Ma Yunzhi, Popple Richard, Suh Tae-Suk, Xing Lei
Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305-5847, USA.
Int J Radiat Oncol Biol Phys. 2009 Dec 1;75(5):1587-95. doi: 10.1016/j.ijrobp.2009.05.003. Epub 2009 Sep 3.
To use angular beam's-eye-view dosimetrics (BEVD) information to improve the computational efficiency and plan quality of inverse planning of aperture-modulated arc therapy (AMAT).
In BEVD-guided inverse planning, the angular space spanned by a rotational arc is represented by a large number of fixed-gantry beams with angular spacing of approximately 2.5 degrees. Each beam is assigned with an initial aperture shape determined by the beam's-eye-view (BEV) projection of the planning target volume (PTV) and an initial weight. Instead of setting the beam weights arbitrarily, which slows down the subsequent optimization process and may result in a suboptimal solution, a priori knowledge about the quality of the beam directions derived from a BEVD is adopted to initialize the weights. In the BEVD calculation, a higher score is assigned to directions that allow more dose to be delivered to the PTV without exceeding the dose tolerances of the organs at risk (OARs) and vice versa. Simulated annealing is then used to optimize the segment shapes and weights. The BEVD-guided inverse planning is demonstrated by using two clinical cases, and the results are compared with those of a conventional approach without BEVD guidance.
An a priori knowledge-guided inverse planning scheme for AMAT is established. The inclusion of BEVD guidance significantly improves the convergence behavior of AMAT inverse planning and results in much better OAR sparing as compared with the conventional approach.
BEVD-guidance facilitates AMAT treatment planning and provides a comprehensive tool to maximally use the technical capacity of the new arc therapeutic modality.
利用角束视角剂量学（BEVD）信息提高孔径调制弧形治疗（AMAT）逆向计划的计算效率和计划质量。
在BEVD引导的逆向计划中，旋转弧所跨越的角空间由大量固定机架角度间隔约为2.5度的射束表示。每个射束被赋予一个由计划靶区（PTV）的射束视角（BEV）投影确定的初始孔径形状和一个初始权重。不是任意设置射束权重，因为这会减慢后续优化过程并可能导致次优解，而是采用从BEVD得出的关于射束方向质量的先验知识来初始化权重。在BEVD计算中，对于那些能在不超过危及器官（OAR）剂量耐受的情况下向PTV输送更多剂量的方向给予更高分数，反之亦然。然后使用模拟退火来优化射野形状和权重。通过两个临床病例展示了BEVD引导的逆向计划，并将结果与无BEVD引导的传统方法的结果进行比较。
建立了一种用于AMAT的先验知识引导的逆向计划方案。与传统方法相比，纳入BEVD引导显著改善了AMAT逆向计划的收敛行为，并在保护OAR方面取得更好效果。
BEVD引导有助于AMAT治疗计划制定，并提供了一个全面的工具来最大程度利用这种新弧形治疗方式的技术能力。
