FIG 1. Time-enhancement curves for four temporal sampling intervals: 0.5 second, 1 second, 2 seconds, and 4 seconds. The area under the curve is approximately the same for the first three sampling intervals. For the interval of 4 seconds, however, the peak points of the curve are undersampled (circle), resulting in a reduction in the area under the curve. This would result in significant errors in the calculation of rCBV.