IN VIVO RADIONUCLIDE QUANTITATION USING EMISSION CT

活体放射性核素活度测定的定量准确性 使用单光子发射计算机断层扫描(SPECT)受以下因素影响 收购和计算过程中涉及的物理和计算过程 重建过程。其中最重要的因素是 如下：1)散射光子的检测，2)初级光子的衰减 光子，3)有限空间分辨率和几何胶合响应 与距离有关，以及4)可用检测器利用不足 区域。尽管已经开发了一阶方法来补偿 在这些因素中，这些方法还没有得到正确的评估 更复杂的源几何形状，如临床成像中出现的。 长期目标包括评估量化的 SPECT的准确性和开发新的和改进的方法 尽量减少限制SPECT定量的因素。具体来说，我们 建议开发一个统一的数学重建过程，需要 考虑到SPECT获取中的内在不足 投射数据。该算法是基于逆蒙特卡罗的使用 (IMOC)生成概率矩阵所需的技术，以关联 测量的投影数据到重建图像。 非一致衰减和散射几何的一般类将 使用精确的蒙特卡罗模拟来定量描述 允许非均匀衰减和三维散射 几何图形。这些模拟将使用仔细执行的 幻影实验。一阶和二阶的有效性 补偿方式将会确定。 改进的SPECT准直器概念，包括轴向会聚和锥形 将使用计算机建模和可行性来评估梁的几何形状 实验。将开发三维重建方法 对于锥形梁几何图形。 临床应用将包括使用 多门控SPECT血池图像和I-123的SPECT分布 脑内标记的羟基碘丙二胺(HIPDm)。建议数 调查为长期的进步提供了一种平衡的方法 SPECT的采集和重建方法，以及实用性 在量化临床应用方面的改进。

The quantitative accuracy of determining in vivo radionuclide activities using single photon emission computed tomography (SPECT) is influenced by the physical and computational processes involved in the acquisition and reconstruction processes. Among the most important factors are the following: 1) detection of scattered photons, 2) attenuation of primary photons, 3) finite spatial resolution and geometric collumator response with distance, and 4) inadequate utilization of the available detector area. Although first-order methods have been developed to compensate for some of these factors, these methods have not been adquately evaluated for more complex source geometries such as occur in clinical imaging. The long term objectives include the assessment of the quantitative accuracy of SPECT and the development of new and improved approaches to minimize the factors limiting SPECT quantification. Specifically, we propose to develop a unified mathematical reconstruction process that takes into consideration intrinsic inadequacies in the acquisition of SPECT projecton data. This algorithm is based on the use of Inverse Monte Carlo (IMOC) techniques to generate the probability matrix required to relate the measured projection data to the reconstructed image. General classes of nonuniformly attenuating and scattering geometries will be quantitatively characterized using accurate Monte Carlo simulations that allow for nonuniform attenuation and three dimensional scattering geometries. These simulations will be validated using carefully executed phantom experiments. The effectiveness of first- and second-order compensation methods will be determined. Improved SPECT collimator concepts including axially converging and cone beam geometries will be evaluated using computer modeling and feasibility experiments. Three dimensional reconstruction methods will be developed for the cone beam geometry. Clinical applicaitons will include evaluations of ventricular volumes using multigated SPECT blood pool images, and SPECT distributions of I-123 labeled hydroxyiodopropyldiamine (HIPDm) within the brain. The proposed investigations offer a balanced approach for long term advancements in SPECT acquisition and reconstruction methods, as well as practical improvements in quantitative clinical applications.