Answer:
In the 1994 article titled, "Color-flow duplex scanning in the preoperative assessment of TRAM flap perforators: A report of 32 consecutive patients," the authors propose this imaging method as a means of defining each individual's vascular anatomy in order to assure that the dominant vessels are captured in the flap harvest, and survival of the flap is maximized. Perforator locations were identified according to their vertical position relative to the umbilicus and their lateral location relative to the abdominal midline. The periumbilical regions (zone I and III) contained 80.5% of the perforators, with the majority of cases demonstrating some degree of asymmetry on either side of midline. The flap survival rate in this series was 97.9% (46 of 47).