The method comprises: a) receiving a plurality of imaging signals of the object over a period of time； b) measuring the signal intensity in each of the plurality of imaging signals corresponding to a point on the object； and c) curve fitting the measured signal intensity of the point on the object to a bi-exponential function comprising a first and a second exponential term, the first exponential term representing the decrease in concentration of the contrast agent which is free over time and the second exponential term representing a decrease in concentration of the contrast agent which is retained on the object over time.
