Present embodiments are directed to a monitor system, such as a pulse oximetry system. The system may include a detection feature, an emission feature capable of emitting light into tissue and arranged relative to the detection feature such that the detection feature is capable of detecting the light from the tissue after passing generally through a portion of the tissue, a modulator capable of modulating the light to generate photon density waves at a modulation frequency generally in a range of 50 MHz to 3 GHz, a detector communicatively coupled with the detection feature, wherein the detector is capable of detecting characteristics of the photon density waves comprising amplitude changes and phase shifts, and a processor capable of making determinations relating to a value of a physiologic parameter of the tissue based at least in part on the detected characteristics.
