Various embodiments of an eccentric balloon catheter are disclosed. In some embodiments, an eccentric balloon catheter includes an eccentrically positioned guidewire tube, with an interior lumen, that extends at least a portion of the length of the catheter body. Optical fibers may extend the length of the catheter body and may also be eccentrically positioned within the catheter body. An inflatable balloon may be positioned within a window within the catheter body near the distal end of the catheter. When inflated, the balloon and catheter may slide relative to one another. When used within a vessel, an inflated balloon may press against a vessel wall and bias the catheter toward an opposite vessel wall.