Division of Medical Physics, Department of Radiation Oncology, Erasmus MC-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2011 Nov 15;81(4):1160-7. doi: 10.1016/j.ijrobp.2010.09.013. Epub 2010 Oct 29.
To develop a method for margin evaluation accounting for all measured displacements during treatment of prostate cancer.
For 21 patients treated with stereographic targeting marker-based online translation corrections, dose distributions with varying margins and gradients were created. Sets of possible cumulative delivered dose distributions were simulated by moving voxels and accumulating dose per voxel. Voxel motion was simulated consistent with measured distributions of systematic and random displacements due to stereographic targeting inaccuracies, deformation, rotation, and intrafraction motion. The method of simulation maintained measured correlation of voxel motions due to organ deformation.
For the clinical target volume including prostate and seminal vesicles (SV), the probability that some part receives <95% of the prescribed dose, the changes in minimum dose, and volume receiving 95% of prescription dose compared with planning were 80.5% ± 19.2%, 9.0 ± 6.8 Gy, and 3.0% ± 3.7%, respectively, for the smallest studied margins (3 mm prostate, 5 mm SV) and steepest dose gradients. Corresponding values for largest margins (5 mm prostate, 8 mm SV) with a clinical intensity-modulated radiotherapy dose distribution were 46.5% ± 34.7%, 6.7 ± 5.8 Gy, and 1.6% ± 2.3%. For prostate-only clinical target volume, the values were 51.8% ± 17.7%, 3.3 ± 1.6 Gy, and 0.6% ± 0.5% with the smallest margins and 5.2% ± 7.4%, 1.8 ± 0.9 Gy, and 0.1% ± 0.1% for the largest margins. Addition of three-dimensional rotation corrections only improved these values slightly. All rectal planning constraints were met in the actual reconstructed doses for all studied margins.
We developed a system for margin validation in the presence of deformations. In our population, a 5-mm margin provided sufficient dosimetric coverage for the prostate. In contrast, an 8-mm SV margin was still insufficient owing to deformations. Addition of three-dimensional rotation corrections was of minor influence.
开发一种考虑前列腺癌治疗过程中所有测量位移的边缘评估方法。
对 21 例接受立体定向靶向标记物在线平移校正的患者，创建了具有不同边缘和梯度的剂量分布。通过移动体素和累积每个体素的剂量，模拟了一系列可能的累积剂量分布。体素运动的模拟与由于立体定向靶向不准确、变形、旋转和分次内运动引起的系统和随机位移的测量分布一致。模拟方法保持了由于器官变形而导致的体素运动的测量相关性。
对于包括前列腺和精囊（SV）在内的临床靶区，部分靶区接受<95%处方剂量的概率、最小剂量变化以及与计划相比接受 95%处方剂量的体积分别为 80.5%±19.2%、9.0±6.8Gy 和 3.0%±3.7%，对于最小研究的边缘（3mm 前列腺、5mmSV）和最陡的剂量梯度。对于最大边缘（5mm 前列腺、8mmSV）和临床调强放疗剂量分布，相应值分别为 46.5%±34.7%、6.7±5.8Gy 和 1.6%±2.3%。对于单纯前列腺临床靶区，最小边缘时的数值为 51.8%±17.7%、3.3±1.6Gy 和 0.6%±0.5%，最大边缘时的数值为 5.2%±7.4%、1.8±0.9Gy 和 0.1%±0.1%。添加三维旋转校正仅略微改善了这些值。对于所有研究的边缘，所有直肠计划限制在实际重建剂量中均得到满足。
我们开发了一种在存在变形的情况下进行边缘验证的系统。在我们的人群中，5mm 边缘为前列腺提供了足够的剂量覆盖。相比之下，由于变形，8mmSV 边缘仍然不足。添加三维旋转校正的影响较小。
