title: Comparison of Quantitative MRI and CT Washout Analysis for Differentiation of Adrenal Pheochromocytoma From Adrenal Adenoma.
abstract: OBJECTIVE
  The purpose of this study was to use quantitative analysis to assess MRI and washout CT in the diagnosis of pheochromocytoma versus adenoma.
  
  
  METHODS
  Thirty-four pheochromocytomas (washout CT, 5; MRI, 24; both MRI and CT, 5) resected between 2003 and 2014 were compared with 39 consecutive adenomas (washout CT, 9; MRI, 29; both MRI and CT, 1). A blinded radiologist measured unenhanced attenuation, 70-second peak CT enhancement, 15-minute relative and absolute percentage CT washout, chemical-shift signal intensity index, adrenal-to-spleen signal intensity ratio, T2-weighted signal intensity ratio, and AUC of the contrast-enhanced MRI curve. Comparisons between groups were performed with multivariate and ROC analyses.
  
  
  RESULTS
  There was no difference in age or sex between the groups (p > 0.05). For CT, pheochromocytomas were larger (4.2 ± 2.5 [SD] vs 2.3 ± 0.9 mm; p = 0.02) and had higher unenhanced attenuation (35.7 ± 6.8 HU [range, 24-48 HU] vs 14.0 ± 20.9 HU [range, -19 to 52 HU]; p = 0.002), greater 70-second peak CT enhancement (92.8 ± 31.1 HU [range, 41.0-143.1 HU] vs 82.6 ± 29.9 HU [range, 50.0-139.0 HU ]; p = 0.01), lower relative washout CT (21.7 ± 24.7 [range, -29.3 to 53.7] vs 65.3 ± 22.3 [range, 32.9-115.3]; p = 0.002), and lower absolute washout CT (31.9 ± 42.8 [range, -70.6 to 70.2] vs 76.9 ± 10.3 [range, 60.3-89.6]; p = 0.001). Thirty percent (3/10) of pheochromocytomas had absolute CT washout in the adenoma range (> 60%). For MRI, pheochromocytomas were larger (5.0 ± 4.2 vs 2.0 ± 0.7 mm; p = 0.003) and had a lower chemical-shift signal intensity index and higher adrenal-to-spleen signal intensity ratio (-3.5% ± 14.3% [range, -56.3% to 12.2%] and 1.1% ± 0.1% [range, 0.9-1.3%] vs 47.3% ± 27.8% [range, -9.4% to 86.0%] and 0.51% ± 0.27% [range, 0.13-1.1%]) (p < 0.001) and higher T2-weighted signal intensity ratio (4.4 ± 2.4 vs 1.8 ± 0.8; p < 0.001). There was no statistically significant difference in contrast-enhanced MRI AUC (288.9 ± 265.3 vs 276.2 ± 129.9 seconds; p = 0.96). The ROC AUC for T2-weighted signal intensity ratio was 0.91 with values greater than 3.8 diagnostic of pheochromocytoma.
  
  
  CONCLUSIONS
  In this study, the presence of intracellular lipid on unenhanced CT or chemical-shift MR images was diagnostic of adrenal adenoma. Elevated T2-weighted signal intensity ratio was specific for pheochromocytoma but lacked sensitivity. There was overlap in all other MRI and CT washout parameters.
authors.affiliation: 1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Nicola
authors.initials: N
authors.lastname: Schieda
authors.affiliation: 1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Abdulmohsen
authors.initials: A
authors.lastname: Alrashed
authors.affiliation: 2 Department of Anatomical Pathology, The Ottawa Hospital, The University of Ottawa, Ottawa, ON, Canada.
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Flood
authors.affiliation: 1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Karim
authors.initials: K
authors.lastname: Samji
authors.affiliation: 1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Wael
authors.initials: W
authors.lastname: Shabana
authors.affiliation: 1 Department of Medical Imaging, The Ottawa Hospital, The University of Ottawa, 1053 Carling Ave, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Matthew D F
authors.initials: MD
authors.lastname: McInnes
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging*; D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging*; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010673:Pheochromocytoma / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
keywords: CT; MRI; adenoma; adrenal; pheochromocytoma; washout