TECHNETIUM-99M-MIBI SCINTIGRAPHY OF THYROID-NODULES IN AN ENDEMIC GOITER AREA

Technetium-99m-methoxyisobutylisonitrile (MIBI) was introduced for myo cardial imaging as an alternative to Tl-201. According to biodistribut ion studies, MIBI also accumulates in tile thyroid gland. The aim of t his study was to find out which thyroid nodules retain MIBI and whethe r preoperative evaluation of malignancy is possible, Methods Single in jection, dual-phase (30 min and 2 hr) thyroid scintigraphy with Tc-99m -MIBI was performed on 62 patients who showed a cold nodule on previou sly performed Tc-99m scintigraphy. MIBI scans were considered positive if there was a clear tracer retention in the late 120-min image compa red to the early 30-min image. Sonographic examination and fine-needle aspiration biopsy, guided by ultrasonography, was also done on each p atient. In the following days and weeks, all patients underwent surger y. Results: Histopathological diagnoses revealed a total of 12 thyroid carcinomas, five were MIBI positive and seven MIBI negative. Out of 2 7 patients with thyroid adenomas (nine microfollicular, ten follicular , eight oxyphilic), 18 were MIBI positive and nine MIBI negative. Ther e was no MIBI retention on the scans of 22 patients with degenerative changes in the goiter and the one with Hashimoto's disease. Conclusion : These results indicate that MIBI accumulation and retention is not s pecific for thyroid malignancy. Indeed, all evidence points to the fac t that a positive MIBI scan is more likely to indicate thyroid adenoma than a malignant tumor.