RESUMO
Objective To explore the susceptibility weighted imaging (SWI) appearance of paramagnetic and diamagnetic materials, its imaging theory, and its value of differential diagnosis from their appearance. Methods The diamagnetic and paramagnetic phantom were made and the X-Y axial SWI phase image of phantom then was obtained. Twenty-eight cases of intracerebral calcium and 21 cases of hemorrhage examined with MRI scan and CT scan were retrospectively investigated. The appearance of calcium and hemorrhage on SWI were analyzed and compared with their appearance on CT and conventional MRI. Results Phantom experiment indicated that the equator plane scan of diamagnetic sphere showed high signal in centre surrounded by low signal ring and high signal in two poles of sphere along Z axis of main magnetic field. The paramagnetic sphere appeared the opposite appearance of diamagnetic sphere with centre low signal surrounded by high signal ring in equator plane and low signal in two poles of sphere along Z axis of main magnetic field. The SWI manifestations of 4 cases of intracerebral sphere or sphere-like calcification ( chorioidal calcification) and 9 cases of sphere or sphere-like hemorrhage(2 cases of traumatic hemorrhage, 1 case of hypertension related basal ganglion hemorrhage, 4 cases of metastasis hemorrhage and 2 cases of cavernous hemangioma hemorrhage)were consistent with diamagnetic and paramagnetic sphere phantom respectively. Four cases of calcification in basal ganglion showed the mixed high and low signal. Seven cases of irregular calcification ( neoplastic calcification) aside from basal ganglion appeared complex appearance, though mainly in high signal. Other sphere or sphere-like calcification aside from basal ganglion ( 14 cases of pineal calcification, 4 cases of chorioidal calcification, 2 cases of cerebral cysticercosis calcification and 1 case of neoplastic calcification ) showed markedly high signal. Nine cases of intracerebral iobular hemorrhage (2 cases of hypertension related basal ganglion hemorrhage, 4 cases of unknown casual hemmorrhge and 3 cases of cavernous hemangioma hemorrhage) displayed a multiple concentric circle appearance, other 3 hemorrhage showed complex appearance, though mainly in low signal. Ten cases of calcification had no specific appearance on T1 WI and T2WI. Conclusion Phase image of SWI is helpful in differentiating intracerebral diamagnetic from paramagnetic materials and it has some advantage in detecting calcification over T WI and T2 WI.