Diagnostic performance of 4D-CT in cases of Primary hyperparathyroidism with negative SPECT 99mTc Sestamibi scan

1162 Introduction: Diagnostic performance of 4D-CT in cases of Primary hyperparathyroidism with negative SPECT 99mTc Sestamibi scan Background: Pre-surgical localization of hyperfunctioning parathyroid gland in cases of Primary hyperparathyroidism have shown improved clinical outcome [1]. 99mTc Sestamibi scans has been widely used for this purpose, however, it has moderate rate of false negative results [2] which limits its efficacy and makes treatment challenging. Lately, 4D-CT has emerged as a highly accurate modality in evaluation of hyperfunctioning parathyroid glands. We assessed the performance of 4D-CT for localizing pathologically proved parathyroid adenoma/hyperplasia in scintigraphycally negative patients with hyperparathyroidism. Materials and Methods: A total of 18 cases with Primary hyperparathyroidism were retrospectively reviewed between January 2018 and October 2019 (5 males, 13 females, age 52 to 87), with PTH levels ranging from 81-1615 pg/mL). All cases had negative SPECT 99mTc Sestamibi scan (scans were performed with intravenous injection of 20-25 mCi of 99mTc Sestamibi, followed by SPECT imaging; 8 out of 18 cases had additional SPECT-CT imaging). Patients also had preoperative 4D-CT imaging for localization purpose. Correlation of results were made with postsurgical histopathology and sensitivity, specificity and accuracy of 4D-CT imaging was determined. Results: In total 30 parathyroid glands were removed surgically, of which 28 were localized by 4D-CT. Histopathology of 22/30 glands demonstrated hyperplasia, 2/30 glands showed parathyroid adenoma, 4/30 glands demonstrated normal glandular formation and 2/30 glands were determined to be lymph nodes. All patients were followed up till date. 11/18 patients (61%) had improvement clinically and biochemically. Additionally, 4D-CT facilitated detection of multigland involvement, coexistent thyroid pathology and provided superior accuracy in patients with prior neck surgery. Conclusions: 4D-CT outperformed SPECT 99mTc Sestamibi imaging by accurately localizing hyperfunctioning parathyroid gland/adenoma with sensitivity of 92.3% and specificity of 80%. Overall clinical improvement was seen in 61% of cases. Hence, this modality may allow for more robust diagnostic accuracy than traditional nuclear scintigraphy imaging techniques. References: 1.Concise parathyroidectomy: The impact of preoperative SPECT 99mTc sestamibi scanning and intraoperative quick parathormone assay, Sally E Carty, MD, FACS, M.Jonathan Worsey, MBBS, FRCS(Engl), Mohamed A Virji, MD, PhD, Manuel L Brown, MD, Charles G Watson, MD, FACS DOI:https://doi.org/10.1016/S0039-6060(97)90215-4. 2.The false negative technetium-99m-sestamibi scan in patients with primary hyperparathyroidism: correlation with clinical factors and operative findings. Merlino JI1, Ko K, Minotti A, McHenry CR, Am Surg. 2003 Mar;69(3):225-9; discussion 229-30.