Article

Simultaneous quantification of fat content and fatty acid composition using MR imaging.

Department of Medical Radiation Physics, Malmö, Department of Clinical Sciences, Malmö, Lund University, Skånes University Hospital, SE-205 22, Malmö. .
Magnetic Resonance in Medicine (Impact Factor: 3.27). 04/2012; DOI: 10.1002/mrm.24297
Source: PubMed

ABSTRACT Not only the fat content but also the composition of fatty acids (FAs) in stored triglycerides might be of interest in the research on nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. In this study, a novel reconstruction approach is proposed that uses theoretical knowledge of the chemical structure of FAs to simultaneously quantify the fat fraction (FF) and the FAs composition (chain length cl, number of double bonds ndb, and number of methylene-interrupted double bonds nmidb) from multiple gradient echo images. Twenty phantoms with various fat contents (FF = 9-100%) and FA compositions (cl = 12.1-17.9, ndb = 0.23-5.10, and nmidb = 0.04-2.39) were constructed and imaged in a 3-T Siemens scanner. In addition, spectra were acquired in each phantom. Slopes and "standard deviations from true values" were used to investigate the accuracy of the two methods. The imaging method holds well in a comparison to the previously suggested spectroscopy method and showed similar overall accuracy. The in vivo feasibility was demonstrated in the thigh adipose tissue of a healthy volunteer. In conclusion, our developed method is a promising tool for FF and FA composition quantification. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

0 Bookmarks
 · 
98 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Liver fat, iron, and combined overload are common manifestations of diffuse liver disease and may cause lipotoxicity and iron toxicity via oxidative hepatocellular injury, leading to progressive fibrosis, cirrhosis, and eventually, liver failure. Intracellular fat and iron cause characteristic changes in the tissue magnetic properties in predictable dose-dependent manners. Using dedicated magnetic resonance pulse sequences and postprocessing algorithms, fat and iron can be objectively quantified on a continuous scale. In this article, we will describe the basic physical principles of magnetic resonance fat and iron quantification and review the imaging techniques of the "past, present, and future." Standardized radiological metrics of fat and iron are introduced for numerical reporting of overload severity, which can be used toward objective diagnosis, grading, and longitudinal disease monitoring. These noninvasive imaging techniques serve an alternative or complimentary role to invasive liver biopsy. Commercial solutions are increasingly available, and liver fat and iron quantitative imaging is now within reach for routine clinical use and may soon become standard of care.
    Topics in magnetic resonance imaging: TMRI 03/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: To introduce a novel method for skeletal muscle water T2 determination in fat-infiltrated tissues, using a tri-exponential fit of the global muscle signal decay. In all, 48 patients with various neuromuscular diseases were retrospectively selected and their thigh muscles analyzed. Each patient was imaged using a multispin-echo (MSME) sequence with a 17-echo train. The transmit field (B1+) inhomogeneities were evaluated using the actual flip angle imaging method toward voxel sorting. Muscle water T2 was quantified using a tri-exponential signal decay model. The difference between water T2 of voxels within the same muscle but having different fat ratio was analyzed using nonparametric statistical tests. In addition, we evaluated the correlation between fat ratio and T2 values obtained using both a mono- and tri-exponential approach. The results showed that muscle water T2 values obtained using a tri-exponential approach combined with B1+ map-based voxel sorting were independent of the fat infiltration degree inside the muscle (R(2) < 0.03). This was not the case using the mono-exponential model, which measured different T2s between voxels of the same muscle but with various fat ratio (R(2) > 0.67; P < 10e(-4) ). The tri-exponential model is an accurate tool to monitor muscle tissue disease activity devoid of bias introduced by fat infiltration.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 03/2014; · 2.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: To investigate various sources of bias in MRI-based quantification of fat fraction (FF) and fatty acid composition (FAC) using chemical shift-encoded techniques. Methods: Signals from various FFs and FACs and individual relaxation rates of all signal components were simulated. From these signals, FF and FAC parameters were estimated with and without correction for differences in individual relaxation rates. In addition, phantom experiments were conducted with various flip angles and number of echoes to validate the simulations. Results: As expected, T1 weighting resulted in an overestimation of the FF, but had much smaller impact on the FAC parameters. Differences in T2 values of the signal components resulted in overestimation of the FAC parameters in fat/water mixtures, whereas the estimation in pure oil was largely unaffected. This bias was corrected using a simplified signal model with different T2 values of water and fat, where the accuracy of the modeled T2 of water was critical. The results of the phantom experiment were in agreement with simulations. Conclusion: T1 weighting has only a minor effect on FAC quantification in both fat/water mixtures and pure oils. T2 weighting is mainly a concern in fat/water mixtures but may be corrected using a simplified model. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 12/2013; · 3.27 Impact Factor