Optimized IMRT Incorporating Beam Delivery

描述（由申请人提供）：调强放射治疗（IMRT）旨在向选定的靶体积提供高度适形的肿瘤杀伤剂量，同时避免邻近的正常组织和关键结构。IMRT假定最佳计划剂量可以精确无误地交付给患者，并且最终计划相对于期望的治疗目标是最佳的。然而，目前的IMRT计划系统在计划优化期间使用简化的快速剂量计算，并将优化和计划交付划分为单独的过程。简化的剂量计算可能导致剂量预测误差（dpe），即实际剂量与计算剂量之间的差异为10%或更多，而使用具有dpe的算法进行优化以及从优化参数空间到可交付参数空间的转换会导致优化收敛误差（OCEs）。oce会妨碍找到真正的最佳方案，并可能导致临界结构剂量比必要剂量高出20%。由于3%-5%的剂量差异可产生临床可检测的反应变化，DPEs和OCEs可能显著影响临床结果。该项目的目标是：(1)开发准确的IMRT剂量计算方法，将dpe降低到临床不显著的水平。蒙特卡罗（MC）方法将用于评估由患者异质性、事件影响预测和患者设置错误引起的dpe的来源和临床影响，并确定和开发方法，将所有患者的IMRT剂量计算误差减少到2%以下。(2)制定优化流程，将oes降低到临床不显著的水平。这将通过将目标1中确定的算法整合到IMRT优化过程中来实现，该算法可以准确地模拟通过多叶准直器和患者的辐射传输。这种可交付的优化将允许每个调强光束部分补偿其他光束的局限性，并可能导致在相同的计划目标体积剂量下显著减少对关键结构的剂量。(3)提高目标2中开发的精确的理想交付优化流程的计算效率，使其在不影响计划准确性或最优性的情况下具有临床实用性。这将允许精确的、可交付的优化计划用于常规临床IMRT，而以前由于需要过多的计算时间而不实际。该项目的长期目标是开发快速、准确的IMRT剂量计算和优化方法，使剂量预测和优化收敛误差最小，利用这些更精确的IRMT积累更可靠的剂量-反应数据，并通过更适形的方法改善患者预后。

DESCRIPTION (provided by applicant): Intensity Modulated Radiation Therapy (IMRT) seeks to deliver highly conformal tumorcidal doses to selected target volumes while conformably avoiding nearby normal tissues and critical structures. IMRT assumes that the optimized planned doses can be precisely and accurately delivered to the patient and that the final plan is optimal relative to the desired treatment objectives. Yet, current IMRT planning systems use simplified fast dose calculations during plan optimization and divides optimization and plan delivery into separate processes. The simplified dose computations can result in dose prediction errors (DPEs), which are differences between actual and computed doses, of 10% or more, while optimization with algorithms that have DPEs and the transformation from optimized to deliverable parameter spaces lead to optimization convergence errors (OCEs). OCEs prevent the true optimal plan from being found and can result in critical structure doses that are as much as 20% greater than necessary. Since dose differences of 3%-5% can produce clinically detectable changes in response, DPEs and OCEs may significantly impact clinical outcome. The goals of this project are: (1) To develop accurate IMRT dose-calculation methods that reduce DPEs to clinically insignificant levels. Monte Carlo (MC) methods will be used to evaluate the sources and clinical impacts of DPEs caused by patient heterogeneities, incident fluence prediction, and patient set-up errors and to identify and develop methods to reduce IMRT dose-calculation errors to less than 2% for all patient cases. (2) To develop optimization processes that reduces OCEs to clinically insignificant levels. This will be achieved by incorporating algorithms, identified in goal 1, that accurately model radiation transport through the multi-leaf collimator and the patient into the IMRT optimization process. Such deliverable optimization will allow each intensity-modulated beam to partially compensate for the limitations of other beams and may result in significantly reduced doses to critical Istructures for the same planning target volume dose. (3) To improve the computational efficiency of accurate Ideliverable-optimization processes developed in goal 2 to make them clinically practical without compromising plan laccuracy or optimality. This will allow accurate, deliverable optimized plans to be used for routine clinical IMRT, Iwhere previously it was not practical due to the excessive calculation time required. The long-term objectives of' this project are to develop rapid, accurate IMRT dose calculation and optimization} methods that result in minimal dose prediction and optimization convergence errors, to use these more accurate IRMT to accumulate more reliable dose-response data, and to improve patient outcomes through more conformal.