Comparison of Technetium-99m-MIBI, Technetium-99m-Tetrofosmin, Ultrasound and MRI for Localization of Abnormal Parathyroid Glands

Abnormal parathyroid tissue can be identified by radionuclide imaging with either 99m Tc-MIBI or 99m Tc-tetrofosmin. This study compared the relative sensitivity of these two agents to localize parathyroid hyperplasia and adenoma. Methods: Twenty patients with primary (n = 9) or secondary (n = 11) hyperparathyroidism were studied with 99m Tc-MIBI and 99m Tc-tetrofosmin parathyroid imaging, ultrasonography and MRI. Radionuclide images of the neck were acquired 10 min and 2-3 hr after radiopharmaceutical injection. The images were visually evaluated for abnormal focal areas of increased tracer localization in the neck and mediastinum. A parathyroid gland/normal thyroid tissue activity ratio (referred to as the P/T uptake ratio) was calculated for each positive scan. Results: Of the 46 parathyroid glands surgically explored, the overall sensitivity and specificity of MIBI imaging were 83% and 83% (38/46); tetrofosmin imaging 87% and 83% (40/46); ultrasonography 78% and 40% (36/46); and MRI 80% and 60% (37/46), respectively. Both radiopharmaceuticals performed well in the nine patients found to have adenoma. The sensitivity and specificity of MIBI imaging were 100% and 100% (9/9); tetrofosmin imaging 100% and 100% (9/9); ultrasonography 78% and 67% (7/9); and MRI 100% and 100% (9/9), respectively. In the 37 glands with hyperplasia, MIBI imaging had a sensitivity of 78% and specificity of 75%; tetrofosmin imaging 84% and 75%; utrasonography 78% and 43%; and MRI 73% and 60%, respectively. Conclusion: All imaging techniques localized abnormal parathyroid glands. The radiotracers have equal sensitivity for the localization of abnormal parathyroid glands. The sensitivity of these tracers was high as compared to ultrasonography or MRI.