What are the disadvantages of MRI?
MRI examinations of the heart are lengthy, taking up to one hour, compared to minutes for CT. The examination also requires a good deal of patient cooperation with many breath holds of 15 to 20 seconds each. Claustrophobic patients may not be able to undergo the examination. MRI is costly and is generally not performed in patients with pacemakers or defibrillators, which limits its usage for many cardiac diseases. Also, CT has better spatial resolution than magnetic resonance angiography (MRA) in noninvasive coronary artery imaging, allowing for visualization of both calcified and noncalcified plaques as well as luminal obstruction. Furthermore, CT allows for simultaneous assessment of the lung parenchyma, which is more limited on MRI.