Kang Yixiu, Zhang Xiaodong, Chang Joe Y, Wang He, Wei Xiong, Liao Zhongxing, Komaki Ritsuko, Cox James D, Balter Peter A, Liu Helen, Zhu X Ronald, Mohan Radhe, Dong Lei
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030-4009, USA.
Int J Radiat Oncol Biol Phys. 2007 Mar 1;67(3):906-14. doi: 10.1016/j.ijrobp.2006.10.045.
To investigate strategies for designing compensator-based 3D proton treatment plans for mobile lung tumors using four-dimensional computed tomography (4DCT) images.
Four-dimensional CT sets for 10 lung cancer patients were used in this study. The internal gross tumor volume (IGTV) was obtained by combining the tumor volumes at different phases of the respiratory cycle. For each patient, we evaluated four planning strategies based on the following dose calculations: (1) the average (AVE) CT; (2) the free-breathing (FB) CT; (3) the maximum intensity projection (MIP) CT; and (4) the AVE CT in which the CT voxel values inside the IGTV were replaced by a constant density (AVE_RIGTV). For each strategy, the resulting cumulative dose distribution in a respiratory cycle was determined using a deformable image registration method.
There were dosimetric differences between the apparent dose distribution, calculated on a single CT dataset, and the motion-corrected 4D dose distribution, calculated by combining dose distributions delivered to each phase of the 4DCT. The AVE_RIGTV plan using a 1-cm smearing parameter had the best overall target coverage and critical structure sparing. The MIP plan approach resulted in an unnecessarily large treatment volume. The AVE and FB plans using 1-cm smearing did not provide adequate 4D target coverage in all patients. By using a larger smearing value, adequate 4D target coverage could be achieved; however, critical organ doses were increased.
The AVE_RIGTV approach is an effective strategy for designing proton treatment plans for mobile lung tumors.
研究使用四维计算机断层扫描（4DCT）图像为移动性肺部肿瘤设计基于补偿器的三维质子治疗计划的策略。
本研究使用了10例肺癌患者的四维CT数据集。通过合并呼吸周期不同阶段的肿瘤体积来获得内部大体肿瘤体积（IGTV）。对于每位患者，我们基于以下剂量计算评估了四种计划策略：（1）平均（AVE）CT；（2）自由呼吸（FB）CT；（3）最大强度投影（MIP）CT；以及（4）将IGTV内的CT体素值替换为恒定密度的AVE CT（AVE_RIGTV）。对于每种策略，使用可变形图像配准方法确定呼吸周期中产生的累积剂量分布。
在单个CT数据集上计算的表观剂量分布与通过合并传递到4DCT各阶段的剂量分布计算的运动校正4D剂量分布之间存在剂量差异。使用1厘米涂抹参数的AVE_RIGTV计划具有最佳的总体靶区覆盖和关键结构保护。MIP计划方法导致不必要的大治疗体积。使用1厘米涂抹的AVE和FB计划在所有患者中均未提供足够的4D靶区覆盖。通过使用更大的涂抹值，可以实现足够的4D靶区覆盖；然而，关键器官剂量增加。
AVE_RIGTV方法是为移动性肺部肿瘤设计质子治疗计划的有效策略。
