INL, CNRS UMR5270, Université Lyon 1, Villeurbanne F-69622, France.
Phys Med. 2013 Sep;29(5):487-92. doi: 10.1016/j.ejmp.2012.12.007. Epub 2013 Jan 11.
For dosimetric measurements using an implantable optical fiber probe with GaN (Gallium Nitride) scintillator as radioluminescence (RL) transducer, a bi-channel method is proposed to reject the background contribution of the irradiated fiber segment. It is based on spectral differences between the narrow-band light emission from GaN and the large-band background from the irradiated optical fiber. Experimental validation of this method using 6 MV photon beam has shown that the remaining background contribution after subtraction is below 1.2% for square field sizes ranging from 3 cm to 20 cm. Furthermore, a compensation method for the over-response of GaN is also proposed, since GaN is not tissue equivalent. The over-response factor of GaN exhibits a linear increase with square field aperture and depends on depth from phantom surface. This behaviour is modelled to allow compensation in specific conditions. The proposed method has been evaluated and has shown a maximum deviation of 3% for a 6 MV photon beam and 1% for an 18 MV photon beam at a depth beyond the build-up region.
对于使用带有 GaN（氮化镓）闪烁体的植入式光纤探头进行剂量测量，提出了一种双通道方法来消除辐照光纤段的背景贡献。它基于 GaN 窄带光发射与辐照光纤的宽带背景之间的光谱差异。使用 6 MV 光子束对该方法进行了实验验证，结果表明，减去后剩余的背景贡献对于 3 cm 至 20 cm 的方形射野大小均低于 1.2%。此外，还提出了一种针对 GaN 过响应的补偿方法，因为 GaN 与组织等效。GaN 的过响应因子随方形射野孔径呈线性增加，并取决于离体模表面的深度。这种行为被建模为允许在特定条件下进行补偿。所提出的方法已经过评估，结果表明在 6 MV 光子束和 18 MV 光子束在超过 buildup 区域的深度处，最大偏差分别为 3%和 1%。
