背景:在当前的临床实践中,使用1.1的恒定相对生物有效性(cRBE)生成强度调节质子治疗(IMPT)头颈癌(HNC)计划。这项研究的主要目标是在双边HNCIMPT计划的背景下,使用可变RBE(vRBE)模型探索质子范围不确定性对RBE加权剂量(RWD)分布的剂量学影响。
方法:本研究包括10例接受光子治疗的双侧HNC患者的计算机断层扫描(CT)数据集。每个患者的计划是使用三个IMPT光束生成的,以将剂量传递到CTV_High和CTV_Low,剂量为70Gy(RBE)和54Gy(RBE),分别,通过同时集成增强(SIB)技术在35个部分中。以1.1的cRBE计算的每个标称计划的范围不确定性为±3%。McNamaravRBE模型用于RWD计算。对于每个病人来说,比较了RWD和标称剂量分布之间剂量测定指标的差异.
结果:收缩肌,口腔,parotids,喉部,甲状腺,和食管显示平均剂量(Dmean)值的平均差异高达6.91Gy(RBE),表明质子范围不确定性对RWD分布的影响。同样,臂丛神经,大脑,脑干,脊髓,和下颌骨在最大剂量(Dmax)值(2.78-10.75Gy(RBE))上表现出不同程度的平均差异。从RWD分布到CTV的Dmean和Dmax在标称计划中的剂量测定结果的±2%之内。
结论:与cRBE模型相比,McNamaravRBE模型对OAR的平均和最大剂量的一致趋势强调了在双边HNCIMPT计划中评估OAR剂量时需要考虑质子范围不确定性。
BACKGROUND: In current clinical practice, intensity-modulated proton therapy (IMPT) head and neck cancer (HNC) plans are generated using a constant relative biological effectiveness (cRBE) of 1.1. The primary goal of this study was to explore the dosimetric impact of proton range uncertainties on RBE-weighted dose (RWD) distributions using a variable RBE (vRBE) model in the context of bilateral HNC IMPT plans.
METHODS: The current study included the computed tomography (CT) datasets of ten bilateral HNC patients who had undergone photon therapy. Each patient\'s plan was generated using three IMPT beams to deliver doses to the CTV_High and CTV_Low for doses of 70 Gy(RBE) and 54 Gy(RBE), respectively, in 35 fractions through a simultaneous integrated boost (SIB) technique. Each nominal plan calculated with a cRBE of 1.1 was subjected to the range uncertainties of ±3%. The McNamara vRBE model was used for RWD calculations. For each patient, the differences in dosimetric metrices between the RWD and nominal dose distributions were compared.
RESULTS: The constrictor muscles, oral cavity, parotids, larynx, thyroid, and esophagus showed average differences in mean dose (Dmean) values up to 6.91 Gy(RBE), indicating the impact of proton range uncertainties on RWD distributions. Similarly, the brachial plexus, brain, brainstem, spinal cord, and mandible showed varying degrees of the average differences in maximum dose (Dmax) values (2.78-10.75 Gy(RBE)). The Dmean and Dmax to the CTV from RWD distributions were within ±2% of the dosimetric results in nominal plans.
CONCLUSIONS: The consistent trend of higher mean and maximum doses to the OARs with the McNamara vRBE model compared to cRBE model highlighted the need for consideration of proton range uncertainties while evaluating OAR doses in bilateral HNC IMPT plans.