1. A perfusion assessment system including: means for providing an echo-power signal indicative of a reperfusion of a contrast agent in a body-part of a living subject following destruction of a significant portion of the contrast agent in the body-part, means for associating the echo-power signal to a perfusion function with an S-shape based on a plurality of elementary perfusion functions with said S-shape each one for a corresponding value of at least one perfusion parameter, the elementary perfusion functions being weighted according to a probability density distribution of the at least one perfusion parameter, wherein the S-shape includes an initial portion with substantially zero first derivatives, a final portion with substantially zero first derivatives, and a central portion between the initial portion and the final portion changing monotonically from a value of the initial portion to a value of the final portion, means for determining at least one shape indicator of the probability density distribution, and means for comparing the at least one shape indicator with at least one predetermined further shape indicator to identify morphological characteristics of the body-part according to a result of the comparison.