T 2 Accuracy on a whole‐body imager

MR oximetry requires a T 2 measurement that is accurate within 5% in vivo. Simple methods are susceptible to signal loss and tend to underestimate T 2 . Current methods utilize RF pulses or RF cycling patterns that prevent signal loss at each data acquisition. However, using these methods with imperfect pulses, T 2 tends to be overestimated due to temporary storage of the magnetization along the longitudinal axis where it decays more slowly with a time constant T 1 T 2 . To reduce the T 1 dependence while preventing signal loss, we utilize simple 90 x 180 y 90 x composite pulses and good RF cycling patterns. These trains are critical for T 2 accuracy over typical ranges of RF and static field inhomogeneities and refocusing intervals. T 1 signal decay during each 90 x 180 y 90 x pulse must be accounted for to yield accuracy within 5% when the pulse‐width is 10% or more of the refocusing interval. A simple correction scheme compensates for this T 1 ‐related error effectively.