Deterministic Radiotherapy Dose Calculation Method

描述(由申请人提供)：目前需要为体外放射治疗的临床治疗计划开发准确和有效的剂量计算方法。由于图像引导定位技术的最新进展以及更精确的射束传输方法的发展，如调强放射治疗(IMRT)和立体定向放射外科(SRS)，存在着大幅降低边缘和改善剂量一致性的潜力。然而，今天临床上使用的大多数剂量计算方法使用的近似限制了它们的精度和使用范围，特别是在存在不均匀的窄束的情况下。因此，采用蒙特卡罗等更精确的方法被认为是非常可取的。然而，蒙特卡罗计算可能很耗时，限制了它们对临床治疗计划的有效性。提出了一种新的确定性剂量计算方法，该方法求解中性粒子和带电粒子输运方程的微分形式。初步研究表明，这种方法有可能提供与详细的蒙特卡罗模拟相当的精度，并且计算速度明显更快。该方法结合了各向异性单元自适应，有效地解决了复杂的解剖特征和尖锐的解梯度，并辅之以对可变大小的四面体单元使用高阶间断有限元方法。在第一阶段，将开发一个概念验证过程来量化患者特定剂量计算的性能。这一点将通过使用宽束和窄束的选定治疗计划的详细蒙特卡罗结果进行验证，这些治疗计划结合了骨、空气和肺的异质性。成功的衡量标准将是相对于蒙特卡洛的表现，即结合速度和准确性。将确定在第二阶段进一步提高效率的潜在增强，并将提供可实现的临床表现的估计。

DESCRIPTION (provided by applicant): A present need exists for the development of accurate and efficient dose calculation methods for clinical treatment planning in external beam radiotherapy. Due to recent advances in image guided localization techniques and the development of more precise beam delivery methods such as Intensity Modulated Radiation Therapy (IMRT) and Stereotactic Radiosurgery (SRS), the potential exists to substantially reduce margins and improve dose conformity. However, most dose calculation methods in clinical use today employ approximations that limit their accuracy and scope of use, especially with narrow beams in the presence of heterogeneities. As a result, the adoption of more accurate methods such as Monte Carlo is seen as highly desirable. However, Monte Carlo calculations can be time consuming, limiting their effectiveness for clinical treatment planning. The application of a novel deterministic dose calculation method, which solves the differential form of the governing transport equations for neutral and charged particles is proposed. As indicated in preliminary studies, this approach has the potential to provide accuracy comparable to detailed Monte Carlo simulations with a substantially faster computational speed. The proposed approach incorporates anisotropic element adaptation to efficiently resolve complex anatomical features and sharp solution gradients, which is aided by the use of higher-order discontinuous finite element methods on variably sized tetrahedral elements. In Phase 1, a proof-of-concept process will be developed to quantify performance for patient specific dose calculations. This will be validated with detailed Monte Carlo results for selected treatment plans incorporating bone, air and lung heterogeneities, using both wide and narrow beams. Success will be measured on performance relative to Monte Carlo, defined in terms of combined speed and accuracy. Potential enhancements to further improve efficiency in Phase 2 will be identified, and an estimate of achievable clinical performance will be provided.