ee Ty ee hae eee em et ee Ai a vent ade Ee . -5cervical spine, or larynx and fluoroscopy of the larynx or eso the thyroid gland may be exposed to a fraction of a roentgen u several roentgens. These are frequent procedures, and to date However, of cancer of the thyroid have been attributed to such exposures systematic effort to determine such a relationship has not been made to our knowledge, b. Therapeutic X-ray In radiation treatment of hyperthyroidism, the thyroi gland may be exposed to doses of several thousand roentgens. This proced re has been carried out on thousands of patients, and carcinoma of the thyr id is an extremely rare complication. Another practice, no longer in common use, is to treat sup enlarged thymus glands in infants and children by exposing the and neck to doses of 100 r to 600 r or more of X-ray. When lar ports, particularly those placed posteriorly, were used, the th often received the full depth dose from the primary X-ray beam. exposures of the thyroid may result from X-ray treatment of enl cal lymph nodes or skin diseases. Subsequent studies of these both retrospective and prospective, by several authors, have di small but significant incidence of thyroid cancer in excess of rate as determined by comparison with control groups of sibling indicates that the thyroid gland in children is susceptible to induction by radiation at relatively high doses. Evidence at 1 is incomplete. . 5. osedly pper chest e treatment roid gland Similar rged cervi- atients, closed a he expected . This Exposure to Iodine-131 a. Diagnostic Procedures The use of iodine-131 was introduced into clinical me icine about 25 years ago, and for 15 years it has been widely used in a var ety of diagnostic procedures. Most of these diagnostic procedures uti ize between 5 to 100 microcuries of iodine-131, and most of the retained do e concentrates in the thyroid. No cases of thyroid cancer induction ha e been reported in the patients who have undergone these procedures. b. . yw we VOL Therapeutic Procedures The principal uses of iodine-131 are in the treatment of hyperthyroidismand inthe management of some cases of thyroid cance . The latter cases must be exteed from present consideration since t e radia- 3. tions were acting on tissues already cancerous. There is littl evidence at hand that any of the treatments for hyperthyroidism has prod thyroid cancer, although doses have ranged from a few thousand ads upward. Ablative doses would in effect rule out the possibility of tumo induction. Sstaffurth, J. S.: Thyroid Cancer After 131-I Therapy for Thyrdtoxicosis. Brit. J. Radiol.39:471-473, 1966 IDOE ARCHIVES