Abstract: A light delivery apparatus to provide light treatment to a patient includes a catheter assembly having a light source that transmit light towards a target site within a patient. A balloon surrounds the light source and has a plurality of tissue engaging elements movable between first positions and second positions. In one embodiment, each element extends radially inward in the first position and radially outward in the second position. An insertion tool is used to deliver the light delivery apparatus. During use, the light delivery apparatus is rotationally locked with the insertion tool for improved steering, navigation, and aiming of emitted light.