title: Contrast-enhanced dynamic MRI of adrenal masses: classification of characteristic enhancement patterns.
abstract: OBJECTIVE
  This study evaluated the usefulness of dynamic MRI to differentiate various adrenal tumours.
  
  
  METHODS
  Sixty-five adrenal tumours (28 adenomas, 22 metastases, seven phaeochromocytomas, five neurogenic tumours and three tuberculous granulomas) were evaluated 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 after bolus administration of 0.1 mmol/kg Gd-DTPA.
  
  
  RESULTS
  All 28 adenomas showed peak enhancement in the early phase (< 2 min) and quick washout. Fourteen of 22 metastases showed peak enhancement in the early or middle phase (< 9 min) and slow washout. Six of seven phaeochromocytomas revealed marked peak enhancement in the early phase and little washout. All neurogenic tumours showed gradually increasing enhancement. Granulomas showed little enhancement. As a result, only 14 adrenal masses (27/65, 42%) were correctly classified according to contrast enhancement patterns. However, if we consider each type of enhancement pattern to be specific to adenoma, metastasis, phaeochromocytoma, neurogenic 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.
  
  
  CONCLUSIONS
  Dynamic MR imaging at 1.5 T is useful in the differentiation of adrenal masses. Imaging at 0.5 T with gradient-echo sequences seems less useful to distinguish adenomas from metastases.
authors.affiliation: Department of Radiology, Yamanashi Medical College, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ichikawa
authors.forename: K
authors.initials: K
authors.lastname: Ohtomo
authors.forename: G
authors.initials: G
authors.lastname: Uchiyama
authors.forename: H
authors.initials: H
authors.lastname: Fujimoto
authors.forename: K
authors.initials: K
authors.lastname: Nasu
mesh_terms: D000236:Adenoma / Q000175:diagnosis; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis* / Q000556:secondary; D000328:Adult; D000368:Aged; D005260:Female; D005682:Gadolinium; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018302:Neoplasms, Neuroepithelial / Q000175:diagnosis; D010673:Pheochromocytoma / Q000175:diagnosis; D012189:Retrospective Studies; D014375:Tuberculoma / Q000175:diagnosis
chemical_list: D005682:Gadolinium