Evaluating the preoperative diagnostic value of 99mTc-MIBI/99mTcO4- dual-isotope SPECT/CT fusion imaging and ultrasonography in suspected primary hyperparathyroidism

Background: This study aimed to assess the preoperative diagnostic performance of ultrasonography (US) and ^99m Tc-MIBI/ ^99m TcO ₄ ^- dual-isotope SPECT/CT fusion imaging in primary hyperparathyroidism (PHPT) and investigate the relationship between serum parameters and parathyroid adenoma volume. Methods: A retrospective analysis was conducted on 75 patients with elevated parathyroid hormone (PTH) levels and suspected primary hyperparathyroidism between September 2023 and November 2024. All patients underwent ^99m Tc-MIBI/ ^99m TcO ₄ ^- dual-isotope SPECT/CT fusion imaging and US. Using surgical histopathology as the gold standard, the sensitivity and positive predictive value (PPV) of both imaging modalities in detecting parathyroid lesions were calculated. Additionally, a preliminary analysis was performed to assess the relationship between lesion volume and preoperative serum biochemical markers. Results: Among the 75 patients, 68 were confirmed as PHPT cases, with a total of 74 parathyroid lesions identified. As per patient-based analysis, the diagnostic sensitivities of ^99m Tc-MIBI/ ^99m TcO ₄ ^- dual-isotope SPECT/CT fusion imaging and US were 94.12% (64/68) and 86.76% (59/68), respectively, with SPECT/CT demonstrating superior sensitivity. Per lesion-based analysis revealed that SPECT/CT significantly outperformed US in both sensitivity (97.01% vs. 79.10%, P < 0.001) and PPV the (85.87% vs. 80.72%, P = 0.006). Subgroup analysis showed that in group of the classical primary hyperparathyroidism (CPHPT), SPECT/CT exhibited higher sensitivity (96.22% vs. 84.91%, P < 0.001) and PPV (94.64% vs. 82.45%, P = 0.039) compared to US, whereas no significant difference was observed in group of the normocalcemic primary hyperparathyroidism (NPHPT). Additionally, in group of the CPHPT, moderate correlations were found between lesion volume and corrected serum calcium (Cs Ca) (r = 0.435, P = 0.003) as well as PTH levels (r = 0.303, P = 0.045). Conclusion: The dual-isotope SPECT/CT fusion imaging demonstrates high diagnostic efficacy for PHPT, providing precise lesion localization and reliable preoperative guidance for surgical intervention. In patients with normocalcemia but clinical symptoms suggestive of PHPT, the combined use of Sdual-isotope SPECT/CT fusion imaging and US offers additional diagnostic value. Furthermore, the degree of elevation in serum calcium and PTH levels shows predictive potential for estimating parathyroid adenoma volume and assessing glandular metabolic activity. These biochemical markers serve as important indicators to guide clinicians in selecting appropriate candidates for dual-isotope SPECT/CT fusion imaging evaluation.