title: Low yield of chemical shift MRI for characterization of adrenal lesions with high attenuation density on unenhanced CT.
abstract: OBJECTIVE
  To investigate the threshold unenhanced CT density of adrenal nodules at which further evaluation with chemical shift MRI is unlikely to be definitive and therefore not helpful in further characterizing some indeterminate adrenal lesions.
  
  
  METHODS
  Retrospective evaluation of 44 adrenal lesions imaged with unenhanced CT and chemical shift MRI and followed for at least 1 year. Qualitative and quantitative assessment of signal loss on chemical shift MRI was performed. Adenomas were diagnosed if the lesion measured equal or less than 10 HU on unenhanced CT; on MRI a SI index greater than 16.5% or adrenal:spleen chemical shift ratio less than 0.71 was considered diagnostic of adenoma.
  
  
  RESULTS
  31.8% (14/44), 47.7% (21/44), and 20.5% (9/44) of the adrenal lesions had an unenhanced CT attenuation density ≤10, 10-30, and >30 HU. Adrenal lesions with an unenhanced CT density 10-30 and >30 HU had a 76.2% (16/21) and a 33.3% (3/9) chance of being categorized as an adenoma using MRI SI index, respectively.
  
  
  CONCLUSIONS
  Adrenal lesions with unenhanced attenuation CT density >30 HU had a 66.6% of remaining indeterminate even after evaluation with chemical shift MRI.
  
  
  CONCLUSIONS
  Chemical shift MRI is reasonable for evaluating adrenal lesions with an unenhanced CT attenuation density less than 30 HU. The likelihood of chemical shift MRI detecting signal loss in lesions CT density greater than 30 HU, however, is low.
authors.affiliation: Massachusetts General Hospital Imaging, 55 Fruit Street, Boston, MA, 02114, USA.
authors.forename: Ronnie
authors.initials: R
authors.lastname: Sebro
authors.forename: Rizwan
authors.initials: R
authors.lastname: Aslam
authors.forename: Valdair Francisco
authors.initials: VF
authors.lastname: Muglia
authors.forename: Z Jane
authors.initials: ZJ
authors.lastname: Wang
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Westphalen
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000175:diagnosis*; D000311:Adrenal Glands / Q000000981:diagnostic imaging / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D055815:Young Adult