T2* mapping with background gradient correction using different excitation pulse shapes.

SUMMARY: Background gradients induced by magnetic susceptibility variations near air-filled cavities in the brain cause signal-intensity loss in gradient-echo images and shorten T2* considerably. With a correction method in which the exponential decay is restored with section-profile-dependent correction factors, parts of the signal intensity can be recovered. While uncorrected T2* values drop by 20% at a gradient strength of 75 μT/m, with correction and exponential excitation pulses, this boundary is pushed to 220 μT/m.