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Figure 4 Time course of brachial artery flow-mediated vasodilation (FMD) in a healthy individual. The FMD was determined with the occlusion cuff on the upper arm as previously described (17). Images of the brachial artery were digitized (one image/cardiac cycle on the R-wave) at baseline (Pre) and continuously for 2 min beginning 20 s after cuff release using a commercially available image acquisition system (CVI Acquisition, Information Integrity, Stow, Massachusetts). Brachial artery diameters were measured using an automated edge-detection system (Brachial Tools, Medical Imaging Applications, Iowa City, Iowa).