Crowe Scott B, Bennett Jane, Lathouras Marika, Lancaster Craig M, Sylvander Steven R, Chua Benjamin, Bettington Catherine S, Lin Charles Y, Kairn Tanya
Cancer Care Services, Royal Brisbane & Women's Hospital, Herston, QLD 4029, Australia.
Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4000, Australia.
Phys Imaging Radiat Oncol. 2020 May 20;14:12-16. doi: 10.1016/j.phro.2020.04.004. eCollection 2020 Apr.
Radiopacifiers are introduced to bone cements to provide the appearance of bone in kilovoltage (kV) radiographic images. For higher energy megavoltage (MV) radiotherapy treatment beams, however, these radiopacifiers do not cause a bone-like perturbation of dose. This study therefore aimed to determine the impact of the barium-contrasted plastic-based cement materials on radiotherapy dose calculations.
The radiological properties of a physical sample of bone cement were characterised by computed tomography (CT) imaging and transmission measurements. Monte Carlo simulations of percentage depth-dose profiles were performed to determine the possible dose error for MV treatment beams. Dose differences were then investigated for clinical volumetric modulated radiotherapy treatment plans, with and without density overrides applied.
Differences of up to 7% were observed at the downstream interface of a 0.6 cm thick bone cement layer, compared to bone. Differences in planning target volume dose-volume metrics varied between -0.5% and 2.0%.
Before planning radiotherapy treatments for patients who have undergone cranioplasty, every effort should be made to identify whether a radiopacified bone cement has been implanted. Density overrides should be applied to minimise dose calculation errors, whenever bone cement is used.
向骨水泥中添加射线不透光剂，以便在千伏（kV）X线影像中呈现出骨骼的影像。然而，对于能量更高的兆伏（MV）放射治疗束而言，这些射线不透光剂不会引起类似骨骼的剂量扰动。因此，本研究旨在确定含钡对比剂的塑料基骨水泥材料对放射治疗剂量计算的影响。
通过计算机断层扫描（CT）成像和透射测量对骨水泥物理样本的放射学特性进行表征。进行蒙特卡罗模拟以确定兆伏治疗束的可能剂量误差。然后针对应用和未应用密度覆盖的临床容积调强放射治疗计划，研究剂量差异。
与骨骼相比，在0.6厘米厚的骨水泥层下游界面观察到高达7%的差异。计划靶体积剂量-体积指标的差异在-0.5%至2.0%之间变化。
在为接受颅骨成形术患者制定放射治疗计划之前，应尽一切努力确定是否植入了含射线不透光剂的骨水泥。无论何时使用骨水泥，都应应用密度覆盖以尽量减少剂量计算误差。
