Abstract:Objective: Apparent diffusion coefficient(ADC) can reflect the micro status of tumor cell, this study is to discuss the value of ADC in primary cerebellar tumor. Methods: Forty-four patients with histologically proved primary cerebellar tumor were reviewed retrospectively. There were 11 heamangioblastoma, 12 pilocytic astrocytomas, 11 medulloblastomas, 6 ependymomas, 2 lymphoma and 2 choroid plexus papillomas. All patients were examined by conventional MRI; DWI; and ADC value obtained from ADC maps. Absolute ADC values and ADC ratios of heamangioblastoma, pilocytic astrocytomas, medulloblastomas, ependymomas were calculated and compared by using one-way analysis of variance and Bonferronit t test. Results: The differences of both absolute ADC value and ADC ratio were significant among these 4 tumor types. ADC values were significantly higher in heamangioblastomas[(1.97±0.214)×10-3mm2/s] than in pilocytic astrocytomas[(1.643±0.223)×10-3mm2/s](P=0.001), ADC values in medulloblastomas[(0.698±0.124)×10-3mm2/s] were significantly lower than in ependymomas[(1.062±0.148)×10-3mm2/s](P=0.003). And pilocytic astrocytomas demonstrated significantly higher ADC values than ependymomas(P<0.001). Our cut off values of <0.8×10-3mm2/s, (0.9~1.2)×10-3mm2/s, (1.3~1.7)×10-3mm2/s, >2.1×10-3mm2/s for medulloblastomas, ependymomas, pilocytic astrocytomas and heamangioblastomas respectively were 100% specific. Conclusion: ADC value is an easy and useful tool in diagnosing primary cerebellar tumor.