Fig 1. A, An example of ICA flow territory (red) in a population with a nonvariant type of circle of Willis. B and C, CBF (mL/100 g per minute) and MTT (seconds) perfusion maps of 1 patient with a nonvariant type of circle of Willis, showing the regions of interest placed on the territory of distribution of the ICA. No CBF and MTT changes are appreciable on visual inspection.