Although most cardiac MRI studies have been performed on scanners with a strength of 1.5T, scanners with a greater strength of 3T are now increasingly available for cardiac MRI applications. Cardiac MRI studies require an appropriate combination of temporal and spatial resolution. Cardiac imaging with a strength of 3T offers improved speed, the ability to obtain higher spatial and temporal resolution, an increase in SNR, decreased imaging time, reduced background noise, and better image contrast as compared to 1.5T imaging. With the increase in SNR with 3T, heart perfusion images provide better visual delineation of perfusion abnormalities and cardiac ischemic evaluation.
An increased SNR with 3T MRI also reduces the loss of image quality due to patient movement, which is an important consideration in cardiac MRI due to heart motion. Furthermore, cardiac patients are often very sick and may suffer from irregular heart rates, and could therefore experience difficulty holding their breath during the procedure. New cardiac MRI protocols and technologic advancements have improved imaging speed, resulting in the ability to perform free breathing techniques for patients unable to hold their breath during the procedure. Likewise, frequency artifacts or flow artifacts prevalent during cine imaging (bright blood imaging) in earlier versions of 3T cardiac imaging have been resolved with improvements in software frequency correction techniques. This software allows the MRI technologist to run a frequency scout in any of the cardiac imaging planes. A set of 6 images can be obtained at 1 location with 6 different frequencies. The technologist reviews the images and simply selects the image with the least amount of frequency artifacts and inputs the correct frequency into the frequency selection card for the desired sequence.
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