[In vivo proton MR spectroscopy of normal liver parenchyma: technique and results].

PURPOSE

To analyze the proton magnetic resonance spectroscopic data ( (1)H MRS) of normal liver parenchyma with regard to age, sex, body mass index and location in the liver.

MATERIALS AND METHODS

45 healthy volunteers age 24 to 65 years were examined with an optimized single-voxel (1)H MRS using a 1.5-T scanner. A spin echo sequence with a TR of 1500 ms and a TE of 135 ms was used, allowing in-phase detection of the choline signal. Weak water suppression was achieved using a chemical shift selective suppression (CHESS) technique. Each examination included the measurement of three voxels with a voxel size of 18 x 18 x 18 mm (3) in different areas of the liver. The volunteers were divided into different age-based groups (young: < or = 44 years; older: > or = 44 years), BMI (normal weighted: < 25 kg/m (2); obese: > 25 kg/m (2)) and sex.

RESULTS

In the acquired spectra different lipid (e. g. [CH (2)] (n)), choline, glutamine, glutamate and glycogen-glucose-complex resonances were detected. The analysis of the spectra, however, only focused on the concentrations of choline and (CH (2)) (n) and the relative concentrations of the choline-to-(CH (2)) (n)-ratios. In the older volunteers the relative concentration of the choline-to-(CH (2)) (n)-ratio was significantly decreased by 0.213 +/- 0.193 in comparison to the younger subjects (p = 0,031). Further statistical analysis confirmed a significant decrease of the choline-to-(CH (2)) (n)-ratio by 0.223 +/- 0.180 in obese volunteers compared to volunteers of a standard weight (p = 0,016). The significant difference between the choline-to-(CH (2)) (n)-ratio in female versus male volunteers was calculated with an increase of 0.483 +/- 0.172 (p = 0,000). The location of the voxel in the liver parenchyma did not yield a significant difference in the choline-to-(CH (2)) (n)-ratio.

CONCLUSION

The analysis of the proton liver MRS of healthy volunteers indicated a significant difference in the choline-to-(CH (2)) (n)-ratio depending on age, sex, and BMI with a confidence interval of 95 %. The different choline-to-(CH (2)) (n)-ratio could be the result of the body fat distribution depending on age and sex and also of the increased fat portion of the body in obese volunteers.