In vivo relaxation behavior of liver compounds at 7 Tesla, measured by single-voxel proton MR spectroscopy.
OBJECTIVE
To assess the proton T1 and T2 relaxation of in vivo hepatic water, choline and lipid resonances with possible J-coupling behavior of lipids in healthy volunteers at 7 Tesla (T).


METHODS
Relaxation measurements were conducted on corn oil phantoms and on the hepatic tissue of 11 healthy volunteers at 7 T using a surface coil and a STEAM sequence. T1 's were determined by monoexponential fitting, and T2 's by both monoexponential and enhanced-exponential fitting (empirically designed to consider J-coupling of lipid resonances).


RESULTS
In vivo T1 's at 7 T were estimated as follows: water (4.70 ppm), 1362 ± 83 ms; methyl- (0.90 ppm), 1026 ± 162 ms; methylene- (1.30 ppm), 514 ± 25 ms; α-olefinic- (2.02 ppm), 488 ± 220 ms; α-carboxyl- (2.24 ppm), 476 ± 89 ms; diacyl- (2.77 ppm), 479 ± 260 ms group of lipid chains; and choline compounds (3.22 ppm), 1084 ± 52 ms. The T2 's calculated with enhanced fitting were as follows: water, 15 ± 2 ms; methyl-, 34 ± 10 ms; methylene-, 41 ± 8 ms; α-olefinic-, 44 ± 19 ms; α-carboxyl-, 39 ± 15 ms; diacyl-, 44 ± 5 ms group of lipid chains; and choline compounds, 32 ± 9 ms.


CONCLUSIONS
An accurate knowledge of in vivo relaxation and J-coupling behavior will significantly improve the quantification of an extended number of resolved liver metabolites at 7 T.
MR Center of Excellence Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Austria.
Martin
M
Gajdošík
Marek
M
Chmelík
Ivica
I
Just-Kukurová
Wolfgang
W
Bogner
Ladislav
L
Valkovič
Siegfried
S
Trattnig
Martin
M
Krššák
D000328:Adult; D001834:Body Water / Q000737:chemistry*; D002794:Choline / Q000032:analysis / Q000737:chemistry*; D005260:Female; D006801:Humans; D008055:Lipids / Q000032:analysis / Q000737:chemistry*; D008099:Liver / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
D008055:Lipids; D002794:Choline
7 T; J-coupling; STEAM; hepatic lipids; magnetic resonance spectroscopy; relaxation times