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Figure 1 Phase-contrast images of the brachial artery cross-section in a normal subject. Each image consists of a magnitude (anatomic) and a phase (velocity) component. Images were acquired at baseline, during arterial occlusion by cuff inflation (the magnitude component shows the flattened cross-section; the phase component shows absence of flow), during peak hyperemia immediately after cuff release and at 1 min after cuff release, when flow-mediated dilation had occurred. The images are smoothed (but the raw data used for measurements and calculations are unaffected).