Accurate method for computer-generating tungsten anode x-ray spectra from 30 to 140 kV
Accurate method for computer-generating tungsten anode x-ray spectra from 30 to 140 kV
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DOI：
10.1118/1.597953
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发表时间：
1997-11-01
期刊：
影响因子：
3.8
通讯作者：
Seibert, JA
中科院分区：
文献类型：
--
作者：
Boone, JM;Seibert, JA
使用插值多项式（TASMIP）的钨阳极光谱模型被用来计算X射线光谱在1 keV的间隔在30 kV至140 kV的范围内。TASMIP不是半经验的，并且不使用关于X射线产生的物理假设，而是内插由Fewell等人[Handbook of Computed Tomography X-ray Spectra（U.S.Government Printing Office，华盛顿，华盛顿特区，1981）]。X射线输出测量（mR/mAs在1米处测量）进行了校准的恒电位发生器在我们的实验室从50千伏至124千伏，并与0 - 5毫米添加铝过滤。Fewell光谱略有修改（数字硬化）和归一化的基础上的衰减和输出特性的恒电位发生器和金属插入X射线管在我们的实验室。然后，使用不同kV的修改的Fewell谱，使用形式为phi（E）= a（0）[E]+ a（1）[E] kV + a（2）[E] kV（2）+.+的多项式函数来表征在从10 keV到140 keV的能量范围内的每个1 keV能量仓（E）处的光子注量phi。a（n）[E] kV（n）.总共使用了131个多项式函数来计算精确的X射线光谱，每个函数需要两到四个项。由此产生的TASMIP算法产生的X射线光谱与我们实验室的X射线系统的质量和数量特征相匹配。对于光谱中峰值注量的10%以上的光子注量，修改后的Fewell光谱和TASMIP光子注量之间的（和标准偏差）为-1.43%（3.8%），对于50 kV频谱，-0.89%（1.37%），对于70 kV光谱，以及对于80、90、100、110、120、130和140 kV光谱，光谱间的平均差异均小于0.20%，标准偏差小于1.1%。该模型还扩展到包括发电机感应的kV纹波的影响。最后，对于各种（水当量）患者厚度（0、10、20和30 cm），计算X射线光子通量（单位：光子/mm（2）/mR）作为HVL、kV和纹波因子的函数。这些值可用于计算X射线检测器系统的检测量子效率DQE（f）。TASMIP算法和辅助数据可在www.example.com上在线获得。org/epaps/epaps. HTML. (C)1997年美国医学物理学家协会。
A tungsten anode spectral model using interpolating polynomials (TASMIP) was used to compute x-ray spectra at 1 keV intervals over the range from 30 kV to 140 kV. The TASMIP is not semi-empirical and uses no physical assumptions regarding x-ray production, but rather interpolates measured constant potential x-ray spectra published by Fewell et al. [Handbook of Computed Tomography X-ray Spectra (U.S. Government Printing Office, Washington, D.C., 1981)]. X-ray output measurements (mR/mAs measured at 1 m) were made on a calibrated constant potential generator in our laboratory from 50 kV to 124 kV, and with 0-5 mm added aluminum filtration. The Fewell spectra were slightly modified (numerically hardened) and normalized based on the attenuation and output characteristics of a constant potential generator and metal-insert x-ray tube in our laboratory. Then, using the modified Fewell spectra of different kVs, the photon fluence phi at each 1 keV energy bin (E) over energies from 10 keV to 140 keV was characterized using polynomial functions of the form phi(E) = a(0)[E] + a(1)[E] kV + a(2)[E] kV(2) +...+ a(n)[E] kV(n). A total of 131 polynomial functions were used to calculate accurate x-ray spectra, each function requiring between two and four terms. The resulting TASMIP algorithm produced x-ray spectra that match both the quality and quantity characteristics of the x-ray system in our laboratory. For photon fluences above 10% of the peak fluence in the spectrum, the average percent difference (and standard deviation) between the modified Fewell spectra and the TASMIP photon fluence was -1.43% (3.8%) for the 50 kV spectrum, -0.89% (1.37%) for the 70 kV spectrum, and for the 80, 90, 100, 110, 120, 130 and 140 kV spectra, the mean differences between spectra were all less than 0.20% and the standard deviations were less than similar to 1.1%. The model was also extended to include the effects of generator-induced kV ripple. Finally, the x-ray photon fluence in the units of photons/mm(2) per mR was calculated as a function of HVL, kV, and ripple factor, for various (water-equivalent) patient thicknesses (0, 10, 20, and 30 cm). These values may be useful for computing the detective quantum efficiency, DQE(f), of x-ray detector systems. The TASMIP algorithm and ancillary data are made available on line at http://www.aip. org/epaps/epaps. html. (C) 1997 American Association of Physicists in Medicine.