Development of spiral wobbler system for compact carbon-therapy facility

We propose an amplitude modulation wobbler-scatterer system, a so-called spiral-wobbler system, to produce a large irradiation field in a relatively short irradiation port for heavy-ion radiation therapy. The system has an advantage in that the residual range at the isocenter is larger than that obtained using the conventional wobbler-scatter system. The wobbler parameters, such as the wobbler-radius-modulation function, wobbler radial frequency and rotational frequency, are optimized. Experimental results of the spiral-wobbler system have been obtained. By using a wobble radial frequency of 23 Hz and a wobbler rotational frequency of 59 Hz, an irradiation field with a uniformity of 3-5% is obtained for an irradiation duration of 1 s. The spiral-wobbler system is applicable to respirating-gated irradiation. (author)