Preoperative localization of parathyroid lesions -: Value of 99mTc-MIBI tomography and factors influencing detection

The aim of our study was to assess retrospectively the value of Tc-99m-MIBI SPECT in the localization of parathyroid lesions in primary hyperparathyroidism and to determine the impact of PTH level, age, sex, characteristics of the lesions and thyroid nodules on the sensitivity of imaging. Patients, methods: Fifty nine patients who were cured after the resection of 60 lesions (50 adenomas, 9 hyperplasias and 1 carcinoma, 9 of them in ectopy) were selected. (TcO4)-Tc-99m; early and late Tc-99m-MlBI planar images (n = 59), Tc-99m-MIBI SPECT(n = 8) and ultrasound (n = 50) performed preoperatively were analyzed. The imaging results were compared to surgical and histological findings and correlated to different factors suspected of influencing the imaging's sensitivity. Results: Sensitivity of double phase Tc-99m-MIBI/(TcO4)-Tc-99m scintigraphy was higher than that of early or late scintigraphy alone. SPECT increased the sensitivity of scintigraphy from 85% to 92% and was useful to confirm doubtful foci and to localize ectopic lesions. Ultrasound (US) had the lowest sensitivity (56%) and the highest rate of false-positive results (n = 10), but identified 2 adenomas which were not detected by scintigraphy. Combining all imaging modalities, sensitivity reached 96%. Better sensitivities were observed when age < 69 years, preoperative PTH level >= 155 pg/ml, weight of the gland >= 0.80 g and in the absence of thyroid nodules. US was more influenced by these factors than scintigraphy. Conclusion: Combination of US, double-phase Tc-99m-MIBI/(TcO4)-Tc-99m planar scintigraphy and SPECT is the most accurate method for the detection of parathyroid lesions and should be performed before minimally invasive surgery, especially when PTH level is low, in older patients and in cases of multinodular goiter.