The advantages and limitations of radionuclide techniques in the patient with vascular disease an overview.

Radionuclides have been used to objectively assess the circulation for a half century (1). Techniques employing radioactivity were developed to provide true tracers which do not affect the process being measured. Radionuclides provide a unique sensitivity with the ability to detect and quantitate several thousand molecules. Ultimately, this inherently quantitative ability may prove most useful. Relative distribution of activity and hence relative blood flow can be readily determined using particles which are completely trapped by the capillary bed during a single circulatory transit (2). Actual quantitative measurements of flow per unit weight can also be determined either by measuring clearance of intraarterial injection of a diffusible indicator such as