Department of Medical Physics, Tata Memorial Center, Homi Bhabha Cancer Hospital, Sangrur, Punjab; Chitkara University Institute of Engineering and Technology, Chitkara University, Punjab, India.
Department of Radiotherapy, King George Medical University, Lucknow, Uttar Pradesh, India.
J Cancer Res Ther. 2023 Apr-Jun;19(3):793-800. doi: 10.4103/jcrt.jcrt_967_21.
The present study was undertaken to evaluate the performance of different algorithms for flattening filter-free (FFF) and flattened (FF) photon beams in three different in-homogeneities.
Computed tomography (CT) image sets of the CIRS phantom maintained in the SAD setup by placing the ionization chamber in the lung, bone, and tissue regions, respectively, were acquired. The treatment planning system (TPS) calculated and the ionization chamber measured the doses at the center of the chamber (in the three mediums) were recorded for the flattened and non-flattened photon beams.
The results were reported for photon energies of 6 MV, 10 MV, 15 MV, 6 FFF, and 10 FFF of field sizes 5 × 5 cm, 10 × 10 cm, and 15 × 15 cm. In the bone inhomogeneity, the pencil beam algorithm predicted that the maximum dose variation was 4.88% of measured chamber dose in 10-MV photon energy for the field size 10 × 10 cm. In water inhomogeneity, both the collapsed cone and Monte Carlo algorithm predicted that the maximum dose variation was ± 3% of measured chamber dose in 10-MV photon energy for the field size 10 × 10 cm and in 10-MV FFF photon energy for the field size 5 × 5 cm, whereas in lung inhomogeneity, the pencil beam algorithm predicted that the highest dose variation was - 6.9% of measured chamber dose in 10-MV FFF photon energy for the field size 5 × 5 cm.
FF and FFF beams performed differently in lung, water, and bone mediums. The assessment of algorithms was conducted using the anthropomorphic phantom; therefore, these findings may help in the selection of appropriate algorithms for particular clinical settings in radiation delivery.
本研究旨在评估不同算法在三种不同不均匀性中对平扫（FF）和扁平化（FF）光子束的平坦化效果。
采用放置在肺、骨和组织区域的电离室，在 SAD 设置中获取 CIRS 体模的 CT 图像集。治疗计划系统（TPS）计算并记录了在三个介质（在三个中等介质中）中心电离室测量的平坦化和非平坦化光子束剂量。
报告了光子能量为 6MV、10MV、15MV、6FFF 和 10FFF，射野大小为 5×5cm、10×10cm 和 15×15cm 的结果。在骨不均匀性中，铅笔束算法预测在 10MV 光子能量的 10×10cm 射野中，最大剂量变化为测量腔室剂量的 4.88%。在水不均匀性中，无论是 collapsed cone 算法还是蒙特卡罗算法，均预测在 10MV 光子能量的 10×10cm 射野和 5×5cm 射野的 10MVFFF 光子能量中，最大剂量变化为测量腔室剂量的±3%，而在肺不均匀性中，铅笔束算法预测在 5×5cm 射野的 10MVFFF 光子能量中，最大剂量变化为测量腔室剂量的-6.9%。
FF 和 FFF 束在肺、水和骨介质中表现不同。使用人体模型评估算法；因此，这些发现可能有助于在放射治疗中为特定临床环境选择合适的算法。
