HIGH RESOLUTION INTERACTIVE CORONARY ARTERY MRA

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DESCRIPTION (Adapted from Applicant's Abstract): The applicants proposed to apply fast MR imaging pulse sequences and real-time signal processing techniques in developing techniques for high resolution MR imaging of the coronary arteries. The specific hypothesis is that 1 mm isotropic resolution of images of the native coronary arterial tree can be reliably obtained in humans during a single or limited number of breathholds. Current techniques for coronary artery MRA are limited from factors which include: a large number of required phase encoding views, limited SNR, unsharpness due to cardiac and respiratory-induced motion, and limited blood-to-background contrast. These all become more severe as resolution is improved. The applicants proposed to address these limitations in the projects of: 1. Cardiac MR Fluoroscopy. Near real-time cardiac imaging will be used to interactively identify the targeted coronary artery vessels, position the desired oblique imaging plane or slab, and provide instant switching to a high resolution angiographic sequence. One or more such slabs will be identified for each of the three major coronary arteries, enabling formation of a "selective" angiogram for each. Real-time breathhold feedback will provide reproducible and yet allow flexible breathholding; 2. High Resolution Magnetization-Prepared Gradient Echo MR Angiography. An inversion recovery magnetization-prepared gradient echo sequence will be adapted for coronary angiographic imaging. Nulling of background myocardium will enable small branches and more distal vasculature to be better seen than with current techniques. Double oblique acquisition will allow considerable reduction of the required number of phase encodings and thus scan time reduction, allowing acquisition over only several breathholds. The inversion slab will be tailored to avoid saturation of arterial blood; and 3. High Resolution Multi-Shot Echo-Planar MR Angiography. 2-D and 3-D multi-shot EPI techniques will be adapted for coronary angiography. The number of shots per cardiac cycle, views per shot, and degree of gradient moment nulling will be optimized for angiographic imaging. EPI techniques are expected to provide an increased (>3X) number of views per unit time compared to current methods and enable single breathhold imaging of a complete coronary artery tree. The applicants projected that the techniques developed in this project can form the starting point for an eventual interactive system for performing many elements of a cardiac imaging examination.