A method of ablating a lesion in a vessel includes advancing a guidewire through the vessel; advancing a sheath over the guidewire, the sheath having a proximal end, a distal end, and a lumen extending therethrough; advancing a flexible driveshaft over the guidewire and through the sheath, the driveshaft having a proximal end, a distal end, and an abrasive element attached thereto, the abrasive element having a first diameter; advancing the abrasive element out of the distal end of the sheath; increasing the first diameter of the abrasive element by rotating the driveshaft; and ablating the lesion.