Department of Radiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Kyoto 602-8566 Japan.
Anticancer Res. 2013 Dec;33(12):5675-9.
To analyze an intrafractional organ motion for patients with prostate cancer using soft tissue matching by megavolt computed tomography (MVCT) images during the course of image-guided intensity-modulated radiotherapy (IGRT-IMRT) using helical tomotherapy.
Data from a total of 10 patients with prostate cancer who received IGRT-IMRT were analyzed, and MVCT images were acquired before and after radiation therapy. Intra-fractional movement and PTV margins for soft tissue matching were calculated by comparing treatment planning images with 740 MVCT images for right-left (RL), superior-inferior (SI), and anteroposterior (AP) dimensions. A total of 74 Gy/37 fractions were administered. A margin to compensate for these variations was calculated using the van Herk's equation.
The intrafractional motion was 0.03 (-1.3 to 1.4) ±0.39 mm in the RL dimension, 0.08 (-1.8 to 0.28) ±0.73 mm in the SI dimension, and 0.52 (-1.8 to 1.8) ±0.63 mm in the AP dimension. The required PTV margin was 0.60 mm, 1.10 mm, and 0.78 mm in the RL, SI, and AP dimensions, respectively. Only one patient exhibited a deviation greater than 5 mm only once in 37 fractions (1/370=0.2%) caused by anal contraction.
The PTV margin in soft tissue matching IGRT-IMRT by helical tomotherapy for a patient with prostate cancer was 3 mm or less, and our tentative PTV margin of 3-5 mm is sufficient for most patients, if adequate instruction for avoiding anal contraction is given.
通过螺旋断层放疗（Helical Tomotherapy，HT）的图像引导调强放疗（Image-guided Intensity-modulated Radiotherapy，IGRT-IMRT），使用兆伏 CT（megavolt computed tomography，MVCT）图像对前列腺癌患者的分次内器官运动进行分析，该方法基于软组织匹配。
分析了 10 例接受 IGRT-IMRT 的前列腺癌患者的数据，在放疗前后采集 MVCT 图像。通过将治疗计划图像与 740 次 MVCT 图像进行比较，计算右-左（right-left，RL）、上-下（superior-inferior，SI）和前-后（anteroposterior，AP）方向的分次内运动和 PTV 边缘。共给予 74 Gy/37 个分次。使用 van Herk 方程计算补偿这些变化的边缘。
RL 方向的分次内运动为 0.03（-1.3 至 1.4）±0.39mm，SI 方向为 0.08（-1.8 至 0.28）±0.73mm，AP 方向为 0.52（-1.8 至 1.8）±0.63mm。RL、SI 和 AP 方向的 PTV 边缘分别为 0.60mm、1.10mm 和 0.78mm。在 37 个分次中，只有 1 名患者（1/370=0.2%）出现 1 次大于 5mm 的偏差，原因是肛门收缩。
螺旋断层放疗的前列腺癌患者的软组织匹配 IGRT-IMRT 的 PTV 边缘为 3mm 或更小，如果给予充分的避免肛门收缩的指导，我们暂定的 3-5mm 的 PTV 边缘对大多数患者是足够的。
