A medical device configured to apply energy from an energy supply into a region of tissue and draw suction from a vacuum source , the medical device comprising: a catheter assembly having a working end; a hood member at the working end and having a top surface and a bottom surface , the hood member having an open face on the bottom surface that exposes a recess within an interior of the hood member , the open face having a perimeter with a first edge and second edge extending lengthwise along a longitudinal axis of the hood member , where at least a portion of the perimeter contacts the region of tissue when the open face is positioned on the region of tissue; a first electrode and a second electrode each positioned respectively along the first edge and the second edge, where the first electrode and second electrode are configured to deliver energy from the energy supply to the region of tissue; a plurality of walls extending along the longitudinal axis of the hood member and within the interior of the hood member , where the plurality of walls form one or more perfusion channels and one or more vacuum channels within the interior of the hood member ; where the one or more perfusion channels extend along the longitudinal axis of the hood member and are in fluid communication with a perfusion lumen located within the hood member ; where the one or more vacuum channels extend along the longitudinal axis of the hood member and are in fluid communication with a vacuum lumen located within the hood member ; and wherein the medical device is configured such that, when the open face is positioned on the region of tissue, application of a vacuum from the vacuum source produces a vacuum in the one or more vacuum channels to draw a surface of the region of tissue into the open face and into the recess against the plurality of walls . a catheter assembly having a working end; a hood member at the working end and having a top surface and a bottom surface , the hood member having an open face on the bottom surface that exposes a recess within an interior of the hood member , the open face having a perimeter with a first edge and second edge extending lengthwise along a longitudinal axis of the hood member , where at least a portion of the perimeter contacts the region of tissue when the open face is positioned on the region of tissue; a first electrode and a second electrode each positioned respectively along the first edge and the second edge, where the first electrode and second electrode are configured to deliver energy from the energy supply to the region of tissue; a plurality of walls extending along the longitudinal axis of the hood member and within the interior of the hood member , where the plurality of walls form one or more perfusion channels and one or more vacuum channels within the interior of the hood member ; where the one or more perfusion channels extend along the longitudinal axis of the hood member and are in fluid communication with a perfusion lumen located within the hood member ; where the one or more vacuum channels extend along the longitudinal axis of the hood member and are in fluid communication with a vacuum lumen located within the hood member ; and wherein the medical device is configured such that, when the open face is positioned on the region of tissue, application of a vacuum from the vacuum source produces a vacuum in the one or more vacuum channels to draw a surface of the region of tissue into the open face and into the recess against the plurality of walls . <EOS>