Cryogenic ablation system and method

A controlled balloon expansion assembly, for use with a balloon placeable within an open region of a body, the balloon having a balloon interior and being placeable in inflated and deflated states, the assembly comprising:

• an exhaust passageway tube having first, second and third positions and defining an exhaust passageway coupleable to the balloon interior at the first position along the exhaust passageway tube;
• the exhaust passageway consisting essentially of an uninterrupted exhaust passageway between the first, second and third positions;
• and
• a relief valve assembly comprising:
• a relief valve comprising a chamber having an inlet fluidly coupled to the exhaust passageway at the second position along the exhaust passageway tube, an outlet fluidly coupled to an exhaust gas dumping region, and a pressure sensitive sealing element between the inlet and the outlet, the sealing element configured to provide a seal positioned between the inlet and the outlet according to a level of pressure applied to the sealing element;
• the chamber of the relief valve being a closed chamber with the exception of the inlet and outlet only;
• the inlet of the chamber of the relief valve being directly connected to the second position along the exhaust passageway through tubing only;
• a pressurization device;
• a valving selectively fluidly coupling the pressurization device to and fluidly isolating the pressurization device from (1) the sealing element, and (2) the exhaust passageway at the third position along the exhaust passageway tube;
• and
• the valving being directly connected to the sealing element and to the exhaust passageway at the third position along the exhaust passageway through tubing only.