Radioimmunoassay

Radioimmunoassay (RIA) is a scientific method used to test antigens (for example, hormone levels in the blood) without the need to use a bioassay. It involves mixing known quantities of radioactive antigen (frequently labeled with gamma-radioactive isotopes of iodine attached to tyrosine) with antibody to that antigen, then adding unlabeled or "cold" antigen and measuring the amount of labeled antigen displaced.
See more at Wikipedia.org...

Radioimmunoassay /ra·dio·im·mu·no·as·say/ a highly sensitive and specific assay method that uses the competition between radiolabeled and unlabeled [more]Radioimmunoassay - Community and Resources

Noun
1. immunoassay of a substance that has been radioactively labeled
(hypernym) immunoassay, immunochemical assay

A very sensitive, specific laboratory test (assay) using radiolabeled (and unlabeled) substances in an immunological (antibody-antigen) reaction.

المقايسة المناعية الشعاعية