Susceptibility-sensitive magnetic resonance imaging detects human myocardium supplied by a stenotic coronary artery without a contrast agent
Christian M. Wacker, MD*,
Andreas W. Hartlep, PhD ,
Stefan Pfleger, MD ,
Lothar R. Schad, PhD,
Georg Ertl, MD* and
Wolfgang R. Bauer, MD, PhD*,*
* Medical Clinic, University of Wuerzburg, Wuerzburg, Germany
Department of Biophysics and Medical Physics, German Cancer Research Center (DKFZ), Heidelberg, Germany
I. Medical Clinic Mannheim, University of Heidelberg, Mannheim, Germany
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Figure 1 The T2* map of a healthy volunteer (short-axis view of left ventricle). Note the homogeneous distribution in T2* values. Colors from black to white reflect T2* values from 15 to 50 ms.
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Figure 2 The T2* maps of two different patients with high-grade stenosis of the left anterior descending coronary artery (by X-ray) and septal wall motion abnormalities (by stress echocardiography). Areas with reduced T2* values in the anteroseptal and septal regions are clearly detectable. Colors from black to white reflect T2* values from 15 to 50 ms.
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Figure 3 (a) Individual T2* values of stenotic and nonstenotic myocardial areas (examination at rest). (b) Relative changes in T2* before and after administration of dipyridamole (DIP). Results of all patients. Error bars represent the standard deviation.
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Figure 4 Patient with high-grade stenosis of the proximal left anterior descending coronary artery (LAD). Coronary angiograms in typical (a) right anterior oblique (RAO) and (b) left anterior oblique (LAO) projections. The T2* maps (short-axis view of left ventricle) before (c) and after (d) administration of dipyridamole. In the latter case, the magnetic resonance examination had to be interrupted during dipyridamole infusion owing to severe angina of the patient. Note the reduced T2* in the anteroseptal area (the region which is associated with the diseased vessel). The dark region at the inferolateral zone (d) is due to susceptibility artifacts arising from phrenicomediastinal recess. Ten weeks after dilation of the LAD (e), the measurement (also with dipyridamole) was finished without complications. When observing the obtained T2* maps, differences between regions with reduced T2* values and regions of normal myocardium were less pronounced than they were before percutaneous transluminal coronary angioplasty. Colors from black to white reflect T2* values from 15 to 50 ms. LCx = circumflex branch of left coronary artery.
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Figure 5 The T2* maps of a patient with high-grade stenosis of the proximal left anterior descending coronary artery. (a) Before coronary artery bypass graft surgery (CABG), areas with reduced T2* values in the septal region are clearly detectable. (b) Twenty weeks after CABG of the left internal mammary artery, differences in T2* were less pronounced. Note the homogeneity in the septal region after the intervention. Colors from black to white reflect T2* values from 15 to 50 ms.
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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.
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