Department of Radiation Oncology, Emory University, Atlanta, Georgia.
Department of Radiation Oncology, Emory University, Atlanta, Georgia; Winship Cancer Institute, Emory University, Atlanta, Georgia.
Pract Radiat Oncol. 2011 Oct-Dec;1(4):243-50. doi: 10.1016/j.prro.2011.02.008. Epub 2011 May 14.
Intensity modulated radiation therapy (IMRT) has allowed accurate delivery of prostate radiotherapy; Volumetric modulated arc therapy (VMAT) offers an advancement of this technique with possible dosimetric advantages and delivery in a shorter time than standard IMRT. We hypothesize that treatment duration is a controllable factor associated with intrafraction target motion.
Included patients were treated for localized prostate cancer using IMRT or VMAT (RapidArc, Varian Medical Systems, Palo Alto, CA). Continuous motion data were monitored simultaneously using electromagnetic transponders (Calypso 4D Localization System, Calypso Medical Technologies, Inc, Seattle, WA). Displacements were recorded in the RL (right-left), SI (superior-inferior), and AP (anterior-posterior) directions at 10/second (Hz). Daily motion was reported as the mean (R̄̄) and 95th percentile (R95) displacement value for the entire session. Time effect was assessed by measuring daily displacement variables (R̄̄, R95) after each successive minute of treatment.
Thirty-seven patients were included, accounting for 1332 treatment sessions. Mean session time was 7.4 minutes (range, 0.5-37.2; interquartile range, 4.8-9.2). R̄̄ (0.06, 0.08, 0.11, 0.18) and R95 (0.14, 0.18, 0.23, 0.36) values (RL, SI, AP, 3-dimensional [3D], respectively) were evaluated for the entire cohort. Regression analysis showed treatment time to be the strongest predictor of observed displacements (P < .001 AP, SI, 3D; P < 0.05 RL). Ninety-five displacements increased continuously from 0.05 cm, 0.09 cm, 0.12 cm, and 0.16 cm after 1 minute to 0.21 cm, 0.20 cm, 0.29 cm, and 0.47 after 10 minutes (RL, SI, AP, and 3D). Mean session time for VMAT was 4.6 minutes compared to 8.4 minutes for IMRT (difference = 3.8 min, P < .0001); VMAT was associated with reduced motion for both (difference = 0.02, 0.03, 0.05, 0.07 cm) and (0.03, 0.04, 0.11, 0.12 cm) displacements.
Our study is unique in exploring the role of session duration on intrafraction motion in the setting of electromagnetic transponders as well as VMAT. Our main results demonstrate that observed intrafraction prostate motion during radiotherapy is greater with increasing session time. Additionally, VMAT, due to shorter treatment sessions, resulted in significant reduction (30%-40%) in intrafraction displacements.
调强放射治疗（IMRT）能够实现前列腺放射治疗的精确投递；容积调强弧形治疗（VMAT）是这项技术的进步，在更短的时间内完成治疗的同时可能具有更好的剂量学优势。我们假设治疗时间是与分次内靶区运动相关的可控因素。
本研究纳入了接受 IMRT 或 VMAT（RapidArc，Varian Medical Systems，Palo Alto，CA）治疗的局限性前列腺癌患者。连续运动数据使用电磁传感器（Calypso 4D 定位系统，Calypso Medical Technologies，Inc，西雅图，WA）同步监测。在 RL（右-左）、SI（上-下）和 AP（前-后）方向上以 10/秒（Hz）的频率记录位移。全天运动以整个治疗过程中平均（R̄̄）和 95 百分位数（R95）位移值报告。通过测量每次治疗后连续分钟的每日位移变量（R̄̄、R95）评估时间效应。
共纳入 37 例患者，共 1332 个治疗疗程。平均治疗时间为 7.4 分钟（范围：0.5-37.2；四分位间距：4.8-9.2）。整个队列分别评估了 RL、SI、AP 和 3D 方向的 R̄̄（0.06、0.08、0.11、0.18）和 R95（0.14、0.18、0.23、0.36）值。回归分析显示，治疗时间是观察到的位移的最强预测因素（AP、SI、3D 方向，P<0.001；RL 方向，P<0.05）。95%的位移值从 1 分钟时的 0.05 cm、0.09 cm、0.12 cm 和 0.16 cm 连续增加到 10 分钟时的 0.21 cm、0.20 cm、0.29 cm 和 0.47 cm（RL、SI、AP 和 3D）。VMAT 的平均治疗时间为 4.6 分钟，而 IMRT 为 8.4 分钟（差值=3.8 分钟，P<0.0001）；VMAT 与（差值=0.02、0.03、0.05、0.07 cm）和（差值=0.03、0.04、0.11、0.12 cm）的运动减少有关。
我们的研究在使用电磁传感器和 VMAT 的情况下，探索了治疗时间对分次内运动的作用，这是独特的。我们的主要结果表明，在放射治疗期间观察到的分次内前列腺运动随治疗时间的增加而增加。此外，由于治疗时间较短，VMAT 导致分次内位移减少 30%-40%。
