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

Abstract

Measuring T(2) 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 T(2) 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 T(2) compared to a nonlinear fit, the optimum spin echo time was approximately equal to the expected T(2) and decreasing the number of gradient echoes minimized the error of the estimated T(2). T(2), T'(2), and T*(2) decreased with field strength in frontal gray matter, occipital gray matter, and white matter, with T(2) 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).