Enhanced thermal imaging to detect microvasculature during surgery: Real-time image acquisition

Abstract

We are developing a new IR imaging technique, enhanced thermal imaging (ETI), that can delineate blood vessels embedded in water-rich tissue in real time. The technique is a combination of thermal IR imaging (8-10 μm) and selective heating of blood (∼0.5°C) relative to surrounding water-rich tissue using LED sources (530 nm) at low powers (irradiance <500 mW/cm2). Blood absorbs light strongly at these wavelengths, while absorption by soft tissues is lower. Illumination of tissue containing vessels with the LED heats the blood compared to surrounding tissue so that the vessels appear brighter in the thermal image. In previous work, we successfully highlighted vessels embedded in porcine heart tissue and the blood-rich vascular region that is routinely targeted for surgical excision around mammary tumor masses in a murine model. However, in this earlier work the IR images were recorded, and extensive post-acquisition processing was necessary to highlight the presence of the vascular structures. In this work, we describe recent progress in making ETI a real-time technique. A tissue model with simulated blood vessels and a porcine heart tissue model were both imaged with a FLIR thermal camera. Frame-to-frame temporal and spatial derivatives were calculated in real-time and then used to identify regions exhibiting rapid changes in temperature, thus highlighting the structure of blood-rich regions.