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Figure 1 Magnetic resonance imaging (MRI) of brachial artery reactivity to hyperemia. (a) Set up for brachial artery imaging in the magnetic resonance scanner with a pressure cuff on the forearm distal to the imaging site (curved arrow) and a surface coil placed above the elbow region for optimal magnetic resonance signal detection (straight arrow). (b to d) High-resolution MRIs aligned perpendicular to the brachial artery (arrows). (b) Baseline conditions (scale bar = 3 mm). Note the increase in brachial artery cross-section area (c) 1 min after cuff release (representing flow-mediated dilation) and (d) 3 min after GTN application (endothelium-independent relaxation).