Diagnostic Accuracy of 4D CT in Detecting Parathyroid Adenoma Compared With Ultrasound and Sestamibi SPECT/CT in Primary Hyperparathyroidism: A Retrospective Study

Background The accurate preoperative localization of parathyroid adenomas is crucial for minimally invasive parathyroidectomy (MIP) in primary hyperparathyroidism (PHPT). This study assessed the diagnostic performance of four-dimensional computed tomography (4D CT) in detecting parathyroid adenomas, compared with ultrasound (USG) and technetium methoxy isobutyl isonitrile single photon emission computed tomography (99mTc-sestamibi SPECT/CT). Methods We retrospectively analyzed 53 patients with biochemically confirmed PHPT who underwent all three preoperative imaging modalities, followed by parathyroidectomy from January 2020 to January 2025. Imaging findings were validated against intraoperative localization, histopathology, and intraoperative parathyroid hormone (PTH) dynamics. Multi-gland diseases were excluded. Sensitivity, positive predictive value (PPV), and concordance were calculated. Percentage arterial enhancement (PAE) was analyzed as a radiological marker. Results The mean age was 42.7 ± 14.7 years, with 29 (54.7%) women. Forty-nine (88.7%) patients had typical adenomas, three (0.05%) had carcinoma, and one (0.01%) had an atypical adenoma. The majority of lesions (24, 45%) were located in the right inferior parathyroid gland, followed by the left inferior (16, 30%). Overall, preoperative imaging was able to localize 50/53 (94.3%) lesions correctly. 4D CT correctly localized 45 lesions, outperforming USG and 99mTc-sestamibi SPECT/CT by identifying eight and 12 additional lesions, respectively. Sensitivity was highest for 4D CT (88.2%), followed by 99mTc-sestamibi SPECT/CT (82.4%) and USG (72.6%), with all three modalities showing high PPV (>94%). Among small adenomas (<20 mm), 4D CT demonstrated superior detection (21/21, 100%) compared to USG (16/21, 76.2%) and 99mTc-sestamibi SPECT/CT (15/21, 71.4%). Dynamic enhancement patterns on 4D CT distinguished adenomas from mimickers. However, applying a fixed PAE cutoff (128.9%), as previously proposed, yielded limited sensitivity (75%) and specificity (31.6%). Conclusion 4D CT outperformed USG and 99mTc-sestamibi SPECT/CT in localizing parathyroid adenomas in PHPT and was particularly useful when USG or 99mTc-sestamibi SPECT/CT results were inconclusive. While all three modalities showed high positive predictive value, 4D CT localized additional lesions missed by others. Its dynamic contrast patterns effectively differentiated adenomas from mimics. However, the utility of a fixed PAE cutoff was limited by protocol-dependent variability, indicating a need for tailored thresholds.