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Figure 4 Circumferential profiles for five representative short-axis slices spanning the heart for the control study shown in Figure 3. There is normal variability in the relative image intensity, but no data points fall below 50% of the maximum (for any of the control studies). The anteriolateral reduction in intensity in the apical slice could be the result of apical thinning and the partial volume effect. The threshold for classifying a point as abnormal was set at 50%. Diamonds = apex; squares = apex and midventricular region; triangles = midventricular region; circles = base and midventricular region; rectangles = base.