CN108939317B - Single-period multi-step active energy-changing slow extraction method for synchrotron - Google Patents
Single-period multi-step active energy-changing slow extraction method for synchrotron Download PDFInfo
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- CN108939317B CN108939317B CN201810498238.XA CN201810498238A CN108939317B CN 108939317 B CN108939317 B CN 108939317B CN 201810498238 A CN201810498238 A CN 201810498238A CN 108939317 B CN108939317 B CN 108939317B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1077—Beam delivery systems
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1085—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy characterised by the type of particles applied to the patient
- A61N2005/1087—Ions; Protons
Abstract
Single-cycle multi-step active energy-changing slow speed of synchrotronThe extraction method comprises the following steps: injecting a beam, and accelerating the energy of the beam to a maximum value; decelerating the beam to a first energy value E1Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number; continuing to decelerate the beam current to a second energy value E2Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number; continuously reducing the energy value of the beam step by step and slowly leading out the beam until a preset number of energy values E are obtainednThe particles of (1). The method can greatly improve the utilization efficiency of the beam, and reduce the pollution and waste of the beam; because active energy change is utilized without using an energy degrader, the beam current does not act with the energy degrader, nuclear fragments are not generated, and the size of a beam spot is not changed along with the thickness of the energy degrader; the active energy conversion can be realized in a single period, so that the time of beam injection, acceleration and power supply return to zero can be saved, the irradiation time can be shortened, and the irradiation efficiency can be improved.
Description
Technical Field
The invention relates to a single-period multi-step active energy-changing slow extraction method of a synchrotron, which can realize multiple times of energy conversion in one pulse period, quickly provide beam current with various energies for a terminal, greatly save irradiation time and improve irradiation efficiency.
Background
Because the irradiation of the heavy ion beam to the organism has the characteristics of reversed depth dose distribution, smaller side scattering, higher relative biological effect, lower oxygen increment ratio and the like, the heavy ion cancer therapy becomes an international advanced and effective cancer radiotherapy method. The beam energy of the common deep heavy ion cancer therapy is 120MeV/u-400MeV/u (heavy ion).
The equivalent Bragg peak of the heavy ion beam in water is related to beam energy, and different energies correspond to different depths of Bragg peak positions. Usually, the desired dose in the focal zone is obtained by stacking bragg peaks at different depths in the treatment plan and the dose in the incident channel is controlled to a reasonable value. For spot scanning or uniform scanning of 2DLS and 3DLS, the required population per energy slice is typically 0.1-1e9While the synchrotron may provide 1e per pulse10So that only 1-10% of the particles are transported to the terminal end and the rest are all lost in the synchronization loop or sent to the beam dump. This will cause serious beam waste, and radiation caused by beam loss may also affect the stable operation and service life of the equipment, even cause equipment activation, and increase the difficulty of equipment maintenance.
The synchrotron is operated in a pulsed mode, each pulse provides a beam with one energy, for a typical lesion, about 30 Bragg peaks are usually needed to be superposed at a target body, and at least about 30 pulse beams with different energies need to be provided by the synchrotron. Taking the wuweiqia heavy ion therapy device HIMM as an example, the operating period per pulse is 8s, and it takes at least 240s, i.e., about 4 minutes, to provide 30 pulsed beams. In the actual treatment process, the number of particles required by each energy layer is different, the required time is longer, and when tumors of moving target areas such as the lung and the like are treated, respiratory gating is required, and the required irradiation time is increased by 2-3 times on the basis of the time.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a single-period multi-step active energy-changing slow extraction method of a synchrotron, which is used for improving the irradiation efficiency.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a single-period multistep active energy-changing slow extraction method of a synchrotron, which comprises the following steps:
injecting a beam, and accelerating the energy of the beam to a maximum value;
decelerating the beam to a first energy value E1Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuing to decelerate the beam current to a second energy value E2Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuously reducing the energy value of the beam step by step and slowly leading out the beam until a preset number of energy values E are obtainednThe particles of (1).
Preferably, when the residual particle number is insufficient, the beam is re-injected, the energy of the beam is accelerated to a maximum value, then the beam is decelerated to a preset energy value, and the particles are continuously extracted until the particle number of all the energy reaches a preset number.
The invention provides another method for changing energy and slowly leading out a synchronous accelerator, which comprises the following steps:
injecting a beam current, adding the beam current to the nth energy value EnSlowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuously accelerating the beam current to the n-1 energy value En-1Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuously increasing the energy value of the beam step by step and slowly leading out the beam until a preset number of energy values E are obtained1The particles of (a);
accelerating the beam energy to the maximum value and then reducing the beam energy to 0, and ending the slow extraction.
Preferably, when the residual population is insufficient, the beam is re-injected, the energy of the beam is accelerated to a preset energy value, and the extraction of the particles is continued until the population of all the energy reaches a preset number.
Preferably, the method includes determining a current value of the corresponding magnet according to the different energy values, and then determining and storing a current variation curve.
Preferably, the current variation curve is a smooth curve composed of a quadratic curve and a straight line.
Preferably, when energy is switched, the current values corresponding to different energy values are connected according to a pre-stored current change curve.
Preferably, the method includes calculating a voltage and frequency change curve of the corresponding high-frequency cavity according to a current change curve of the dipolar iron, so as to ensure that the high-frequency cavity and the power supply keep changing synchronously.
Preferably, when the beam is extracted, the corresponding excitation voltage and frequency curve is called according to the beam energy value, and then the beam is extracted.
Compared with the prior art, the invention has the following beneficial effects:
1. the method can greatly improve the utilization efficiency of the beam, and reduce the pollution and waste of the beam;
2. the method of the invention uses the accelerator to change energy actively without using the energy degrader, so that nuclear fragments are not generated, the size of the beam spot is not changed along with the thickness of the energy degrader, and the irradiation precision can be improved;
3. the method can omit the time of beam injection, acceleration and power supply return to zero due to the realization of active energy conversion in a single period, thereby reducing the irradiation time and improving the irradiation efficiency.
Drawings
FIG. 1 illustrates the operating mode of the HIMM synchronizer ring for two poles;
FIG. 2 is a graph of current variation in an embodiment of the present invention;
FIG. 3 illustrates an exemplary embodiment of an operating mode for implementing multiple energy extraction;
fig. 4 shows an operation mode for realizing multiple energy extraction according to another embodiment of the present invention.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
In a synchrotron, a typical cycle of operation is generally shown in fig. 1. Firstly, beam injection is carried out, and then the beam is accelerated to an energy value E1Then slowly extracting until the number of extracted particles reaches N1The slow extraction is stopped, after the slow extraction is finished, the current rises to a maximum value (the main purpose of rising to the maximum value is to eliminate hysteresis influence) and then falls to zero, and the pulse period supplies energy to the terminal as E1The number of particles is N1Beam current (if one pulse provides a population < N)1Then the above process is repeated until the number of particles reaches N1). Then in the same way the terminal is supplied with energy E2The number of particles is N2…, to E1To EnThe beam is totally distributed to the terminal.
With the development of the current accelerator technology, the medical heavy ion synchrotron can easily store, accelerate and extract near to or even exceeding 1e in each operating period10A beam of ions. In practice, during irradiation, a beam with high current intensity is not needed for one energy layer, and thus the beam which is not utilized by a terminal is naturally lost in a synchronous ring or thrown into a beam garbage can. Because the energy of the beam is high, the beam is lost and then is irradiated on related equipment of a vacuum pipeline or an accelerator, so that the equipment is easily damaged or the equipment or components are activated to generate radioactivity, the long-term stable operation of the equipment is not facilitated, and the maintenance and the repair of the equipment are also not facilitated.
In general, in order to save irradiation time, an energy reducer is adopted to adjust beam current energy. After the energy degrader is added on a beam transmission path, the beam can generate a scattering effect with the energy degrader, so that nuclear fragments such as neutrons are generated, the nuclear fragments are not expected to appear during irradiation, the irradiation effect can be interfered, and unexpected influence can be generated on some key organs at the rear part of a target area due to strong penetrating power of the nuclear fragments such as neutrons; meanwhile, after the beam current and the energy degrader act, the beam spot is enlarged, and the irradiation precision is reduced.
Due to the inherent operation mode of the synchrotron, the method can undergo four stages of beam injection, acceleration, extraction and power supply return to zero when providing beams with each energy, and the irradiation efficiency is low.
Therefore, aiming at the operation characteristics of the synchrotron, the invention provides that in a pulse period, the beam energy is changed according to the terminal requirement in the pulse period by controlling the high-frequency electric field, the magnetic fields of dipolar iron, quadrupole iron and hexapole iron and the transverse excitation electric field of the synchrotron, and the beam is slowly led out.
The specific control steps are as follows:
1. introducing data of an irradiation plan into an irradiation control system, extracting corresponding parameters, such as energy required by irradiation and the number of particles corresponding to each energy, determining a current value of a corresponding magnet according to different energy values, and then determining and storing a current change curve, wherein the current change curve is preferably a smooth curve composed of a quadratic curve and a straight line, as shown in fig. 2;
2. the accelerator is instructed to increase the current of all the dipolar, quadrupolar and hexapolar irons of the synchrotron from 0, and the curve of the current increase is shown in fig. 3. Firstly, the power supply is raised from 0 to an injection platform to realize beam injection, then the current is raised to a maximum value, and then the current is reduced to E1The corresponding current value. The method comprises the steps of sending an instruction to a high-frequency system, calculating a voltage and frequency rising curve of a corresponding high-frequency cavity according to a current rising curve of a dipolar iron, so as to ensure that the high frequency and a power supply are synchronously raised or lowered, and the beam loss is reduced to the minimum;
3. at the beam energy reaching E1When the beam current is detected, the power supply and the high-frequency system are immediately instructed to stop decelerating and maintain the beam current energy to be E1And simultaneously, sending an instruction to the transverse excitation system, and calling a corresponding excitation voltage and frequency curve according to the energy value of the platform to lead out the beam current. When the number of the extracted particles reaches N1When the system is in use, the system sends out instructions to the transverse excitation system to stop the extraction of beam current, and simultaneously, the high-frequency system, the dipolar iron and the dipolar iron are subjected to beam current extractionThe power supplies of the iron poles and the six-pole iron send out instructions to continue to decelerate the beam current;
4. when the beam current in the synchronous ring is decelerated to E2When the number of the extracted particles reaches N, an instruction is sent out to carry out slow extraction2When the water is discharged, the extraction is stopped;
5. repeating the above steps until the energy is EnThe number of particles of (2) meets the terminal requirements.
Therefore, the slow extraction of the single-period multi-energy variable energy is realized. The beam energy is less than En and the number of remaining particles in the synchronization ring is insufficient, and at this time, the injection, acceleration and deceleration are performed again, and then the above process is repeated for the previous energy value.
The method utilizes the beam intensity of the synchrotron to the maximum extent, can greatly shorten the irradiation time and improve the irradiation efficiency.
Of course, the drawing may be performed while accelerating. I.e. after the injection is finished, the beam energy is accelerated to E respectivelyn，En-1，…，E1And slow extraction is performed on the energy points in sequence, and finally the power supply is increased to the maximum value and then reduced to 0, and the operation mode of the power supply is shown in fig. 4. Similarly, there is a possibility that the beam energy is less than E1And under the condition that the number of the residual particles in the synchronous ring is insufficient, the injection and the acceleration are needed to be performed again, and then the previous energy value is repeated.
The method of the invention omits the rise and return-to-zero of the power supply of each pulse and the waiting time of the pulse interval in the prior art, thereby greatly shortening the irradiation time. In addition, the particles in the synchronizing ring are fully utilized, and for the last energy layer, if the particles in the synchronizing ring have surplus, the beam can be decelerated to lower energy and then lost in the synchronizing ring or sent into a beam garbage can, so that the influence of beam radiation is reduced as far as possible. The invention breaks the original thinking set, and leads out a beam with fixed energy from one accelerator operation period to become a beam with a plurality of energy from one accelerator operation period. The key is that the control modes for the synchrotron power supply and the high frequency system are different from the conventional case.
When single energy is led out, data waveforms of all magnet power supplies and high-frequency systems are calculated and then sent to memories of the power supplies and the high-frequency systems, different led-out energies correspond to different current-voltage curves, the waveform curves with different energies are respectively identified by certain serial numbers, and the waveform curves with corresponding serial numbers are called according to the different led-out energies.
When the multi-energy variable energy is led out slowly, parameters such as a current platform value of a power supply and the voltage frequency of a high-frequency system are changed at any time according to the irradiation requirement of the terminal. The basic control logic is as follows: firstly, the value of beam current energy (E) required by a patient is determined according to the requirements of an irradiation plan (for example, according to relevant information of tumors of the patient and the dose prescribed by a doctor)1，E2，…，En) And the number of particles (N) corresponding to each energy value1，N2，…，Nn) And then, sending an instruction to the accelerator to realize the injection, acceleration and deceleration of the beam, and leading out the energy one by one according to the energy descending (or ascending) mode.
Therefore, the control mode of directly calling the waveform number in the prior art is changed into a mode of monitoring beam energy and terminal particle counting in real time in a pulse period and switching the beam on and off and energy at any time.
The method of the invention does not need to use an energy degrader on the beam line, thereby avoiding the action of the beam and the energy degrader and having higher safety and irradiation precision. The invention saves the time of injecting a large amount of beam, accelerating and returning to zero by the power supply, and only needs to consume the time of energy switching, thereby greatly shortening the irradiation time and greatly improving the irradiation efficiency.
The invention is not only suitable for medical heavy ion synchrotrons, but also suitable for medical proton accelerators, and synchrotrons for scientific research or other purposes. The method of the invention can be used for heavy ion cancer treatment, biological irradiation, material manufacture, nuclear physics experiments and the like.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A single-period multi-step active energy-changing slow extraction method of a synchrotron is characterized by comprising the following steps:
injecting a beam, and accelerating the energy of the beam to a maximum value;
decelerating the beam to a first energy value E1Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuing to decelerate the beam current to a second energy value E2Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuously reducing the energy value of the beam step by step and slowly leading out the beam until a preset number of energy values E are obtainednThe particles of (1).
2. The method of claim 1, wherein when the remaining population is insufficient, re-injecting the beam accelerates the beam energy to a maximum and then decelerates to a predetermined energy value, and continuing to extract the particles until all energies reach a predetermined number.
3. A single-period multi-step active energy-changing slow extraction method of a synchrotron is characterized by comprising the following steps:
injecting a beam current, adding the beam current to the nth energy value EnSlowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuously accelerating the beam current to the n-1 energy value En-1Slowly extracting, and stopping extracting when the number of extracted particles reaches a preset number;
continuously increasing the energy value of the beam step by step and slowly leading out the beam until a preset amount of energy is obtainedValue E1The particles of (a);
accelerating the beam energy to the maximum value and then reducing the beam energy to 0, and ending the slow extraction.
4. The method of claim 3, wherein when the remaining population is insufficient, re-injecting the beam, accelerating the beam energy to a predetermined energy value, and continuing to extract the particles until the population of all energies reaches a predetermined number.
5. The method according to any one of claims 1-4, wherein the method comprises determining the current values of the corresponding magnets from different energy values, and then determining and storing a current profile.
6. The method of claim 5, wherein the current profile is a rounded curve consisting of a quadratic curve and a straight line.
7. The method according to claim 5, wherein when energy switching is performed, current values corresponding to different energy values are connected according to a pre-stored current change curve.
8. The method according to any one of claims 1-4, wherein the method comprises calculating voltage and frequency profiles of the corresponding high frequency cavity from the current profiles of the dipolar iron to ensure that the high frequency cavity and the power supply remain synchronized.
9. The method as claimed in any one of claims 1 to 4, wherein, when extracting the beam current, the corresponding excitation voltage and frequency curve is called according to the energy value of the beam current, and then the beam current is extracted.
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| CN1331902A (en) * | 1998-12-24 | 2002-01-16 | 离子束应用股份有限公司 | Method for treating target volume with particle beam and device implementing same |
| CN102548182A (en) * | 2012-01-14 | 2012-07-04 | 中国科学院近代物理研究所 | Operation method for eliminating hysteresis effect influence of synchronous accelerator |
| CN104274914A (en) * | 2014-09-25 | 2015-01-14 | 中国科学院近代物理研究所 | Breath guide device and method for ion beam respiratory-gated treatment |
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| US8841866B2 (en) * | 2008-05-22 | 2014-09-23 | Vladimir Yegorovich Balakin | Charged particle beam extraction method and apparatus used in conjunction with a charged particle cancer therapy system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1331902A (en) * | 1998-12-24 | 2002-01-16 | 离子束应用股份有限公司 | Method for treating target volume with particle beam and device implementing same |
| CN102548182A (en) * | 2012-01-14 | 2012-07-04 | 中国科学院近代物理研究所 | Operation method for eliminating hysteresis effect influence of synchronous accelerator |
| CN104274914A (en) * | 2014-09-25 | 2015-01-14 | 中国科学院近代物理研究所 | Breath guide device and method for ion beam respiratory-gated treatment |
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