Parathyroid imaging by Tc/Tl scintigraphy

Between 1983 and 1988, a total of 224 99mTc/201Tl subtraction parathyroid scintigraphy studies were performed in 214 patients (136 women, 78 men, average age 50, +/- 15 years) with clinical and biochemical signs of hyperparathyroidism. Of the 214 patients, 113 underwent surgical exploration, and 127 benign parathyroid lesions were found, 48 of which were correctly localized by scintigraphy (sensitivity 38%). We detected 30 of 71 adenomas (42%) and 18 of 56 hyperplastic glands (32%). Additionally, the scans localized 2 of 6 parathyroid carcinomas in 5 patients. Overall, 83 parathyroid lesions were missed. There was no significant difference in size between detected and missed lesions. Previous neck surgery (65 of 113 patients) was not a significant detriment to scan sensitivity; but correct detection did depend upon the anatomic site of the lesion: 39% (n = 109) were detected in the typical site, 44% (n = 9) intrathyroidal, and 11% (n = 9) in the anterior and/or superior mediastinum. In conclusion, these results show only limited value for this 99mTc/201Tl subtraction scintigraphy protocol as the initial procedure for localization of abnormal parathyroid tissue prior to surgical exploration.