Nakagawa Keiichi, Fukuhara Noboru, Kawakami Hideyuki
Department of Radiology, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655 Japan.
Department of Radiology, Sagamihara Kyodo Hospital, 2-8-18, Hashimoto, Sagamihara-city, Kanagawa 229-1188 Japan.
Med Phys. 2005 Jul;32(7Part1):2231-2235. doi: 10.1118/1.1929148.
A packed building-block compensator (TETRIS-RT) for IMRT (Intensity Modulated Radiation Therapy) delivery has been proposed. The compensator contains two kinds of cubic blocks: x-ray absorbing blocks for intensity modulation and x-ray transparent blocks for packing. The packed blocks are placed inside a rectangular enclosure, and the resulting compensators can be attached to a linac gantry head through a rotatable mount for efficient multiportal IMRT. A fabrication device and a sorting device were also developed. The fabrication device can automatically stack two different types of blocks to produce a compensator while the sorting device can separate each type of the blocks for subsequent fabrication. Preliminary film experiments have shown that an additional leakage dose through the rounded edges of the ten-layered x-ray absorbing blocks was 0.9% of the delivered dose with a total shielded dose ratio of 10% including the peak leakage. It was observed that the proposed compensator may provide a highly modulated dose distribution. This suggests its feasibility for IMRT delivery with a limit of 1cm×1cm spatial resolution at isocenter in the plane perpendicular to the beam, and larger discrete intensity steps of approximately 10% compared to conventional compensators. Advantages of the proposed compensator include that the compensator blocks are reusable and can be utilized to automatically and quickly fabricate a compensator, thereby minimizing human labor.
已提出一种用于调强放射治疗（IMRT）的密集积木式补偿器（TETRIS-RT）。该补偿器包含两种立方块：用于强度调制的X射线吸收块和用于填充的X射线透明块。将填充好的块放置在一个矩形外壳内，制成的补偿器可通过可旋转支架连接到直线加速器机架头部，以实现高效的多野IMRT。还开发了一种制造装置和一种分拣装置。制造装置可自动堆叠两种不同类型的块以生产补偿器，而分拣装置可将每种类型的块分开以便后续制造。初步的薄膜实验表明，通过十层X射线吸收块的圆角的额外泄漏剂量为输出剂量的0.9%，包括峰值泄漏在内的总屏蔽剂量比为10%。据观察，所提出的补偿器可提供高度调制的剂量分布。这表明其在垂直于射束平面的等中心处具有1cm×1cm空间分辨率限制且与传统补偿器相比具有约10%的更大离散强度步长的IMRT递送的可行性。所提出的补偿器的优点包括补偿器块可重复使用，并且可用于自动快速制造补偿器，从而最大限度地减少人力。
