Diagnosis of Parathyroid Adenoma Using Tc-99m /Tc-99m Mibi Scintigraphy and Neck Ultrasonography

Full text: The aim of this study was to evaluate a protocol for imaging parathyroid adenomas based on 99mTc/99mTc-MIBI scintigraphy and neck ultrasonography. We selected 18 patients (17 women, 1 man), aged 35-73 years (mean 53.7 years), with elevated parathyroid hormone (range 53.4- 1930 pg/ml, mean 303.7±433.3) and normo or hypercalcemia. US was performed before scintigraphy in 15 cases and after in other 3 cases, using a transducer for small parts. Before scintigraphy 6 patients underwent neck surgery for thyroid or parathyroid diseases. We perform double tracer scintigraphy with 60-70 MBq of 99mTc and 500-740 MBq of 99mTc-MIBI followed by substraction. 20 minutes after 99mTc injection we obtained the anterior image of neck and mediastinum. With patient motionless on the table we injected 99mTc-MIBI. 20 minutes after we obtained another anterior image for 10 min. The images were processed by successive substractions. The wash-out images were obtained 2 hours p.i. Results: In 3 cases scintigraphy and US detected a parathyroid adenoma, one of them being an ectopic inferior adenoma, undetectable by surgeon after an other adenoma excised. All parathyroid adenomas were confirmed postoperative by histopathological exam. In 6 cases we detected thyroid diseases (multinodular goitre, Graves disease, single thyroid nodule) and in 1 case a metastatic cervical lymph node. In 5 patients examined postoperative, scintigraphy was negative in 2 cases and detected nodular goitres in 3. In one patient US and scintigraphy were discordant. The rest 3 patients (2 of them with nodules on US examination) were positive on scintigraphy. Evolution after surgery (3 patients) or medical therapy (12 patients) make us to believe that in this cases parathyroid were simple hypertrofic. In 9 cases the substraction wasn't performed because patient has moved. Conclusion: Double tracer scintigraphy and neck US are able to detect normally located or ectopic parathyroid adenomas and to assist surgeon in rapid and complete excision of these. In parathyroid hyperplasia scintigraphic detection are difficult, especially in the presence of thyroid nodules. Metastatic cervical lymph nodes are responsible for false positive results. (author)