Quantitative magnetization transfer imaging in postmortem brain at 3T using bSSFP

Introduction Balanced steady state free precession (bSSFP) has been proposed recently for quantitative magnetization transfer (qMT) imaging [1]. Basically, bSSFP allows the determination of fundamental parameters of the two pool model [2], provided that T1 and B1 data are available. A critical point is the estimation of G0, which is the on-resonant singularity of the superlorentzian absorption line shape [3] and closely linked to the transverse relaxation time of the bound pool T2,restricted. G0 has a strong influence on the resulting qMT parameters, but can vary significantly according to the estimation procedure. For in-vivo studies reference data from other qMT techniques can be used to calibrate G0. To our knowledge there are no such reference qMT data for postmortem studies on healthy brains available. Therefore, we present an empirical calibration method for G0 which is based on cross-linked BSA (bovine serum albumin) probes of different concentrations, mimicking brain tissue with different bound pool fractions. First results of postmortem in-situ brain-scans are shown.