Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, New York 10065, USA.
J Radiat Res. 2023 Jan 20;64(1):105-112. doi: 10.1093/jrr/rrac080.
A new film dosimetry system consists of the new OrthoChromic™ OC-1 film, and a novel calibration procedure was evaluated. Two films, C1 and C2, were exposed simultaneously using the 6FFF beam with a step-wedge pattern of five steps ranging from 590 to 3000 cGy. C1 was used for calibration, and C2 was used for calibration curve validation. The second scan of C2 was done by rotating the film by 90-deg. To evaluate the effectiveness of the non-uniform scanner response correction with the new system, a film was exposed to a 20 × 20 cm2 field. The beam profile measured with the film was compared to the IBA cc04 measurements in water. Films were irradiated to characterize the energy response, dynamic range and temporal growth effect. Open (MLC-defined) and clinical fields were radiated to evaluate the overall performance of the new system. The new calibration procedure was validated with an average dose difference of 1.6% and a gamma (2%,2 mm) passing rate of 100%. With C2 scanned 90-deg rotated, the average dose difference was 1.3%. The average difference between cc04 and film was 0.4%. The St between films and diode/cc04 were within -0.3% difference for 1 × 1 to 14 × 14 cm2 and -2.8% for 0.5 × 0.5 cm2. For clinical fields, the average gamma (3%,2 mm) was 98.8%. These results were consistent with EBT3 film and MapCheck measurements with a dose > 400 cGy. The results have shown that the OC-1 film system can achieve accurate results for QA measurements, but more considerable uncertainty was observed within the low dose range.
一种新的放射治疗剂量测定系统由新型的 OrthoChromic™ OC-1 胶片和一种新的校准程序组成。使用 6FFF 射束对两片胶片 C1 和 C2 进行了同时曝光，射束中具有五个从 590 到 3000 cGy 的台阶楔形图案。C1 用于校准，C2 用于校准曲线验证。C2 的第二次扫描是通过将胶片旋转 90 度完成的。为了评估新系统中非均匀扫描仪响应校正的有效性，对一张胶片进行了曝光，曝光面积为 20×20 cm2。用胶片测量的射束轮廓与 IBA cc04 在水中的测量结果进行了比较。对胶片进行了照射，以表征能量响应、动态范围和时间增长效应。照射开放（MLC 定义）和临床射野，以评估新系统的整体性能。新的校准程序经过验证，平均剂量差异为 1.6%，伽马（2%，2mm）通过率为 100%。当 C2 旋转 90 度扫描时，平均剂量差异为 1.3%。cc04 和胶片之间的平均差异为 0.4%。胶片与二极管/cc04 之间的 St 在 1×1 到 14×14 cm2 之间的差异在-0.3%以内，在 0.5×0.5 cm2 之间的差异为-2.8%。对于临床射野，平均伽马（3%，2mm）为 98.8%。这些结果与 EBT3 胶片和 MapCheck 测量结果一致，剂量大于 400 cGy。结果表明，OC-1 胶片系统可以实现 QA 测量的精确结果，但在低剂量范围内观察到更大的不确定性。
