Magnetic resonance imaging in preoperative localization of diseased parathyroid glands: a comparison with isotope scanning and ultrasonography.

The value of magnetic resonance imaging (MRI) in the preoperative localization of parathyroid glands was assessed through a comparison of the findings with those obtained by ultrasonography and isotope scanning. The localization findings in 37 patients with primary hyperparathyroidism were compared with the operative findings. The sensitivities of the three modalities as defined by the ability to detect a parathyroid adenoma were 67% (isotope scanning), 44% (ultrasonography) and 36% (MRI). The differences were not significant. The sensitivities as defined by the ability to predict the correct side of the lesion were 48% (isotope scanning) 33% (ultrasonography) and 36% (MRI). No correlation was found between the sensitivity of a given localization test and factors such as the presence of thyroid abnormalities, size of the lesion, type of lesion and preoperative calcium and parathormone levels. The low sensitivity and high cost of all three preoperative localization studies render them unnecessary in the management of uncomplicated parathyroid disease. However, if preoperative imaging is necessary, ultrasonography and isotope scanning are recommended, since MRI was not found to be superior.