Measuring physiological parameters under the skin using visible/NIR light

Using visible/NIR light has recently gained popularity within biomedical imaging due to its safety and flexibility in implementation. Safe, reliable methods for measuring physiological parameters like perfusion, heart rate, and vascularization is crucial for monitoring severe disease pathologies. Here we discuss recent progress in optical imaging approaches for measuring these parameters on the surface (within a millimeter) and deep (millimeters to centimeters) within tissue. We restrict our discussion to only PPG measurements (for surface monitoring) and DOT (for deep imaging).