Pre-, Intra-, and Postoperative Use of Dynamic Infrared Thermography (DIRT) Provides Valuable Information on Skin Perfusion in Perforator Flaps Used in Reconstructive Surgery

A perforator flap is a piece of skin and subcutaneous (fatty) tissue that is transferred from one part of the body to another in the same person so called autologous transplantation. In plastic surgery, perforator flaps are often used to reconstruct or to close defects due to trauma, tumor resection, and pressure sores. A transplanted perforator flap relies on its blood supply from one artery and one vein, so-called perforating blood vessels. During surgery, these vessels are reconnected to blood vessels at the site of the defect using microsurgical techniques since the vessel caliber is often only 1 to 2 mm. There are three phases in free perforator flap surgery the preoperative, intraoperative, and postoperative phase. In the preoperative phase, the surgeon has to select a suitable perforator that can perfuse the flap. The variability in the vascular anatomy, the distribution and size of perforators makes this rather challenging. In the intraoperative phase the successful reconnection of the blood vessels is a critical point and the tiny perforator may easily become damaged and as a result the blood supply to the flap may become impaired. Postoperative monitoring of flap perfusion is also important since early recognition of impaired perfusion allows early intervention and prevention of partial or total flap failure. A simple and reliable imaging technique that helps the surgeon to select the most suitable perforator (preoperative phase), as well be able to evaluate blood perfusion in flaps both intraand post-operatively, would be very beneficial. During the last 5 years, we have successfully employed dynamic infrared thermography (DIRT) in all three phases of perforator flap surgery. The DIRT technique involves observing changes in temperature as well as the temperature distribution in an area of interest following a thermal challenge. By applying a thermal challenge, the subsequent recovery of the skin temperature towards its thermal equilibrium is evaluated. In practice, the skin area being examined is subjected to a thermal stress by fan cooling or by applying cold objects to the skin surface. The thermal images can be analyzed with respect to the rate and thermal pattern of recovery, both of which are dependant on the amount of blood perfusing the flap. By using DIRT in our studies, we have been able to improve the surgical outcome of perforator flaps.