The disclosure describes an elongated housing, e.g., a catheter, configured to be inserted into a lumen of a patient to diagnose or treat a patient. The elongated housing includes a scope channel that accepts a cystoscope and a viewing window at the distal end of the elongated housing. The user may use the cystoscope to view tissue adjacent to the viewing window. The viewing window may take up at least 10 percent of the length of the elongated housing to allow the user to identify a large area of tissue in the lumen without moving the elongated housing with respect to the tissue. Once the user identifies the target tissue, the user may position the elongated housing graduations on the viewing window and the proximal end of the elongated housing. An ablation needle electrode may be extended into the target tissue to deliver ablation therapy to the target tissue.
