Impact of acquisition timing and background uptake on [131I]meta-iodobenzylguanidine SPECT/CT interpretation in pheochromocytoma and adrenal adenoma

Objective Pheochromocytoma is an intra-adrenal sympathetic paraganglioma that carries an inherent potential for metastasis, although such events are seldom encountered. Its clinical symptoms and signs are nonspecific. Early and precise identification is essential for effective clinical management and treatment; however, the diagnostic accuracy of pheochromocytoma is influenced by multiple factors, and studies addressing these influences remain limited. This study aimed to investigate the impact of different imaging backgrounds and acquisition times on the diagnostic performance of [ 131 I]meta-iodobenzylguanidine ([ 131 I]MIBG) single‐photon emission computed tomography (SPECT)/computed tomography (CT) in differentiating pheochromocytoma from adrenocortical adenoma. Methods This retrospective study included 67 patients who had not undergone adrenal surgery before enrollment, underwent [ 131 I]MIBG SPECT/CT, and subsequently received surgical treatment within 2–5 months after imaging, with all lesions histopathologically confirmed. [ 131 I]MIBG SPECT/CT scans were acquired for each patient at different acquisition time points and under varying imaging conditions. Clinical characteristics and imaging data were collected and analyzed to evaluate the diagnostic performance of [ 131 I]MIBG SPECT/CT in differentiating pheochromocytoma. Results Significant differences in semiquantitative values of [ 131 I]MIBG SPECT/CT were observed for the same lesion across different imaging backgrounds and acquisition times ( P < 0.0001). The highest diagnostic performance for pheochromocytoma was achieved when the liver was used as the imaging background and images were acquired 48 h postinjection, yielding an area under the curve greater than 0.95. In addition, other imaging parameters also contributed to improving diagnostic accuracy. Conclusion Optimizing imaging background and acquisition time significantly enhances the diagnostic performance of [ 131 I]MIBG SPECT/CT for pheochromocytoma, facilitating timely and effective patient management.