Diagnostic imaging in patients with paragangliomas. Computed tomography, magnetic resonance and MIBG scintigraphy comparison.

OBJECTIVE: We compared iodine-131 metaiodobenzylguanidine (MIBG), computed tomography (CT) and magnetic resonance (MR) imaging studies in 40 patients with suspected or proven paragangliomas. PATIENTS: 21 patients were studied during the initial evaluation, while 19 were evaluated after surgery for paragangliomas. Furthermore, in 18 patients with benign (n = 10) or malignant (n = 8) tumors, MIBG uptake, MR signal intensity ratios (SIR) and CT parameters were analyzed.
RESULTS: In patients studied during the initial evaluation, CT and MR had a significant (p < 0.05) higher diagnostic sensitivity (100% for both) compared to MIBG (82%); conversely, MIBG showed a higher specificity (100%) compared to CT and MR (50% for both); the accuracy of MIBG (86%), CT and MR (91% for both) were similar. In patients evaluated after surgery, MIBG and MR had slightly better sensitivity (85% for both) compared to CT (77%). MIBG showed again better specificity (100%) than CT and MR (83% for both); the accuracy of MIBG, MR and CT were respectively 90%, 84% and 79%. While no significant differences were observed in MR SIR and CT findings between benign and malignant tumors, MIBG uptake was significantly higher in malignant compared to benign lesions (p < 0.03).
CONCLUSIONS: Our results suggest that CT and MR are particularly useful in the initial evaluation of patients with suspected paragangliomas. MIBG should be recommended during the post-surgical follow-up of such patients since recurrent, malignant or extra-adrenal disease frequently occur. Finally, while MR SIR and CT features are not able to distinguish malignant paragangliomas from benign tumors, MIBG uptake is higher in malignant lesions compared to benign tumors providing a diagnostic criterion to differentiate these lesions.