This proposal aims to use T2* weighted MRI to measure myocardial blood oxygenation. This is based on the notion that the deoxyhemoglobin is paramagnetic, and its presence in venous blood in the myocardium is expected to shorten T2* of the myocardium, which is the BOLD effect. Therefore, if Changes occur in the extend of blood oxygenation, either because of a reduction, or an increase in myocardial perfusion, this is expected to lead to changes in T2*. The investigations propose to measure T2* by a gradient echo MRI technique. The proposal aims to improve the MRI techniques to measure myocardial T2*. Instead of measuring images at 2TE's they propose to use 3 TE values, which is expected to improve the accuracy of the calculated T2*. Presaturation pulses will be used to avoid the effect of possible changes in T1, which is to be expected with changes in blood flow. Arterial blood will be presaturated by a double inversion method, as to avoid interference of an intense blood signal form the LV and the coronary arteries. The techniques will be validated in a series of canine model studies. Myocardial blood flow and oxygenation levels will be manipulated by drug intervention (dobutamine, adenosine), and by hypoxemia induced by reducing oxygen contents of the inspired gas. Then the method will be evaluated on its ability to detect regional changes in blood oxygenation. This will done in a canine model with simulated coronary artery disease. Finally, the proposed methods will be used to measure myocardial oxygenation in patients with coronary artery disease.
