Hepatic disorders are often associated with changes in the concentration of phosphorus31 (31P) metabolites. Absolute quantification offers a way to assess those metabolites directly but introduces obstacles, especially at higher field strengths (B0 7T).
To introduce a feasible method for in vivo absolute quantification of hepatic 31P metabolites and assess its clinical value by probing differences related to volunteers' age and body mass index (BMI).
Four healthy volunteers included in the reproducibility study and 19 healthy subjects arranged into three subgroups according to BMI and age. Phantoms containing 31P solution for correction and validation.
Phaseencoded 3D pulseacquire chemical shift imaging for 31P and singlevolume 1H spectroscopy to assess the hepatocellular lipid content at 7T.
A phantom replacement method was used. Spectra located in the liver with sufficient signaltonoise ratio and no contamination from muscle tissue, were used to calculate following metabolite concentrations: adenosine triphosphates ( and ATP); glycerophosphocholine (GPC); glycerophosphoethanolamine (GPE); inorganic phosphate (Pi); phosphocholine (PC); phosphoethanolamine (PE); uridine diphosphateglucose (UDPG); nicotinamide adenine dinucleotidephosphate (NADH); and phosphatidylcholine (PtdC). Correction for hepatic lipid volume fraction (HLVF) was performed.
Differences assessed by analysis of variance with Bonferroni correction for multiple comparison and with a Student's ttest when appropriate.
The concentrations for the young lean group corrected for HLVF were 2.56 0.10 mM for ATP (mean standard deviation), ATP: 2.42 0.15 mM, GPC: 3.31 0.27 mM, GPE: 3.38 0.87 mM, Pi: 1.42 0.20 mM, PC: 1.47 0.24 mM, PE: 1.61 0.20 mM, UDPG: 0.74 0.17 mM, NADH: 1.21 0.38 mM, and PtdC: 0.43 0.10 mM. Differences found in ATP levels between lean and overweight volunteers vanished after HLVF correction.
Exploiting the excellent spectral resolution at 7T and using the phantom replacement method, we were able to quantify up to 10 31Pcontaining hepatic metabolites. The combination of 31P magnetic resonance spectroscopy imaging data acquisition and HLVF correction was not able to show a possible dependence of 31P metabolite concentrations on BMI or age, in the small healthy population used in this study.