Abstract
In nonalcoholic steatohepatitis (NASH) the fat quantification is necessary. One of the most used in vivo quantification method is the magnetic resonance spectroscopy (MRS). It is well known the importance of T2 correction to improve the accuracy and precision of this method; however the T2 measurements require time consumption. In this work we estimated the T2 values for water and fat in NASH patient with different fat contents in order to verify if a generic T2 correction is adequate for fat quantification in the clinical routine.
19 NASH patients (48±10 years, 9 female) underwent MR procedure several times. Imaging was performed on a 3.0T clinical MRI scanner using a 3P-Dixon method. MRS data was acquired using single voxel (3×3×3 cm) PRESS acquisition (TR=1500ms, 1024points, 2 KHz bandwidth). The PRESS acquisition was performed in a single TE (60 ms, 32 averages) and multiple TE (32,45,80 and 135 ms; 16 averages). The software jMRUI was used for peak quantification. The MRS results were T2 corrected using generic values (T2fat=55ms and T2water=25 ms) for single TE data and individual values estimated from multi-TE data before fat fraction calculation. A linear correlation was estimated between the fat fraction obtained using 3P-Dixon and the spectroscopy methods.
The T2 values estimated were 69±14 and 27±3 ms for fat and water, respectively. The correlation coefficients between 3P-Dixon and the spectroscopy methods were: 0.75 for MRS-individual and 0.82 for MRS-general.
The procedure using a generic T2 value was more correlated to Dixon than one using individual values, suggesting that is more important a good signal-to-noise ratio than a very precise T2 value for correction. The reduced range of T2water values doesn't reflect any considerable iron deposition in NASH patients. In diseases with low iron deposition it's not necessary the individual T2 correction for fat quantification from MRS data.