charge amount confirmation signal 501 after the next unit is output based on the scanning time (Tscan) and irradiation stop time (Toff) of one unit starting from the input of the beam extraction control signal 502 input from the timing system 50. Although the detection is performed based on the signal calculated by the control device 20, a device for generating the accumulated beam charge amount confirmation signal 501 corresponding to all irradiation surfaces is provided outside the emission control device 20 such as the irradiation control device 44. The effect will not change.

  In the beam emission control in this embodiment, the beam emission control signal 502 from the timing system 50 is input to the emission control device 20, and the beam emission control is performed from the target beam current correction calculation unit 29 every time one unit of irradiation is completed. By opening the high frequency switch 25 based on the signal 252, the supply of the beam from the synchrotron 13 to the irradiation device 30 is stopped during the irradiation stop time (Toff) between one unit of irradiation.

  The ion beam 10 c emitted from the synchrotron 13 passes through the beam transport device 14 and arrives at the irradiation device 30. Further, the ion beam 10d travels along the beam path in the irradiation device 30, the ion beam 10d is scanned by the scanning magnet 32, SOBP is formed by the energy absorber 33, and the affected area of the patient is irradiated.

  A dose monitor 31 measures the dose of the ion beam irradiated to the affected area. The detection signal 311 at the dose monitor 31 is input to the outgoing beam current feedback control circuit 24, and the amplitude control value of the high frequency voltage based on the deviation between the target beam current value (Ifb) and the detected beam current value (Idose) at the dose monitor 31. Is controlled to a constant value by feedback correction.

  When the irradiation of one unit to the affected part is completed, the beam emission control is stopped, the excitation amount of the scanning magnet is returned to the irradiation start position, and the cumulative irradiation charge amount (Qsum) is recorded. Thereafter, the accumulated beam charge amount is measured. The target beam current value is corrected based on the measurement result, and irradiation of one unit is started again. These controls are repeated, and the beam is irradiated until the cumulative irradiation charge amount (Qsum) reaches the total irradiation charge amount (Qtarget).

  In addition, in the apparatus which comprises the particle beam irradiation system 1, when some trouble which prevents the beam irradiation to a patient arises during irradiation control, the interlock system 60 is a signal (abnormal) which shows that the apparatus state is abnormal. Signal) 601 is output to the interlocking high-frequency switch 26 of the emission control device 20 in parallel with the overall control device 41. The emission control device 20 receives the abnormal signal 601 from the interlock system 60 as a beam emission stop command, and immediately opens the interlock high-frequency switch 26. When the interlocking high frequency switch 26 is opened, the application of the high frequency signal for emission to the high frequency electrode 16 is stopped. Thereby, the synchrotron 13 can realize interlock control for stopping the emission of the ion beam 10b.

  According to the present embodiment, the following effects can be obtained.

  (1) In this embodiment, the irradiation area is managed as one unit of scanning range from the irradiation start position to the end position, and this one unit of scanning range is managed as the irradiation unit. Then, before starting the beam irradiation to the irradiation range of one unit, the accumulated beam charge amount (Qmeas) in the synchrotron 13 is sequentially measured, and the accumulation with respect to the charge amount (Qscan) necessary for one unit irradiation is performed. The beam current value emitted from the synchrotron 13 is controlled by correcting the target beam current value of the emission beam current feedback control circuit 24 by the target beam current correction calculation unit 29 according to the beam charge amount (Qmeas). . Thereby, it is possible to suppress the depletion of the accumulated beam charge amount in the synchrotron 13 during irradiation of one unit.

  (2) In the present embodiment, as described above, the accumulated beam charge amount in the synchrotron 13 is sequentially measured before irradiating one surface, and the target beam current of the output beam current feedback control is based on the measurement result. Since the value is corrected, depletion during irradiation of one surface does not occur. Therefore, unlike the conventional case, it is not necessary to lower the target beam current value of the outgoing beam current feedback control in consideration of the deterioration of the dose uniformity when the accumulated beam charge amount is depleted halfway. This makes it possible to increase the target beam current value of the outgoing beam current feedback control when irradiating one surface, to improve the dose rate and to shorten the treatment time.

  (3) In this embodiment, it is not necessary to sequentially monitor the depletion of the accumulated beam charge amount 70, and the beam emission control and the beam scanning control stop process associated with the depletion of the accumulated beam charge amount 70 are not necessary. It is possible to simplify the configuration and control method of the control device that constitutes the beam irradiation system. In the system that sequentially monitors whether or not the accumulated beam charge amount 70 in the synchrotron 13 is depleted during irradiation of one surface, when the beam 10b is depleted, the beam scanning with the scanning electromagnet 32 is stopped along with the stop of the emission control of the beam 10b. Stop control. After that, after the beam is incident / accelerated again by the synchrotron 13, it is necessary to continue the beam emission control from the synchrotron 13 and the beam scanning control by the scanning electromagnet 32.

  2 shows a second embodiment of the present invention. The apparatus configuration of this embodiment is the same as that of the first embodiment, but the method of correcting the target beam current value (Ifb) in the target beam current correction calculation unit 29 is different.

  The beam irradiation control flow will be described with reference to FIG. The difference from FIG. 6 is that the target beam current value based on the carry irradiation charge amount (Qcarry) instead of the correction control (818 to 820 in FIG. 6) of the target beam current value (Ifb) based on the comparison charge amount (Qcomp). (Ifb) carry correction control (825 to 828 in FIG. 9) is provided.

  In the case of the first embodiment, the accumulated beam charge amount (Qmeas) decreases with the elapse of the synchrotron emission control time (Text). In the second half of the emission control time (Text), it may be considered that the accumulated beam charge amount (Qmeas) is very small with respect to the charge amount (Qscan) necessary for one unit of irradiation. Similarly, when the irradiation control is advanced and the remaining irradiation charge amount (Qrest) is decreased, it is necessary to irradiate only a small amount of charge. Therefore, in order to use the accumulated beam charge amount (Qmeas) effectively or to satisfy the total irradiation charge amount (Qtarget), it is necessary to perform irradiation control of one unit.

  Such a process is performed when the beam charge amount (Qmeas) accumulated in the synchrotron 13 after acceleration control is not an integral multiple of the charge amount (Qscan) necessary for one unit of irradiation. It occurs every time of the operation cycle.

  Therefore, in this embodiment, after setting the comparative charge amount (Qcomp) (control flow of 815 to 817 in FIG. 9), the carry-up irradiation charge amount (Qcarry) shown in (Expression 6) is calculated (825).

  The carry irradiation charge amount (Qcarry) shown in (Expression 6) is obtained by subtracting the charge amount (Qscan) necessary for one unit of irradiation from the comparison charge amount (Qcomp). This carry irradiation charge amount (Qcarry) is compared with the charge amount (Qscan) required for one unit irradiation (826).

  When the carry irradiation charge amount (Qcarry) is smaller than the charge amount (Qscan) required for one unit of irradiation (Qcarry ≦ Qscan), the carry-over correction of the target current value is not performed (827), and the carry irradiation charge amount ( When Qcarry) is larger than the amount of charge (Qscan) required for one unit of irradiation (Qcarry> Qscan), the target current value carry-up correction shown in (Expression 7) is performed (828).

  The carry irradiation charge amount (Qcarry) is obtained by subtracting the charge amount (Qscan) necessary for one unit of irradiation from the comparison charge amount (Qcomp) used in the determination of correction of the target current value in the first embodiment. It has become. That is, by subtracting the amount of charge (Qscan) required for one unit of irradiation twice, the accumulated beam charge amount (Qmeas) is less than twice the amount of charge (Qscan) required for one unit of irradiation. In this case, the irradiation time can be shortened by raising the accumulated beam charge amount (Qmeas) to one irradiation.

  The above can also be expressed as comparing the charge amount (Qscan) required for one unit of irradiation with the doubled charge amount (Qcomp). When the comparative charge amount (Qcomp) is less than twice the charge amount (Qscan) required for one unit of irradiation, the target beam current value (Ifb) is set to be smaller than the beam current value (Iscan) required for one unit of irradiation. By correcting so as to be larger, the irradiation time can be shortened by the forward irradiation. Specifically, as shown in (Expression 7), the target beam current value (Ifb) is obtained by dividing the accumulated beam charge amount (Qmeas) by the scanning time (Tscan) required for one unit of irradiation.

  As described above, as a criterion for determining whether correction is necessary, by using a comparison value between the comparison charge amount (Qcomp) and the charge amount (Qscan) necessary for one unit of irradiation, the accumulated beam charge amount (Qmeas) is obtained. Appropriate control can be performed accordingly. That is, when the comparative charge amount (Qcomp) is smaller than the charge amount (Qscan) required for one unit of irradiation as in the first embodiment, the control is performed to increase the beam efficiency while avoiding beam depletion during one-surface irradiation. Can do. Further, as shown in Example 2, when the comparative charge amount (Qcomp) is appropriately higher than the charge amount (Qscan) required for one unit of irradiation, the irradiation time can be shortened by the forward irradiation. It is also possible to adopt a judgment standard that combines the judgment standard of the first embodiment and the judgment standard of the second embodiment. In this case, both merits can be enjoyed.

  In Example 2, the charge amount (Qscan) necessary for one unit of irradiation is doubled with the comparative charge amount (Qcomp). An effect is obtained. The number of times can be determined by how much charge can be irradiated with one unit of irradiation. If the accumulated beam charge amount in the synchrotron is slightly larger than the charge amount required for one unit of irradiation in the second half of the emission control period, the beam irradiation is completed once by the irradiation charge amount raising means. Compared to the separate irradiation of the beam, the time required for irradiation with a predetermined dose can be shortened and the treatment time can be shortened.

  A target beam current value at the time of beam irradiation control according to the control flow at the time of beam irradiation and the temporal change of the accumulated beam charge amount associated therewith will be described using FIG. For easy understanding, the accumulated beam charge amount (Qmeas1) and the charge amount (Qscan) required for one unit irradiation after the end of the acceleration control in FIG. 10 are the same as those in FIG.

  In FIG. 10, in the first to third measurements (Qmeas1 to Qmeas3) of the accumulated beam charge amount, no carry-out irradiation is performed, but in the fourth measurement (Qmeas4), by carrying out the carry-out irradiation, FIG. The amount of charge that has been irradiated in two times is raised to one time for irradiation. Therefore, compared with FIG. 7, the target beam current value (Ifb) of the fourth irradiation is higher than the reference beam current value (Iscan) of one unit of irradiation, and the fifth irradiation control is performed. Instead, by shifting to the deceleration control, the irradiation time can be shortened by an amount corresponding to one unit of scanning time (Tscan) and irradiation stop time (Toff) between one unit of irradiation.

  According to this embodiment, the accumulated beam charge amount (Qmeas) after completion of the acceleration control does not become an integral multiple of the charge amount (Qscan) necessary for one unit of irradiation. The irradiation time can be shortened by performing irradiation with a stored beam charge amount smaller than (Qscan). Such a carry-up process occurs every time the synchrotron is operated, so that the effect of shortening the irradiation time is great, and the treatment time can be further shortened.

  As a result, when the accumulated beam charge in the synchrotron is slightly larger than the charge required for one unit irradiation in the second half of the emission control period, the amount of irradiation charge that was irradiated in two parts Since the beam irradiation can be completed once by the lifting means, the time required for irradiation with a predetermined dose can be shortened and the treatment time can be shortened.

  In the particle beam irradiation system of each embodiment described above, the irradiation controller 44 calculates a beam current value (Iscan) necessary for one unit of irradiation, and the stored beam charge amount measuring means stores the stored beam charge in the synchrotron. The target beam current emitted from the synchrotron 13 by measuring the quantity (Qmeas) and the target current setting means correcting the beam current value (Iscan) necessary for one unit of irradiation based on the accumulated beam charge quantity (Qmeas) The emission control device 20 that sets the value (Ifb) and has the emission beam current correction control means corrects the charged particle beam by controlling the beam current based on the target beam current value (Ifb). By correcting the charged particle beam in this way, it is possible to realize a particle beam irradiation system capable of increasing the beam utilization efficiency without reducing the irradiation dose uniformity.

DESCRIPTION OF SYMBOLS 1 Particle beam irradiation system 10a, 10b, 10c, 10d Beam 11 Ion beam generator 12 Pre-accelerator 13 Synchrotron 14 Beam transport device 15 Accumulated beam charge amount detection means 16 High frequency electrode 17 High frequency power amplifier 18 Bending electromagnet 20 Control device for extraction 21 High-frequency oscillator for emission (high-frequency oscillator)
22 Band-limited high-frequency signal generator 23 Amplitude modulator 24 Beam current feedback control circuit 25, 26 High-frequency switch 27 Emission high-frequency signal processor 29 Target beam current correction calculator 30 Irradiation device 31 Dose monitor 32 Scanning electromagnet 33 Energy absorber 34 Collimator 35 Bolus 36 Patient 37 Affected part shape 38 Beam scanning path 40 Accelerator control device 41 Overall control device 42 Storage device 43 Treatment planning device 44 Irradiation control device 50 Timing system 60 Interlock system 221 High-frequency mixer 241 242 Feedback loop gain adjuster 243 Addition calculation circuit 252 Beam extraction control signal 311 Dose monitor detection signal 501 Accumulated beam charge amount confirmation signal 502 Beam extraction control signal Qtarget Total irradiation charge amount Qscan Necessary for one unit of irradiation Charge amount Qrest Remaining irradiation charge amount Qsum Accumulated irradiation charge amount Qmeas Accumulated beam charge amount Qcomp Comparison charge amount Qcarry Raising irradiation charge amount Qext Emission beam charge amount from synchrotron Extraction control time Tscan One unit scanning time Toff One unit irradiation Irradiation stop time Nr Number of repaints Nscan Number of irradiation times of one unit within the emission control time Iscan Reference beam current value Ifb in one unit of irradiation Target beam current value Idose Beam current value

Claims (9)

In a particle beam irradiation system that includes a synchrotron that accelerates and emits an ion beam and an irradiation device that irradiates the ion beam emitted from the synchrotron, and performs irradiation of one unit multiple times from the irradiation device.
Accumulated beam charge measuring means for measuring the accumulated beam charge in the synchrotron;
Target current setting means for setting a target beam current value emitted from the synchrotron based on the accumulated beam charge amount measured by the accumulated beam charge amount measuring means;
A particle beam irradiation system comprising: an exit beam current correction control unit configured to control a beam current based on the target beam current value obtained by the target current setting unit. In the particle beam irradiation system of Claim 1,
Receiving means for receiving a total irradiation charge amount necessary for the plurality of irradiations;
An emission control device for calculating the cumulative irradiation charge amount,
When the remaining irradiation charge amount obtained by subtracting the cumulative irradiation charge amount from the total irradiation charge amount and the smaller one of the accumulated beam charge amount is set as a comparison charge amount,
The particle beam irradiation system, wherein the comparison charge amount is used to determine a target value of the target beam current by the target current setting means. The particle beam irradiation system according to claim 2,
It has an irradiation control device that calculates the amount of charge required for one unit of irradiation,
The target beam correcting unit uses a comparison value between the comparative charge amount and the charge amount necessary for the unit of irradiation as a determination criterion for the necessity of correction. The particle beam irradiation system according to claim 2 or 3,
It has an irradiation control device that calculates the beam current value required for one unit of irradiation,
The particle beam irradiation system, wherein the target current setting means determines the target value of the beam current by correction based on a beam current value necessary for the unit irradiation. In the particle beam irradiation system according to any one of claims 2 to 4,
The target current setting means makes the target beam current value smaller than the beam current value necessary for the unit of irradiation when the comparison charge amount is smaller than the charge amount necessary for the unit of irradiation. Particle beam irradiation system characterized by correcting to In the particle beam irradiation system of Claim 5,
The target beam current value is obtained by correcting the beam current value necessary for the unit irradiation with the ratio of the comparative charge amount to the charge amount necessary for the one-surface irradiation. system. In the particle beam irradiation system according to any one of claims 2 to 6,
The target current correction unit may set the target beam current value to be smaller than the beam current value necessary for the unit of irradiation when the comparative charge amount is less than twice the amount of charge necessary for the unit of irradiation. A particle beam irradiation system which is corrected so as to increase. In the particle beam irradiation system of Claim 7,
The particle beam irradiation system, wherein the target beam current value is obtained by dividing the accumulated beam charge amount by a scanning time required for one unit of irradiation. Charge of a particle beam irradiation system comprising: a synchrotron that accelerates and emits an ion beam; and an irradiation device that irradiates the ion beam emitted from the synchrotron, and performs irradiation of one unit multiple times from the irradiation device In the particle beam correction method,
The irradiation controller calculates the beam current value required for one unit of irradiation,
The accumulated beam charge measuring means measures the accumulated beam charge in the synchrotron,
The target current setting means sets the target beam current value emitted from the synchrotron by correcting the beam current value necessary for the unit of irradiation based on the accumulated beam charge amount,
The method of correcting a charged particle beam of a particle beam irradiation system, wherein the emission beam current correction control unit controls a beam current based on the target beam current value.