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Coronary Artery Imaging
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Overview:
MR depiction of the coronary arteries is a non-invasive technique that does not require ionizing radiation. As such, it is very appealing as a means of screening for disease or for routine evaluation following therapy. MR visualization, however, is challenged by cardiac and respiratory motion, as well as the stringent resolution requirements for adequately delineating coronary morphology. Research in this area is focused on improving coronary vessel conspicuity with an assortment of different MR techniques.
Findings:
We have focused on free-breathing acquisition strategies in which the position of the diaphragm is monitored via a 2D navigator pulse. Data is only accepted when the diaphragm is within a 5 mm window, and the acquisition volume is adjusted in space in proportion to the offset within this window. The acquisition window is further limited to 80-100 ms towards the end of each cardiac cycle. Data acquisition is from a 3D volume angulated such that a large fraction of the right or left coronary vessels are included.
Optimization of signal readout during this accetpable period of image acquisition is crucial. The figure above shows 4 different acquisition stategies for the right coronary artery in a volunteer. TFE-cart is the standard cartesian turbo field echo acquisition that was used in a recent multi-center trial [1]. A balanced turbo field echo (steady state acquisition) was also used with cartesian (b-TFE cart) and radial (b-TFE rad) k-space filling. Finally, a spiral acquisition strategy was also investigated (FFE spiral). Our preliminary findings indicate a very strong potential application for balanced acquisition stategies. They appear to demonstrated superior vessel conspicuity and reveal longer vessels segments.
[1] W.Y. Kim et al. "Coronary Magnetic Resonance Angiography for the Detection of
Coronary Stenoses" New England Journal of Medicine Vol 345, page 1863-1869.
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Last update: December 10, 2001