Intracranial calcification on gradient-echo phase image: depiction of diamagnetic susceptibility.

PURPOSE To differentiate calcification from hemorrhage on the basis of susceptibility at magnetic resonance imaging. MATERIALS AND METHODS Gradient-recalled echo (GRE) phase imaging was performed at 1.5 T in 101 calcified areas (15 in the basal ganglia, 86 out of the basal ganglia) and 39 uncalcified locations (13 choroid plexus and pineal glands, 26 old hemorrhages). Experiments with a small lead particle and a numerical simulation were also performed. RESULTS The majority of calcifications outside the basal ganglia (n = 63) revealed a phase shift that represents diamagnetic susceptibility and was similar to the phase shift in the lead particle and to the calculated phase shift for a diamagnetic sphere. All hemorrhages and almost all calcified basal ganglia revealed a phase shift that represents paramagnetic susceptibility. All uncalcified choroid plexus and pineal glands revealed no obvious phase shift. Any location without calcification did not reveal the diamagnetic phase shift. CONCLUSION GRE phase imaging differentiated paramagnetic from diamagnetic susceptibility, which was specific for calcification.