37004JCHO Tokyo Shinjuku Medical Center, Shinjuku-ku, Japan.
13081Suzuka University of Medical Science, Suzuka, Japan.
Technol Cancer Res Treat. 2021 Jan-Dec;20:15330338211045497. doi: 10.1177/15330338211045497.
Hippocampus-sparing whole-brain radiotherapy (HS-WBRT) using tomotherapy is known to provide a better dose distribution than volumetric-modulated arc therapy but requires an extended irradiation time. The present study aimed to investigate whether irradiation time can be shortened by reducing the modulation factor (MF) without losing the target dose distribution. Using six tilted computed tomography images in the head area, the planning target volume (PTV) and hippocampal doses, and the irradiation time was investigated with a jaw width of 1 cm, a pitch of 0.200, and the MF changed from 3.0 to 2.6, 2.2, 1.8, and 1.4. No significant changes in the PTV or hippocampus were found with MF in the range from 3.0 to 1.8, but marked deterioration was found with that of 1.4. The irradiation time showed a linear relationship with the MF within the range from 3.0 to 1.8, with 1334, 1158, 986, and 817 s at modulation factors of 3.0, 2.6, 2.2, and 1.8, respectively. However, when the MF was 1.4, the irradiation time was 808 s. When HS-WBRT is performed with a tilted body position and a jaw width of 1 cm, with a MF of 1.8, a favorable balance between dose parameters and irradiation time is achieved, whereas with a MF of 1.4, the quality of the radiotherapy plan deteriorates, and the irradiation time is approximately the same as that with a MF of 1.8.
海马回避全脑放疗（HS-WBRT）使用调强放疗被认为比容积旋转调强放疗（VMAT）提供更好的剂量分布，但需要更长的照射时间。本研究旨在探讨在不损失靶区剂量分布的情况下，通过降低调制因子（MF）是否可以缩短照射时间。
使用头区六个倾斜的 CT 图像，研究了在颌宽为 1cm、螺距为 0.200 时，调制因子从 3.0 降低到 2.6、2.2、1.8 和 1.4 时的计划靶区（PTV）和海马剂量及照射时间。在 MF 范围从 3.0 到 1.8 时，PTV 或海马无明显变化，但 MF 为 1.4 时则明显恶化。照射时间与 MF 呈线性关系，在 MF 范围从 3.0 到 1.8 时，调制因子分别为 3.0、2.6、2.2 和 1.8 时，照射时间分别为 1334、1158、986 和 817s。然而，当 MF 为 1.4 时，照射时间为 808s。
当使用倾斜体位和颌宽 1cm 进行 HS-WBRT 时，MF 为 1.8 时，可以在剂量参数和照射时间之间取得良好的平衡，而 MF 为 1.4 时，放疗计划质量恶化，照射时间与 MF 为 1.8 时大致相同。
