Ponmalar Y Retna, Manickam Ravikumar, Godson Henry Finlay, Ganesh Kadirampatti Mani, Saminathan Sathiyan, Chandraraj Varatharaj, Raman Arun
Department of Radiation Oncology, Christian Medical College, Vellore, India.
Department of Radiotherapy, Sri Shankara Cancer Hospital & Research Centre, Bangalore, 560 004, India.
Radiol Phys Technol. 2025 Mar;18(1):275-286. doi: 10.1007/s12194-025-00883-5. Epub 2025 Jan 25.
The estimation of peripheral dose (PD) is vital in cancer patients with long life expectancy. Assessment of PD to radiosensitive organs is important to determine the possible risk of late effects. An attempt has been made to assess the peripheral dose using optically stimulated luminescence dosimeter (OSLD) with megavoltage photon beams as a function of field size, depth, energy, and distance from the field edge. The PD measurements were carried out at 13 locations starting from 1.5 cm to 20.8 cm from radiation field edge for three different field sizes at three different depths with 6 and 18 MV photon beams. In addition, the measurements were carried out to analyze the response in PD due to the presence of wedge. The %PD decreases gradually with an increase in distance from the radiation field edge. The %PD at surface for 10 × 10cm with 6MV photon beams was 6.77 ± 0.32% and 1.0 ± 0.04% at 1.5 cm and 20.8 cm away from field edge. For 20 × 20 cm field, %PD was found to be much higher at surface than at 5 cm depth for all distances from field edge. This study demonstrates the suitability of OSLD for PD assessment in megavoltage photon beams. The PD increases as field size increases, primarily due to greater amount of out-of-field scatter generated by larger surface area of the collimator defining the larger field size. An enhancement in PD was observed with wedge when the thick end was oriented towards the OSLDs. This study assessed PD that would be a risk factor of the normal tissue complication and secondary cancer induction.
对于预期寿命较长的癌症患者，外周剂量（PD）的评估至关重要。评估对放射敏感器官的PD对于确定迟发效应的可能风险很重要。已尝试使用光激励发光剂量计（OSLD）结合兆伏级光子束来评估外周剂量，该评估是作为射野大小、深度、能量以及距射野边缘距离的函数进行的。使用6和18兆伏光子束，在三个不同深度针对三种不同射野大小，从距辐射野边缘1.5厘米至20.8厘米的13个位置进行了PD测量。此外，还进行了测量以分析由于楔形板的存在而导致的PD响应。%PD随着距辐射野边缘距离的增加而逐渐降低。对于6兆伏光子束的10×10厘米射野，在距野边缘1.5厘米和20.8厘米处表面的%PD分别为6.77±0.32%和1.0±0.04%。对于20×20厘米射野，发现在距野边缘的所有距离处，表面的%PD均远高于5厘米深度处的%PD。本研究证明了OSLD适用于兆伏级光子束的PD评估。PD随着射野大小的增加而增加，这主要是由于定义较大射野大小的准直器较大表面积产生的更多野外散射所致。当楔形板的厚端朝向OSLD时，观察到PD有所增强。本研究评估了作为正常组织并发症和继发性癌症诱发风险因素的PD。
