Evaluation of colloids for RES function studies

Much of the basic physiology of the RES has been elucidated in animal models by observing the clearance rates and gross and microscopic localization of a variety of radioactive and nonradioactive particles and emulsions. The functional capacity of the RES has been evaluated in animals and man in excellent investigations using 131I-labeled microaggregated albumin. This type of study, however, accounts for a very small fraction of the medical use of radiocolloids. Likewise, radiocolloids are used infrequently in cancer therapy but may be useful as a relatively localized radiation source following intracavitary or interstitial injection in certain cancer patients. By far the largest use of radiocolloids in nuclear medicine is for medical diagnosis. Liver imaging, for instance, is a primary diagnostic test for many problems in gastroenterology, oncology, and infectious diseases. Well over a million diagnostic studies of the RES are performed annually. Thus the current evaluation of radiocolloids is largely an evaluation of the diagnostic or potential diagnostic agents used in nuclear medicine. A rather large variety of colloids and radioactive labels have been used or considered