Figure 1. Graph showing the change in contrast concentration against time in a single voxel of normal grey matter of a normal brain. Crosses represent the original measurement points and a straight line shows the optimal curve fit result. Notice that the curve fitting process effectively removes the noise present in the original data. Since the curve fitting procedure uses only data during the early part of the first passage of the contrast bolus it also removes the effect of re-circulation of contrast which is responsible for the elevation of measurements in the later part of the curve.