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FIGURE 1. Normalized response of Ctiss to a rectangular flow change (A) and a more physiologic flow change (B). In A, flow was assumed to change from 50 to 100 and back to 50 mL/min/100 mL. In B, the curves were calculated as follows: First, the calculated cerebellar time course of CBF after ACZ of 1 patient was approximated by the equation CBFsim = CBFbase + 
CBF(1 – e–ln2/Txt), where baseline CBF (CBFbase) = 50 mL/min/100 g, CBF = 50 mL/min/100 g, and time (T) = 165 s. Simulated CBF (CBFsim) was then assumed to be true CBF (CBFtrue). CBFtrue and a constant ca were fed into Equation 1 to calculate a simulated time course of Ctiss (Ctiss sim). Ctiss sim was then back-converted to CBFc values using the equilibrium equation, Equation 4. For display purposes, all values were normalized to baseline and expressed as a percentage. The deviation of CBFc from CBFtrue is, at maximum, 13% (2 min after ACZ).
