The role of 18F-FDG PET/CT and single isotope 99mTc-tetrofosmin scintigraphy combined with SPECT in diagnosis of multiple endocrine neoplasia type 1 syndrome

Abstract

We present a case of a 47-year-old woman with type 1 multiple endocrine neoplasia, primary hyperparathyroidism, insulinoma, and nonfunctioning pituitary adenoma. In July 2017, the patient was referred to the Department of Nuclear Medicine of St George University Hospital in Plovdiv for a PET/CT scan because of persistent hypoglycemic episodes and high serum insulin levels. A whole-body PET/CT examination was performed 65 min after intravenous application of 188 MBq 18F-FDG on a hybrid PET/CT scanner (Biograph mCT 64, Siemens). We detected a low metabolically active lesion 10 mm in diameter (SUVmax - 2.00), located below the left thyroid lobe suspicious for parathyroid adenoma. In the remaining scanned areas there were no PET/CT data for other areas with increased glucose metabolism with malignant characteristics that could be associated with the underlying disease.  For further characterisation of the lesion, two months later we performed a single-isotope dual-phase 99mTc-tetrofosmin scintigraphy combined with an early SPECT technique on a SPECT gamma camera (SYMBIA E DUAL). The examination visualized a zone of hyperfixation located dorsally to the caudal portion of the left thyroid lobe associated with a hyperfunctioning parathyroid adenoma. This case allowed us to compare two nuclear medicine modalities with different equipment and radiopharmaceuticals – PET/CT with 18F-FDG and single-isotope dual-phase 99mTc-tetrofosmin scintigraphy combined with an early SPECT in one and the same patient. Different factors can explain the acquired different diagnostic information.