Shaw Maddison, Lye Jessica, Alves Andrew, Lehmann Joerg, Sanagou Masoumeh, Geso Moshi, Brown Rhonda
Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia; School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia.
Australian Clinical Dosimetry Service, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia; Olivia Newton John Cancer Wellness and Research Centre, Austin Health, Australia.
Phys Med. 2023 Aug;112:102632. doi: 10.1016/j.ejmp.2023.102632. Epub 2023 Jul 3.
Stereotactic Body Radiotherapy (SBRT) for lung tumours has become a mainstay of clinical practice worldwide. Measurements in anthropomorphic phantoms enable verification of patient dose in clinically realistic scenarios. Correction factors for reporting dose to the tissue equivalent materials in a lung phantom are presented in the context of a national dosimetry audit for SBRT. Analysis of dosimetry audit results is performed showing inaccuracies of common dose calculation algorithms in soft tissue lung target, inhale lung material and at tissue interfaces.
Monte Carlo based simulation of correction factors for detectors in non-water tissue was performed for the soft tissue lung target and inhale lung materials of a modified CIRS SBRT thorax phantom. The corrections were determined for Gafchromic EBT3 Film and PTW 60019 microDiamond detectors used for measurements of 168 SBRT lung plans in an end-to-end dosimetry audit. Corrections were derived for dose to medium (D) and dose to water (D) scenarios.
Correction factors were up to -3.4% and 9.2% for in field and out of field lung respectively. Overall, application of the correction factors improved the measurement-to-plan dose discrepancy. For the soft tissue lung target, agreement between planned and measured dose was within average of 3% for both film and microDiamond measurements.
The correction factors developed for this work are provided for clinical users to apply to commissioning measurements using a commercially available thorax phantom where inhomogeneity is present. The end-to-end dosimetry audit demonstrates dose calculation algorithms can underestimate dose at lung tumour/lung tissue interfaces by an average of 2-5%.
立体定向体部放射治疗（SBRT）用于肺部肿瘤已成为全球临床实践的主要手段。在人体模型中的测量能够在临床实际场景中验证患者剂量。在一项针对SBRT的国家剂量学审核背景下，给出了在肺部模型中向组织等效材料报告剂量的校正因子。对剂量学审核结果进行了分析，显示了常见剂量计算算法在软组织肺靶区、吸气肺材料以及组织界面处的不准确之处。
针对改良的CIRS SBRT胸部模型的软组织肺靶区和吸气肺材料，基于蒙特卡洛模拟了非水组织中探测器的校正因子。在一项端到端剂量学审核中，针对用于测量168个SBRT肺部计划的Gafchromic EBT3薄膜和PTW 60019微型金刚石探测器确定了校正因子。得出了介质剂量（D）和水剂量（D）场景下的校正因子。
野内和野外肺部的校正因子分别高达-3.4%和9.2%。总体而言，应用校正因子改善了测量剂量与计划剂量之间的差异。对于软组织肺靶区，薄膜和微型金刚石测量的计划剂量与测量剂量之间的一致性平均在3%以内。
为这项工作开发的校正因子提供给临床用户，以应用于使用存在不均匀性的市售胸部模型进行的调试测量。端到端剂量学审核表明，剂量计算算法在肺部肿瘤/肺组织界面处平均会低估剂量2 - 5%。
