Francois P, Coste F, Bonnet J, Caselles O
Centre Claudius Regaud, Unité de Physique, Toulouse, France.
Med Phys. 1997 May;24(5):769-73. doi: 10.1118/1.597998.
We have previously investigated a method of high-energy x-ray spectral reconstruction from transmission data by direct resolution of a matrix system. This technique uses the spectral vectorial algebra formalism. The resolution has previously been tested on a 12 MV photon beam. To extend and to test the validity of the results to the entire radiotherapy energy range, we have performed the method on photon beams with nominal energies of 6, 12, 15, and 25 MV. The influence on the 6 MV spectrum of a 60 degrees built-in wedge has also been investigated to test the sensitivity of the method and the results are reported. To validate our reconstructed spectra, dosimetric quantities such as tissue phantom ratios (TPR), water-to-air stopping power ratios (S/p) air water, and quality indexes TPR 10 (20) have been calculated. The results show good agreement between the measured and calculated data. Mean mass energy absorption coefficient ratios for different materials have also been computed and compared to data published recently and the results are very close (within +/- 0.5%). Primary depth dose functions in water have also been computed to deduce primary dose attenuation coefficients.
我们之前研究了一种通过直接求解矩阵系统从透射数据进行高能X射线光谱重建的方法。该技术使用光谱矢量代数形式。此前已在12MV光子束上对该分辨率进行了测试。为了将结果的有效性扩展并测试到整个放射治疗能量范围，我们对标称能量为6、12、15和25MV的光子束执行了该方法。还研究了60度内置楔形对6MV光谱的影响，以测试该方法的灵敏度，并报告了结果。为了验证我们重建的光谱，计算了诸如组织体模比（TPR）、水与空气的阻止本领比（S/p）空气水以及质量指标TPR 10（20）等剂量学量。结果表明测量数据与计算数据之间具有良好的一致性。还计算了不同材料的平均质量能量吸收系数比，并与最近发表的数据进行了比较，结果非常接近（在+/- 0.5%以内）。还计算了水中的原发射线深度剂量函数，以推导原发射线剂量衰减系数。
