Abstract: A method and apparatus for deriving a physiological description and clinically-useful data reboarding the cardiovascular system of an individual subject. The method includes obtaining a measurement sample associated with cardiovascular flow and utilizing a model, which may be distributed and/or non-linear to derive a description and data. The model generates and uses functions of source parameters and may, in an embodiment, match measurement samples against a library of stored predicted samples. A best-matching, predicted sample may then be associated with a measurement sample. An apparatus is provided which, according to an embodiment, includes an input for obtaining a measurement sample, a processor to derive the description and data, and an output. The apparatus may also include a digital storage medium to store a library of predicted samples.