Cardiac magnetic resonance imaging (CMR)

Cardiac magnetic resonance imaging (CMR)

Cardiac magnetic resonance imaging is the most accurate and reproducible technique for imaging the heart, with outstanding image resolution and intrinsic tissue contrast. It is safe, non-invasive and does not expose the subject to ionizing radiation.

White blood and dark blood imaging in CMR:

For functional imaging white blood imaging is used while dark blood imaging is used for morphological evaluation.

Delayed enhancement with gadolinium:

Delayed enhancement is seen in myocardial infarction and is due to relative excess of gadolinium in pathological tissues compared to normal tissue. Transmural delayed enhancement indicates poor prospects of revascularization. Delayed enhancement is not specific for ischemic injury and can occur with acute myocarditis, hypertrophic cardiomyopathy with fibrosis and dilated cardiomyopathy with fibrosis. Delayed enhancement indicates more of interstitial tissue into which gadolinium is concentrated.

Dobutamine stress MRI:

Dobutamine stress MRI has high specificity but low sensitivity. Increased systolic wall thickening of more than 2 mm is indicative of viability.

MRI for coronary evaluation:

MRI is useful for evaluation of coronary anomalies. But it is not an ideal modality for assessment of coronary stenosis.

Unlike MRI of other parts, CMR has the dual problem of cardiac and respiratory movements. Breathholding can overcome respiratory motion artefacts, but limits the duration of study. Another option is synchronous cardiac and respiratory gating [1].

Reference

1. Wen-Yih Isaac Tseng, Mao-Yuan Marine Su, Yao-Hui Elton Tseng. Introduction to Cardiovascular Magnetic Resonance: Technical Principles and Clinical Applications. Acta Cardiol Sin. 2016 Mar;32(2):129-44.