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Figure 6 Concept of the blood oxygenation level-dependent (BOLD)-related effect of capillary recruitment on T₂*. (a) Under normal perfusion conditions at rest, only a fraction of capillaries was open, contributing to the BOLD effect (the large arteriovenous difference along the capillary is represented by the dark end of the capillary). (b) Dipyridamole (DIP) produced enhanced coronary vasodilation without increasing heart work (light end of the capillary represents a decreased arteriovenous difference). (c) In the presence of a coronary artery stenosis, autoregulation induced compensatory relaxation of coronary resistance vessels and precapillary sphincters, which maintain sufficient blood supply under rest conditions. (d) Hence, DIP cannot produce further vasodilation. The green curve symbolizes the magnetic field inhomogeneities.