A focal ablation assembly, for use with an endoscope comprising an endoscopic tube having proximal and distal ends and defining a channel extending between the proximal and distal ends, the focal ablation assembly comprising: a cryogenic catheter placeable within the channel, the cryogenic catheter defining a catheter lumen and having a distal end placeable at the distal end of the endoscopic tube; a cap mountable to at least one of the distal end of the endoscopic tube and the distal end of the cryogenic catheter, the cap extending distally of both of the distal ends; the cap comprising a material which substantially maintains its shape during use while not causing tissue trauma; the cap defining a limited area therapeutic region; the cap defining a cap volume defined by a wall of the cap and the therapeutic region; and the therapeutic region being a chosen one of: an open therapeutic region; and a covered, optically transparent therapeutic region providing effectively no thermal insulation, characterized in that the assembly further comprises: a delivery catheter extending along the channel and having a distal portion fluidly coupled to the cap volume, whereby refrigerant can be introduced into the cap volume and towards the therapeutic region by the delivery catheter; and a balloon extending from the distal end of the cryogenic catheter within the therapeutic region so that the refrigerant can be introduced into the balloon within the cap volume by the delivery catheter. a cryogenic catheter placeable within the channel, the cryogenic catheter defining a catheter lumen and having a distal end placeable at the distal end of the endoscopic tube; a cap mountable to at least one of the distal end of the endoscopic tube and the distal end of the cryogenic catheter, the cap extending distally of both of the distal ends; the cap comprising a material which substantially maintains its shape during use while not causing tissue trauma; the cap defining a limited area therapeutic region; the cap defining a cap volume defined by a wall of the cap and the therapeutic region; and the therapeutic region being a chosen one of: an open therapeutic region; and a covered, optically transparent therapeutic region providing effectively no thermal insulation, characterized in that the assembly further comprises: a delivery catheter extending along the channel and having a distal portion fluidly coupled to the cap volume, whereby refrigerant can be introduced into the cap volume and towards the therapeutic region by the delivery catheter; and a balloon extending from the distal end of the cryogenic catheter within the therapeutic region so that the refrigerant can be introduced into the balloon within the cap volume by the delivery catheter. an open therapeutic region; and a covered, optically transparent therapeutic region providing effectively no thermal insulation, characterized in that the assembly further comprises: a delivery catheter extending along the channel and having a distal portion fluidly coupled to the cap volume, whereby refrigerant can be introduced into the cap volume and towards the therapeutic region by the delivery catheter; and a balloon extending from the distal end of the cryogenic catheter within the therapeutic region so that the refrigerant can be introduced into the balloon within the cap volume by the delivery catheter. a delivery catheter extending along the channel and having a distal portion fluidly coupled to the cap volume, whereby refrigerant can be introduced into the cap volume and towards the therapeutic region by the delivery catheter; and a balloon extending from the distal end of the cryogenic catheter within the therapeutic region so that the refrigerant can be introduced into the balloon within the cap volume by the delivery catheter.