The added value of 123I-MIBG SPECT/CT in the diagnosis of pheochromocytoma compared to planar imaging

Objectives 123I-MIBG (MIBG) scintigraphy is the standard approach for the diagnosis of pheochromocytoma (PCT). The aim of this study was to assess the significance and the added value of MIBG SPECT/CT imaging for the detection and diagnosis of pheochromocytoma in comparison to planar imaging.

Methods A total of 24 patients (15 men, median age: 56 y/o) with suspected pheochromocytoma underwent MIBG scan. All patients received planar scans 4 and 24 h as well as SPECT/CT 24 h after injection. Histological findings and clinical follow ups served as reference standard. The sensitivity, specificity, NPV and PPV of MIBG SPECT/CT were compared with planar images.

Results After performing MIBG scan 14 patients have been operated. The median follow up was 27 months. The sensitivity, specificity, PPV and NPV of MIBG SPECT/CT and planar images were 100%, 80 %,75 %,100% ; 56%, 100%, 79% , 100% respectively. Compared to planar images, in 18/24 cases (75%) SPECT/CT could provide additional diagnostic information considering the anatomic localization of the hot spots, especially in two cases with paraganglioma.

Conclusions SPECT/CT increases the sensitivity of the scan dramatically but because of FP findings in the adrenals the specificity of MIBG SPECT/CT is lower compared to planar imaging. However, SPECT/CT is a useful modality to exactly localize the adrenal glands and especially the extra-adrenal findings.