A Postoperative Free Flap Monitoring System: Circulatory Compromise Detection Based on Visible-Light Image

Microvascular free flap surgery has been a reliable reconstruction method, but some flaps may have circulatory compromise within five to seven days of surgery. Besides, many auxiliary devices are expensive and complex to operate. Therefore, most of the medical personnel still use the manual observation. To decrease heavy workload on medical personnel, the monitoring system was developed to analyze the color variation of free flap by a visible-light camera with advantages such as fast operation, low cost, noninvasive behavior, and contactless and nonradiative operation would be also needed for patients. The proposed system was mainly comprised of a longitudinal image registration without markers and a circulatory compromise detection, which were aiming to reduce the deformation from patients’ motion and eliminate the influence of illumination variation from the surrounding, respectively. In the clinical trial, the performance assessment of image registration reveals that the average and the standard variation of dice similarity coefficient (DSC) can reach 0.959 and 0.011, respectively. The relationship among the situation of blood perfusion and the results of circulatory compromise detection at flap was summarized and shown that the detection system not only determined the moment of vascular occlusion but also the type of occlusion. In addition, vascular congestion was even detected much earlier than manual observation. Therefore, our monitoring system is expected to relieve the workload on medical personnel and could be a reliable tool for the surgeon to hold onto the chance of repairing the free flap with vascular obstruction.