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