Effects of Interfractional Anatomical Changes on Water-Equivalent Pathlength in Charged-Particle Radiotherapy of Lung Cancer
Effects of Interfractional Anatomical Changes on Water-Equivalent Pathlength in Charged-Particle Radiotherapy of Lung Cancer
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DOI：
10.1269/jrr.09032
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发表时间：
2009-11-01
影响因子：
2
通讯作者：
Chen, George T. Y.
中科院分区：
文献类型：
--
作者：
Mori, Shinichiro;Lu, Hsiao-Ming;Chen, George T. Y.
分次内运动和分次间变化影响放射治疗中输送剂量的准确性，特别是在带电粒子放射治疗中。最近的研究重点是油分次运动（呼吸运动）。在这里，我们报告了带电粒子肺治疗中油水等效路径长度（WEL）的分段变化影响的定量模拟分析。在自由呼吸条件下进行连续四维 (4D) CT 扫描；第一次和第二次 4DCT 扫描之间的时间间隔为五周。我们量化了由于分次间变化（特纳收缩和组织密度变化）导致的第一次和第二次 CT 扫描之间的 WEL 变化，并比较了使用相同初始推注的连续 4DCT 扫描之间的粒子束停止点。在治疗过程中，在一名患者身上观察到肿瘤缩小和肺密度变化。第一次和第二次 CT 扫描之间，肺密度下降约 0.1 g/cm(3)，导致 WEL 变化 1.5 cm。肿瘤缩小导致 WEL 变化约 3 cm。如果在整个治疗过程中使用相同的初始推注和计划。由于肿瘤收缩和国王密度变化，分数间变化会发生意想不到的显着光束超调。
Intrafractional motion and interfractional changes affect the accuracy of the delivered dose in radio- therapy, particularly in charged-particle radiotherapy. Most recent studies are focused oil intrafractional motion (respiratory motion). Here, we report a quantitative Simulation analysis of the effects of interfractional changes oil 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 (turner 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 king density variation.