(from Abstract): The broad objective of this research is to develop fast coronary magnetic resonance angiography (CMRA) techniques that can reliably image small coronary arteries. Technical advances proposed in this research seek to achieve 1 mm resolution, the size of significant coronary stenoses. Three criteria are identified for 1 mm (CMRA: 1) The motion induced point-spread-function (PSF) size has to be < 1 mm; 2) The signal-to-noise ratio has to meet the Rose Model criterion; 3) The voxel size has to be < 1 mm. These three criteria will be satisfied through four specific aims.
Aim 1. Develop cardiac motion prescan.
Aim 2. Develop efficient spiral data acquisition.
Aim 3. Develop integrated navigator techniques for suppressing both cardiac and respiratory motion effects.
Aim 4. Implement and test contrast enhanced navigator spiral CMRA in an animal model. Imaging artifacts from cardiac and respiratory motion continue to be the major challenge for CMRA. Motion blurring has to be reduced to < 1 mm for accurate imaging of significant coronary stenoses. Cardiac contraction motion will be estimated using M-mode navigator echoes. All components of respiratory motion will be measured using hybrid navigator echoes. A k-space time approach for motion reduction is proposed in this research. This k-space time approach allows synergistic integration of existing and new motion suppression methods including gating, view ordering and signal correction. Effects of both cardiac and respiratory motion will be suppressed simultaneously and effectively using this integrated method. T1-shortening contrast agent can substantially increase MR signal of blood, generating reliable vascular contrast free from flow-related artifacts. Contrast enhancement will be used to improve SNR and shorten scan time of CMRA. Efficient spiral acquisition will be developed to minimize scan time and optimize signal-to-noise ratio. Navigator based contrast enhanced CMRA will be developed via imaging the recirculation of an intravascular gadolinium agent. CMRA techniques will be evaluated on appropriate in vitro and in vivo models as they are developed. Successful development of this research will result in a motion-resistant 1 mm resolution CMRA technique with adequate SNR and reasonable scan time, allowing reliable imaging of significant coronary stenoses.
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