A flush catheter is provided which is configured to be introduced into an orifice to create a flush zone therein. The flush catheter includes a catheter body having an inner cavity, the inner cavity being configured to communicate with a source of flush solution, one or more openings configured to expel therethrough flush solution, and a sheath at least partially covering the one or more openings, wherein when flush solution is expelled through the one or more openings, the flush solution is directed by the sheath to flow along an outer surface of the catheter body, thereby creating a flush zone along a length of the outer surface of the catheter body. The flush catheter may be used in combination with an image catheter/probe such as an image catheter/probe utilized in OCT imaging systems.