Program Information
Relaxation Times of Lipid Resonances in NAFLD Animal Model Using Enhanced Curve Fitting
K-H Song1*, C-H Yoo1 , S-I Lim1 , B-Y Choe1 , (1) Department of Biomedical Engineering, and Research Institute of Biomedical Engineering, The Catholic University of Korea College of Medicine, Seoul, Korea
Presentations
SU-F-I-63 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:The objective of this study is to evaluate the relaxation time of methylene resonance in comparison with other lipid resonances.
Methods:The examinations were performed on a 3.0T MRI scanner using a four-channel animal coil. Eight more Sprague-Dawley rats in the same baseline weight range were housed with ad libitum access to water and a high-fat (HF) diet (60% fat, 20% protein, and 20% carbohydrate). In order to avoid large blood vessels, a voxel (0.8x0.8x0.8 cm³) was placed in a homogeneous area of the liver parenchyma during free breathing. Lipid relaxations in NC and HF diet rats were estimated at a fixed repetition time (TR) of 6000 msec, and multi echo time (TEs) of 40-220 msec. All spectra for data measurement were processed using the Advanced Method for Accurate, Robust, and Efficient Spectral (AMARES) fitting algorithm of the Java-based Magnetic Resonance User Interface (jMRUI) package.
Results:The mean T2 relaxation time of the methylene resonance in normal-chow diet was 37.1 msec (M₀, 2.9±0.5), with a standard deviation of 4.3 msec. The mean T2 relaxation time of the methylene resonance was 31.4 msec (M₀, 3.7±0.3), with a standard deviation of 1.8 msec. The T2 relaxation times of methylene protons were higher in normal-chow diet rats than in HF rats (p<0.05), and the extrapolated M₀ values were higher in HF rats than in NC rats (p<0.005). The excellent linear fit with R²>0.9971 and R²>0.9987 indicates T2 relaxation decay curves with mono-exponential function.
Conclusion:In in vivo, a sufficient spectral resolution and a sufficiently high signal-to-noise ratio (SNR) can be achieved, so that the data measured over short TE values can be extrapolated back to TE = 0 to produce better estimates of the relative weights of the spectral components. In the short term, treating the effective decay rate as exponential is an adequate approximation.
Contact Email: