Methods treat a tissue region. In one arrangement, the methods deploy an endoscope in an esophagus and visualize with the endoscope a Z-line that marks a transition between esophageal tissue and stomach tissue by observing tissue color change at or near the Z-line. The methods deploy an electrode support structure over the endoscope at or near the Z-line visualized by the endoscope, wherein the endoscope serves as a guide for the electrode support structure. The methods introduce from the electrode support structure a tissue-piercing needle electrode into tissue at or near the Z-line and observe introduction of the tissue-piercing needle electrode using the endoscope. The methods couple the tissue-piercing electrode to a source of radio frequency energy to ohmically heat tissue and create a subsurface tissue lesion in tissue at or near the Z-line, and observe creation of the tissue lesion using the endoscope.