Objective To compare the difference of MRI characteristics of pilomyxoid astrocytomas (PMA)and pilocytic astrocy-tomas (PA)in hypothalamus/optic chiasma region.Methods The MR images and clinical materials of 20 PMAs and 20 PAs proved by pathology were reviewed retrospectively.Imaging characteristics and clinical materials were analyzed,including age,gender, size,the signal characteristics of the tumor,growth,enhancement pattern,hydrocephalus and leptomeningeal dissemination.Results There were statistically significant differences in streaky low signal intensity among the high intensity of T2 WI and leptomeningeal dissemination between PMA and PA (P <0.05).However,no statistically significant differences were found in the other character-istics and clinical materials between the two types of tumors.Conclusion PMA and PA in hypothalamus/optic chiasma region are difficult to make differential diagnosis.The streaky low signal intensity among the high intensity of T2 WI and more frequent lepto-meningeal dissemination are helpful differential features of PMA as compared to PA.

Objective To investigate the application value of DWI and SWI in the diagnosis of diffuse axonal injury (DAI). Methods MR imaging was performed in 23 patients with clinically diagnosed DAI including the routine se-quences, DWI and SWI sequences.The detected number of lesions was compared among the different sequences.The characteristics of sig|lal and distribution of lesions were analyzed. Results DAI lesions located in the white matter,juncfional zone of cortex and medulla,basal ganglia, corpus eaihsum brain stem arm cerebelhm. The detected number of non-hemorrhagic lesion on DWl was the highest and significantly higher than that on other sequences.The deteced number of hemorrhagic lesion on SWI was the highest and significantly higher than that on other sequences. Conclu-sion Combination of DWl and SWI can improve detection ratio of DAI lesions, provide more image evidence for early clinical diagnosis,so DWI and SWI should be the first and naltilm sequence in the MRI exaafination of DAI detection.

Objective To explore the diagnostic value of MR susceptibility weighted imaging (SWI) in the cerebral micro-bleedings(CMBs). Methods Conventional MR sequences including TSE , FLAIR and SWI sequences were per-formed in 50 patients as well as SWI sequence.The numbers of CMB and sensitivity of positive rare on SWI and conventional sequences were compared and statistically analyzed. Results SWI sequences clearly exhibited dot,stripe,round or ring-shaped low signal shadows. With diameter from 0.4 to 6.5 mm. Cerebral microbleeds mainly located in cortex, subcortex and basal ganglia in 50 patients. Compared to 23 cases with spin echo TSE, and 20 cases with FLAIR. Conclusion SWI has predomin flilt advantage over conventional MRI sequences in detecting CMBs. SWI provides an important reference for the treatment and evaluating prognosis of cerebral infarction.