IN VIVO RADIONUCLIDE QUANTITATION USING EMISSION CT

定量单光子发射计算机断层扫描(SPECT)已经被 主要受探测到的光子数量不足的限制 投射、体内衰减、包含散乱 投影中的光子，以及准直器响应随 距离。该项目的长期目标是：1)增加 通过使用新的采集几何结构检测到的光子数，以及2) 开发和评估SPECT的统一重建方法 使用统计贝叶斯公式。锥形光束准直(CB)可以 导致探测到的光子数量增加了三倍 具有类似分辨率的平行束(PB)准直器 特点。贝叶斯图像处理(BIP)可以包括 先验信源分布的信息，泊松性质 测量的投影数据以及其他先验信息 关于移位可变的点扩散函数。已过滤 反投影(FBP)因其具有实用的优点而得到广泛的应用 具有快速的计算速度；然而，BIP提供了更多 精准重建。其他统计估计值，如最大 似然(ML)和最大熵(MAXENT)可直接从 贝叶斯公式。该项目将评估锥束SPECT使用 FBP和BIP正在接近。一种有效的收购蒙特卡罗模型 几何形状将被用来确定系统响应矩阵。接收机 将使用操作员特征(ROC)曲线来评估病变 CB、扇束(FB)和PB SPECT的可探测性。趋同 BIP的特性将与ML和MAXENT进行定量比较， 作为迭代次数的函数。模拟和实验获得的 将使用模体投影来评估BIP以量化 活度、活度比、分辨率和噪声锥束SPECT。有耐心的 将对CB、FB和平行孔准直获得的扫描进行比较。 早期的结果表明，锥束准直提供了潜在的 改进的SPECT成像。一种统一的BIP算法的应用 同时补偿衰减、散射和准直器 不同的版本应该会进一步提高 重建，并为SPECT的根本性进展提供基础 量化。

Quantitative single photon emission compute tomography (SPECT) has been limited mainly by the inadequate number of detected photons in the projections, attenuation within the body, the inclusion of scattered photons in the projections, and variations in collimator response with distance. The long term objectives of this project are: 1) to increase the number of detected photons by using new acquisition geometries, and 2) to develop and evaluate a unified reconstruction methodology for SPECT using a statistical Bayesian formulation. Cone beam collimation (CB) can result in a three-fold increase in the number of detected photons, compared with a parallel beam (PB) collimator having similar resolution characteristics. Bayesian image processing (BIP) can integrally include the a priori source distribution entropy information, the Poisson nature of the measured projection data, as well as other a priori information concerning the shift-variant point spread function. Filtered backprojection (FBP) is widely used since it offers the practical advantage of fast computational speed; however, BIP offers the potential for a more accurate reconstruction. Other statistical estimators, such as maximum likelihood (ML) and maximum entropy (MAXENT) are directly derivable from the Bayesian formulation. This project will evaluate cone beam SPECT using FBP and BIP approaches. A validated Monte Carlo model of the acquisition geometry will be used to determine the system response matrix. Receiver operator characteristic (ROC) curves will be used to evaluate lesion detectability for CB, fan beam (FB), and PB SPECT. The convergence characteristics of BIP will be quantitatively compared with ML and MAXENT, as a function of iteration number. Simulated and experimentally acquired projections of phantoms will be used to evaluate BIP for quantification of activity, activity ratios, resolution, and noise cone beam SPECT. Patient scans acquired with CB, FB, and parallel hole collimation will be compared. Early results indicate that cone beam collimation offers the potential for improved SPECT imaging. The application of a unified BIP algorithm that simultaneously compensates for attenuation, scatter, and collimator variations should offer further improvements in the accuracy of the reconstruction, and provide the basis for fundamental advances in SPECT quantification.