Interpretation of Tc-99m sestamibi parathyroid SPECT-CT scans made easy for better surgical outcomes in patients with primary hyperparathyroidism

Isis W Gayed,1 Ron J Karni,2 David Q Wan,1 Jeena M Varghese,3 Kelly L Wirfel,3 Kyoung S Won,4 Usha A Joseph1 1Nuclear Medicine Section, Department of Diagnostic and Interventional Imaging, 2Department of Otorhinolaryngology, Head and Neck Surgery, 3Department of Internal Medicine – Endocrinology, Diabetes and Metabolism, Medical School at Houston Health Science Center, Houston, TX, USA; 4Department of Nuclear Medicine, Keimyung University Dongsan Medical Center, Daegu, South Korea Objective: This study aims to evaluate the accuracy of Tc-99m sestamibi parathyroid scan (SPS) with single-photon emission computerized tomography/computerized tomography (SPECT/CT) in patients with primary hyperparathyroidism after optimizing the interpretation of the scans with a systematic and simple method for localization of the abnormal parathyroid gland.Materials and methods: Consecutive patients, who underwent SPS followed by surgical intervention, were included. Data were collected retrospectively including patients’ demographics, serum calcium and parathyroid hormone (PTH) levels, SPS findings, and surgical and pathological findings. Our optimized systematic method of interpretation of SPS starts by reviewing initial and 3 hours delayed planar images; subsequently we reviewed coronal and axial SPECT/CT images. A simple clockwise localization of the abnormal gland in relation to the trachea and its level in relation to the thyroid in a cranio-caudal level facilitates intraoperative localization of parathyroid adenomas.Results: A total of 53 patients were included; 9 males and 44 females with an average age of 58.3±14 years. The average preoperative serum calcium and PTH were 10.5 mg/dL and 165.4 pg/m, respectively. The median interval between the scan and operative resection was 50 days. Our SPS interpretation method correlated perfectly with the surgical finding in 48/53 patients (90.6%); it was on the correct side of the surgical finding but not the exact location in 3/53 (5.7%) and nonlocalizing in 2/53 (3.7%). The average intraoperative PTH after resection of the adenoma was 39.7 pg/mL.Conclusion: Our optimized method for interpretation of SPS demonstrated high accuracy with good surgical outcomes. Keywords: parathyroid scan, Tc-99 sestamibi, primary hyperparathyroidism, SPECT-CT, parathyroid adenoma