Early planar and early SPECT Tc-99m sestamibi imaging: can it replace the dual-phase technique for the localization of parathyroid adenomas by omitting the delayed phase?

Purpose: To evaluate whether an early protocol (EP) (early planar and early SPECT) with Tc-99m sestamibi could demonstrate the delayed image of the established dual-phase scintigraphy unnecessary without any decrease in sensitivity for the localization of parathyroid adenomas.

Materials And Methods: A study was carried out in 80 consecutive patients with primary hyperparathyroidism (65 women; mean age, 61.8±14.2 years). Final diagnosis by surgery was possible in 79 patients and confirmed parathyroid adenoma in 76 patients, 1 hyperplasic gland in 1 patient, 2 hyperplasic glands in 1 patient, and differentiated thyroid carcinoma in another patient. Ten minutes after intravenous injection of 740 MBq (20 mCi) of Tc-99m sestamibi, a planar image followed by a SPECT and a 2 to 3 hours delayed planar image were acquired. Two sets of images were evaluated, one without (EP) and the other with the delayed image (dual-phase protocol [DPP]). An abnormality rating of 0 to 4 was given to each set and was compared with the final diagnosis.

Results: When any focal uptake, no matter the intensity, was considered positive, that is setting the threshold in the abnormality rating 1, 71 of the 76 adenomas were correctly localized by DPP and EP (sensitivity: 93.4%).

Conclusions: The delayed planar image could be omitted without any loss in sensitivity for the localization of parathyroid adenomas, and therefore EP could replace DPP.