A note on cardiac magnetic resonance (CMR) imaging

I started hearing about cardiac magnetic resonance (CMR) imaging when there were 1.5 Tesla units around. Once I heard of a 0.5 Tesla unit, though it was not being used for cardiac imaging. Later came the news of 3 Tesla units. It was only today that I read of 7 Tesla for CMR spectroscopy! They provide higher signal-to-noise ratio and more precise quantification of myocardial high-energy phosphates. CMR has a role in the diagnostic work up of complex congenital heart disease as well. It has an edge over computed tomography in that it does not involve ionizing radiation. CMR is now routinely used in the evaluation of cardiomyopathies and myocarditis. In fact the Lake Louise criteria for diagnosis of myocarditis is based on CMR findings.

CMR is also useful in the assessment of myocardial masses and fibrosis. Dobutamine stress CMR is a sensitive and accurate method for detection and quantification of myocardial ischemia. Repeated CMR evaluations can be done to track progression of disease processes and results of therapeutic interventions, without fear of radiation hazards.

Three dimensional imaging and 4D imaging which encodes the velocity of flowing blood can be visualised using specialised software. But this requires complex post processing and needs relatively long acquisition times. Still it finds application in complex congenital heart disease and for research into cardiovascular flow characteristics.