gms | German Medical Science

Background: Technetium-99m methoxyisobutylisonitrile (⁹⁹Tc-MIBI) is a well-established agent for myocardial perfusion imaging and the preoperative localization of hyperparathyroidism. In addition ⁹⁹Tc-MIBI scintigraphy is used in the evaluation of thyroid nodules suspicious for malignancy. Because several studies show conflicting results in predicting malignancy of thyroid nodules we report on our experience with ⁹⁹Tc-MIBI in the diagnostic work up of thyroid pathologies.

Materials and methods: In this retrospective study, we evaluated data of patients who underwent preoperative ⁹⁹Tc-MIBI scintigraphy and thyroid surgery in our hospital. All ⁹⁹Tc-MIBI scans were performed by only one referring physician. The uptake of ⁹⁹Tc-MIBI was compared to normal thyroid tissue. Nodules with an increased uptake were considered MIBI positive. Surgery included single node excision, hemithyroidectomy, subtotal and total thyroidectomy. All specimens resected were histopathologically evaluated and preoperative ⁹⁹Tc-MIBI results were compared to the histopathological reports.

Results: A total of 115 patients, 86 women and 29 men, were included in the study. In 71 patients (62%) ⁹⁹Tc-MIBI was positive. Of these only 11 patients (15%) had thyroid malignancy. In 4/44 patients (9%) with a ⁹⁹Tc-MIBI negative scan histopathology showed a malignant tumor. The sensivity and specifity in detecting malignant thyroid nodules were 69% and 39%, the positive predictive value was 12% and the negative predictive value was 91%.

Conclusion: ⁹⁹Tc-MIBI is not appropriate to definitely predict malignancy in thyroid nodules. However a ⁹⁹Tc-MIBI negative scan is highly predictive for benign thyroid pathologies.