Previous studies have demonstrated that infrared (IR) intraoperative imaging is a reliable tool to identify perfusion of brain tumors and kidneys in human surgery. To explore further imaging specific to organ structure and ischemic injuries, intra-operative IR and fluorescent imagery was performed on a porcine model. ? ? Ureter: Both IR and fluorescent imaging enabled the surgeon to view, record, replay, print, and archive high quality, real-time images of a ureter during infusion of contrast agent. However, as a result of tissue saturation with the fluorescent agent, ICG, fluorescent imaging was not useful after the second bolus injection. IR imaging was repeated multiple times by slightly changing temperature of infused saline (cooler or warmer then previous bolus by ~1 degree C). Synthesis of derivative images from collected IR images allowed visualization of the velocity pattern of the bolus within the ureter and, therefore, any non-uniformity of structures within the ureter. Fusion of IR and visible images allowed outlining the ureter based on functional (IR) and surface structural features.? ? Bowel: The site of ischemic injury was visualized by fluorescent imaging with more detail than with IR. The region of bowel rendered ischemic did not pick up the agent and therefore did not fluoresce, making identification simple. Adjacent vascular arcades were visualized and showed striking fine vessels structure. However, the observed washout time (5-7 min) was a limiting factor. ? ? Kidney: Both IR and fluorescent methods allowed visualization of gross renal perfusion. However, as in the previous example with the ureter, fluorescent imaging failed to visualize partial occlusion and reperfusion due to ICG buildup in the kidney parenchyma. IR imaging immediately showed what segment of the kidney was occluded or reperfused. Further analysis of the IR data demonstrated low frequency oscillations attenuated substantially at the site of ischemic segments but not in the perfused segments of the kidney.? ? Intraoperative imaging offers a promising modality for real time ureteral identification and assessment of renal and bowel perfusion. Because of limited penetration capabilities of the light and an increase in background fluorescence during acquisition of successive fluorescent images, the fluorescent method can be used only for visualization of ischemic area involving superficial vessels. Kidney perfusion focal deficits were easily identified using IR imaging, even without bolus injection. Observed low frequency blood flow oscillations were probably related to local vasomotion and endothelial layer damage at the site of ischemia. This phenomenon may be useful for the assessment of ischemic injury and endothelial cell integrity.?
