This work investigates the suitability of locally fabricated 6 mol% Ge-doped optical fibres as dosimeters for small-field output ratio measurements. Two fabrications of fibre, cylindrical (CF) and flat (FF) fibres, were used to measure doses in small photon fields, from 4 to 15 mm. The findings were compared to those of commercial Ge-doped fibre (COMM), EBT3 film and an IBA CC01 ionization chamber. Irradiations were carried out using a 6 MV SRS photon beam operating at a dose rate of 1000 cGy min⁻¹, delivering a dose of 16 Gy. To minimise the possibility of the fibres failing to be exposed to the intended dose in small fields, the fibres were accommodated in a custom-made Perspex phantom. For the 4 mm cone the CF and FF measured output ratios were found to be smaller than obtained with EBT3 film by 32% and 13% respectively. Conversely, while for the 6 to 15 mm cone fields the FF output ratios were consistently greater than those obtained using EBT3 film, the CF output ratios differed from those of EBT3 film by at most 3.2%, at 6 mm, otherwise essentially agreeing with EBT3 values at the other field sizes. For the 4 to 7.5 mm cones, all output ratios obtained from Ge-doped optical fibre measurements were greater than those of IBA CC01 ionization chamber. The measured FF and CF output ratios for the 7.5 to 15 mm cones agreed with published MC estimates to within 15% and 13%, respectively. Down to 6 mm cone field, present measurements point to the potential of CF as a small-field dosimeter, its use recommended to be complemented by the use of EBT3 film for small-field dosimetry.

这项工作研究了局部制造的 6 mol% Ge 掺杂光纤作为剂量计用于小场输出比测量的适用性。两种纤维制造，圆柱形 (CF) 和扁平 (FF) 纤维，用于测量 4 到 15 毫米的小光子场中的剂量。将这些发现与商业掺锗光纤 (COMM)、EBT3 薄膜和 IBA CC01 电离室的发现进行了比较。^{使用以 1000 cGy min -1}的剂量率操作的 6 MV SRS 光子束进行照射，提供 16 Gy 的剂量。为了尽量减少纤维未能在小范围内暴露于预期剂量的可能性，这些纤维被安置在定制的有机玻璃体模中。对于 4 mm 锥体，CF 和 FF 测得的输出比被发现比 EBT3 薄膜获得的输出比分别小 32% 和 13%。相反，虽然对于 6 至 15 mm 锥场，FF 输出比始终大于使用 EBT3 薄膜获得的那些，但 CF 输出比在 6 mm 处与 EBT3 薄膜的差异最多 3.2%，否则与 EBT3 基本一致其他字段大小的值。对于 4 至 7.5 毫米锥体，从掺锗光纤测量中获得的所有输出比均大于 IBA CC01 电离室的输出比。7. 测得的 FF 和 CF 输出比率。5 至 15 毫米锥体与已公布的 MC 估计值一致，分别在 15% 和 13% 以内。低至 6 mm 的锥形场，目前的测量结果表明 CF 作为小场剂量计的潜力，建议使用 EBT3 薄膜作为小场剂量测定的补充。