A Comparison of Accuracy between Dynamic Infrared Thermography (DIRT) and Handheld Doppler Ultrasonography in Free Flap Reconstruction Perforator Mapping: A Prospective Study

Abstract

Background: Preoperative perforator mapping is one of fundamental steps for successful surgery in microsurgical perforator free flap. Currently, there is still no gold standard for preoperative perforator mapping. Objective: The present study aims to compare accuracy in perforator mapping between dynamic infrared thermography (DIRT) and handheld doppler which is the main method we used in our hospital. Materials and Methods: Twenty patients scheduled for microsurgical free flap reconstruction between October 2018 to December 2020 was enrolled. Preoperative perforator mapping was performed by both handheld doppler and smartphone dynamic infrared thermography (DIRT). During rewarming period, “Hot spots” were marked. Then flaps were raised intraoperatively, numbers, diameter and location of each perforators were recorded. Location of perforators at its piercing fascia were reflected to skin. Distance from actual perforators to the nearest preoperative perforator marking point by each method were measured. Results: There were 9 male and 11 female patients enrolled in the present study with mean age of 54.30 years. The average body mass index was 23.85 kg/m2. Hand-held doppler and DIRT images were obtained for 20 flaps, including 15 anterolateral thigh flaps (75%), 1 anteromedial thigh flap (5%) and 4 fibular free flaps (20%). The mean caliber of selected perforators was 2.62 mm at point of their emergence through fascia. All the flap survived without postoperative major complication. The mean distance from actual perforator to the nearest perforator from handheld doppler was 11.88+7.51 mm, and to the nearest perforator from thermal images was 12.68+8.96 mm. The mean distance difference of both methods was 0.80 mm. Perforators were usually within a 20 mm radius of preoperative marking both handheld doppler and DIRT. Conclusion: Dynamic infrared thermography is low cost, non-invasive and reliable methods for preoperative perforator mapping.