Blanck Oliver, Masi Laura, Chan Mark K H, Adamczyk Sebastian, Albrecht Christian, Damme Marie-Christin, Loutfi-Krauss Britta, Alraun Manfred, Fehr Roman, Ramm Ulla, Siebert Frank-Andre, Stelljes Tenzin Sonam, Poppinga Daniela, Poppe Björn
Universitätsklinikum Schleswig-Holstein, Klinik für Strahlentherapie, Kiel, Germany; Saphir Radiochirurgie Zentrum, Frankfurt und Güstrow, Germany.
IFCA, Department of Medical Physics and Radiation Oncology, Firenze, Italy.
Phys Med. 2016 Jun;32(6):838-46. doi: 10.1016/j.ejmp.2016.05.060. Epub 2016 May 27.
High precision radiosurgery demands comprehensive delivery-quality-assurance techniques. The use of a liquid-filled ion-chamber-array for robotic-radiosurgery delivery-quality-assurance was investigated and validated using several test scenarios and routine patient plans.
Preliminary evaluation consisted of beam profile validation and analysis of source-detector-distance and beam-incidence-angle response dependence. The delivery-quality-assurance analysis is performed in four steps: (1) Array-to-plan registration, (2) Evaluation with standard Gamma-Index criteria (local-dose-difference⩽2%, distance-to-agreement⩽2mm, pass-rate⩾90%), (3) Dose profile alignment and dose distribution shift until maximum pass-rate is found, and (4) Final evaluation with 1mm distance-to-agreement criterion. Test scenarios consisted of intended phantom misalignments, dose miscalibrations, and undelivered Monitor Units. Preliminary method validation was performed on 55 clinical plans in five institutions.
The 1000SRS profile measurements showed sufficient agreement compared with a microDiamond detector for all collimator sizes. The relative response changes can be up to 2.2% per 10cm source-detector-distance change, but remains within 1% for the clinically relevant source-detector-distance range. Planned and measured dose under different beam-incidence-angles showed deviations below 1% for angles between 0° and 80°. Small-intended errors were detected by 1mm distance-to-agreement criterion while 2mm criteria failed to reveal some of these deviations. All analyzed delivery-quality-assurance clinical patient plans were within our tight tolerance criteria.
We demonstrated that a high-resolution liquid-filled ion-chamber-array can be suitable for robotic radiosurgery delivery-quality-assurance and that small errors can be detected with tight distance-to-agreement criterion. Further improvement may come from beam specific correction for incidence angle and source-detector-distance response.
高精度放射外科手术需要全面的剂量传递质量保证技术。研究了使用充液电离室阵列进行机器人放射外科手术剂量传递质量保证，并通过多个测试场景和常规患者计划进行了验证。
初步评估包括射野轮廓验证以及源-探测器距离和射野入射角响应依赖性分析。剂量传递质量保证分析分四个步骤进行：（1）阵列与计划配准，（2）根据标准伽马指数标准进行评估（局部剂量差异≤2%，距离一致性≤2mm，通过率≥90%），（3）剂量轮廓对齐和剂量分布偏移，直至找到最大通过率，（4）使用1mm距离一致性标准进行最终评估。测试场景包括预期的体模错位、剂量校准错误和未传递的监测单位。在五个机构的55个临床计划上进行了初步方法验证。
与微钻石探测器相比，1000SRS射野测量结果在所有准直器尺寸下均显示出足够的一致性。每10cm源-探测器距离变化，相对响应变化可达2.2%，但在临床相关的源-探测器距离范围内仍保持在1%以内。在0°至80°的角度范围内，不同射野入射角下的计划剂量和测量剂量偏差低于1%。通过1mm距离一致性标准检测到了小的预期误差，而2mm标准未能发现其中一些偏差。所有分析的剂量传递质量保证临床患者计划均在我们严格的公差标准范围内。
我们证明了高分辨率充液电离室阵列适用于机器人放射外科手术剂量传递质量保证，并且使用严格的距离一致性标准可以检测到小误差。进一步的改进可能来自针对入射角和源-探测器距离响应的射野特定校正。
