JPWO2014207852A1 - Charged particle beam irradiation system and beam extraction method thereof - Google Patents

Abstract

When performing ion beam extraction control from the synchrotron, suppress the generation of the output beam current ripple caused by the high frequency voltage applied to the extraction high frequency electrode that increases the betatron oscillation amplitude of the circulating ion beam, In order to improve the dose rate, the emission control device 20 does not exceed the stability limit so that the beam that circulates inside the synchrotron 13 is not emitted outside the synchrotron as a high-frequency voltage applied to the high-frequency electrode 16a for emission. A high frequency voltage composed of a first high frequency voltage Fs for increasing the vibration amplitude and a second high frequency voltage Fe for emitting a beam from the synchrotron is applied.

Description

  The present invention relates to a charged particle beam irradiation system and a charged particle beam extraction method, and more particularly, to a particle beam therapy apparatus that treats cancer by irradiating an affected area with a charged particle beam (ion beam) such as protons or heavy ions. The present invention relates to a charged 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 or heavy ions is irradiated to a cancerous part of a patient to treat it. The particle beam therapy apparatus used for this treatment includes an ion beam generator, a beam transport system, and an irradiation device. 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 circular orbit (for example, 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 voltage) is applied to the extraction high-frequency electrode, and the characteristic of the circulating ion beam The betatron vibration amplitude which is vibration is increased (Patent Document 1). An example of a high-frequency voltage that efficiently increases the betatron oscillation amplitude is a band-limited high-frequency voltage composed of a plurality of line spectrum signals (Patent Document 2). 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. In the irradiation apparatus, attention is focused on a beam scanning method in which a beam is scanned and irradiated in accordance with the shape of an affected part. The beam scanning method includes a spot scanning irradiation method and a raster scanning irradiation method.

  In the spot scanning irradiation method, the affected area is divided into areas called spots, and an irradiation dose to be given to each spot is set according to a treatment plan. The dose irradiated to the spot is sequentially measured with a dose monitor. When the irradiation dose measured by the dose monitor reaches a predetermined dose, the ion beam irradiation is stopped. After stopping the ion beam irradiation, the excitation amount of the scanning magnet is changed to an excitation amount corresponding to the next spot position, and the ion beam is irradiated. By repeating such scanning and irradiation, irradiation in the plane of the affected area is performed. Further, when the irradiation in the affected area plane direction is completed, the depth direction of the irradiation surface is changed. Irradiation in the affected area depth direction is controlled by changing the range of the ion beam. Specifically, it can be realized by changing the energy of the ion beam supplied to the irradiation apparatus.

In contrast to the spot scanning irradiation method, the raster scanning irradiation method performs irradiation while scanning the ion beam along the irradiation path. For this reason, in the raster scanning irradiation method, the ion beam current is set low in consideration of the time structure of the output beam current, and scanning is performed in multiple times in the plane of the affected area (hereinafter referred to as repainting). The irradiation dose is expired while ensuring a predetermined dose uniformity.
In this way, the beam scanning method irradiates an ion beam that matches the shape of the affected area. Therefore, as in the conventional scatterer irradiation method, the uniform absorbed dose range (expanded black peak (Spread-Out) Bragg Peak) (hereinafter referred to as “SOBP”) and a patient-specific device such as a bolus and a collimator that match the shape of the affected part are not required and are supplied from the ion beam generator to the irradiation device. It is possible to efficiently irradiate the affected area with an ion beam.

  When using a synchrotron as the ion beam generator, the energy of the ion beam supplied to the irradiation device can be controlled by the frequency of the high-frequency voltage supplied to the acceleration cavity and the magnetic field strength of the deflection electromagnet. In addition, the current of the ion beam supplied from the synchrotron to the irradiation device can be controlled by the amplitude value of the extraction high-frequency voltage. The irradiation control of the ion beam for each spot required in the scanning beam scanning method can be realized by applying and stopping application of the high frequency voltage for extraction. In particular, when the irradiation of the ion beam is stopped when the irradiation dose to the spot reaches a predetermined dose, it is necessary to increase the accuracy of the irradiation dose by quickly stopping the ion beam emitted from the synchrotron.

Japanese Patent No. 2596292 Japanese Patent No. 3053175

  However, the above prior art has the following problems. In the beam scanning method, in order to control the irradiation dose with high accuracy, it is necessary to control the beam current emitted from the synchrotron with high accuracy. At this time, the emitted beam current has a low frequency component of several hundred Hz to several kHz. Is superimposed as a current ripple. It has been found that this low frequency component current ripple is caused by the frequency component contained in the high frequency voltage applied to the output high frequency electrode. For example, as described in Patent Document 2, when a band-limited high-frequency voltage composed of a plurality of line spectrum data is used as a high-frequency voltage necessary for beam emission, a frequency component corresponding to the interval between line spectra is used. Current ripple occurs.

  This current ripple appears as a time structure of several hundreds μs to several ms depending on the line spectrum interval of the high frequency voltage applied to the high frequency electrode for emission. The spot irradiation time in the spot scanning irradiation method is around several ms, and the beam scanning time per one time on the affected plane in the raster scanning irradiation method is several tens of ms. Therefore, a current having a time structure of several hundred μs to several ms. Ripple cannot be ignored. Further, since the intensity of the current ripple changes according to the intensity of the high-frequency voltage applied to the high-frequency electrode for emission, it is difficult to suppress only the current ripple component with the conventional beam emission control method.

  When such a low-frequency component current ripple is superimposed, there are the following two problems. First, when a low dose is irradiated, the current ripple superimposed on the output beam current cannot be controlled independently, so that it is difficult to control the dose irradiated due to the current ripple. Therefore, when irradiating a low dose, it is necessary to set the beam current emitted from the synchrotron low in advance and to keep the dose irradiated due to the current ripple low. Therefore, the irradiation time in an affected part plane takes time, and the subject that a dose rate falls is mentioned. In particular, in the raster scanning irradiation method in which irradiation is performed while scanning the beam, the time structure of the current ripple generated in the output beam current directly affects the dose distribution in the scanning region. It is necessary to perform repainting of several hundred times, which hinders improvement of the dose rate.

  Second, when stopping the beam irradiation, the application of the high-frequency voltage to the extraction high-frequency electrode is stopped based on the beam stop command, but the time until the beam is actually stopped after the beam stop command is input (hereinafter, The beam stop time depends on the output beam current value at the timing when the application of the high-frequency voltage is stopped. Therefore, when the outgoing beam current at the timing when the application of the high-frequency voltage is stopped overlaps the peak value or the bottom value of the current ripple, the beam stop time may vary. In particular, in the spot scanning irradiation method in which irradiation is performed while managing the irradiation dose for each spot, the beam emission and stop are repeated for each irradiation spot, so the variation in spot dose due to fluctuations in beam stop time affects the formation of the dose distribution. . For this reason, it is necessary to suppress the variation of the spot dose even when the outgoing beam current is set low and the time structure of the current ripple occurs, which hinders the improvement of the dose rate.

  It is an object of the present invention to provide an output beam current ripple caused by a high-frequency voltage applied to an extraction high-frequency electrode that increases the betatron oscillation amplitude of the circulating ion beam when performing ion beam extraction control from a synchrotron. It is an object of the present invention to provide a charged particle beam irradiation system and its beam extraction method that can suppress the occurrence of the above and improve the dose rate.

  A feature of the present invention that realizes the above object is that the high-frequency voltage applied to the high-frequency electrode for emission provided in the synchrotron exceeds the stability limit so that the beam circulating in the synchrotron is not emitted outside the synchrotron. A high-frequency voltage composed of a first high-frequency voltage (supply high-frequency voltage) for increasing the vibration amplitude within a range and a second high-frequency voltage (extraction control high-frequency voltage) for emitting a beam from the synchrotron. It is in the point to apply. The second high-frequency voltage is applied so as to perform beam extraction (application of the second high-frequency voltage) and beam stop (stop of the second high-frequency voltage) based on the beam extraction control command. Similar to the second high-frequency voltage, the first high-frequency voltage may be applied based on the beam extraction control command, but may be applied during the beam extraction control period regardless of the beam extraction control command.

  As described above, the high-frequency voltage applied to the emission high-frequency electrode is the first high-frequency voltage (for supply) that increases the vibration amplitude within a range not exceeding the stability limit so that the beam circulating in the synchrotron is not emitted outside the synchrotron. High frequency voltage and low frequency components that cause current ripple are included in the high frequency voltage by applying the function separately to the second high frequency voltage (radiation control high frequency voltage) for emitting the beam from the synchrotron. Even if it is, generation | occurrence | production of the current ripple of an emitted beam current can be suppressed. Moreover, since generation | occurrence | production of a current ripple can be suppressed, an emitted beam current can be raised and a dose rate can be improved.

  Specifically, the first high-frequency voltage (supply high-frequency voltage) is generated using a band-limited high-frequency voltage composed of a plurality of frequency components, and the frequency range and intensity of the first high-frequency voltage (supply high-frequency voltage). Is set so that the circular beam does not exceed the stability limit (that is, is not emitted). The frequency of the second high-frequency voltage (extraction control high-frequency voltage) is set between the stability limit and the center frequency of the first high-frequency voltage, and the intensity of the second high-frequency voltage depends on the required output beam current. Control.

  Of the high-frequency voltages applied to the extraction high-frequency electrode, the first high-frequency voltage (supply high-frequency voltage) is applied in advance before the start of beam extraction control, and the second high-frequency voltage (extraction control high-frequency voltage) is The first high-frequency voltage is applied after the pre-application control. Thereby, quick beam current control corresponding to application of the second high-frequency voltage, which is a high-frequency voltage for emission control, can be realized.

  Further, the first high-frequency voltage and the second high-frequency voltage are applied to the beam circulating in the synchrotron, and a third high-frequency voltage (single high-frequency voltage) composed of one frequency component near the stability limit is applied. ) Is superimposed on the second high-frequency voltage and applied based on the beam extraction control command. As described above, the third high-frequency voltage (single high-frequency voltage) that preferentially emits particles near the stability limit is superimposed on the second high-frequency voltage as the high-frequency voltage to be applied to emit the beam from the synchrotron. By using, the diffusion speed (beam emission speed) of the circulating beam distributed near the stability limit can be further increased, and beam control response, that is, the response at the time of beam extraction and beam stop based on the beam extraction control command. The speed can be further increased.

  According to the present invention, when performing extraction control of an ion beam from a synchrotron, the current ripple of the output beam caused by the high-frequency voltage applied to the output high-frequency electrode that increases the betatron oscillation amplitude of the circulating ion beam Can be suppressed and the dose rate can be improved.

It is a figure which shows the structure of a structure of the charged particle beam irradiation system of 1st Example to which this invention is applied. It is a figure which shows the application method of the high frequency voltage applied to the radiation | emission high frequency electrode which is the characteristics of 1st Example to which this invention is applied. It is a figure which shows the structure of the radiation | emission control apparatus which implement | achieves 1st Example to which this invention is applied. It is a figure which shows the relationship between the control command value of the radiation | emission control apparatus which implement | achieves 1st Example to which this invention is applied, and radiation | emission beam energy. It is a figure which shows the timing chart at the time of the beam emission control of 1st Example to which this invention is applied. It is a figure which shows the timing chart at the time of the beam emission control in the modification of 1st Example to which this invention is applied. It is a figure which shows the timing chart at the time of the beam emission control of 2nd Example to which this invention is applied. It is a figure which shows the application method of the high frequency voltage applied to the radiation | emission high frequency electrode which is the characteristics of 3rd Example to which this invention is applied. It is a figure which shows the structure of the radiation | emission control apparatus which implement | achieves 3rd Example to which this invention is applied. It is a figure which shows the timing chart at the time of the beam emission control of 3rd Example to which this invention is applied. It is a figure which shows the application method of the high frequency voltage applied to the conventional radiation | emission high frequency electrode. It is a figure which shows the beam current at the time of the outgoing beam stop by a conventional method. It is a figure which shows the beam current at the time of the outgoing beam stop by a conventional method.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 is a diagram showing a configuration of a charged particle beam irradiation system according to a preferred embodiment of the present invention. As shown in FIG. 1, the charged particle beam irradiation system 1 of the present embodiment includes an ion beam generator 11, a beam transport device 14, and an irradiation device 30, and the beam transport device 14 includes the ion beam generator 11 and a treatment room. The irradiating device 30 arranged in the is communicated.

  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.

  The synchrotron 13 is a high-frequency accelerator 19 (acceleration cavity) that applies a high-frequency voltage to the ion beam 10b that circulates along a circular orbit and accelerates to a target energy, and a betatron oscillation amplitude of the circulating ion beam. The output high-frequency electrode 16a to be increased and the output deflector 16b for extracting the ion beam from the circular orbit are provided.

  The beam 10 b incident on the synchrotron 13 is accelerated to a desired energy by being given energy by an acceleration high-frequency voltage applied to the high-frequency acceleration cavity 19. At this time, the intensity of the magnetic field of the deflecting electromagnet 18a, the quadrupole electromagnet 18b, etc. and the acceleration cavity are 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 around the synchrotron 13 is constant. The frequency of the high frequency voltage applied to 19 is increased.

  The ion beam 10b accelerated to a desired energy satisfies the condition (the orbital beam stability limit 15) that the orbiting beam 10b can be emitted by the excitation amount of the quadrupole electromagnet 18b and the hexapole electromagnet (not shown) by the extraction preparation control. Let After the exit preparation control is finished, a high frequency voltage (Fext) is amplified from the exit control device 20 by the high frequency amplifier 17 and then applied to the exit high frequency electrode 16a, and the betatron oscillation amplitude of the beam 10b circulating around the synchrotron 13 is set. Increase. Due to the increase of the betatron oscillation amplitude, the circular beam 10b exceeding the stability limit 15 (FIG. 2) is emitted from the synchrotron 13 to the high energy beam transport system 14. Beam emission control from the synchrotron 13 is performed by beam emission (application of a high-frequency voltage (Fext)) and beam stop (stop of a high-frequency voltage (Fext)) by a high-frequency voltage applied to the emission high-frequency electrode 16a by the emission control device 20. ) By controlling.

  The beam 10 c emitted from the synchrotron 13 is transported to the irradiation device 30 by the high energy beam transport system 14. In the irradiation apparatus 30, the dose monitor 31 that measures the irradiation dose of the beam 10 d irradiated to the patient sequentially confirms the dose intensity of the beam 10 d to be irradiated, and the scanning electromagnet 32 scans the beam 10 d according to the shape of the affected area. Further, the beam range in the affected area depth direction is changed by changing the energy of the beam 10b accelerated by the synchrotron 13 and emitted, thereby forming an irradiation field that matches the shape of the affected area.

  Next, a method of applying a high-frequency voltage (Fext), which is a feature of the present invention, will be described with reference to FIGS. 2 and 10 and FIGS. FIG. 2 is a diagram showing a method of applying a high-frequency voltage applied to the emission high-frequency electrode, which is a feature of this embodiment. FIG. 10 is a diagram illustrating a method of applying a high frequency voltage applied to a conventional high frequency electrode for emission.

  The beam 10b in the synchrotron 13 circulates around the design trajectory with betatron oscillation. The betatron frequency per revolution of the synchrotron 13 is called tune (ν), and the beam tune (νbeam) has a width (Δν) according to the momentum width of the clustered ion beam 10b. As shown in FIG. 10, in the conventional beam extraction control method, the oscillation amplitude of the circulating ion beam 10b is adjusted by applying an extraction high-frequency voltage (Fe) in a frequency range (Δf) corresponding to the tune width Δν. The beam was emitted by increasing and exceeding the stability limit 15. The center frequency (fc) and frequency width (Δf) of the high-frequency voltage applied to the emission high-frequency electrode 16a at this time are expressed by the following equations (1) and (2), respectively.

  Here, frev is the circulation frequency of the ion beam 10b, and νmax and νmin respectively indicate the maximum value and the minimum value of the tune width (Δν). Here, the high frequency voltage (Fext) applied to the high frequency electrode 16a for emission is only the high frequency voltage (Fe) for emission control. The current of the outgoing beam is controlled by the amplitude value (Ve) of the high frequency voltage (Fe) for outgoing control.

  11A and 11B are diagrams showing beam currents when the outgoing beam is stopped in the conventional method. As described above, in the beam scanning method, in order to control the irradiation dose with high accuracy, it is necessary to control the beam current emitted from the synchrotron with high accuracy, but this is included in the high frequency voltage applied to the high frequency electrode for emission. Due to the frequency component, a low frequency component of several hundred Hz to several kHz is superimposed on the outgoing beam current as a current ripple (Irip).

  As described above, in the conventional method, the beam emission can be stopped at a high speed by stopping the application of the high-frequency voltage (Fext) applied to the emission high-frequency electrode 16a. At this time, as shown in FIG. When the outgoing beam current (Ioff) at the time is at the peak of the current ripple (Irip), the dose (Qoff) emitted after the beam is stopped increases. Similarly, as shown in FIG. 11B, when the emission beam current (Ioff) is at the bottom of the current ripple (Irip) when the beam emission is stopped, the dose (Qoff) emitted after the beam is stopped decreases. As described above, the dose (Qoff) after the beam stop command varies depending on the difference between the peak and bottom of the current ripple (Irip) of the output beam current (Ioff) when the beam is stopped.

  On the other hand, in the present invention, as shown in FIG. 2, the high-frequency voltage (Fext) applied to the emission high-frequency electrode 16a does not exceed the stability limit so that the beam circulating in the synchrotron is not emitted outside the synchrotron. A high-frequency voltage (supply high-frequency voltage) (Fs) applied so as to increase the vibration amplitude in the range and a circular beam diffused to the vicinity of the stability limit 15 by the supply high-frequency voltage (Fs) are emitted from the synchrotron 13 In order to achieve this, it is constituted by a high frequency voltage (Fe) for emission control applied (Fext = Fs + Fe).

  By applying the supply high-frequency voltage (Fs) to the circulating beam distribution 101 before the application of the high-frequency voltage, the circulating beam distribution is expanded within a range not exceeding the stability limit 15 (103). With respect to the circulating beam distribution 103 spread by the application of the supply high-frequency voltage (Fs), the application of the emission control high-frequency voltage (Fe) widens the circulating beam to exceed the stability limit 15 (102), and the synchrotron 13 is The circulating beam 10 b is emitted out of the synchrotron 13.

  Here, the supply high-frequency voltage (Fs) is not applied to emit the beam 10b out of the synchrotron 13, but is applied to supply a beam emitted by the emission control high-frequency voltage (Fe). Therefore, unlike the conventional beam extraction control method, even if the high frequency voltage applied as the supply high frequency voltage (Fs) includes a frequency component that causes current ripple (Irip), the output beam current is directly affected. Absent. That is, by applying the high-frequency voltage applied to the high-frequency electrode for extraction 16a to the high-frequency voltage for supply (Fs) and the high-frequency voltage for output control (Fe) separately, the current ripple (Irip) is applied to the high-frequency voltage. Even if a low-frequency component that is a cause is included, the temporal structure of the outgoing beam current is not affected. Thereby, generation | occurrence | production of the current ripple of the outgoing beam current which was a subject by the conventional outgoing control method can be suppressed, and the dose rate can be improved by increasing the outgoing beam current.

  The supply high-frequency voltage (Fs) is applied in the vicinity of the center frequency νs of the tune (νbeam) of the circulating ion beam 10b, and the betatron oscillation amplitude is increased within a range not exceeding the stability limit 15. That is, it is applied in a narrow range (Δνs <Δν) with respect to the tune width (Δν) of the circulating ion beam 10b. In the present embodiment, the center frequency (fcs) of the supply high-frequency voltage is obtained by multiplying the circulation frequency (frev) of the ion beam 10b and the center frequency νs of the tune (νbeam) of the ion beam 10b that circulates (the following ( 3) Refer to equation).

  Further, the frequency width (Δfs) of the supply high-frequency voltage is set to a range (Δνs <Δν) narrower than Δν shown in the equation (2) so that the beam is not emitted by the supply high-frequency voltage ((4) below). See formula).

  The amplitude value (Vs) of the supply high-frequency voltage is not emitted when the supply high-frequency voltage (Fs) is applied, but is emitted when the extraction control high-frequency voltage (Fe) is applied. Adjust as follows.

  Next, by applying the emission control high-frequency voltage (Fe) between the stability limit 15 and the supply high-frequency voltage (Fs), the beam is emitted from the stability limit 15 to the outside of the synchrotron 13. At this time, the emission control high-frequency voltage (Fe) is increased within the beam stop period by increasing the diffusion speed (beam emission speed) of the circular beam 10b whose vibration amplitude is increased by applying the supply high-frequency voltage (Fs). Reduce the emission of the beam. Therefore, the center frequency (fce) of the emission control high-frequency voltage (Fe) is set between the stability limit 15 (νres) and the supply high-frequency voltage (Fs) (νres <νe <νs) (formula (5) below) reference).

  In addition, the frequency width (Δfe) of the extraction control high-frequency voltage is set to the center frequency (fce) of the extraction control high-frequency voltage (Fe) in consideration of the amount of beam that is emitted within the beam extraction time and the beam stop period. ) And adjust appropriately.

  At this time, in order to prevent the current ripple caused by the frequency component of the high frequency voltage applied to the output high-frequency electrode 16a in the beam 10c emitted from the synchrotron 13, the application of the output control high-frequency voltage (Fe). It is desirable to separate the frequency width (Δfe) serving as the range from the frequency width (Δfs) serving as the application range of the supply high-frequency voltage (Fs). Further, the amplitude value (Ve) of the emission control high-frequency voltage functions as a control parameter for the emission beam current (Iext), and is therefore controlled according to the required emission beam current.

  Next, a method for controlling the high frequency voltage (Fext) applied to the emission high frequency electrode 16a, which is a feature of the present invention, will be described. FIG. 3 shows the configuration of the emission control device. The output control device 20 includes a supply high-frequency voltage (Fs) output circuit 201, an output control high-frequency voltage (Fe) output circuit 202, a combiner 26 that combines these two high-frequency voltages, and a combiner 26. The high-frequency switches 271 and 272 that control the transmission of the output high-frequency voltage to the high-frequency amplifier 17 and the controller 28 that controls the control command values of the output circuits 201 and 202 for these high-frequency voltages. The controller 28 receives outgoing beam energy information En and high-frequency voltage control setting values (fcs, fws, fdivs, Vs, fce, fwe, fdiv, Ve) from the host control system 40.

  Control signals are transmitted from the timing system 50 and the interlock system 60 to the high-frequency switches 25 s, 25 e, 271, and 272 constituting the emission control device 20. From the timing system 50, a timing signal 51 indicating a beam extraction control section is transmitted to the high frequency switch 271 of the extraction control device 20. From the interlock system 60, the beam extraction control command 61 is transmitted to the high-frequency switches 25s, 25e, and 272 of the extraction control device 20 after confirming the soundness of the control equipment constituting the particle beam therapy system 1.

  The high frequency voltage (Fext) applied to the output high-frequency electrode 16a generates a supply high-frequency voltage (Fs) and an output control high-frequency voltage (Fe) by the output circuits 201 and 202, and generates two high-frequency voltages ( Fs and Fe) are synthesized by the synthesizer 26 and then amplified by the high-frequency amplifier 17.

  The supply high-frequency voltage (Fs) and the output control high-frequency voltage (Fe) output circuits 201 and 202 will be described. The supply high-frequency voltage output circuit 201 outputs an oscillator 21s that outputs the center frequency (fcs) of the supply high-frequency voltage (Fs) and a band-limited signal based on the frequency range (Δfs) of the supply high-frequency voltage (Fs). The band limiting signal generator 22s, the multiplier 23, the amplitude modulation circuit 24s, and the high frequency switch 25s are configured. A sine wave signal having a center frequency (fcs) set by the controller 28 is output from the oscillator 21s. The band limit signal generator 22s outputs a band limit signal composed of a plurality of line spectrum signals based on the set values of the spectrum width (fws) and the spectrum interval (fdivs) set from the controller 28. These two output signals are input to the multiplier 23s.

  The multiplier 23s outputs a band-limited high-frequency voltage having a center frequency of fcs and a spectrum width of 2fws. At this time, the frequency width of the high-frequency voltage output from the band-limited high-frequency oscillator 22s is doubled (fcs ± fws) by the calculation in the multiplier 23s. Therefore, the spectrum width (fws) of the band limited high-frequency oscillator 22s is set to be 1/2 of the frequency width (Δfs) of the supply high-frequency voltage (Fs). In this embodiment, a band-limited signal composed of a plurality of line spectra is used, but an output signal of a white noise generator (not shown) is output only in the frequency range (Δfs) of the supply high-frequency voltage (Fs). The output frequency of the sine wave oscillator 21s may be the frequency of the supply high-frequency voltage (Fs) without using the band-limited high-frequency generator 22s and the multiplier 23s. Sweeping may be performed in the frequency range (Δfs), but in separating the functions of the supply high-frequency voltage (Fs) and the emission control high-frequency voltage (Fe), the sideband of the band-limited signal does not widen, A band limited signal composed of a line spectrum is preferred.

  The amplitude value (Vs) of the supply high-frequency voltage (Fs) set by the controller 28 is controlled by the amplitude modulation circuit 24s with respect to the frequency calculation result of the supply high-frequency voltage (Fs). The supply high-frequency voltage (Fs) whose amplitude value is controlled is sent to the high-frequency switch 25 s, and the high-frequency switch 25 s is controlled based on the beam extraction control command 61 output from the interlock system 60. In order to apply an RF signal when the beam is emitted, the high frequency switch 25s is closed. In order to stop the application of the RF signal when the beam is stopped, the high frequency switch 25s is opened. The supply high-frequency voltage (Fs) output through the high-frequency switch 25 s is input to the synthesizer 26.

  Similarly, the output control high-frequency voltage (Fe) output circuit 202 will be described. Since the configuration of the output control high-frequency voltage output circuit 202 is substantially the same as that of the supply high-frequency voltage output circuit 201, differences from the supply high-frequency voltage output circuit 201 will be described.

  The center frequency (fce) of the emission control high-frequency voltage is set from the controller 28 to the sine wave oscillator 21e, and the band limit signal generator 22e is set to the spectrum width (fwe) and spectrum interval (fdiv) set from the controller 28. Based on the set value, a band-limited signal composed of a plurality of line spectrum signals is output. At this time, when a high frequency voltage of one frequency is used as the emission control high frequency voltage (Fe), the switch 231 prepared on the transmission line from the band limit signal generator 22e to the multiplier 23e is opened. This switch 231 makes it possible to control the input of the band limiting signal to the multiplier 23e, and the frequency width of the emission control high frequency voltage can be easily switched between a high frequency signal of one frequency and a band limited high frequency signal.

  In the present embodiment, a band limiting signal composed of a plurality of line spectra is used as in the case of the supply high-frequency voltage (Fs), but the output signal of a white noise generator (not shown) is used as the emission control high-frequency. It may be generated using a bandpass filter (not shown) that outputs only the frequency range (Δfe) of the voltage (Fe), or without using the band-limited high-frequency generator 22e and the multiplier 23e, the sine wave oscillator 21e. The output frequency may be swept within the frequency range (Δfe) of the extraction control high-frequency voltage (Fe), but in separating the functions of the supply high-frequency voltage (Fs) and the extraction control high-frequency voltage (Fe), A band-limited signal composed of a plurality of line spectrums in which the sideband of the band-limited signal does not spread is preferable.

  The amplitude value (Ve) of the emission control high-frequency voltage (Fe) is controlled by the amplitude modulation circuit 24e with respect to the frequency calculation result of the emission control high-frequency voltage (Fe). The amplitude control-controlled emission control high-frequency voltage (Fe) is sent to the high-frequency switch 25e, and the high-frequency switch 25e is controlled based on a beam emission control command 61 output from the interlock system 60. Since the RF signal is applied when the beam is emitted, the high frequency switch 25e is closed. In order to stop the application of the RF signal when the beam is stopped, the high frequency switch 25e is opened. The emission control high-frequency voltage (Fe) output via the high-frequency switch 25e is input to the combiner 26.

  The synthesizer 26 synthesizes two high frequency voltages (Fs, Fe). The synthesized signal is output to the high frequency amplifier 17 through the two high frequency switches 271 and 272.

  A method for managing control set values from the controller 28 of the emission control device 20 to each control circuit will be described with reference to FIGS.

  Control set values of the supply high-frequency voltage (Fs) and the emission control high-frequency voltage (Fe) include the center frequency (fcs, fce) of the sine wave oscillator 21, the spectrum width (fws, fwe), and spectrum of the band-limited signal, respectively. There are intervals (fdivs, fdiv) and amplitude values (Vs, Ve). These are stored in advance in a memory (not shown) of the controller 28 in a state associated with the beam energy information (En) emitted from the synchrotron 13 as shown in FIG. The treatment plan information 431 created for each patient in the treatment plan device 43 is stored in the storage device (database) 42. At the start of irradiation treatment operation, the overall control device 41 extracts the treatment plan information 431 from the storage device 42 and transmits it to the host control system 40, and the host control system 40 transmits the treatment plan information 431 to the controller 28. The treatment plan information 431 includes outgoing beam energy information (En), and the controller 28 controls the control setting values (fcs, fws, fdivs, Vs) stored in the memory of the controller 28 based on the outgoing beam energy information (En). , fce, fwe, fdiv, Ve), and outputs a control set value to each control circuit.

  Next, the control timing during the emission control will be described with reference to the timing chart shown in FIG. 5A. The extraction control section of the synchrotron 13 is the section from the end of acceleration control to the adjustment of the excitation amount of the quadrupole electromagnet or the hexapole electromagnet until the completion of beam extraction control after the completion of setting the extraction conditions and the cancellation of the extraction conditions. And is defined by a timing signal 51 output from the timing system 50. FIG. 5A (a) shows an emission control interval, and the timing signal 51 outputs ON in the emission control interval and OFF in the emission stop interval. FIG. 5A (b) shows a beam extraction control command 61 for irradiating the irradiation spot with a beam. In the emission control section, the beam is emitted (ON) until the dose to each irradiation spot expires, and the beam irradiation is stopped (OFF) at the timing when the dose has expired. After confirming the beam stop, the irradiation device 30 scans the scanning electromagnet 32 to the next irradiation spot position (not shown). After the scanning electromagnet 32 is scanned, the beam is irradiated again until the irradiation spot dose expires. By repeating such control, irradiation spots in the irradiation area are sequentially expired.

  FIG. 5A (c) shows the time change of the supply high-frequency voltage (Fs), which is a feature of the present invention. The supply high-frequency voltage (Fs) is based on the amplitude value (Vs) of the amplitude control data (Vs) based on the beam emission control command 61 (ON / OFF command) for irradiating the beam to the irradiation spot shown in FIG. ) Is updated and output. That is, when irradiating a beam to the irradiation spot (when the beam extraction control command 61 is ON), the supply high-frequency voltage (Fs) is output and when the beam irradiation to the irradiation spot is stopped (beam extraction control command). When 61 is OFF), the output of the supply high-frequency voltage (Fs) is stopped. At this time, the present embodiment shows a case where the amplitude value (Vs) of the supply high-frequency voltage (Fs) is always controlled at a constant value in the emission control section. As the number of particles decreases, the extraction efficiency decreases. Therefore, a control (not shown) for gradually increasing the amplitude value (Vs) of the supply high-frequency voltage (Fs) with the progress of the beam extraction control may be applied. .

  By performing the control as described above, as shown in FIG. 5A (e), the exit beam current can be stopped at a high speed and the generation of the current ripple of the exit beam current can be suppressed. In addition, the generation of spike current waveforms at the start of extraction can be suppressed.

  The supply high-frequency voltage (Fs) may be applied during the beam extraction control section based on the timing signal 51. FIG. 5B is a diagram showing such a modification. As shown in (c) of FIG. 5B, the supply high-frequency voltage (Fs) is based on the timing signal 51 indicating the emission control section shown in (a) of FIG. 5B, and the amplitude of the supply high-frequency voltage (Fs). The value (Vs) is updated and output. As a result, the beam near the stability limit can be reliably distributed, and the beam control response, that is, the response speed at the time of beam extraction and beam stop based on the beam extraction control command can be further increased. In this embodiment as well, the amplitude value (Vs) of the supply high-frequency voltage (Fs) is set to the beam emission in the emission control section in order to compensate for the reduction in the emission efficiency due to the decrease in the number of particles of the circulating beam with the beam emission control. You may apply control which raises gradually according to progress of control.

  According to the present embodiment, when the extraction control of the ion beam from the synchrotron 13 is performed, the emission beam caused by the high-frequency voltage applied to the extraction high-frequency electrode that increases the betatron oscillation amplitude of the circulating ion beam. Generation of current ripple can be suppressed and the dose rate can be improved.

(Example 2)
FIG. 6 shows a control timing chart for realizing the beam emission control method according to the second embodiment of the present invention. Since the configuration of the present embodiment is almost the same as that of the first embodiment, differences from the first embodiment will be described.

  In the control timing chart of the first embodiment shown in FIG. 5A, the emission control high-frequency voltage (Fe) and the supply high-frequency voltage (Fs) are applied as the beam emission starts. At this time, when a high emission beam current (Iext) is required immediately after the start of beam extraction, the ion beam 10b that circulates in the synchrotron 13 increases the betatron oscillation amplitude by applying the supply high-frequency voltage (Fs). Since it takes time (diffusion speed is slow), there is a possibility that a desired beam current cannot be obtained quickly even when an emission control high-frequency voltage (Fe) is applied. The same thing is also concerned when the outgoing beam current is controlled for each irradiation spot.

  For this reason, in this embodiment, as shown in FIG. 6, when a spot immediately after the start of beam extraction (spot number: # 1 shown in FIG. 6) is irradiated, a supply high-frequency voltage (Fs) is applied in advance. A section 62 is provided, and a high frequency voltage (Fe) for emission control is applied after the processing of the pre-application section 62 is completed. In this way, desired beam current control can be realized immediately after the start of the extraction control by supplying the beam emitted by the application of the extraction control high-frequency voltage (Fe) in advance by the supply high-frequency voltage (Fs) in advance. .

  Although not shown, even when beam emission control is in progress, the same effect can be obtained by providing a section similar to the pre-applied section 62 after emitting a beam with a high beam current.

(Example 3)
A high-frequency voltage application method for realizing the beam emission control method according to the third embodiment of the present invention will be described with reference to FIGS. Since the configuration of the present embodiment is almost the same as that of the first embodiment, differences from the first embodiment will be described.

  In this embodiment, as shown in FIG. 7, as the high-frequency voltage (Fext) applied to the emission high-frequency electrode 16a, the supply high-frequency voltage (Fs) and the emission control high-frequency voltage (Fe) shown in the first embodiment. At the same time, a high-frequency voltage (single high-frequency voltage) (Fm) emitted with priority given to the particle distribution near the stability limit 15 is superimposed and applied (Fext = Fs + Fe + Fm). This single high-frequency voltage (Fm) is applied to a region (νm) closer to the stability limit 15 (νres) than the application range (Δνe) of the emission control high-frequency voltage (Fe). The beam distribution 104 in the fluctuation range 15a can be emitted at a higher speed. At this time, the single high frequency voltage (Fm) is applied in synchronization with the extraction control high frequency voltage (Fe) to further increase the response speed at the time of beam extraction and beam stop based on the beam extraction control command. it can.

  FIG. 8 shows the configuration of the emission control device that realizes the high-frequency voltage (Fext) as shown in FIG. The emission control device in the first embodiment shown in FIG. 3 includes a sinusoidal oscillator 21m that generates a single high frequency voltage (Fm) in the emission control high frequency voltage output circuit 202, and a single high frequency voltage (Fm). The difference is that an amplitude modulator 24m for controlling the amplitude value and a synthesizer 261 for synthesizing the emission control high-frequency voltage (Fe) and the single high-frequency voltage (Fm) are added.

  The amplitude value (Vm) of the single high frequency voltage (Fm) may be applied at a constant value in order to preferentially emit the particle distribution in the vicinity of the stability limit 15, and as shown in FIG. It is controlled independently of the amplitude value (Ve) of (Fe). By applying such control, it becomes possible to further reduce the beam distribution in the vicinity of the stability limit 15 as compared with the beam extraction control method shown in the first embodiment, and at the time of beam extraction and beam stop based on the beam extraction control command. The response speed at the time can be further increased.

1 charged particle beam irradiation system 100 control system (control device)
10a, 10b, 10c, 10d Beam 101 Circulating beam distribution 102 before applying high-frequency voltage Circulating beam distribution 103 when applying high-frequency voltage for supply 103 Circulating beam distribution when applying high-frequency voltage for emission control 104 Circulating beam when applying a single high-frequency voltage Distribution 11 Ion beam generator 12 Pre-accelerator 13 Synchrotron 14 Beam transport device 15 Stability limit 15a Stability limit fluctuation range 16a due to synchrotron vibrations High-frequency electrode 16b for output Deflector 17 for output High-frequency amplifier 18 Deflection electromagnet 19 Quadrupole electromagnet 20 Output control Device 201 Supply high-frequency voltage output circuit 202 Output control high-frequency voltage output circuit 21s, 21e, 21m Sine wave oscillator 22s, 22e Band-limited signal generator 23s, 23e Multiplier 231 Switch 24s, 24e, 24m Amplitude modulator 25s 25e High-frequency switch 26, 261 Synthesizer 271, 272 High-frequency switch 28 Controller 30 Irradiation device 31 Dose monitor 311 Dose measurement data 32 Scanning magnet 34 Collimator 36 Patient 40 Accelerator control device 41 Overall control device 42 Storage device 43 Treatment planning device 431 Treatment plan Information 50 Timing system 51 Timing signal 60 Interlock system 61 Beam extraction control command 62 Pre-application period of high frequency voltage for supply

Claims (10)

In a charged particle beam irradiation system having a synchrotron that accelerates and emits an ion beam, and an irradiation device that irradiates the ion beam emitted from the synchrotron,
To increase the vibration amplitude within a range that does not exceed the stability limit so that the beam that circulates inside the synchrotron is not emitted outside the synchrotron as a high-frequency voltage applied to the emission high-frequency electrode provided in the synchrotron A charged particle beam irradiation system comprising: an emission control device that applies a high-frequency voltage composed of the first high-frequency voltage and a second high-frequency voltage for emitting a beam from the synchrotron. The charged particle beam irradiation system according to claim 1,
The emission control device includes:
The first high-frequency voltage is generated using a band-limited high-frequency voltage composed of a plurality of frequency components, and the frequency of the band-limited high-frequency voltage and the signal intensity exceed the stability limit. A charged particle beam irradiation system characterized in that it is set so as not to exist. The charged particle beam irradiation system according to claim 1,
The emission control device includes:
Generating the second high-frequency voltage using a high-frequency voltage composed of one or more frequency components, setting a frequency range of the high-frequency voltage between a stability limit and a center frequency of the first high-frequency voltage; A charged particle beam irradiation system that controls the intensity of a high-frequency voltage according to a required outgoing beam current. The charged particle beam irradiation system according to claim 1,
The emission control device includes:
The charged particle beam irradiation system, wherein the first high-frequency voltage is applied in advance before the start of beam extraction control, and the second high-frequency voltage is applied after the pre-application control of the first high-frequency voltage. The charged particle beam irradiation system according to claim 1,
The emission control device includes:
The second high-frequency voltage is generated as a high-frequency voltage applied to emit a beam from the synchrotron, and a third high-frequency voltage composed of one frequency component near the stability limit is generated to generate the second high-frequency voltage. A charged particle beam irradiation system in which these two high-frequency voltages are superimposed on a voltage and applied based on a beam extraction control command. The charged particle beam irradiation system according to claim 1,
The emission control device includes:
A charged particle beam irradiation system that controls application and stop of the first and second high-frequency voltages so as to execute beam extraction and beam stop based on a beam extraction control command. The charged particle beam irradiation system according to claim 1,
The emission control device includes:
Regardless of the beam extraction control command, the application of the first high-frequency voltage is controlled so that it is applied during the beam extraction control period, and the second high-frequency voltage is set so as to execute beam extraction and beam stop based on the beam extraction control command. A charged particle beam irradiation system characterized by controlling application and stop of the laser beam. In a beam extraction method of a charged particle beam irradiation system having a synchrotron that accelerates and emits an ion beam, and an irradiation device that irradiates the ion beam emitted from the synchrotron,
To increase the vibration amplitude within a range that does not exceed the stability limit so that the beam that circulates inside the synchrotron is not emitted outside the synchrotron as a high-frequency voltage applied to the emission high-frequency electrode provided in the synchrotron A beam emitting method for a charged particle beam irradiation system, wherein a high frequency voltage composed of the first high frequency voltage and a second high frequency voltage for emitting a beam from the synchrotron is applied. In the beam extraction method of the charged particle beam irradiation system according to claim 7,
The charged particle beam irradiation system characterized in that the first high-frequency voltage is applied in advance from the start of beam extraction control, and the second high-frequency voltage is applied after the pre-application control of the first high-frequency voltage. Beam extraction method. In the beam extraction method of the charged particle beam irradiation system according to claim 7,
The second high-frequency voltage is generated as a high-frequency voltage applied to emit a beam from the synchrotron, and a third high-frequency voltage composed of one frequency component near the stability limit is generated to generate the second high-frequency voltage. A beam extraction method for a charged particle beam irradiation system, wherein the two high-frequency voltages are superimposed on a voltage and applied based on a beam extraction control command.

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