Addition of arterial-phase contrast-enhanced CT to 99mTc-sestamibi SPECT/CT improves pre-operative localisation of parathyroid adenomas

Preoperative localisation of parathyroid adenomas is essential for effective surgical planning in primary hyperparathyroidism (PHPT) to reduce operating time and complications. The most used imaging modalities for this purpose are ultrasound (US), 99m Tc-sestamibi single photon emission computed tomography-computed tomography (SPECT/CT), four-dimensional computed tomography (4D CT) and 18 F-choline positron emission tomography/computed tomography (PET/CT). Up to 90% of adenomas are detected on the arterial phase of 4D-CT. Conventional 99m Tc-sestamibi SPECT/CT is performed with unenhanced CT. Our centre has added a contrast arterial phase to our 99m Tc-sestamibi SPECT/CT protocol to improve diagnostic accuracy. This retrospective study evaluated the additional diagnostic value of arterial phase CT (A-CECT) to 99m Tc-sestamibi SPECT/CT to detect parathyroid adenomas. The objective of this study was to compare the localisation accuracy of arterial phase CT, 99m Tc-sestamibi SPECT/CT, and their combination. Secondary objective is to examine the utility of 18 F-choline PET/CT in diagnostically challenging cases. We performed a retrospective review of 73 PHPT patients who had arterial phase CT, 99m Tc-sestamibi SPECT/CT and underwent surgery between March 2023 and May 2025. Imaging outcomes were correlated with intraoperative and postoperative biochemical markers. 20 patients underwent 18 F-choline PET/CT for indeterminate diagnostic cases. Arterial phase CT, 99m Tc-sestamibi SPECT/CT and their combination correctly identified respectively 84.9%, 75.6% and 84.9% of adenomas. A-CECT detected 8 adenomas that were missed with 99m Tc-sestamibi SPECT/CT. 99m Tc-sestamibi SPECT/CT did not detect adenomas missed with A-CECT. All adenomas correctly identified with 99m Tc-sestamibi SPECT/CT were also detected on A-CECT. In the subgroup of 20 patients with indeterminate or complex imaging requiring 18 F-Choline PET/CT, achieved 80.6% sensitivity (25/31 adenomas localised), and identified 5 false-positive glands. The addition of arterial phase CT to 99m Tc-sestamibi SPECT/CT improved diagnostic accuracy for pre-surgical localisation of parathyroid adenomas.