Yu T, Sabol J M, Seibert J A, Boone J M
Department of Radiology, University of California, Davis, USA.
Med Phys. 1997 Feb;24(2):279-85. doi: 10.1118/1.598071.
The widespread effort in developing digital imaging systems has led to large area high pixel density photodetectors such as charge coupled devices (CCDs), amorphous silicon photodiode arrays, and complementary metal oxide semiconductor (CMOS) imagers. These photodetectors have different capabilities, characteristics, and requirements than conventional silver-halide-based film, and this fact had led to a new generation of exotic scintillators, including fiber optic screens made from scintillating glass. The scintillator performance characteristics of five different scintillating fiber optic screens and two conventional Gd2O2S:Tb screens (one 34 mg/cm2 and the other 60 mg/cm2) were measured and compared. The measurements that were made included the angular dependence of light emission relative to the normal, the modulation transfer function (MTF), and the absolute effective conversion efficiency (light photons per absorbed x-ray photon). It was found that the light emission of scintillating fiber optic screens is markedly forward peaked (depending on the sample) compared to conventional screens or Lambertian emitters. The MTFs of the five scintillating fiber optic screens measured were comparable and fell approximately midway between the two conventional screen MTFs. One of the scintillating fiber optic screens demonstrated light efficiency similar to the thick (60 mg/cm2) conventional screen, another had light output capabilities similar to the thin (34 mg/cm2) conventional screen, and the three others were less efficient than the thin screen. The non-Lambertian characteristics of the fiber optic scintillators will cause errors of up to 75% in lens efficiency calculations if a Lambertian source is assumed. The conventional screens were found to conform within about 5% of an ideal Lambertian emitter.
开发数字成像系统的广泛努力催生了大面积高像素密度的光电探测器，如电荷耦合器件（CCD）、非晶硅光电二极管阵列和互补金属氧化物半导体（CMOS）成像器。这些光电探测器与传统的卤化银基胶片具有不同的能力、特性和要求，这一事实催生了新一代奇特的闪烁体，包括由闪烁玻璃制成的光纤屏。对五种不同的闪烁光纤屏和两种传统的Gd2O2S:Tb屏（一种为34 mg/cm2，另一种为60 mg/cm2）的闪烁体性能特征进行了测量和比较。所进行的测量包括相对于法线的光发射角度依赖性、调制传递函数（MTF）和绝对有效转换效率（每吸收一个X射线光子产生的光光子数）。结果发现，与传统屏或朗伯发射体相比，闪烁光纤屏的光发射明显向前 peaked（取决于样品）。所测量的五种闪烁光纤屏的MTF相当，大约落在两种传统屏MTF之间的中间位置。其中一种闪烁光纤屏的光效率与厚（60 mg/cm2）传统屏相似，另一种的光输出能力与薄（34 mg/cm2）传统屏相似，另外三种的效率低于薄屏。如果假设为朗伯源，光纤闪烁体的非朗伯特性将导致透镜效率计算中高达75%的误差。发现传统屏符合理想朗伯发射体的约5%以内。 （注：“向前peaked”这里原文似乎表述有误，可能影响理解，正常可能是“向前 peaked分布”之类更准确表述，但按要求未做修改）
