A method of treating a target site within a vascular channel of the body uses a catheter assembly having proximal and distal occluders which are positioned in occluding states at positions proximal and distal of a target site to define an occluded region therebetween. An agent is injected into the region. An intervention is performed at the target site while the vessel is occluded and the agent is in the region. The catheter assembly is removed from the channel. Intervention may include expanding a balloon within a temporary stent structure against the channel, collapsing balloon and then removing the collapsed balloon and stent structure from the channel. A balloon stent assembly comprises a catheter assembly, a temporary stent surrounding a balloon, the temporary stent placeable in a contracted state by the catheter assembly and in an expanded state by inflation of the balloon.