MRI Signal Response Mapping (SIRMA) to Dephaser to Quantify Susceptibility Gradient

florence franconi¹, Jean-Jacques Le Jeune², Pascal Richomme¹, Laurent Lemaire²

SIgnal Response MApping to dephaser (SIRMA) method is proposed to quantify susceptibility gradient. In gradient echo acquisitions, the SIRMA method measures the echo shifts in k-space of susceptibility affected spins from a series of dephased images collected with additional incremental slice refocusing gradient offset or incremental reconstruction window off-centering. SIRMA applicability and performances have been demonstrated in vitro through quantization of susceptibility gradient induced in a cylinder model and in vivo through the quantitative detection of SPIO distribution volume. With respect to its quantitative nature, its computational simplicity, this method deserves further attention for application in molecular or cellular imaging.