Lipid/water ratio of bone marrow measured by phase-encoded proton nuclear magnetic resonance spectroscopy

Proton NMR spectroscopy (spatially resolved) at 0.7 Tesla with a whole body superconducting magnet was performed on bone marrow from human lumbar spine to measure the lipid/water ratio. Phase-encoded proton spectroscopy was performed by using (1) a spin-echo sequence with selective 90 degrees and 180 degrees rf pulses on the Z and X axes; (2) 64 different phase encodes along the Y axis; and (3) echo acquisition with no gradient. The lipid/water ratios also were measured by the Folch chemical extraction technique. The set of phase-encoded spectra obtained from the spine demonstrates the chemical difference between the vertebral disk (large water peak and no lipid peak) and the marrow (smaller water peak and detectable lipids). Lipid/water ratios were lower than the chemically measured ratios. The phase-encoded proton spectroscopic technique presented in this study allowed rapid acquisition of localized spectra from the bone marrow in each of three vertebral bodies of the intact human spine. This technique provided a measure of the mobile lipid/water ratio weighted by relaxation times.