A monitoring system that may include an emission feature capable of emitting light into tissue, a modulator capable of modulating the emitter at a modulation frequency generally in a range of about 50 MHz to 3.0 GHz to generate resolvable photon density waves, a detection feature capable of detecting photons of the photon density waves after passage through the tissue and capable of providing a distribution of detected photons over a time period for the photon density waves, and a processor capable of calculating a skewness of the distribution and making determinations relating to a value of a physiologic parameter of the tissue based at least in part on the skewness of the distribution.
