Objective To analyze the MRI features of central neurocytoma (CNC),and to improve the diagnostic accuracy of this lesion.Methods The MRI findings of 12 patients with CNC confirmed by surgery and pathology were evaluated retrospectively.All patients underwent contrast-enhanced and uncontrast-enhanced MR scan,and 3 patients also received plain CT scan.Results The lesions of 12 cases were all located in the lateral ventricles of septum pellucidum,which were close to the Monro's foramen.5 lesions located in the right lateral ventricle,5 lesions located in both lateral ventricles with 1 case reached the third ventricle,2 lesions located in the left lateral ventricle with 1 case reached the third ventricle.The mean diameter of the CNC lesions was 4.8 cm (ranged from 2.2 to 7.8 cm).11cases (92％) had vavious degrees of cystic change,8 cases (66.7％) had a spongy or soap bubble appearance and 1 case(8.3％) had completely cystic change.3 cases (25％) had a scalloping appearance on sagittal T1-weighted MRI.The solid part of the tumor was similar to the gray matter in signal intensity,with slightly high signal intensity on T2FLAIR.Among 9 cases with DWI,7 cases showed high signal intensity,1 case showed equal signal intensity,and 1 case showed slightly low signal intensity.On enhanced MRI,the solid part of tumors showed slight to medium (83％) or obvious (17％) enhancement.Conclusion CNC should be first considered when a young adult has a lesion located in the lateral ventricles of septum pellucidum,accompainied by varying degrees of cysts,showed slight to medium enhancement in the solid part of the tumor.

Objective To study the MRI features of primary central nervous system lymphoma (PCNSL)to improve its diagnosis. Methods The MRI data of 1 3 patients with PCNSL confirmed by biopsy or surgical pathology were analyzed retrospectively.All patients underwent nonenhanced and contrast-enhanced MRI examinations.Results Multiple lesions in 8 cases and solitary one in 5 cases were found.Five leisons (38.5%)were located in the cerebral hemispheres.Eight(61.5%)were located in deep structures of the brain including periventricular white matter,basal ganglia,thalami and corpus callosum,6 (46.2%)of whom involved in the ependyma including 1 involved in the ependyma of the 4 th ventricle.One leison(7.7%)was located in the cerebellar hemisphere.The tumor showed isointense or mildly hypointense signal on T1WI,mildly hyperintense signal on T2WI and hyperintense signal on DWI.Mild to moderate perilesional edema was noted.The tumors in 13 cases showed remarkable homogeneous enhancement after the contrast agent was injected with the signs of characteristic notch,butterfly and satellite.Focal necrosis occurred in 1 lesions.Conclusion PCNSL shouldbe first considered when a lesion located in the deep central structeres of the brain,multiple and involve ependymal membrane,showed isointensity on T1WI and T2WI,highintensity on DWI in tumoral parenchyma demonstrated,significantly enhancement in the solid part of the tumor.