407841 APARTADO DEL ACTA RADIOLOGICA INTERAMERICANA VOLUMEN VII N° 3--f a ( 1957 P>xc L| Radioiodine Uptake Measurement MARSHALL BRUCER, M. D.1 URING the past decade radioiodine upDrake measurements have become a very popular and widely used procedure. Currently the largest portion of the total number of shipments of radioisotopes that are made from Oak Ridge are radioiodine. This totals a little less than one curie per month. It is estimated that about two thirds of about G000 shipments per month are ultimately used for thyroid radioiodine uptake measurements. About 1800 physicians are doing thyroid radioiodine studies in the United States alone. The procedure is therefore an important one but its reliability has been questioned. At a meeting in Oak Ridge in 1953, a group of internists discussed the validity of these measurements and set up a committee to study the problem. This is known as the Thyroid Uptake Calibration Committee of ORINS. The committee set out initially to answer one question: Is there a significant variation in thyroid uptage measurements as currently perfomed throughout the world? Even before the surveywas complete, the answer to this question was obvious. Variation in thyroid uptake measurements among laboratories is significant. This paper is a report on the survey and the extension of the committee’s work toward a methodof calibration. There are many reasons for believing that measurements of thyroid uptake might show considerable variation. Almost every physi- clan is using a different combination of standards, instruments, distances, techniqués, and formulas for measuring thyroid uptake. The standards currently in use range from point sources to milk-bottle-sized containers. The instruments used range from Geiger-Muller end-window tubes hastily connected with out- moded scalers to the newestscintillation crystals on automatic scanners. When the various methods used for calculating thyroid uptake are surveyed, there should be no question of variation of results. The surprising thing is thar there is any useful unanimity of opinion. 1 Chairman, The Medical Division Oak Ridke Instituteof Nuclear Studies Oak Ridge, Tennessee. (Under Contract with the United States Atomic Energy Comission.) ®