Riddle W R, Roselli R J, Pou N A
Department of Radiology and Radiological Sciences, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232.
J Appl Physiol (1985). 1990 Jun;68(6):2434-42. doi: 10.1152/jappl.1990.68.6.2434.
Several groups of investigators are using external detection of radiolabeled protein to study the flux of protein from plasma into the pulmonary interstitium. A basic assumption for these studies has been that the unbound (free) tracer concentration is small and insignificant. The purpose of this study is to evaluate how free tracer influences the determination of normalized slope index. A five-compartment model for the lung was used with transport equations for both unbound and bound nuclide flux. Parameters of the unbound and bound transport equations were varied to evaluate the sensitivity of normalized slope index to each parameter. The model was also compared with published protein flux data to investigate the validity of the transport model. Application of the model to external scan data provides a sensitive method for evaluating the flux of bound and unbound tracers into the pulmonary interstitium. We conclude that because the distribution volume for unbound tracer is large with respect to protein distribution volume, even a small amount of unbound tracer (2-5%) can create large errors in the determination of normalized slope index.
几组研究人员正在利用放射性标记蛋白的外部检测来研究蛋白质从血浆进入肺间质的通量。这些研究的一个基本假设是未结合（游离）示踪剂浓度很低且微不足道。本研究的目的是评估游离示踪剂如何影响标准化斜率指数的测定。使用了一个五室肺模型以及未结合和结合核素通量的传输方程。改变未结合和结合传输方程的参数，以评估标准化斜率指数对每个参数的敏感性。该模型还与已发表的蛋白质通量数据进行比较，以研究传输模型的有效性。将该模型应用于外部扫描数据，为评估结合和未结合示踪剂进入肺间质的通量提供了一种灵敏的方法。我们得出结论，由于相对于蛋白质分布体积而言，未结合示踪剂的分布体积很大，即使少量的未结合示踪剂（2 - 5%）也会在标准化斜率指数的测定中产生很大误差。
