Absolute Quantification of Phosphor-Containing Metabolites in the Liver Using 31 P MRSI and Hepatic Lipid Volume Correction at 7T Suggests No Dependence on Body Mass Index or Age.

Abstract

BACKGROUND:

Hepatic disorders are often associated with changes in the concentration of phosphorus-31 (31 P) metabolites. Absolute quantification offers a way to assess those metabolites directly but introduces obstacles, especially at higher field strengths (B0 ≥ 7T).

PURPOSE:

To introduce a feasible method for in vivo absolute quantification of hepatic 31 P metabolites and assess its clinical value by probing differences related to volunteers' age and body mass index (BMI).

STUDY TYPE:

Prospective cohort.

SUBJECTS/PHANTOMS:

Four healthy volunteers included in the reproducibility study and 19 healthy subjects arranged into three subgroups according to BMI and age. Phantoms containing 31 P solution for correction and validation.

FIELD STRENGTH/SEQUENCE:

Phase-encoded 3D pulse-acquire chemical shift imaging for 31 P and single-volume 1 H spectroscopy to assess the hepatocellular lipid content at 7T.

ASSESSMENT:

A phantom replacement method was used. Spectra located in the liver with sufficient signal-to-noise ratio and no contamination from muscle tissue, were used to calculate following metabolite concentrations: adenosine triphosphates (γ- and α-ATP); glycerophosphocholine (GPC); glycerophosphoethanolamine (GPE); inorganic phosphate (Pi ); phosphocholine (PC); phosphoethanolamine (PE); uridine diphosphate-glucose (UDPG); nicotinamide adenine dinucleotide-phosphate (NADH); and phosphatidylcholine (PtdC). Correction for hepatic lipid volume fraction (HLVF) was performed.

STATISTICAL TESTS:

Differences assessed by analysis of variance with Bonferroni correction for multiple comparison and with a Student's t-test when appropriate.

RESULTS:

The concentrations for the young lean group corrected for HLVF were 2.56 ± 0.10 mM for γ-ATP (mean ± standard deviation), α-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.

DATA CONCLUSION:

Exploiting the excellent spectral resolution at 7T and using the phantom replacement method, we were able to quantify up to 10 31 P-containing hepatic metabolites. The combination of 31 P magnetic resonance spectroscopy imaging data acquisition and HLVF correction was not able to show a possible dependence of 31 P metabolite concentrations on BMI or age, in the small healthy population used in this study.

LEVEL OF EVIDENCE:

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:597-607.

• Authors: Lorenz Pfleger, Martin Gajdošík, Peter Wolf, Sabina Smajis, Paul Fellinger, Andre Kuehne, Patrik Krumpolec, Siegfried Trattnig, Yvonne Winhofer, Michael Krebs, Martin Krššák, Marek Chmelík
• Journal: Journal of magnetic resonance imaging : JMRI (J Magn Reson Imaging) Vol. 49 Issue 2 Pg. 597-607 (02 2019) ISSN: 1522-2586 [Electronic] United States
• PMID: 30291654 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2018 The Authors. Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Chemical References

• Phosphorus

Topics

• Adult
• Age Factors
• Aged
• Body Mass Index
• Calibration
• Female
• Healthy Volunteers
• Heart Ventricles (diagnostic imaging)
• Humans
• Liver (diagnostic imaging, metabolism)
• Liver Diseases (metabolism)
• Magnetic Resonance Imaging (methods)
• Magnetic Resonance Spectroscopy
• Male
• Middle Aged
• Phantoms, Imaging
• Phosphorus (analysis)
• Prospective Studies
• Reproducibility of Results