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Fig 1. A, Time course of the signal intensity from 1 section of a multisection gradient-echo EPI dataset at 1.5T during gadopentetate dimeglumine passage, TR/TE = 1,125/49 ms. During the first pass, signal intensity decreases due to the microscopic field-strength variations and water diffusion through gradients created by the intravascular contrast agent. B, Signal intensity versus time for regions of interest in the gray and white matter. C, From these curves and an estimate of the AIF, maps of perfusion-weighted parameters such as CBV, CBF, MTT, and Tmax can be created. Note the prolonged MTT and Tmax in the left hemisphere, representing ischemic tissue within the left middle cerebral artery territory. Sec indicates seconds; au, arbitrary units. Image courtesy of Dr. Rexford Newbould, Stanford University.
