Sketch of residual hepatic VX2 carcinoma following RFA. The oval-shaped area of "adbe" represents the whole tumor. The line "ab" is the minor axis of the tumor and the line "de" is the major axis. The tumor center was also designated as the RFA center. The measured minor axis of the tumor was used to guide the release of the RFA needle electrode. Thus, residual tumor was left on both sides of the measured major tumor axis (shadowed area).