THE DIAGNOSTIC USE OF I132*†

Abstract

THE physical characteristics of I¹³¹ have made it an almost ideal isotope for use in the study, diagnosis and treatment of diseases of the thyroid. There are a few situations, however, in which it might be desirable to utilize a radioisotope of iodine with a shorter half-life. The difficulty in using short-lived isotopes in other than their sites of production has precluded general distribution of isotopes with a half-life of less than 10 or 12 hours. I¹³², which has desirable beta and gamma radiation and a 2.33-hour halflife is eminently suitable for certain studies of thyroid disease, and recently a method has been devised so that it may be shipped many miles and used for several weeks (1). Briefly, tellurium¹³² decays by beta emission with a half-life of 77 hours into I¹³². The half-life of Te¹³², the parent, determines the amount of I¹³² that may be recovered, so that the effective half-life of the available I¹³² is 77 hours. Furthermore, simple means of separation of tellurium and iodine have been devised (2). The present report describes the practical application of I¹³² in some preliminary studies of thyroid function in man.