Respiratory motion-corrected proton magnetic resonance spectroscopy of the liver.
OBJECTIVE
To develop a post-processing, respiratory-motion correction algorithm for magnetic resonance spectroscopy (MRS) of the liver and to determine the incidence and impact of respiratory motion in liver MRS.


METHODS
One hundred thirty-two subjects (27 healthy, 31 with nonalcoholic fatty liver disease and 74 HIV-infected with or without hepatitis C) were scanned with free breathing MRS at 1.5 T. Two spectral time series were acquired on an 8-ml single voxel using TR/TE=2500 ms/30 ms and (1) water suppression, 128 acquisitions, and (2) no water suppression, 8 acquisitions. Individual spectra were phased and frequency aligned to correct for intrahepatic motion. Next, water peaks more than 50% different from the median water peak area were identified and removed, and remaining spectra averaged to correct for presumed extrahepatic motion. Total CH(2)+CH(3) lipids to unsuppressed water ratios were compared before and after corrections.


RESULTS
Intrahepatic-motion correction increased the signal to noise ratio (S/N) in all cases (median=11-fold). Presumed extrahepatic motion was present in 41% (54/132) of the subjects. Its correction altered the lipids/water magnitude (magnitude change: median=2.6%, maximum=290%, and was >5% in 25% of these subjects). The incidence and effect of respiratory motion on lipids/water magnitude were similar among the three groups.


CONCLUSIONS
Respiratory-motion correction of free breathing liver MRS greatly increased the S/N and, in a significant number of subjects, changed the lipids/water ratios, relevant for monitoring subjects.
Noworolski
Susan M
SM
Department of Radiology and Biomedical Imaging, University of California-San Francisco, San Francisco, CA, USA. sue@radiology.ucsf.edu
Tien
Phyllis C
PC
Merriman
Raphael
R
Vigneron
Daniel B
DB
Qayyum
Aliya
A
D000328:Adult; D000465:Algorithms; D016477:Artifacts; D005234:Fatty Liver / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D006526:Hepatitis C / Q000175:diagnosis* / Q000378:metabolism; D006801:Humans; D008055:Lipids / Q000032:analysis*; D008099:Liver / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D008055:Lipids; D011522:Protons