OPTIMIZATION OF RCBF MEASUREMENT WITH A 3D PET SCANNER

该项目（1994年7月开始）的目标是确定一个 进行功能性脑映射研究的最佳方法， 三维PET和氧-I5水，一种用于测量 局部脑血流量（rCBF）。目前的断层扫描仪，如 GE Advance最近被NIH收购，允许3D图像采集 和重建，大大提高了扫描仪的灵敏度。 然而，图像噪声在高计数率下增加，在该高计数率下，rCBF 通常进行0- 15水的快速团注的研究。 因此，尽管对于低计数率信噪比提高 研究表明，在高计数率下，改善要少得多。作为 因此，可以使用少量的 放射性，但它是不可能的注入目前使用的 改善信号。有几个因素会影响 每mCi注射的信号，包括每mCi的放射性量 注射、注射次数以及注射的长度和类型。 研究将进行，以找到这些的最佳组合 GE Advance断层扫描仪的参数。模拟、体模和 将进行人体实验。 将进行模拟以计算大脑放射性 这是由不同的0- 15注水量和剖面引起的， 以及变化的扫描长度。此外，还将获得关于大脑的数据 先前扫描注入的0-15水的放射性/mCi 使用Scanditronix PC 2048 - 15 B断层扫描仪进行。扫描数据将 然后使用脑体模在GE Advance扫描仪上获得 充满了衰变的放射性，计数率范围， 将在扫描仪中确定每mCi的图像噪声， 扫描长度。幻影研究的结果将被他用来 估计由大脑产生的信噪比 不同扫描方案的放射性水平， 仿真。基于这些结果，人类研究将 在他们执行一个 激活特定大脑区域的功能性任务。的能力 通过以下方式确定不同方案的激活灶检测 用统计参数映射软件分析PET图像。 理想地，将确定扫描协议以优化对以下的检测： 给定放射性总量的活化灶 管理。

The goal of the project (initiated in July 1994) is to determine an optimal method for performing functional brain mapping studies with three-dimensional PET and oxygen-I5 water, a tracer used to measure regional cerebral blood flow (rCBF). Current tomographs, such as the GE Advance recently acquired by the NIH, permit 3D image acquisition and reconstruction, substantially increasing scanner sensitivity. However, image noise increases at the high count rates at which rCBF studies with bolus injections of 0-I5 water are typically performed. Thus, although the signal-to-noise ratio improves for low count rate studies, the improvement is much less at high count rates. As a result, one can perform CBF studies with smaller amounts of radioactivity, but it is not possible to inject the currently-used amounts to improve signal. There are several factors which affect the signal per mCi injected, including amount of radioactivity per injection, number of injections, and length and type of injection. Studies will he performed to find an optimal combination of these parameters for the GE Advance tomograph. Simulation, phantom, and human experiments will be performed. Simulations will be carried out to calculate the brain radioactivity that results from different 0-I5 water injection amounts and profiles, and varying scan lengths. In addition, data will be obtained on brain radioactivity per mCi of 0-15 water injected from scans previously performed with the Scanditronix PC2048-15B tomograph. Scan data will then be obtained on the GE Advance scanner using a brain phantom filled with decaying radioactivity for a range of count rates, and image noise will be determined per mCi in the scanner for specific scan lengths. The results of the phantom studies will he used to estimate the signal to noise properties resulting from the brain radioactivity levels for different scan protocols as predicted by the simulations. Based on these results, studies in humans will be performed with selected injection protocols while they perform a functional task that activates specific brain regions. The ability to detect activation foci with different protocols will be determined by analyzing the PET images with Statistical Parametric Mapping software. Ideally, a scan protocol will be determined to optimize detection of activation foci for a given total amount of radioactivity administered.