Tata Memorial Centre, Mumbai, India.
Homi Bhabha National Institute, Mumbai, India.
Biomed Phys Eng Express. 2020 Sep 29;6(6). doi: 10.1088/2057-1976/abb319.
Dosimetry of small fields (SF) is vital for the success of highly conformal techniques. IAEA along with AAPM recently published a code of practice TRS-483 for SF dosimetry. The scope of this paper is to investigate the performance of three different detectors with 10 MV with-flatting-filter (WFF) beam using TRS-483 for SF dosimetry and subsequent commissioning of the Eclipse treatment planning system (TPS version-13.6) for SF data. SF dosimetry data ((10)()) measurements were performed for PTW31006-pinpoint, IBA-CC01 and IBA-EFD-3G diode detectors in nominal field size (F.S) range 0.5 × 0.5cmto 10 × 10 cmwith water and solid water medium using Varian Truebeam linac. However, Eclipse-TPS commissioning data was acquired using IBA-EFD-3G diode, and absolute dose calibration was performed with FC-65G detector. The dosimetric performance of the Eclipse-TPS was validated using TLD-LiF chips, IBA-PFD, and IBA-EFD-3G diodes. Dosimetric performance of the PTW31006-pinpoint, IBA-CC01, and IBA-EFD-3G detectors was successfully tested for SF dosimetry. The F.O.Fs were generated and found in close agreement for all F.S except 0.5 × 0.5cm. It is also found that TPR(10) value can be derived within 0.5% accuracy from a non-reference field using Palmans equation. Cross-calibration can be performed in F.S 6 × 6 cmwith a maximum variation of 0.5% with respect to 10 × 10cm. During profile measurement, the full-width half-maxima (FWHM) of F.S 0.5 × 0.5cmwas found maximum deviated from the geometric F.S. In addition, Eclipse-TPS was commissioned along with some limitations: F.O.F below F.S 1 × 1cmwas ignored by TPS, PDD and profiles were dropped from configuration below F.S 2 × 2 cm, and F.O.F which does not satisfy the condition 0.7 < A/B < 1.4 () have higher uncertainty than specified in TRS-483. Validation tests for Eclipse-TPS generated plans were also performed. The measured dose was in close agreement (3%) with TPS calculated dose up to F.S 1.5 × 1.5cm.
小射野（SF）的剂量学对于高度适形技术的成功至关重要。国际原子能机构（IAEA）与美国医学物理师协会（AAPM）最近发布了 TRS-483 号实践规程，用于 SF 剂量学。本文的研究范围是使用 TRS-483 对三种不同的探测器进行 10MV 带平顶滤波器（WFF）光束的性能测试，随后对 Eclipse 治疗计划系统（TPS 版本 13.6）进行 SF 数据的调试。在瓦里安 Truebeam 直线加速器中，使用水和固体水介质，在标称射野尺寸（F.S）范围内 0.5×0.5cm 至 10×10cm 对 PTW31006-微针、IBA-CC01 和 IBA-EFD-3G 二极管探测器进行了 ((10)()) 测量。然而，Eclipse-TPS 的调试数据是使用 IBA-EFD-3G 二极管获得的，并且使用 FC-65G 探测器进行了绝对剂量校准。使用 TLD-LiF 芯片、IBA-PFD 和 IBA-EFD-3G 二极管对 Eclipse-TPS 的剂量学性能进行了验证。PTW31006-微针、IBA-CC01 和 IBA-EFD-3G 探测器的 SF 剂量学性能测试均成功完成。除了 0.5×0.5cm 之外，所有 F.S 的 F.O.Fs 均已生成并发现非常吻合。还发现，可以使用 Palmans 方程从非参考射野中以 0.5%的精度内推 TPR(10)值。在 6×6cm 的 F.S 中可以进行交叉校准，相对于 10×10cm，最大变化为 0.5%。在进行轮廓测量时，发现 0.5×0.5cm 的 F.S 的全宽度半最大值（FWHM）最大偏离了几何 F.S。此外，Eclipse-TPS 的调试还存在一些限制：TPS 忽略了 F.S 小于 1×1cm 的 F.O.F，PDD 和轮廓从 F.S 小于 2×2cm 的配置中被删除，并且不满足条件 0.7<A/B<1.4 的 F.O.F 比 TRS-483 中规定的具有更高的不确定性。还对 Eclipse-TPS 生成的计划进行了验证测试。测量的剂量与 TPS 计算的剂量在 F.S 1.5×1.5cm 以内非常吻合（3%）。
