the Application of Diffusion Tensor Imaging in the Evaluation of Peripheral Neuropathy in ANCA Associated Vasculitis

1. Include qualified 50 ANCA-associated vasculitis(AAV) patients; and the first 27 patients will be divided into 3 groups with different diffused tension image (DTI) parameters and to choose the best strategy； 2. On baseline, 6 months after treatment and 24 months after treatment, the AAV patients will accomplish the Birming-ham vasculitis activity score(BVAS) besides DTI； 3. The new serum biomarkers of AAV associated peripheral neuropathy will be measured by ELISA； (4) Another cohort with 50 patients with AAV associated peripheral neuropathy who were evaluated by traditional methods (electromyogram) and compared to the patients cohort that evaluated using DTI by cost-benefit analysis