Abstract
Conditions such as type II diabetes are linked with elevated lipid levels in the heart, and significantly increased risk of heart failure; however, metabolic processes underlying the development of cardiac disease in type II diabetes are not fully understood. Here we present a non-invasive method for in vivo investigation of cardiac lipid metabolism: namely, IVS-McPRESS. This technique uses metabolite-cycled, non-water suppressed 1H cardiac magnetic resonance spectroscopy with prospective and retrospective motion correction. High-quality IVS-McPRESS data acquired from healthy volunteers allowed us to investigate the frequency shift of extramyocellular lipid signals, which depends on the myocardial fibre orientation. Assuming consistent voxel positioning relative to myofibres, the myofibre angle with the magnetic field was derived from the voxel orientation. For separation and individual analysis of intra- and extramyocellular lipid signals, the angle myocardial fibres in the spectroscopy voxel take with the magnetic field should be within ±24.5°. Metabolite and lipid concentrations were analysed with respect to BMI. Significant correlations between BMI and unsaturated fatty acids in intramyocellular lipids, and methylene groups in extramyocellular lipids were found. The proposed IVS-McPRESS technique enables non-invasive investigation of cardiac lipid metabolism and may thus be a useful tool to study healthy and pathological conditions.
Highlights
Related cardiac disease, it is necessary to distinguish intramyocellular lipids (IMCL) from extramyocellular lipids (EMCL)
Several methods have been applied to improve spectral quality in 1H CMRS, including: rapid single-breath-hold acquisitions25; prospective volume-tracking27,28; respiratory gating with pressure transducers, radar techniques, or navigator echoes27,29–31; and improved image-based B0 shimming to compensate for static field inhomogeneities across the heart32,33
This work introduces the inner-volume-saturated, metabolite-cycled point resolved spectroscopy (IVS-McPRESS) method for robust, high quality 1H CMRS in the human heart. This method is a combination of MC non-water-suppressed 1H CMRS with point resolved spectroscopy (PRESS)37 localisation and inner volume saturation (IVS)38,39 together with cardiac triggering, retrospective respiratory gating, sophisticated B0 shimming33, and post-processing methods34
Summary
Related cardiac disease, it is necessary to distinguish intramyocellular lipids (IMCL) from extramyocellular lipids (EMCL). Robust separation of lipid signals from the two different compartments in human subjects, as well as a comprehensive analysis of these myocardial lipids, has not been forthcoming This can be attributed to relatively poor spectral quality in 1H CMRS, caused by a number of factors, including static field inhomogeneities, poor water suppression, inadequate localisation, and cardiac and respiratory motion. Conditions for the reliable resolution of the different lipid moiety signals are investigated, for use in both cardiac and skeletal muscle studies Combination of this analysis with the IVS-McPRESS acquisition method will enable the separate investigation of IMCL and EMCL components, allowing for detailed examination of myocardial lipid metabolism
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