Torikoshi Masami, Minohara Shinichi, Kanematsu Nobuyuki, Komori Masataka, Kanazawa Mitsukata, Noda Koji, Miyahara Nobuyuki, Itoh Hiroko, Endo Masahiro, Kanai Tatsuaki
Department of Accelerator and Medical Physics, National Institute of Radiological Sciences.
J Radiat Res. 2007;48 Suppl A:A15-25. doi: 10.1269/jrr.48.a15.
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.
碳放疗的临床试验于1994年在日本国立放射医学综合研究所（HIMAC）启动，使用三个治疗室和四个射束端口，两个水平端口和两个垂直端口。采用宽束方法在等中心处形成三维均匀场。从加速器引出的点束通过一对摆动磁铁和一个散射体在横向展开。一个条形脊形滤波器调制束流能量以获得扩展布拉格峰（SOBP）。基于该场由具有不同传能线密度（LET）的各种射束组成的考虑，SOBP被设计为在生物剂量方面是平坦的。最后，在等中心处形成直径为20 cm且均匀度为+/- 2.5%的射野。最大SOBP的宽度为15 cm。当治疗肺部或肝脏等因呼吸而移动的器官时，采用呼吸门控照射方法，仅在呼气期照射射束。这减少了移动靶区的治疗边界。为了防止靶区相邻的正常组织受到不必要的剂量照射，开发了一种分层叠加方法。在这种方法中，具有不同射程的薄SOBP层从靶区的远端到入口逐步堆叠。同时，使用多叶准直器改变孔径形状，使每层的形状与靶区的横截面形状相匹配。该方法已应用于包括骨癌和软组织癌在内的相当大体积的癌症。自临床试验开始以来，在照射系统中仅遇到了一些严重问题。总体而言，这些系统一直稳定可靠地运行。
