There are two main uses of Iodine-131 (131I) in medicine or medical practice.
- Diagnostic application in some procedures
- Therapy for thyroid disorders or thyroid cancer
The Iodine-131 (131I) has a radioactive half life of 8.1 days and its radiations are beta particles(b- particles) and gamma rays (g-rays). This is most widely used radioisotope in the management of hyperthyroidism and thyroid cancer and thyroid function related diagnostic procedures. There are half a dozen investigations associates with the thyroid function which involve the oral or intravenous administration of a few microCuries (mCi) of 131I. Subsequent study of the patient, either by the direct measurement of 131I deposited in the thyroid gland through measurement of 131I excreted in the urine of the patient or by assessment of radioactivity in the blood samples drawn at different time intervals after the administration of 131I. The part of the 131I retained or excreted depends on the normal, hyperthyroid or hypothyroid conditions. The uptake or excretion of 131I exhibits a diagnostic parameter. After absorption of 131I by the thyroid gland the iodine is elaborated into the thyroid hormone which is discharged in the blood. The hyperactive gland produces too much hormone which would be detected in the blood samples taken at 24 to 96 hours after the administration of radioactive iodine (131I). The measurement of the iodine content is computed from the counts of radioactivity detected in the blood samples. The radioactivity is measured as gamma rays (g-rays) by a Geiger Muller counter or it may be measured as beta particles (b-particles) by a Scintillation counter at a 'Hot Laboratory'.
The therapeutic use of Iodine-131 (131I) could be culminated through optimal doses of this radioisotope with reference to the thyroid disorder and the age and weight of the patient. There are specialized clinics at the authorized medical centers having facilities for the Nuclear Medicine and associated research.
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