Measuring Transverse Relaxation in Myocardial Tissue with 3T Magnetic Resonance Imaging

Abstract

The goal of this work was to develop methods to overcome the practical difficulties of 3T human myocardial imaging and to determine reliable reference values for transverse relaxation in normal human myocardium.

Nine healthy volunteers were investigated with three multi-echo, turbo spin-echo (TSE) methods. Each method involved tradeoffs between acquired phase encoding lines per image and the number of echo-image sample points obtained along the T2 decay curve. Three multi-echo turbo field-echo (TFE) methods were also tested. The TFE methods highlighted differences between achievable bandwidth per pixel and echo time constraints versus the number of sample points obtained along the T2* decay curve. Measured transverse relaxation values in pixel maps and regions of interest, quality of monoexponential curve fits, and signal-to-noise ratio (SNR) were assessed among methods to determine accuracy and repeatability.

Measured T2 and T2* values were consistent in reported means and in SNR across all scan methods. T2 for the ventricular septum was 59.5 ± 7.9 ms (N=9) across all TSE methods. The 4-echo method gave the best curve fits. T2* for the ventricular septum was 31.6 ± 6.1 ms (N = 9) with the 4-echo method yielding the highest quality curve fits. Significant differences between measured endo- and epicardial transverse relaxation due to myocardial perfusion were not observed.

These results indicate that the 4- echo methods are best for optimal T2 and T2* sampling in the mid-ventricular septum.