Operation of ion source
We operate various types of ion sources with different principles. These include the PIG type, ECR type, high frequency ECR type, small ECR type (permanent magnet, specialize carbon), and multi-ion source (permanent magnet, multi-ion species). For radiotherapy operation in HIMAC, the backup ion source is always on standby for continuous beam supply from the ion source. Conversely, in joint-use experiments conducted outside radiotherapy operation time, various heavy ions such as Fe (iron) and Kr (krypton) are switched in a pulsed mode and supplied to multiple users simultaneously. Therefore, a stable supply of the beam is required in addition to maintaining the quality of the ion source. It is necessary to operate each ion source to agree with various supply situations. Our technical staff is highly evaluated for their ability to respond not only to operations but also to the development support.
Operation of LINAC
The heavy ion beam generated by the ion source is accelerated by two types of linear accelerators (RFQ Linac and Alvarez Linac). In the operation of linear accelerators, the ion beam is accelerated in the electromagnetic waves generated by the high-power RF amplifier;thus, the most important aspect is the technology to rationally adjust the operating phase between the components. It is necessary to maintain the performance stability and reproducibility such as the frequency, phase and power of the RF cavities.
Our technical staff makes full use of its advanced RF technology and carefully manages the daily temperature and vacuum. Furthermore, to operate the devices stably and with good reproducibility for a long period of time, we are steadily implementing them based on high technology and know-how such as preventive measures based on trend information.
HIMAC is used to equip compact heavy-ion injector system which was developed at NIRS. This system consists of a small ECR type ion source and IH-DTL type (IHL) linear accelerator.
Operation of synchrotron
The synchrotron has a two-layer structure, and the two synchrotrons simultaneously supply multiple heavy ions with different energies to different courses. The operation of the synchrotrons requires complicated timing control that periodically synchronizes them. For beam controlling, it is necessary to control the beam to rotate the central orbit of the synchrotron from injection to just before extraction. It is also necessary to control the beam size and stability when extracting the beam from the synchrotron. Our technical staff responds to the operation of synchrotrons for therapy with advanced and a wide range of field technical support capabilities.
Beam transport to treatment / experimental room Quality assurance
Beamlines have many components and various operating parameters. The HIMAC beam transport system transfers the beam from the upper synchrotron to three treatment rooms and a biological experiment room, and from the lower synchrotron to the physics experiment rooms.
Our technical staff can adjust the beam size and intensity, which are requested from beam users by calculating the optimized parameters of the magnets on the beam transport system based on the beam transport theory. As a quality assurance of the beam, we confirm the irradiation parameters for the treatment, which are obtained from the treatment planning, through the beam measurement and its analysis. Additionally, we inspect and manage the irradiation related equipment (bed, X-ray devices and so on) to maintain the accuracy of the beam irradiation position.
Treatment planning support
In heavy ion radiotherapy, carbon ions cut off the DNA of cancer lesions and prevent
s new division and proliferation. However, heavy ion beams have the same effect on healthy tissue, thus the accurate irradiation of cancer lesions is essential.
Treatment planning realizes accurate irradiation.
Treatment planning is proposed by radiologists in radiotherapy. The first step of treatment planning is to confirm the position, size and shape of the cancer lesion three-dimensionally by CT imaging. The second step of treatment planning is to determine the irradiation region based on the CT image, set the appropriate dose and irradiation angle for the cancer lesion and calculate the dose using a computer. The settings of the irradiation control devices are created by these procedures and the optimized treatment planning for the patient is completed. Regarding the basic data used for treatment planning and dose measurement to maintain the quality of treatment, an accumulated accelerator engineering corporation technique for a long period of time is established.
We also contribute to working on new radiotherapy techniques by association with radiologists.
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