Tissue lipid quantification using narrow bandwidth magnetic resonance imaging with a presaturation pulse

Area of Science:

• Medical Imaging
• Biophysics
• Biochemistry

Background:

• Chemical-shift artifact arises in magnetic resonance imaging (MRI) when presaturation pulses are applied perpendicular to the frequency-encoding axis in narrow bandwidth imaging.
• This artifactual phenomenon can be leveraged for quantitative analysis within biological tissues.

Purpose of the Study:

• To investigate the utility of chemical-shift artifact for quantifying lipid fractions in phantoms simulating biological tissues.
• To establish the accuracy of this artifact-based method by comparing it with established spectroscopic techniques.

Main Methods:

• Twenty phantoms with varying lipid/water ratios were imaged using a 1.5-T MRI scanner with a spin-echo sequence (TR/TE, 2000/20 ms).
• A narrow bandwidth inducing a 6-mm chemical shift and a 6-mm presaturation pulse were employed during imaging.
• Lipid fractions derived from MRI images were compared against values obtained via spectroscopy.

Main Results:

• A strong correlation was observed between image-derived lipid fraction values (LI) and values determined by spectrometry (LS).
• The regression equation was found to be LI = 0.97 + 0.99 LS, with a correlation coefficient (r) of .998, indicating high accuracy.

Conclusions:

• The chemical-shift artifact occurring around presaturation-applied areas offers a straightforward and effective approach for accurate tissue lipid fraction quantification.
• This MRI-based method demonstrates significant potential for non-invasive lipid analysis in various biological and medical applications.