Methods for high resolution myocardial motion and strain quantification and robust coronary MRA in a relaxed cardiac MRI exam

Cardiovascular disease is the leading cause of death in the developed world. Both cardiac motion and strain quantification and coronary artery angiography based on magnetic resonance imaging (MRI) are important tools for the prognosis and diagnosis of cardiovascular disease. The main goal of this thesis is to develop and evaluate techniques that address the limitations of MRI associated with long image acquisition times that compromise patient comfort during imaging.;We have developed TruHARP to address the tradeoff between data acquisition time and the resolution of motion and strain estimates. TruHARP is a combination of optimized single breath-hold data acquisition protocol and a post processing frame-work, which together provide higher spatial resolution (4.37 mm) and more accurate motion and strain quantification than the current state of the art techniques. Monte Carlo simulations were performed to demonstrate improved resolution and to quantify the tradeoffs between resolution and noise. Improvements in strain quantification were demonstrated in six healthy human volunteers.;A fast imaging technique was developed to decrease the time needed to acquire MR images with motion or velocity encoded phase. Undersampling in Fourier space is employed to speedup data acquisition. The artifacts typically associated with under-sampling were suppressed by exploiting the redundancies present in both the phase of the stationary parts of the MR image sequence and the presence of multiple receiver coils. Simulations were performed to evaluate the quality of image reconstruction from undersampled data. An in-vivo human study was performed to demonstrate that a TruHARP dataset that would ordinarily require 35 heartbeats can be accomplished in only 20 heartbeats with less than 15% increase in error for strain estimates.;Coronary MRA scans are carried out during free breathing with the help of respiratory navigators because multiple heartbeats are required to acquire sufficient data. High magnetic field strengths (3T and 7T) can be used to improve both resolution and signal-to-noise ratio in these images, but the navigators are adversely affected at high field strengths. We have optimized the conventional 2D-selective navigator and have proposed a new non-selective navigator for use at 3T and 7T. Coronary MRA were successfully obtained using both navigator techniques in human volunteers at both 3T and 7T magnetic field strengths. They were found to have similar performance but possess tradeoffs that may yield a preference for adopting one or the other in different scenarios.