X-ray imaging performance of structured cesium iodide scintillators
X-ray imaging performance of structured cesium iodide scintillators
复制标题
DOI：
10.1118/1.1782676
复制
发表时间：
2004-09-01
期刊：
影响因子：
3.8
通讯作者：
Rowlands, JA
中科院分区：
文献类型：
--
作者：
Zhao, W;Ristic, G;Rowlands, JA
掺Tl的柱状结构碘化铯(CSI)闪烁体已被广泛应用于间接X射线成像探测器。本文的目的是开发一种方法来系统地研究CSI的固有成像性能作为厚度和设计类型的函数。这一结果将有助于针对不同的X射线成像应用优化CSI层的设计，并允许验证为柱状CSI层中的光通道过程开发的物理模型。不同类型和厚度的CSI样品来自同一制造商。它们针对光输出(HL)或图像分辨率(HR)进行了优化，厚度范围在150至600微米之间。在实验测量过程中，将CSI样品与像素间距为48微米的高分辨率CMOS光传感器直接接触。实验测量了不同CSI结构的探测器的调制传递函数(MTF)、噪声功率谱(NPS)和探测量子效率(DQE)。为了单独估计CSI的MTF，分别确定了CMOS传感器的孔径函数。我们还测量了HL和HR CSI在不同X射线能量下输出光的脉冲高度分布，由此确定了X射线量子效率、斯旺克因子和X射线转换增益。结果表明，HR型的MTF在5个周期/mm时比HL高50%。然而，HR层产生的光输出几乎减少了36%。K型以下的Swank因子HR和HL型分别为0.91和0.93，DQE(0)基本相同。预采样MTF随厚度L的增加而减小。通用MTF(即作为空间频率f与CSI厚度L的乘积的函数)的MTF随L的增加而增加，这表明CSI中的光沟道过程对较厚层的MTF的改善比对较薄层的改善更显著。@2004美国物理学家医学协会。
Columnar structured cesium iodide (CsI) scintillators doped with Thallium (TI) have been used extensively for indirect x-ray imaging detectors. The purpose of this paper is to develop a methodology for systematic investigation of the inherent imaging performance of CsI as a function of thickness and design type. The results will facilitate the optimization of CsI layer design for different x-ray imaging applications, and allow validation of physical models developed for the light channeling process in columnar CsI layers. CsI samples of different types and thicknesses were obtained from the same manufacturer. They were optimized either for light output (HL) or image resolution (HR), and the thickness ranged between 150 and 600 microns. During experimental measurements, the CsI samples were placed in direct contact with a high resolution CMOS optical sensor with a pixel pitch of 48 microns. The modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the detector with different CsI configurations were measured experimentally. The aperture function of the CMOS sensor was determined separately in order to estimate the MTF of CsI alone. We also measured the pulse height distribution of the light output from both the HL and HR CsI at different x-ray energies, from which the x-ray quantum efficiency, Swank factor and x-ray conversion gain were determined. Our results showed that the MTF at 5 cycles/mm for the HR type was 50% higher than for the HL. However, the HR layer produces similar to36% less light output. The Swank factor below K-edge was 0.91 and 0.93 for the HR and HL types, respectively, thus their DQE(0) were essentially identical. The presampling MTF decreased as a function of thickness L. The universal MTF, i.e., MTF plotted as a function of the product of spatial frequency f and CsI thickness L, increased as a function of L. This indicates that the light channeling process in CsI improved the MTF of thicker layers more significantly than for the thinner ones. @ 2004 American Association of Physicists in Medicine.