Fig. 6.

The profile of the concentration signal changes drastically in the range of $\mathit{Da}=1''–''7.5$. From the Gaussian curve with long tail at $\mathit{Da}=0.75$, increasing the value of Da gradually causes a shift back to a symmetric Gaussian distribution, except that the principal transport downstream now occurs in the tissue phase. This shift in signal shape permits an estimation of the values of Da encountered in clinical imaging.