Liver steatosis: concordance of MR imaging and MR spectroscopic data with histologic grade.
OBJECTIVE
To determine if the concordance of magnetic resonance (MR) imaging and MR spectroscopic data with histologic measures of steatosis is affected by histologic magnification level, tissue heterogeneity, or assessment of tissue area versus that of hepatocytes.


METHODS
This study was institutional review board approved and HIPAA compliant. Written informed consent was obtained. In- and out-of-phase MR imaging and MR spectroscopic measures of steatosis were compared in 33 patients with nonalcoholic fatty liver disease and in 15 healthy volunteers. Concordance of MR imaging and MR spectroscopic data with histologic findings was assessed for (a) histologic examination at standard (×40 and ×100) versus high magnification (×200 and ×400), (b) heterogeneity and homogeneity of livers, and (c) percentage of tissue and hepatocytes that contained lipids. Evaluations included linear regression and Fisher exact tests.


RESULTS
In- and out-of-phase MR imaging and MR spectroscopic data were well correlated (R2=0.93) and generally concordant with histologic measures. Patients in whom MR fat fractions were higher than expected compared with steatosis grades at standard magnification histologic examination were upgraded significantly more often when high magnification was used than were the remaining patients (100% [10 of 10] vs 47% [7 of 15], P<.01). MR imaging and MR spectroscopic data of homogeneous livers were significantly more likely than those of heterogeneous livers to be concordant with steatosis grades when high magnification was used (81% [13 of 16] vs 47% [8 of 17], P<.05). For all patients, percentage of fat in tissue was lower than that in hepatocytes, which affected individual patients, but not the overall correlation.


CONCLUSIONS
MR imaging and MR spectroscopic data were generally concordant with histologic measures of steatosis. Discordance between them may reflect differences in magnification at histologic examination and in liver heterogeneity.
Department of Radiology and Biomedical Imaging, Center for Molecular and Functional Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Box 0946, San Francisco, CA 94107, USA. susan.noworolski@ucsf.edu
Susan M
SM
Noworolski
Maggie M
MM
Lam
Raphael B
RB
Merriman
Linda
L
Ferrell
Aliya
A
Qayyum
D000328:Adult; D001706:Biopsy; D005234:Fatty Liver / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012720:Severity of Illness Index