Division of Radiation Biophysics, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States of America.
Phys Med Biol. 2018 Jul 24;63(15):155001. doi: 10.1088/1361-6560/aacfb4.
Definition of the clinical target volume (CTV) is one of the weakest links in the radiation therapy chain. In particular, inability to account for uncertainties is a severe limitation in the traditional CTV delineation approach. Here, we introduce and test a new concept for tumor target definition, the clinical target distribution (CTD). The CTD is a continuous distribution of the probability of voxels to be tumorous. We describe an approach to incorporate the CTD in treatment plan optimization algorithms, and implement it in a commercial treatment planning system. We test the approach in two synthetic and two clinical cases, a sarcoma and a glioblastoma case. The CTD is straightforward to implement in treatment planning and comes with several advantages. It allows one to find the most suitable tradeoff between target coverage and sparing of surrounding healthy organs at the treatment planning stage, without having to modify or redraw a CTV. Owing to the variable probabilities afforded by the CTD, a more flexible and more clinically meaningful sparing of critical structure becomes possible. Finally, the CTD is expected to reduce the inter-user variability of defining the traditional CTV.
临床靶区（CTV）的定义是放射治疗链中的最薄弱环节之一。特别是，无法考虑不确定性是传统 CTV 勾画方法的严重限制。在这里，我们引入并测试了肿瘤靶区定义的新概念，即临床靶区分布（CTD）。CTD 是体素为肿瘤的概率的连续分布。我们描述了一种将 CTD 纳入治疗计划优化算法的方法，并将其实现到商业治疗计划系统中。我们在两个合成病例和两个临床病例（肉瘤和胶质母细胞瘤）中测试了该方法。CTD 易于在治疗计划中实施，并具有几个优点。它允许在治疗计划阶段找到最合适的肿瘤覆盖范围和周围健康器官保护之间的权衡，而无需修改或重新勾画 CTV。由于 CTD 提供的可变概率，可以更灵活和更有临床意义地保护关键结构。最后，预计 CTD 将减少传统 CTV 定义的用户间变异性。
