Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, Switzerland.
Med Phys. 2011 Nov;38(11):5844-56. doi: 10.1118/1.3641866.
The RapidArc volumetric modulated arc therapy (VMAT) planning process is based on a core engine, the so-called progressive resolution optimizer (PRO). This is the optimization algorithm used to determine the combination of field shapes, segment weights (with dose rate and gantry speed variations), which best approximate the desired dose distribution in the inverse planning problem. A study was performed to assess the behavior of two versions of PRO. These two versions mostly differ in the way continuous variables describing the modulated arc are sampled into discrete control points, in the planning efficiency and in the presence of some new features. The analysis aimed to assess (i) plan quality, (ii) technical delivery aspects, (iii) agreement between delivery and calculations, and (iv) planning efficiency of the two versions.
RapidArc plans were generated for four groups of patients (five patients each): anal canal, advanced lung, head and neck, and multiple brain metastases and were designed to test different levels of planning complexity and anatomical features. Plans from optimization with PRO2 (first generation of RapidArc optimizer) were compared against PRO3 (second generation of the algorithm). Additional plans were optimized with PRO3 using new features: the jaw tracking, the intermediate dose and the air cavity correction options.
Results showed that (i) plan quality was generally improved with PRO3 and, although not for all parameters, some of the scored indices showed a macroscopic improvement with PRO3. (ii) PRO3 optimization leads to simpler patterns of the dynamic parameters particularly for dose rate. (iii) No differences were observed between the two algorithms in terms of pretreatment quality assurance measurements and (iv) PRO3 optimization was generally faster, with a time reduction of a factor approximately 3.5 with respect to PRO2.
These results indicate that PRO3 is either clinically beneficial or neutral in terms of dosimetric quality while it showed significant advantages in speed and technical aspects.
快速弧形容积调强弧形治疗（VMAT）计划过程基于一个核心引擎，即所谓的渐进分辨率优化器（PRO）。这是用于确定最佳场形组合、段权重（剂量率和机架速度变化）的优化算法，以在逆规划问题中最佳近似所需的剂量分布。进行了一项研究，以评估两种 PRO 版本的行为。这两个版本主要在描述调制弧的连续变量被采样为离散控制点的方式、在规划效率以及一些新功能的存在方面存在差异。该分析旨在评估（i）计划质量，（ii）技术交付方面，（iii）交付与计算之间的一致性，以及（iv）两个版本的规划效率。
为四组患者（每组 5 名患者）生成 RapidArc 计划：肛门管、晚期肺、头颈部和多发性脑转移，并设计用于测试不同水平的计划复杂性和解剖特征。使用 PRO2（第一代 RapidArc 优化器）进行优化的计划与 PRO3（第二代算法）进行比较。使用 PRO3 优化了具有新功能的附加计划：颌骨跟踪、中间剂量和空气腔校正选项。
结果表明，（i）PRO3 通常会提高计划质量，尽管不是所有参数都如此，但一些评分指标显示 PRO3 具有宏观改善。（ii）PRO3 优化导致动态参数的模式更加简单，特别是对于剂量率。（iii）两种算法在预处理质量保证测量方面没有差异，（iv）PRO3 优化通常更快，与 PRO2 相比，时间减少了大约 3.5 倍。
这些结果表明，PRO3 在剂量质量方面要么具有临床益处，要么具有中立性，同时在速度和技术方面具有显著优势。
