1. A method, comprising: providing an initial estimate of a value representative of a blood flow characteristic at a current timestep; determining a probability distribution of transition, wherein the probability distribution of transition includes potential values of the blood flow characteristic at the current timestep with associated probabilities of occurrence based solely on the initial estimate; obtaining an initial measurement of the blood flow characteristic; determining a probability distribution of measured values, wherein the probability distribution of measured values includes potential values of the blood flow characteristic at the current timestep with associated probabilities of occurrence based on the initial measurement; combining the probability of distribution of transition with the probability of distribution of measured values to determine a meaningful blood flow characteristic value; and posting the meaningful blood flow characteristic value.