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August 4, 1978

Discrepancies Between Iodine and Technetium Thyroid Scintigraphy

JAMA. 1978;240(5):463-464. doi:10.1001/jama.1978.03290050053019

FOR ROUTINE thyroid scanning, the sodium pertechnetate Tc 99m scan is preferred over sodium iodide I 131 scanning in many laboratories. Radiation safety for the patient and reduction of costs are the primary reasons for this.

Discrepancies can occur between iodine scans (iodine I 123 and131I) as compared with99mTc scans: eg, a nodule appearing cold on an iodine scan may be warm with a99mTc scan.1-3 To give other examples of discrepancies that can occur when99mTc is compared with iodine, we present two cases.

Report of Cases 

Case 1.—  A 69-year-old woman was admitted to the hospital for regulation of her diabetes mellitus. She had been insulin-dependent for the past 20 years. At the physical examination, a nodule that was 3 cm in diameter was palpable in the lower part of the right lobe of the thyroid. The nodule was not connected