LOCALIZATION OF PARATHYROID ENLARGEMENT - EXPERIENCE WITH TC-99M METHOXYISOBUTYLISONITRILE AND TL-201 SCINTIGRAPHY, ULTRASONOGRAPHY AND COMPUTED-TOMOGRAPHY

Technetium-99m methoxyisobutylisonitrile (MIBI), like thallium-201, ha s recently been introduced as a myocardial perfusion agent and is now also showing very promising results in parathyroid scintigrapy. The re sults of Tl-201/Tc-99m-pertechnetate and Tc-99m-MIBI/Tc-99m-pertechnet ate subtraction scintigraphy, ultrasonography and computed tomography are presented in a series of 43 patients operated on for hyperparathyr oidism. All four imaging modalities were confirmed to be reliable, sci ntigraphy being the most accurate. Sensitivities ranged from 81% to 95 %, that of Tc-99m-MIBI being the highest. Moreover this tracer, which has more favourable physical and also biochemical properties, yielded images of superior quality. This allowed localization of the lesion by visual inspection only in as many as 86% of the patients with positiv e Tc-99m-MIBI/Tc-99m-pertechnetate subtraction scintigraphy. We believ e that the higher sensitivity, superior image quality and lower cost o f Tc-99m-MIBI imaging will make Tc-99m-MIBI the new radiopharmaceutica l of choice for parathyroid scintigraphy (when one takes into account the stability of labelling with large activities it is possible to per form three or four cardiac studies together with one parathyroid scint igraphic examination using one lyophililzed vial).