Effects of intravenous gadolinium administration and flip angle on the assessment of liver fat signal fraction with opposed-phase and in-phase imaging.
OBJECTIVE
To assess the effects of intravenous gadolinium (Gd) and flip angle (FA) on liver fat quantification by opposed-phase (OP) and in-phase (IP) imaging.


METHODS
Our Institutional Review Board (IRB) approved this Health Insurance Portability and Accountability Act (HIPAA)-compliant, retrospective, clinical study. We identified 79 patients in whom abdominal OP and IP gradient-echoes were obtained at 1.5T before and after Gd administration. All 79 patients were imaged at high FA (> or =70 degrees ); 57 were also imaged at low FA (< or =20 degrees ). Fat signal fraction (FSF) was calculated from pre- and post-Gd liver images for each subject and FA using the formula, FSF = (S(IP) - S(OP))/2S(IP), where S(IP) and S(OP) are the OP and IP signal intensities, respectively. The dataset pairs (pre-Gd vs. post-Gd; high-FA vs. low-FA) were compared using linear regression analysis.


RESULTS
Before Gd, FSF was significantly greater at high FA than at low FA, with regression parameters (slope/intercept) of 1.27*/0.02*, where * indicates P value <0.01. After Gd, FSF was similar at high and low FA (0.99/-0.00). Gd administration caused an FA-dependent reduction in FSF, larger at high FA (0.68*/-0.03*) than at low FA (0.94, -0.01*).


CONCLUSIONS
FSF by OP-IP imaging is highly dependent on FA before Gd, but this dependency is eliminated after administration of Gd. Gd appears to minimize the effect of T1-weighting and may improve the accuracy of liver fat quantification.
Yokoo
Takeshi
T
Department of Radiology, University of California-San Diego, 408 Dickinson Street, San Diego, CA 92122, USA.
Collins
Julie M
JM
Hanna
Robert F
RF
Bydder
Mark
M
Middleton
Michael S
MS
Sirlin
Claude B
CB
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005234:Fatty Liver / Q000175:diagnosis*; D005260:Female; D005682:Gadolinium / Q000008:administration & dosage*; D006801:Humans; D007275:Injections, Intravenous; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
D005682:Gadolinium