Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA.
Scientific RT, Munich, Germany.
J Appl Clin Med Phys. 2024 Jun;25(6):e14290. doi: 10.1002/acm2.14290. Epub 2024 Jan 30.
For individual targets of single isocenter multi-target (SIMT) Stereotactic radiosurgery (SRS), we assess dose difference between the treatment planning system (TPS) and independent Monte Carlo (MC), and demonstrate persistence into the pre-treatment Quality Assurance (QA) measurement.
Treatment plans from 31 SIMT SRS patients were recalculated in a series of scenarios designed to investigate sources of discrepancy between TPS and independent MC. Targets with > 5% discrepancy in DMean[Gy] after progressing through all scenarios were measured with SRS MapCHECK. A matched pair analysis was performed comparing SRS MapCHECK results for these targets with matched targets having similar characteristics (volume & distance from isocenter) but no such MC dose discrepancy.
Of 217 targets analyzed, individual target mean dose (DMean[Gy]) fell outside a 5% threshold for 28 and 24 targets before and after removing tissue heterogeneity effects, respectively, while only 5 exceeded the threshold after removing effect of patient geometry (via calculation on StereoPHAN geometry). Significant factors affecting agreement between the TPS and MC included target distance from isocenter (0.83% decrease in DMean[Gy] per 2 cm), volume (0.15% increase per cc), and degree of plan modulation (0.37% increase per 0.01 increase in modulation complexity score). SRS MapCHECK measurement had better agreement with MC than with TPS (2%/1 mm / 10% threshold gamma pass rate (GPR) = 99.4 ± 1.9% vs. 93.1 ± 13.9%, respectively). In the matched pair analysis, targets exceeding 5% for MC versus TPS also had larger discrepancies between TPS and measurement with no GPR (2%/1 mm / 10% threshold) exceeding 90% (71.5% ± 16.1%); whereas GPR was high for matched targets with no such MC versus TPS difference (96.5% ± 3.3%, p = 0.01).
Independent MC complements pre-treatment QA measurement for SIMT SRS by identifying problematic individual targets prior to pre-treatment measurement, thus enabling plan modifications earlier in the planning process and guiding selection of targets for pre-treatment QA measurement.
对于单等中心多靶（SIMT）立体定向放射外科（SRS）的单个目标，我们评估了治疗计划系统（TPS）和独立蒙特卡罗（MC）之间的剂量差异，并证明其在治疗前质量保证（QA）测量中仍然存在。
对 31 例 SIMT SRS 患者的治疗计划进行了一系列方案的重新计算，旨在调查 TPS 和独立 MC 之间差异的来源。在所有方案后，对 DMean[Gy]差异>5%的靶区用 SRS MapCHECK 进行测量。对这些靶区与具有相似特征（体积和距等中心的距离）但无 MC 剂量差异的匹配靶区进行 SRS MapCHECK 结果的配对分析。
在分析的 217 个靶区中，在去除组织异质性效应之前和之后，分别有 28 个和 24 个靶区的个体靶区平均剂量（DMean[Gy]）超过 5%的阈值，而在去除患者几何形状的影响（通过 StereoPHAN 几何形状计算）后，仅有 5 个靶区超过阈值。影响 TPS 和 MC 之间一致性的显著因素包括靶区距等中心的距离（DMean[Gy]每 2cm 降低 0.83%）、体积（每 cc 增加 0.15%）和计划调制程度（调制复杂性评分每增加 0.01，增加 0.37%）。SRS MapCHECK 测量与 MC 的一致性优于 TPS（2%/1mm/10%阈值伽马通过率（GPR）=99.4±1.9%对 93.1±13.9%，分别）。在配对分析中，与 TPS 相比，MC 超过 5%的靶区与 TPS 测量值之间的差异也更大，没有 GPR（2%/1mm/10%阈值）超过 90%（71.5%±16.1%）；而对于 MC 与 TPS 无差异的匹配靶区，GPR 较高（96.5%±3.3%，p=0.01）。
独立 MC 通过在治疗前测量之前识别有问题的单个靶区，补充了 SIMT SRS 的治疗前 QA 测量，从而能够更早地在计划过程中修改计划，并指导治疗前 QA 测量靶区的选择。
