DEVELOPMENT OF AN EMISSION-TRANSMISSION CT SYSTEM

这项研究将继续开发原型 发射-透射式计算机体层摄影(ETCT)扫描仪 双能X射线CT与放射性核素的同时采集 CT.传输和发射数据通过以下方式同时采集 单个高纯度锗(HPGE)探测器阵列，因此是 在空间和时间上都是相关的。排放的组合 使用ETCT系统传输数据可以(1)准确 排放数据的衰减校正，(2)定性关联 功能图像和形态图像，以及(3)区域的定义 感兴趣的x射线CT图像，用于精确量化 放射性核素数据。 这项建议包括6个具体目标。(1)更正将是 为限制精确度和精密度的效果而开发 定量X射线和放射性核素数据，如光子统计噪声， 散射辐射，以及能量窗的次优位置。(2) 将根据一项分包合同开发重建软件 北卡罗来纳大学教堂山分校(UNC-CH) 重建图像的质量和定量准确性 补偿不均匀的光子衰减、散射辐射和 几何系统和散射响应的空间变异模糊 功能。UNC-CH小组将研究贝叶斯算法以 将来自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)量化 利用相关X射线CT图像对SPECT图像进行改进 本地化，用于衰减校正和补偿 部分体积效应。X射线对噪声传播的影响 将衰减图转化为SPECT重建将被确定。(4)A类 将开发用于使用ETCT对狗的胸部进行成像的门架 系统。补偿滤光片将被添加到X射线光束路径，以 提高衰减贴图的信噪比并降低 射线图像的采集时间。(5)犬类模型将 用来检验这样一种假设，即血流测量使用 99mTC-MIBI和ETCT与心肌灌注的相关性 放射性标记的微球。(6)ETCT的最佳运行配置 将通过测试替代的HPGe探测器和 改进的探测器准直器，导致了一种设计概念 临床可用的ETCT系统。这些研究将评估 ETCT系统用于放射性核素定量研究的性能 理论计算、计算机模拟、实验 在心肌灌注动物模型中进行测量和验证， 长期目标是改善对核素的评估 心肌灌注，以及脑血流量，肿瘤剂量测定， 以及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.