Catala A, Francois P, Bonnet J, Scouarnec C
Centre Claudius REGAUD, Département de Radiothérapie, Toulouse, France.
Med Phys. 1995 Jan;22(1):3-10. doi: 10.1118/1.597523.
An investigation of x-ray spectral reconstruction from transmission data by direct resolution of the matrix system A*F = T (using spectral algebra formalism) has been previously presented. The resolution has been done with simulated spectrum. In this paper, the method on a real case of a 12 MV photon beam was tested. A special study of the setup has been made to estimate and reduce the experimental errors that could alter the results. In order to convert F(E) (a fraction of the signal due to a photon of energy E) into photon fluence phi (E), the chamber energy response R(E) has been studied and an approximated analytical function for its representation was proposed. Spectra reconstructed from different transmission data using different attenuators, buildup caps, and ionization chambers have been compared to verify the uniqueness of the reconstructed spectra. To test the validity of the results, dosimetric values, such as Depth Dose Data have been calculated, from our spectrum, using a specific code developed by Kosunen et al. The results show a good agreement between the measured and calculated data.
先前已经提出了通过直接求解矩阵系统(A*F = T)（使用光谱代数形式）从透射数据进行X射线光谱重建的研究。该分辨率是通过模拟光谱完成的。本文测试了该方法在12 MV光子束实际案例中的应用。对设置进行了专门研究，以估计和减少可能改变结果的实验误差。为了将(F(E))（能量为(E)的光子引起的信号分数）转换为光子注量(\phi (E))，研究了电离室能量响应(R(E))，并提出了其表示的近似解析函数。比较了使用不同衰减器、积累帽和电离室从不同透射数据重建的光谱，以验证重建光谱的唯一性。为了测试结果的有效性，使用Kosunen等人开发的特定代码，从我们的光谱中计算了剂量学值，如深度剂量数据。结果表明测量数据和计算数据之间有很好的一致性。
