BACKGROUND: Primary hyperparathyroidism is often caused by parathyroid adenomas (PAs), which can be ectopic (EPAs) or intrathyroidal (ITPAs). Accurate localization is crucial for effective surgical intervention. This study aimed to determine the detection rate of four-dimensional multidetector computed tomography (4D-MDCT), ultrasonography (US), and technetium 99 m sestamibi scintigraphy (MIBI) in detecting EPAs and ITPAs. Additionally, we explored the role of ultrasound-guided fine-needle aspiration (US-FNA) and evaluated correlations between parathyroid hormone (PTH) levels, adenoma size, and detection performance. METHODS: We retrospectively reviewed the records of 28 patients with 29 EPAs and 27 patients with 27 ITPAs who underwent 4D-MDCT, US (including cine Doppler US and US-FNA), and/or MIBI at our institution. Data were collected on demographics, laboratory values, imaging findings, and intraoperative findings. The detection rate was calculated for each imaging modality and their combination. Logistic regression models were used to assess the relationship between PTH level, adenoma size, and detection performance. RESULTS: The detection rate of EPAs was 96% for 4D-MDCT, 97% for MIBI, and 46% for US. The detection rate of ITPAs was 96% for US, 65% for 4D-MDCT, and 58% for MIBI. Combined multimodality imaging with results concordant between two or more modalities achieved an overall detection rate of 87%. For ITPAs, smaller PA size was associated with significantly worse MIBI detection performance (p <
0.05). The PTH level was not associated with detection performance. CONCLUSIONS: Our study highlights the superior detection rate of 4D-MDCT and MIBI for EPAs and US for ITPAs. Combining imaging modalities enhances the diagnostic detection rate.