Oxygen saturation imaging using dual-wavelength LED-based photoacoustics

Since hypoxia is an early marker for cancer and several microvascular disorders, imaging oxygen saturation with high resolution has profound importance in multiple preclinical and clinical imaging studies. In this work, we demonstrate the potential of dual-wavelength (690/850 nm) LED-based photoacoustic imaging in high resolution real-time oxygen saturation imaging in vivo. We performed two live rat imaging experiments in which the oxygen saturation of the blood vessels in the left hindlimb was imaged for 20 seconds while the animal was breathing pure nitrogen gas to induce hypoxia. For a comparison, we continuously monitored the oxygen level using a pulse oximeter connected to the forelimb. In another experiment, we performed imaging of oxygen saturation changes in the tail vein of the rat while hypoxia was induced over the period of 40 seconds. In this case also, pulse oximeter readings were recorded for a comparison. In all the experiments, photoacoustic-based oxygen saturation values measured over time followed the same trend as the reference values provided by the pulse oximeter. Also, our two wavelength LED-based photoacoustic imaging approach was found to be sensitive even for 3% change in oxygen saturation. Results give a direct confirmation about the potential of LED-based photoacoustic imaging in detection of oxygen saturation with high spatio-temporal resolution, making it an ideal tool for hypoxia detection in longitudinal preclinical and clinical imaging studies.