Quantification of the triglyceride fatty acid composition with 3.0 T MRI

Abstract

The aim of this work was to validate a sequential method for quantifying the triglyceride fatty acid composition with 3.0 T MRI. The image acquisition was performed with a 3D spoiled gradient multiple echo sequence. A specific phase correction algorithm was implemented to correct the native phase images for wrap, zero- and first-order phase and rebuild the real part images. Then, using a model of a fat (1)H MR spectrum integrating nine components, the number of double bonds (ndb) and the number of methylene-interrupted double bonds (nmidb) were derived. The chain length (CL) was obtained from these parameters using heuristic approximation. Validations were performed on different vegetable oils whose theoretical fatty acid composition was used as reference and in five human subjects. In vivo measurements were made in the liver and in the subcutaneous and visceral adipose tissues. Linear regressions showed strong correlations between ndb and nmidb quantified with MRI and the theoretical values calculated using oil composition. Mean ndb/nmidb/CL were 1.80 ± 0.25/0.51 ± 0.21/17.43 ± 0.07, 2.72 ± 0.31/0.94 ± 0.16/17.47 ± 0.08 and 2.53 ± 0.21/0.84 ± 0.14/17.43 ± 0.07 in the liver, subcutaneous and visceral adipose tissues respectively. The results suggest that the triglyceride fatty acid composition can be assessed in human fatty liver and adipose tissues with a clinically relevant MRI method at 3.0 T.

MRI proton density fat fraction is robust across the biologically plausible range of triglyceride spectra in adults with nonalcoholic steatohepatitis

“…This bias is probably not clinically meaningful in most instances, although it may be relevant if reliable detection of slight differences is desired, such as subtle spatial distribution heterogeneity at a cross‐sectional timepoint or small but real longitudinal changes, where the TG chemical structure may change over time. In those situations, one potential solution to uncertainty in the TG spectral model is to simultaneously estimate PDFF and the fat composition parameters (NDB, NMIDB, and CL), although this is currently not commonly done in clinical practice . The finding that the bias associated with varying spectral models is small also suggests that PDFF estimated using different spectral models may be pooled in meta‐analyses, provided that the PDFF estimations were done in a similar manner as in our study.…”

Accurate fatty acid composition estimation of adipose tissue in the abdomen based on bipolar multi‐echo MRI

“…However, there is emerging evidence that characterizing the FAC (i.e., the fractions of unsaturated (UFA), saturated (SFA), mono‐unsaturated (MUFA) and poly‐unsaturated (PUFA) fatty acids with regard to the total fat content) may yield more insights into disease states . Particularly in patients with NAFLD and NASH, both quantification of liver fat deposition and characterization of the types of fatty acid chains in the extrahepatic fat depots is of interest . Potential further applications of MR‐based estimation of the degree of triglyceride saturation include the assessment of breast cancer risk in postmenopausal women, or the risk assessment of spinal or peripheral fragility fractures due to osteoporosis in vertebral marrow fat …”

“…MR spectroscopy (MRS) based approaches quantify the triglyceride saturation state by fitting Gaussian or Lorentzian lineshapes to the measured fat peaks of a 1 H MR spectrum . Since the distribution of fatty acids in various adipose fat compartments is potentially different, MRI‐based FAC methods that provide spatially resolved 3‐D parameter maps and incorporate information about the chemical triglyceride structure are of special interest . As the data are acquired at several discrete echo time points, MRI‐based methods are limited in terms of spectral resolution, and robust estimation of the confounder‐corrected signal model parameters can be challenging in the presence of image noise .…”

3T chemical shift‐encoded MRI: Detection of altered proximal femur marrow adipose tissue composition in glucocorticoid users and validation with magnetic resonance spectroscopy

“…Recent advances in water‐fat imaging methods allows discrimination between different types of fat in terms of their amount of saturation (saturated fat fraction, SFA), poly‐unsaturation (poly‐unsaturated fat fraction, PUFA) and mono‐unsaturation (mono‐unsaturated fat fraction, MUFA). This approach has been validated using MRS in liver, adipose tissue, muscle, bone marrow, and more recently in abdominal adipose tissue using gas chromatography …”