Beam Alignment Procedure for Scanned Ion-Beam Therapy

It\u27s important to control the beam position for the 3D pencil-beam scanning because the position accuracy of the beam has a serious matter on the alignment of the irradiation field. In order to suppress this matter, we have been developed a simple procedure for the beam tuning. The fluctuation of the beam position is tuned with the steering magnets (ST) and the fluorescent screen monitors (SCN). At first, the beam positions are measured by two SCN and the kick angles of two ST are calculated using deviates from the center of the beam position measured by SCN and the transfer matrix. After the tuning, the beam position at the isocenter is checked on the verification system for the alignment of the beam consists of the SCN and the iron sphere phantom. If the beam position is deviated from the center, one of ST placed on most downstream of the beam transport line will be corrected. These adjustments are iterated until the deviation for all energies of the beam are within 0.5 mm. We have been performed the beam commissioning using our procedure in Kanagawa Cancer Center. In this presentation, we will report on the result of these measurements