Abstract: Systems and methods deploy a therapeutic or diagnostic element into contact with a body tissue region. The systems and methods can sense position of the therapeutic or diagnostic element relative to a targeted tissue region without direct or indirect visualization, by sensing fluid pressure in a fluid path having an outlet located at or near the therapeutic or diagnostic element. The systems and methods can also inflate the therapeutic or diagnostic element during use, while taking steps to avoid over-inflation and/or while dynamically monitoring the pressure conditions within the expanded element.