The present invention relates to an imaging apparatus comprising an elongated carrier adapted to be inserted through a proximal opening of a gastrointestinal (GI) tract lumen a piston head, coupled to a distal portion of the carrier, and configured to: be inflated so as to form and maintain a pressure seal with a wall of the GI tract lumen, and be advanced distally through the GI tract in response to pressure from a fluid pressure source a distal balloon coupled to the carrier distal to the piston head and configured and operable to be inflated so as to dilate the lumen thereby creating a working space and a control unit, configured and operable to control simultaneously a pressure level within the piston head and a pressure level within the distal balloon. The control comprises maintaining a constant level of pressure within the piston head thereby maintaining said pressure seal and cyclically modulating the level of pressure within the distal balloon facilitating the distal advancement of the piston head within the GI tract lumen.
