| Magnetic resonance imaging (MRI) is rapidly emerging as a powerful tool for cardiovascular imaging. While respiratory and cardiac motion have complicated traditionally long MR scans, recently developed real-time interactive MRI techniques appear robust. Entire image acquisitions are completed within a fraction of a cardiac cycle (usually <150 ms), with minimal motion artifacts. An important part of cardiovascular MRI is the development of imaging sequences that provide different types of contrast and information in real time. In this thesis, I will present four real-time interactive MRI sequences that are aimed at imaging different aspects of cardiovascular disease. In addition, I will present a new technique for correcting one important type of MR image artifact.; First a method is presented for imaging cardiac blood flow as well as anatomy in real time. Spin velocity and spin density information are acquired and displayed simultaneously, much like color flow ultrasound. This tool is useful for evaluating regurgitant valves and provides great scan flexibility compared to ultrasound.; Secondly, a method is presented for improving contrast and reducing artifacts in cardiac images that are dominated by blood signal. Real-time suppression of flowing blood improves blood-myocardium contrast and eliminates flow artifacts, enabling the fast imaging of heart and vessel wall.; Next, there will be a discussion of two applications that require high spatial and high temporal resolution. First is multislice imaging of the left ventricle, which involves acquiring upwards of 50 images per second to provide multiple slice information under conditions of cardiac stress. Second is the interactive screening of coronary arteries, which requires sub-millimeter image resolution. When designing imaging sequences, one must make decisions about tradeoff between temporal resolution, spatial resolution and signal strength. In both of these cases the limits of temporal and spatial resolution are discussed.; Finally, a new method is presented for estimating and correcting off-resonance artifacts. These artifacts, mainly caused by magnetic field inhomogeneity and chemical shift, cause image blurring in radial-based acquisitions. The new technique corrects for these artifacts and saves scan time compared to existing techniques. |
