A crucial issue in determining quantitative magnetization transfer (qMT) parameters using balanced steady state free precession (bSSFP) is the estimation of the on-resonant singularity of the superlorentzian absorption line shape G0. We present an empirical G0 calibration method for postmortem in-situ brain scans at 3T using cross-linked BSA (bovine serum albumin) probes. For the investigated temperature range from 6-20°C G0 resulted in 2.0*10-5. First qMT results of three postmortem in-situ brain scans revealed decreased bound pool size ratios f in white matter compared to in-vivo scans