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
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
Barth JD, Bakker WH, Hennemann G. Discrepancies Between Iodine and Technetium Thyroid Scintigraphy. JAMA. 1978;240(5):463-464. doi:10.1001/jama.1978.03290050053019