Thyroid imaging agents: a comparison of I-123 and Tc-99m pertechnetate.

Abstract
99mTc pertechnetate and 123I were used to perform thyroid scanning in 122 patients with history or clinical evidence of thyroid disease. Thyroid scans were abnormal in all patients, while thyroid palpation was abnormal in all but 19. The quality of thyroid imaging was similar with both agents in 42%, better with 123I in 18% and better with 99mTc in 7%. In the remaining 33% (40 cases), there were discrepancies between 99mTc and 123I images. The most frequent discrepancies were hot or warm lesions on 99mTc scans that were cold or normal on 123I scans. Neither 99mTc nor 123I is always superior to the other as a thyroid imaging agent.