Improvements in whole-heart coronary artery magnetic resonance angiography

Coronary artery disease (CAD) is the leading cause of death in the United States. The current gold standard for diagnosing CAD, x-ray angiography, is an invasive procedure, and exposes the patient to ionizing radiation. Coronary MRA techniques overcome these problems and have shown promising results in detecting CAD. However, they have not yet gained widespread clinical application due to unresolved challenges including: low spatial resolution, long scan time, suboptimal SNR, and residual respiratory motion artifacts. The goal of this dissertation was to tackle some of these problems.;To address the sub-optimal SNR in contrast-enhanced whole-heart coronary MRA, a novel self-triggering technique was developed. This resulted in an average SNR gain of 27% compared with traditional approaches.;To address the long scan time of current whole-heart coronary MRA techniques, EPI based approaches were explored. Using numerical simulations and phantom studies, a GRE-EPI acquisition scheme was optimized for contrast-enhanced whole-heart coronary MRA at 1.5T. For further reduction in scan time, this technique was extended for use at 3T, where the major problem tackled was phase correction in the presence of increased off-resonance effects. To overcome the GRE-EPI technique's sensitivity to motion, a radial EPI sequence was developed. A novel self-calibrating phase correction method was developed to correct for off-resonance effects in radial EPI. The radial EPI technique acquired whole-heart coronary MRA with 1.0 x 1.0 x 2.0 mm3 spatial resolution in a scan time of 5 minutes. Healthy volunteer and 2 patient studies showed excellent coronary artery visualization.;The third problem tacked in this dissertation was that of respiratory motion compensation during free-breathing coronary MRA. The navigator gating approach currently used for respiratory motion compensation results in low imaging efficiency (30-50%), leading to long imaging times. In this dissertation, a novel respiratory motion correction technique with 100% scan efficiency was developed using a 3DPR k-space trajectory for data acquisition, and a 3D affine transform for motion correction. Healthy volunteer studies showed results comparable with the traditional navigator gating approach. The proposed technique acquired whole-heart coronary MRA with 1.0 mm 3 isotropic spatial resolution with scan time of 7 minutes.