OPTIMIZATION OF RCBF MEASUREMENT WITH A 3D PET SCANNER

本项目的目的是确定一种最佳方法， 进行三维脑功能成像研究， 正电子发射断层扫描（PET）和O-15水， 局部脑血流量（rCBF）。目前的断层扫描仪允许三个- 三维成像，大大提高了灵敏度。然而，图像 噪声在高计数率下增加，在高计数率下， 通常进行O-15水的注射。尽管图像 信噪比（S/N）在低计数率下得到改善， 注入放射性的量，在高计数时改善福尔斯下降 rates.因此，在设计脑图谱时，有几个因素很重要 实验：每次注射的放射性量， 注射和注射类型（快速推注vs.缓慢输注）。 目前正在进行人体模拟和实验， GE Advance断层扫描仪的这些参数的最佳组合。 在人体研究中，扫描数据通过静脉推注获得。 注射2.5至30 mCi的0-15水在4名受试者执行一个字 生成任务。全脑噪声等效计数（NEC）率 在注射剂量为12-15 mCi时达到峰值; 10 mCi的NEC为92%。 峰值。尽管扫描检测到一致的局灶性rCBF变化， 持续时间为60、90和120秒时，其统计学显著性降低 随着扫描时间的增加。因此，我们选择使用10 mCi进行1 min扫描 用于推注。然后，我们进行了模拟，以评估效果 在较长扫描持续时间和缓慢示踪剂输注的S/N上。图像数据 噪声作为局部放射性的函数，通过扫描 脑体模然后，使用模拟来预测组织 放射性，将观察到一个缓慢的示踪剂注入。 将测量的体模噪声数据与预测的组织数据相结合 允许计算S/N。这显示了60秒内的等效S/N 用团注扫描和用缓慢输注的单次较长扫描， 在相同的放射性注入量下。的时间段 示踪剂吸收对总积分计数的贡献更大， 慢输注而不是大剂量注射因此，研究人员可能希望 为不同类型的大脑映射自定义扫描参数 实验，同时保持推注的S/N。

The purpose of this project is to determine an optimal method for performing functional brain mapping studies with three-dimensional positron emission tomography (PET) and O-15 water, a tracer that maps regional cerebral blood flow (rCBF). Current tomographs permit three- dimensional imaging, substantially increasing sensitivity. However, image noise increases at the high count rates at which rCBF studies with bolus injections of O-15 water have typically been performed. Although the image signal-to-noise ratio (S/N) is improved at low count rates with small amounts of injected radioactivity, the improvement falls off at high count rates. Thus, several factors are important in designing brain mapping experiments: the amount of radioactivity per injection, the number of injections, and type of injection (fast bolus vs. slow infusion). Simulations and experiments in humans are being performed to find an optimal combination of these parameters for the GE Advance tomograph. In human studies, scan data were obtained with bolus intravenous injections of 2.5 to 30 mCi of 0-15 water in 4 subjects performing a word generation task. The noise equivalent count (NEC) rate for whole brain peaked at an injected dose of 12-15 mCi; 10 mCi gave an NEC of 92% of the peak value. Although consistent focal rCBF changes were detected with scan durations of 60, 90, and 120 sec, their statistical significance decreased as scan time increased. Therefore, we selected a 1 min scan using 10 mCi for bolus injections. We then performed simulations to evaluate the effect on S/N of longer scan durations with slow tracer infusions. Data on image noise as a function of local radioactivity were obtained by scanning a brain phantom. Then, simulations were used to predict the tissue radioactivity that would be observed with a slow tracer infusion. Combining the measured phantom noise data with the predicted tissue data allowed calculation of the S/N. This showed an equivalent S/N for a 60 sec scan with a bolus injection and a single longer scan with a slow infusion, given the same amount of injected radioactivity. The time over which tracer uptake contributes to the total integrated counts is greater with a slow infusion than a bolus injection. Thus, investigators may wish to customize scanning parameters for different types of brain mapping experiments while maintaining the S/N of bolus injections.