DETERMINATION OF THE PARTITION COEFFICIENT OF 0-15 LABELLED WATER

用PET和0-15 水涉及两个参数的使用，流量和分区 水的系数（p），其被定义为组织和 平衡时的血液示踪剂浓度。p的值反映了 可计算示踪剂在组织和血液中的相对溶解度 作为脑和血水含量的比值，使用published.data 这些价值观。在用于测量CBF和PET的一些方法中，这计算 值用于数学公式中，流量计算公式如下： 测量血液和组织放射性。在替代方法中， 流量和P都是从测量数据中估计的。通过这些方法， 发现p值低于从以下比率预测的值： 脑组织和血液含水量。 为了进一步解决这个问题，开发了一种直接测量p的方法 PET和0-15的水。它涉及构建放射性示踪剂注入 时间表，迅速产生和维持组织之间的平衡， 血这种方法被用来测量狒狒体内的磷。两次注射0-15 每项研究都需要水：静脉注射， 获得动脉脉冲反应，并进行8 min设计输注 由计算机控制的泵来管理。p的值计算为 从3到8分钟的组织与血液浓度的比值为0.80 ml/g（0.006 SD，n=10）。此外，用逐像素的 最小二乘法从脑和血液的完整8分钟时间过程 放射性数据;数值为0.76-0.78 ml/g。这些结果表明 在示踪剂之后短时间内用PET测量体内P 给药后的值小于该值（灰质为0.98， 全脑）基于脑和血液的体外水含量。为了 为了进一步探讨这种差异，我们将测量p的值， 狒狒用上述PET方法。

Methods of measuring regional cerebral blood flow (CBF) with PET and 0-15 water involve the use of two parameters, the flow and the partition coefficient (p) for water, which is defined as the ratio of the tissue and blood tracer concentrations at equilibrium. The value of p reflects the relative solubility of the tracer in tissue and blood and can be calculated as the ration of brain and blood water contents, using published.data for these values. In some methods for measuring CBF and PET, this calculated value is used in the mathematical formulation, and flow is calculated from measured blood and tissue radioactivity. In alternative methods, values for both flow and p are estimated from the measured data. With these methods, the value of p was found to be lower than that predicted from the ratio of brain and blood water contents. To address this issue further, a method was developed to measure p directly with PET and 0-15 water. IT involves constructing a radiotracer infusion schedule which rapidly produces and sustains equilibrium between tissue and blood. This method was used to measure p in baboons. Two injections of 0-15 water are required in each study: a blous i.v. injections from which the arterial impulse response is obtained, and an 8 min designed infusion administered by a computer-controlled pump. The value of p calculated as the ratio of the tissue to blood concentrations from 3 to 8 min was 0.80 ml/g (0.006 SD, n=10). In addition, p was estimated with a pixel-by-pixel least squares method from the full 8 min time course of brain and blood radioactivity data; values were 0.76-0.78 ml/g. These results suggest that the in vivo p as measured with PET within a short period following tracer administration is smaller than the value (0.98 for gray matter, 0.90 for whole brain) based on in vitro water contents of brain and blood. In order to further explore this discrepancy, we will measure the value of p in baboons with the above PET method.