Figure 5.
(a, b) Change in BPND due to a doubling in blood flow (100% increase) simulated with the 3×CO2 pattern shown in Figure 4, for a range of K1, k2 and k3, k4 combinations. (a) The plot depicts that radiotracers with large K1 and small k2 values, i.e. large VD (volume of distribution) values, are most sensitive to changes in blood flow. Yet, even the largest changes deviate by <10% from the true BPND value, which is within test-retest values for most radiotracers. (b) The rate constants k3 and k4 show very small changes no matter what their values are, i.e. binding potential values do not seem to be a factor for flow sensitivity. (c) Changes in BPND for a large range of CBF values and different extraction fractions. For CBF increases up to 100%, BPND values are affected by less than 5%, which is well below test-retest values of most radiotracers.