文章基本信息

标题：Effects of Interfractional Anatomical Changes on Water-Equivalent Pathlength in Charged-Particle Radiotherapy of Lung Cancer
其他标题：Effects of Interfractional Anatomical Changes on Water-Equivalent Pathlength in Charged-Particle Radiotherapy of Lung Cancer
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作者：Shinichiro MORI ; Hsiao-Ming LU ; John A. WOLFGANG 等
期刊名称：Journal of Radiation Research
印刷版ISSN：0449-3060
电子版ISSN：1349-9157
出版年度：2009
卷号：50
期号：6
页码：513-519
DOI：10.1269/jrr.09032
摘要：Intrafractional motion and interfractional changes affect the accuracy of the delivered dose in radiotherapy, particularly in charged-particle radiotherapy. Most recent studies are focused on intrafractional motion (respiratory motion). Here, we report a quantitative simulation analysis of the effects of interfractional changes on water-equivalent pathlength (WEL) in charged-particle lung therapy. Serial four-dimensional (4D) CT scans were performed under free breathing conditions; the time span between the first and second 4DCT scans was five weeks. We quantified WEL changes between the first and second CT scans due to interfractional changes (tumor shrinkage and tissue density changes) and compared the particle-beam-stopping point between the serial 4DCT scans with use of the same initial bolus. Both tumor-shrinkage and lung-density changes were observed in a single patient over the course of therapy. The lung density decreased by approximately 0.1 g/cm 3 between the first and second-CT scans, resulting in a 1.5 cm WEL changes. Tumor shrinkage resulted in approximately 3 cm WEL changes. If the same initial bolus and plan were used through the treatment course, an unexpected significant beam overshoot would occur by interfractional changes due to tumor shrinkage and lung density variation.
关键词：Charged-particle;Four-dimensional;Lung cancer;Lung density;Radiotherapy planning;Beam range variation;Tumor shrinkage