Comparison of time-intensity-curve- (TIC-) analysis of contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced (DCE) MRI for postoperative control of microcirculation in free flaps - first results and critical comments.

Postoperative monitoring of transplanted free flaps is an essential tool to reveal possible complications. The aim of this study was to compare the value of time-intensity-curve- (TIC-) analysis based on grey scale data of contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced (DCE-) magnetic resonance imaging (MRI). Postoperative imaging was performed in 11 patients following free flap transplantation and TIC analysis was obtained in identical regions of interest (ROI) of CEUS and DCE MRI data. Microcirculation was assessed in superficial (0-1 cm), middle (1-2 cm), and deep (2-3 cm) ROIs in one or two different positions within the flap resulting in a total of 46 ROIs evaluated (in very thin flaps only superficial and middle ROIs were assessed). For both imaging methods, mean signal increase was found to be significantly higher in ROIs of normally perfused flaps (n = 40) compared to ROIs with compromised microcirculation (n = 6). Although TIC analysis allows quantification of microcirculation in different regions of the flap, in this preliminary study no distinct threshold could be defined to differentiate flaps with normal and compromised microcirculation.