Comparison of unenhanced CT and chemical shift MRI in evaluating lipid-rich adrenal adenomas.
OBJECTIVE
Our aim was to evaluate adrenal adenomas in patients who underwent both unenhanced CT and chemical shift MRI to determine if adenomas can be characterized with MRI when the findings of CT are indeterminate.


METHODS
Between January 1999 and June 2003, 40 patients (42 adrenal masses) underwent unenhanced CT and chemical shift MRI and were retrospectively analyzed. Hounsfield units, adrenal-to-spleen chemical shift ratio, and signal-intensity index were obtained for each adrenal mass. Qualitative analysis for loss of signal in each adrenal mass on the opposed-phase images was also performed by two reviewers and compared with the quantitative analyses. A lipid-rich adenoma was diagnosed if the mass measured equal to or less than 10 H, had an adrenal-to-spleen chemical shift ratio of less than 0.71, and had a signal-intensity index of greater than 16.5% or if the mass fulfilled two of the preceding criteria and had follow-up imaging without change.


RESULTS
The sensitivities and specificities for diagnosing a lipid-rich adenoma using the qualitative, adrenal-to-spleen chemical shift ratio, signal-intensity index, and unenhanced CT attenuation analyses were 92% (33/36) and 17% (1/6), 100% (36/36) and 100% (6/6), 100% (36/36) and 67% (4/6), and 78% (28/36) and 83% (5/6), respectively. Twenty-eight (67%) lipid-rich adenomas measured equal to or less than 10 H, had an adrenal-to-spleen chemical shift ratio of less than 0.71, and had a signal-intensity index of greater than 16.5%. Eight masses (19%) measured greater than 10 H but had an adrenal-to-spleen chemical shift ratio of less than 0.71 and a signal-intensity index greater than 16.5% and were unchanged at follow-up.


CONCLUSIONS
Eight (62%) of 13 adrenal adenomas measuring greater than 10 H on unenhanced CT were definitively characterized with chemical shift MRI.
Israel
Gary M
GM
Department of Radiology, NYU Medical Center, 560 First Ave., Ste. HW 202, New York, NY 10016, USA. gary.israel@med.nyu.edu
Korobkin
Melvyn
M
Wang
Chun
C
Hecht
Elizabeth N
EN
Krinsky
Glenn A
GA
D000236:Adenoma / Q000737:chemistry / Q000175:diagnosis*; D000310:Adrenal Gland Neoplasms / Q000737:chemistry / Q000175:diagnosis*; D000368:Aged; D005260:Female; D006801:Humans; D050356:Lipid Metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed