Probabilistic interfractional motion carbon ion radiation therapy dose distribution for prostate cancer shows rectum sparing with moderate target coverage degradation

Purpose: This observational study investigates the influence of interfractional motion on clinical target volume (CTV) coverage, planning target volume (PTV) margins, and rectum tissue sparing in carbon ion radiation therapy (CIRT). It reports dose coverage to target structures and organs at risk in the presence of interfractional motion, investigates rectal tissue sparing, and provides recommendations for further lowering the rate of toxicity. We also propose probabilistic DVH for consideration in treatment planning to represent probable dose to the clinic’s patient population. Methods: At Gunma University Hospital intensity-modulated x-ray therapy (IMXT, aka IMRT) prostate cancer patients are positioned on a table which is shifted twice based on cone-beam computed tomography (CBCT) to align bones and then align prostate tissue to isocenter. These shifts thereby contain interfractional motion. 1306 such tableshifts from 85 patients were collected. Normal probability distributions we...研究目的：本观察性研究旨在探讨分次间运动（Interfractional Motion）对碳离子放射治疗（Carbon Ion Radiation Therapy, CIRT）中临床靶体积（Clinical Target Volume, CTV）覆盖度、计划靶体积（Planning Target Volume, PTV）边界以及直肠组织保留效果的影响。本研究将报道存在分次间运动时靶区结构与危及器官的剂量覆盖情况，探讨直肠组织保留策略，并为进一步降低毒性发生率提供建议。此外，本研究还提出了概率性剂量体积直方图（Dose Volume Histogram, DVH），以供治疗计划制定时参考，用以表征该临床中心患者群体的预期剂量分布。 研究方法：在群马大学医院，针对接受调强X射线治疗（Intensity-Modulated X-ray Therapy, IMXT，又称IMRT）的前列腺癌患者，研究人员基于锥形束计算机断层扫描（Cone-Beam Computed Tomography, CBCT）对治疗床进行两次位移调整：首先对齐骨骼结构，随后将前列腺组织对准等中心。此类位移即包含了分次间运动信息。本研究共收集了85例患者的1306次床位移数据。本研究采用正态分布对...