Relationship of Imaging Frequency and Planning Margin to Account for Intrafraction Prostate Motion: Analysis Based on Real-Time Monitoring Data
Relationship of Imaging Frequency and Planning Margin to Account for Intrafraction Prostate Motion: Analysis Based on Real-Time Monitoring Data
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DOI：
10.1016/j.ijrobp.2012.05.044
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发表时间：
2013-03-01
影响因子：
7
通讯作者：
Xia, Ping
中科院分区：
文献类型：
--
作者：
Curtis, William;Khan, Mohammad;Xia, Ping
目的：前列腺运动的校正对于前列腺癌的低分割治疗是非常重要的。本研究的目的是估计一个理想的规划利润率占intrafraction前列腺运动作为一个功能的成像和重新定位的频率在没有连续的前列腺运动monitoring.Methods和材料：对于31例接受调强放射治疗的患者，前列腺的位置采样在10 Hz的治疗过程中使用的Calypso系统进行了分析。使用这些数据，我们模拟了多个频率较低的成像方案，包括每10、15、20、30、45、60、90、120、180和240秒的间隔。对于每个成像协议，通过从该部分中的后续位移中减去前列腺位移来校正成像时的前列腺位移。此外，我们进行了主成分分析，以量化的前列腺motion.Results的方向：平均直方图的每240和60秒的所有患者，矢量位移的前列腺，分别在3和2毫米的治疗时间的95%。在30秒成像中，1 mm的向量边缘实现了91.2%的前列腺覆盖率。所有部分的主成分分析显示，在中矢状面中，前列腺位置在与前方成54度角处的变化最大，这表明前上方到下后方是最大运动方向。结论：前列腺在上-下和前-后两个方向的运动幅度沿着是相当的，最小的运动是在左右方向。在没有连续前列腺运动监测的情况下，在理想情况下，1 mm、2 mm和3 mm向量计划裕度需要每15 mm、60 mm和240 mm的相应成像频率，以考虑分次内前列腺运动，同时在95%的时间内实现足够的几何目标覆盖。(c)2013 Elsevier Inc.
Purpose: Correction for intrafraction prostate motion becomes important for hypofraction treatment of prostate cancer. The purpose of this study was to estimate an ideal planning margin to account for intrafraction prostate motion as a function of imaging and repositioning frequency in the absence of continuous prostate motion monitoring.Methods and Materials: For 31 patients receiving intensity modulated radiation therapy treatment, prostate positions sampled at 10 Hz during treatment using the Calypso system were analyzed. Using these data, we simulated multiple, less frequent imaging protocols, including intervals of every 10, 15, 20, 30, 45, 60, 90, 120, 180, and 240 seconds. For each imaging protocol, the prostate displacement at the imaging time was corrected by subtracting prostate shifts from the subsequent displacements in that fraction. Furthermore, we conducted a principal component analysis to quantify the direction of prostate motion.Results: Averaging histograms of every 240 and 60 seconds for all patients, vector displacements of the prostate were, respectively, within 3 and 2 mm for 95% of the treatment time. A vector margin of 1 mm achieved 91.2% coverage of the prostate with 30 second imaging. The principal component analysis for all fractions showed the largest variance in prostate position in the midsagittal plane at 54 degrees from the anterior direction, indicating that anterosuperior to inferoposterior is the direction of greatest motion. The smallest prostate motion is in the left-right direction.Conclusions: The magnitudes of intrafraction prostate motion along the superior-inferior and anterior-posterior directions are comparable, and the smallest motion is in the left-right direction. In the absence of continuous prostate motion monitoring, and under ideal circumstances, 1-, 2-, and 3-mm vector planning margins require a respective imaging frequency of every 15, 60, and 240 to account for intrafraction prostate motion while achieving adequate geometric target coverage for 95% of the time. (c) 2013 Elsevier Inc.