Division of Radiation Oncology, Department of Molecular Genetics, Course for Molecular and Cellular Medicine, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
J Appl Clin Med Phys. 2010 Sep 7;11(4):3193. doi: 10.1120/jacmp.v11i4.3193.
The aim of this study was to investigate the impact of multileaf collimator width (MLC-W) on intraprostatic dose painting plans for prostate cancer.Prostate cancer maps based on the histopathological findings were superimposed onto simulation CT images. Clinical target volume (CTV) 1 was defined as the prostate and the base of the seminal vesicles, and CTV2 was defined as the dominant intraprostatic lesions. Planning target volume (PTV) 1 and PTV2 were delineated by adding 5 mm margins to CTV1 and CTV2, respectively. For each case, two dose painting plans were created to deliver 74 Gy to PTV1 and 84 Gy to PTV2 with dynamic multileaf collimator technique using two different MLCs: m3 (MLC-W: 3mm) and Millennium (5 mm). Plans were evaluated by comparing the conformation number (CN), a quantity that defines the degree of conformality.The CNs for plans using the m3 and Millennium were 0.68 and 0.67 for PTV1 and 0.59 and 0.58 for PTV2, respectively. The CNs tended to be higher for a thinner leaf width (p < 0.05).Dosimetric advantages associated with smaller leaves were observed. However, differences between 3 mm and 5 mm leaf width were relatively small, which suggested that 5 mm leaf width would be acceptable in dose painting plans for prostate cancer.
本研究旨在探讨多叶准直器宽度（MLC-W）对前列腺癌前列腺内剂量分布的影响。基于组织病理学发现的前列腺癌图谱被叠加到模拟 CT 图像上。临床靶区（CTV）1 定义为前列腺和精囊底，CTV2 定义为主要前列腺内病变。通过向 CTV1 和 CTV2 分别添加 5mm 边界，勾画计划靶区（PTV）1 和 PTV2。对于每个病例，使用两种不同的多叶准直器（m3，MLC-W：3mm 和 Millennium，5mm），采用动态多叶准直器技术创建两个剂量分布计划，将 74Gy 给到 PTV1，将 84Gy 给到 PTV2。通过比较适形度的定量指标——适形指数（CN）来评估计划。使用 m3 和 Millennium 的计划的 PTV1 的 CN 分别为 0.68 和 0.67，PTV2 的 CN 分别为 0.59 和 0.58。叶宽越窄，CN 值越高（p < 0.05）。较小叶片宽度存在剂量学优势。然而，3mm 和 5mm 叶宽之间的差异相对较小，这表明在前列腺癌的剂量分布计划中，5mm 叶宽是可以接受的。
