CONTRAST-ENHANCED DYNAMIC MRI OF ADRENAL MASSES - CLASSIFICATION OF CHARACTERISTIC ENHANCEMENT PATTERNS

Objective: This study evaluated the usefulness of dynamic MRI to diffe rentiate various adrenal tumours. Materials and Methods: Sixty-five ad renal tumours (28 adenomas, 22 metastases, seven phaeochromocytomas, f ive neurogenic tumours and three tuberculous granulomas) were evaluate d with gadolinium-enhanced dynamic MRI (13 at 0.5 T, 52 at 1.5 T), In this technique, a series of 12 sequential images (gradient-echo images at 0.5 T and spin-echo images at 1.5 T) were obtained up to 21 min af ter bolus administration of 0.1 mmol/kg Gd-DTPA. Results: All 28 adeno mas showed peak enhancement in the early phase (<2 min) and quick wash out, Fourteen of 22 metastases showed peak enhancement in the early or middle phase (<9 min) and slow washout. Six of seven phaeochromocytom as revealed marked peak enhancement in the early phase and little wash out. All neurogenic tumours showed gradually increasing enhancement, G ranulomas showed little enhancement, As a result, only 14 adrenal mass es (27/65, 42%) were correctly classified according to contrast enhanc ement patterns, However, if we consider each type of enhancement patte rn to be specific to adenoma, metastasis, phaeochromocytoma, neurogeni c tumour and tuberculous granuloma respectively, 56 of the 65 adrenal masses (86%) could be classified. Seven of the indistinguishable nine tumours were performed at 0.5 T system using gradient-echo sequences. Conclusion: Dynamic MR imaging at 1.5 T is useful in the differentiati on of adrenal masses, Imaging at 0.5 T with gradient-echo sequences se ems less useful to distinguish adenomas from metastases.