Irradiation System for HIMAC

Abstract

Clinical trials of carbon radiotherapy started at HIMAC in 1994 using three treatment rooms and four beam ports, two horizontal and two vertical. The broad beam method was adopted to make a three-dimensionally uniform field at an isocenter. A spot beam extracted from an accelerator was laterally spread out by using a pair of wobbler magnets and a scatterer. A bar ridge filter modulated the beam energy to obtain the spread out Bragg peak (SOBP). The SOBP was designed to be flat in terms of the biological dose based on the consideration that the field consisted of various beams with different LET. Finally, the field of 20 cm in diameter with +/- 2.5% uniformity was formed at the isocenter. The width of the maximum SOBP was 15 cm. When treating the lung or liver, organs that move due to breathing, the beam was irradiated only during the expiration period in a respiration-gated irradiation method. This reduced the treatment margin of the moving target. In order to prevent normal tissues adjacent to the target volume from irradiation by an unwanted dose, a layer-stacking method was developed. In this method, thin SOBP layers which have different ranges were piled up step by step from the distal end to the entrance of the target volume. At the same time, a multi-leaf collimator was used to change the aperture shape to match the shape of each layer to the cross-sectional shape of the target. This method has been applied to rather large volume cancers including bone and soft-tissue cancers. Only a few serious problems in the irradiation systems have been encountered since the beginning of the clinical trials. Overall the systems have been working stably and reliably.

Radiosensitization of glioblastoma cells using a histone deacetylase inhibitor (SAHA) comparing carbon ions with X-rays

“…The facility and broad beam irradiation procedure has been described elsewhere (Kanai et al 1999;Torikoshi et al 2007). Cells were irradiated in either T25 flasks or microscopy flasks (Nunc, New York, USA) at a confluency of about 80%.…”

A dynamic collimation system for penumbra reduction in spot‐scanning proton therapy: Proof of concept

“…MLC-based collimation solves many of the issues with aperture-based collimation by shaping the lateral extent of the beam separately for each energy layer, as implemented with the layer stacking technique. 9 The delivery may be automated, and the need for patient-specific hardware is eliminated. Bues et al 8 have investigated the use of MLC based spot scanning and found that the lateral penumbra was improved for beams with an energy less than 159 MeV.…”

Patient handling system for carbon ion beam scanning therapy

“…The new treatment facility was constructed as an extension of the existing treatment building and shared the accelerator with it 5 , 6 . The goal of the new facility was to provide carbon ion beam scanning irradiation with respiratory gating.…”