Simultaneous quantification of T2 and T′2 using a combined gradient echo-spin echo sequence at ultrahigh field

Abstract

Measuring T2 at 7.0 T is not trivial due to RF inhomogeneity effects, however, gradient echo sampling of a spin echo is insensitive to RF pulse errors, does not suffer from significant distortions, and allows T′2 and T2 to be estimated simultaneously. Gradient echo sampling of a spin echo results are relatively sensitive to noise and therefore fitting methods and timing parameters were optimized: a weighted linear fit reduced the errors in T2 compared to a nonlinear fit, the optimum spin echo time was approximately equal to the expected T2 and decreasing the number of gradient echoes minimized the error of the estimated T2. T2, T′2, and T2 decreased with field strength in frontal gray matter, occipital gray matter, and white matter, with T2 having a linear dependence (frontal gray matter: 87, 76, 47 ms, occipital gray matter: 80, 68, 46 ms and white matter: 80, 71, 47 ms at 1.5, 3.0 and 7.0 T, respectively). © 2010 Wiley-Liss, Inc.