A medical system is provided, including a catheter body having a proximal portion and a distal portion； a shaft slidably disposed within a portion of the catheter body, the shaft defining a distal tip； a fluid injection tube coupled to the distal portion of the catheter body and the distal tip of the shaft, the fluid injection tube being transitionable from a first geometric configuration to a second geometric configuration； a membrane coupled to the shaft and enclosing at least a portion of the fluid injection tube therein； and a coolant source in fluid communication with the fluid injection tube. The first geometric configuration may be substantially linear, the second geometric configuration may be substantially helical, and the membrane may be tensioned across at least a portion of the fluid injection tube in the second geometric configuration.
