DEVELOPMENT OF AN EMISSION-TRANSMISSION CT SYSTEM

这项研究将继续发展一个原型 发射透射计算机断层扫描仪（ETCT）， 双能X线CT与放射性核素同步采集 CT. 传输和发射数据同时采集， 单个高纯度锗（HPGE）探测器阵列，因此 在空间和时间上都有关联。 排放的组合 和传输数据与ETCT系统允许（1）准确 发射数据的衰减校正;（2）定性相关 的功能和形态图像，和（3）区域的定义 感兴趣的X射线CT图像上的精确定量的 放射性核素数据。 该计划包括6个具体目标。(1)更正将 开发的效果，限制了准确性和精度 定量X射线和放射性核素数据，例如光子统计噪声， 散射辐射和能量窗的次优位置。（二） 重建软件将在一个许可证下开发， 位于查佩尔山的北卡罗来纳州大学（UNC-CH） 重建图像的质量和定量精度， 补偿不均匀的光子衰减、散射辐射，以及 由几何系统和散射响应引起的空间变化模糊 功能协调发展的 UNC-CH小组将研究贝叶斯算法， 将来自所述X射线CT图像的先验信息合并到 放射性核素断层图像的重建。(3)的定量 SPECT图像将使用相关的X射线CT图像来改善 定位，用于衰减校正和补偿 部分体积效应 X射线的噪声传播效应 将确定到SPECT重建中的衰减图。(4)一 将开发一个机架，用于使用ETCT对犬胸部进行成像 系统补偿滤波器将被添加到X射线束路径，以 提高衰减图的信噪比， 射线照相图像的采集时间。(5)一个狗模型将 用于检验假设，即使用 99 mTc-MIBI和ETCT与心肌灌注的相关性 放射性标记的微球。(6)ETCT的最佳操作配置 将通过测试替代HPGe探测器进行研究， 改进的探测器准直器，导致一个设计概念， 临床可用ETCT系统。 这些研究将评估 定量放射性核素研究用ETCT系统的性能， 理论计算、计算机模拟、实验 测量，并在心肌灌注的动物模型中验证， 其长期目标是改进放射性核素评估， 心肌灌注，以及脑血流量，肿瘤剂量测定， 和肿瘤在人类患者中的定位。

This research will continue the development of a prototype emission-transmission computed tomographic (ETCT) scanner for simultaneous acquisition of dual-energy x-ray CT and emissionradionuclide CT. The transmission and emission data are acquired simultaneously with a single high-purity germanium (HPGE) detector array, and therefore are correlated both spatially and temporally. The combination of emission and transmission data with the ETCT systems allows (1) accurate attenuation correction of the emission data, (2) qualitative correlation of the functional and morphological images, and (3) definition of regions of interest on the x-ray CT images for precise quantification of the radionuclide data. This proposal encompasses 6 specific aims. (1) Corrections will be developed for effects which limit the accuracy and precision of quantitative x-ray and radionuclide data, such photon statistical noise, scatter radiation, and suboptimum placement of energy windows. (2) Reconstruction software will be developed under a subcontract to the University of North Carolina at Chapel Hill (UNC-CH) to improve the quality and quantitative accuracy of the reconstructed images by compensating for nonuniform photon attenuation, scatter radiation, and spatially-variant blurring by the geometric system and scatter response functions. The UNC-CH group will investigate Bayesian algorithms to incorporate a priori information from the x-ray CT image into reconstruction of the radionuclide tomogram. (3) Quantitation of the SPECT image will be improved using the correlated x-ray CT image localization, for attenuation correction, and compensation of partial-volume effects. The effect of noise propagation from the x-ray attenuation map into the SPECT reconstruction will be determined. (4) A gantry will be developed for imaging the canine thorax using the ETCT system. Compensating filters will be added to the x-ray beam path, to improve the signal-to-noise ratio of the attenuation map and to decrease the acquisition time of the radiographic image. (5) A canine model will be used to test the hypothesis that blood-flow measurements using 99mTc-MIBI and ETCT correlates with myocardial perfusion determined with radiolabelled microspheres. (6) Optimal operating configurations of ETCT will be investigated by testing alternative HPGe detectors and and improved detector collimators, leading to a design concept for a clinically usable ETCT system. These studies will evaluate the performance of the ETCT system for quantitative radionuclide studies by theoretical calculations, computer simulations, experimental measurements, and validation in an animal model of myocardial perfusion, with the long-term goal of improving radionuclide assessments of myocardial perfusion, as well as cerebral blood flow, tumor dosimetry, and tumor localization in human patients.