Rapid single-scan T2*-mapping using exponential excitation pulses and image-based correction for linear background gradients.
Baudrexel S., Volz S., Preibisch C., Klein JC., Steinmetz H., Hilker R., Deichmann R.
A method for fast quantitative T(2)* mapping based on multiple gradient-echo (multi-GE) imaging with correction for static magnetic field inhomogeneities is described, using an exponential excitation pulse. Field gradient maps are obtained from the phase information and modulus data are subsequently corrected, allowing for simple monoexponential T(2)* fitting. Echoes with long echo times suffering from major signal losses due to field inhomogeneities are excluded from the analysis. The acquisition time for a matrix size of 256 x 256, 1 mm in-plane resolution, and 2 mm slice thickness amounts to 15 s per slice. An additional correction for in-plane field gradients further improves accuracy. Phantom experiments show that the method provides accurate T(2)* values for field gradients up to 200 microT/m; for gradients up to 300 microT/m errors do not exceed 15%. In vivo T(2)* values acquired on healthy volunteers at 3T are in excellent agreement with results from the literature.