Addition of Preoperative Ultrasound to 4DCT Increases Radiologist Confidence in Identifying Hyperfunctioning Parathyroid Glands

Background and purpose 4D CT (4DCT) is a key imaging technique for preoperative localization of parathyroid adenomas in primary hyperparathyroidism. Ultrasound (US) is frequently added with the assumption that it enhances diagnostic performance. This study aimed to determine whether incorporating US into a 4DCT-based evaluation improves diagnostic accuracy and to assess its impact on radiologists' diagnostic confidence.Materials and methods In this retrospective study, we reviewed 80 patients with primary hyperparathyroidism who underwent both 4DCT and US followed by curative parathyroidectomy. Each case was reviewed twice, once with 4DCT alone and once with 4DCT plus US, by different neuroradiologists who recorded lesion location and diagnostic confidence using a 5-point Likert scale. Localization accuracy was determined by comparing imaging findings with operative and pathology results. Diagnostic performance was assessed on per-patient and per-lesion bases, with subgroup analyses evaluating gland location, thyroid characteristics, streak artifact, lesion size, and presence of goiter. Paired statistical tests compared performance between modalities.Results Among 94 abnormal glands, sensitivity increased modestly with the addition of US (88.3%-91.5%) without statistical significance, and accuracy remained high for both approaches. Radiologist confidence was higher in the combined 4DCT plus US group compared with the 4DCT-alone group. Although the combined technique increased high-confidence true-positives, it also increased high-confidence false-positives. This reduced the positive predictive value of high-confidence calls in several subgroups. The addition of US to 4DCT provided the greatest benefit for inferior glands and larger lesions, whereas the trade-off between improved sensitivity and reduced positive predictive value was most pronounced in technically challenging scenarios, including smaller lesions and patients with goiter.Conclusions In this cohort, adding US to 4DCT did not significantly improve localization accuracy but did substantially increase radiologist confidence.