Characterization of Local Field Disturbances Through Phase Derivative Mapping

Hendrik de Leeuw¹, Mandy Conijn¹, Peter R. Seevinck¹, Jeroen Hendrikse², Gerrit H. van de Maat¹, Chris J.G. Bakker¹

In MRI studies, magnitude images are often used as the only source of information. Especially in the presence of local field distortions, this might be considered suboptimal, since information on the local magnetic field is encoded in the signal phase. Studies that use signal dephasing only, do not allow discrimination between paramagnetic and diamagnetic disturbances, since signal dephasing is independent of the sign of the field. We will show, by analysis of microbleeds and calcifications in the brain, that by using the phase derivative, local field disturbances can be detected and analyzed in terms of positive or negative susceptibility deviations.