Abstract: An atherectomy burr has an operating diameter that is larger than the diameter of a catheter in which the burr is routed. The burr may include an expandable polymeric balloon having a partially abrasive exterior surface. The maximum expansion of the burr is controlled by an expansion mechanism. Various mechanisms are disclosed for controlling the maximum diameter of the burr thus preventing the burr from over expanding. In addition, the present invention includes systems that are pulled proximally to remove portions of a lesion located in a patient's vasculature. The system includes an ablation burr that has abrasive disposed on the proximal end. The burr may create a seal when expanded to block the ablated particulate so that an aspiration system can remove the particulate from the vasculature. Alternatively, the burr system may include a self expanding seal that is deployed out of the aspiration sheath.