MRI is useful to identify hemorrhage and ischemia in the central nervous system. New MRI techniques utilize perfusion weighted images and blood diffusion to distinguish intracranial hemorrhage and reversible ischemia.  MRI can also be used to image the abdomen when there is GI involvement.
Polyarteritis nodosa MRI
Polyarteritis nodosa CT
Polyarteritis nodosa physical examination
Microscopic polyangiitis MRI
Microscopic polyangiitis CT
Buerger's disease CT scan
Buerger's disease MRI
Takayasu's arteritis x ray