Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA.
J Appl Clin Med Phys. 2022 Sep;23(9):e13747. doi: 10.1002/acm2.13747. Epub 2022 Aug 10.
End-to-end testing (E2E) is a necessary process for assessing the readiness of the stereotactic radiosurgery (SRS) program and annual QA of an SRS system according to the AAPM MPPG 9a. This study investigates the differences between using a new SRS MapCHECK (SRSMC) system and an anthropomorphic phantom film-based system in a large network with different SRS delivery techniques.
Three SRS capable Linacs (Varian Medical Systems, Palo Alto, CA) at three different regional sites were chosen to represent a hospital network, a Trilogy with an M120 multi-leaf collimator (MLC), a TrueBeam with an M120 MLC, and a TrueBeam Stx with an HD120 MLC. An anthropomorphic STEEV phantom (CIRS, Norfolk, VA) and a phantom/diode array: StereoPHAN/SRSMC (Sun Nuclear, Melbourne, FL) were CT scanned at each site. The new STV-PHANTOM EBT-XD films (Ashland, Bridgewater, NJ) were used. Six plans with various complexities were measured with both films and SRSMC in the StereoPHAN to establish their dosimetric correlations. Three SRS cranial plans with a total of sixteen fields using dynamic conformal arc and volumetric-modulated arc therapy, with 1-4 targets, were planned with Eclipse v15.5 treatment planning system (TPS) using a custom SRS beam model for each machine. The dosimetric and localization accuracy were compared. The time of analysis for the two systems by three teams of physicists was also compared to assess the throughput efficiency.
The correlations between films and SRSMC were found to be 0.84 (p = 0.03) and 0.16 (p = 0.76) for γ (3%, 1 mm) and γ (3%, 2 mm), respectively. With film, the local dose differences (ΔD) relative to the average dose within the 50% isodose line from the three sites were found to be -3.2%-3.7%. The maximum localization errors (E ) were found to be within 0.5 ± 0.2 mm. With SRSMC, the ΔD was found to be within 5% of the TPS calculation. E were found to be within 0.7 to 1.1 ± 0.4 mm for TrueBeam and Trilogy, respectively. Comparing with film, an additional uncertainty of 0.7 mm was found with SRSMC. The delivery and analysis times were found to be 6 and 2 h for film and SRSMC, respectively.
The SRS MapCHECK agrees dosimetrically with the films within measurement uncertainties. However, film dosimetry shows superior sub-millimeter localization resolving power for the MPPG 9a implementation.
端到端测试 (E2E) 是根据 AAPM MPPG 9a 评估立体定向放射外科 (SRS) 计划准备情况和 SRS 系统年度质量保证的必要过程。本研究调查了在具有不同 SRS 传输技术的大型网络中使用新型 SRS MapCHECK (SRSMC) 系统和基于人体模型胶片的系统之间的差异。
选择三个不同区域的三个具有 SRS 能力的直线加速器 (Varian Medical Systems，Palo Alto，CA) 代表一个医院网络，一个带有 M120 多叶准直器 (MLC) 的 Trilogy、一个带有 M120 MLC 的 TrueBeam 和一个带有 HD120 MLC 的 TrueBeam Stx。在每个站点对一个人体模型 STEEV 体模 (CIRS，Norfolk，VA) 和一个体模/二极管阵列：StereoPHAN/SRSMC (Sun Nuclear，Melbourne，FL) 进行 CT 扫描。使用新的 STV-PHANTOM EBT-XD 胶片 (Ashland，Bridgewater，NJ)。在 StereoPHAN 中使用两种胶片和 SRSMC 测量了六个具有不同复杂度的计划，以建立它们的剂量学相关性。使用每个机器的定制 SRS 光束模型，使用 Eclipse v15.5 治疗计划系统 (TPS) 为三个具有总共十六个场的 SRS 颅脑计划进行规划，这些计划采用动态适形弧形和容积调制弧形治疗，有 1-4 个靶区。比较了剂量学和定位准确性。还比较了三个物理团队对这两个系统的分析时间，以评估吞吐量效率。
发现胶片和 SRSMC 之间的相关性分别为 0.84(p=0.03)和 0.16(p=0.76)，γ(3%，1mm)和γ(3%，2mm)。使用胶片，发现三个站点的 50%等剂量线内的平均剂量的局部剂量差异 (ΔD) 为 -3.2%至-3.7%。发现最大定位误差 (E) 在 0.5±0.2mm 以内。使用 SRSMC，发现 ΔD 在 TPS 计算的 5%以内。E 分别为 TrueBeam 和 Trilogy 的 0.7 至 1.1±0.4mm。与胶片相比，发现 SRSMC 存在 0.7mm 的额外不确定性。胶片和 SRSMC 的输送和分析时间分别为 6 小时和 2 小时。
SRS MapCHECK 在测量不确定度内与胶片的剂量学一致。然而，胶片剂量学对于 MPPG 9a 的实施具有更好的亚毫米级定位分辨率。
