The invention generally relates to balloon catheters for vascular intervention and particularly to devices for imaging from within a balloon. The invention provides a balloon catheter with an imaging device inside the balloon and capable of viewing a treatment site through a wall of the balloon. The device allows a physician to both view the affected site within the vessel and to inflate the balloon at the location that is in view, thus allowing the balloon to be deployed with good positioning and efficiency while minimizing a stiff length of the catheter to give it good maneuverability.
