Application Of Infrared Thermography In Flap Surgery

Objective :1.To explore the clinical application of Dynamic Infrared Thermography in preoperative design of craniofacial flap transplantation.2.Using of infrared thermal imaging technology to monitor the blood circulation status of SD rat back flap after operation,predict the flap activity;Exploring the reliability and accuracy of infrared thermal imaging technology to evaluate perfusion and predict flap survival after flap operation,and expanding its clinical application in flap surgery.Methods :1.12 patients which need for head and face flap surgery in the Department of Plastic Surgery,the First Affiliated Hospital of Nanchang University were selected.The target vessels were located in the standard environment by infrared thermograph before operation.2.Necrosis random flap models of 10 SD rat were established.Two different plastic surgeons took thermal and physical images of the flap area at 0.5 hours,6 hours,24 hours,3 days and 7 days after operation.the skin flap was cut on the 7th day after operation for histological analysis;the actual necrotic area of the flap was calculated according to the physical map of the 7th day after operation.The flap of thermogram was divided into proximal survival area and distal necrosis area.The normal tissue in the craniofacial region of 2 cm*2 cm was used as control area.By analyzing the thermal image,the difference temperature between the target region and the control region is obtained as statistical data,and the intra-group correlation coefficient and Bland-Altman analysis are carried out to verify the reliability of Infrared Thermography.The data of 5 hours and 6 hours were ROC analyzed to verify the accuracy of thermal imaging technology,and the optimal critical value was obtained according to the ROC curve coordinates and clinical characteristics.Results :1.Using dynamic thermal imaging technology to locate the vascular of maxillofacial region,infrared thermal image showed that the route of the main blood vessel and some branches were clear,according to the route to design the surgical safety area,the postoperative areas were healed as scheduled.2.On the 7th day after operation,10 SD rat flaps all had necrosis.The actual necrosis ratio of flap was 35.54%±4.38。The histological evaluation showed that the flap proximal epidermis and dermis morphological structure is normal,there weren`t obvious inflammatory infiltration;the flap distal epidermis is heavily thickened,the dermis was replaced by a large area of proliferative connective tissue,a large number of fibroblasts can be seen.The statistical analysis of the test data shows that the correlation coefficient was greater than 0.75,and the Bland-Altman showed that the difference between the two subjects was mostly within the 95% confidence interval,which proved that the infrared thermal imaging equipment used in this study had better repeatability;The Area Under ROC Curve of 6 hours was 0.7-0.9,Which indicate that the ability of using infrared thermal imager to predict flap activity according to temperature difference was moderate at 6 hours after operation.According to the curve coordinates and clinical characteristics,the optimal critical value of 3.2℃ was taken,at the same time,the sensitivity was 90% and the specificity was 60%.Conclusion :1.Dynamic infrared thermal imaging is a non-invasive auxiliary detection method,which is simple and economical.During the preoperative,the vessel can be located intuitively by the dynamic infrared thermal imaging technology,and the appropriate vascular pedicle can be selected to guide the design and cut the flap.2.Infrared thermal imaging technique can predict the activity of SD rat back free flap,when the temperature difference between the skin flap area and the flap pedicle normal tissue reaches or above 3.2℃ at 6 hours postoperatively,part or all of the skin flap will occur necrosis;Therefore,We can effectively assess whether the flap will necrosis by observing the thermal image and calculating the temperature difference in the target area,which can help us investigate the abnormal blood perfusion early and treat actively.