Four-wavelength near-infrared imaging of abdominal aorta blood flow under surgical occlusion

This paper presents a four-wavelength near-infrared imaging system that can assist surgeons with intraoperative monitoring and imaging of blood flow of the vessel being occluded. The algorithm for this system, based on the Beer-Lambert law, calculates the relative concentrations of deoxyhemoglobin, oxyhemoglobin and water, which are the major NIR absorbers in tissues. Regional blood volume and oxygen saturation can be determined from these measurements. This proof-of-concept study investigated the utility of the algorithm on detecting rat infrarenal abdominal aortic blood flow subjected to various degrees of occlusion. The images provided a good visualization of the aorta because of the high concentration of oxyhemoglobin in the blood stream. The imager was able to detect when blood flow was completely stopped. Average intensity values of the blood volume images correlated well with the laser Doppler recordings.