The stack of short-axis cine bSSFP images covering the entire heart can be used to quantify a number of useful clinical indicators of cardiac function. Modern post processing software can demarcate the borders of the endocardium and epicardium, as shown in Fig. 8. These can then be used to extract parameters such as ejection fraction, stroke volume, myocardial mass, and regional wall thickening. Controlled doses of dobutamine can also be administered to investigate wall motion abnormalities during stress.6
CMR can also be used to evaluate aspects of valvular heart disease.7 Valvular function can, for example, be observed in cine gradient echo images. . Turbulent flow reduces the synchronicity of the protons being imaged and results in signal loss. A turbulent jet from an aortic valve regurgitation is evident in Fig. 9 as a characteristic dark streak in the otherwise bright blood (white arrow). This is commonly known as a flow void.
Phase contrast velocity encoded MRI allows one to obtain measures of blood velocity plotted over the cardiac cycle through the valves and the great vessels.8 This affords quantitative measures of blood flow which can, for example, be used to estimate the ejected blood volume during systole, or capture flow profiles proximal and distal to a stenosis. Newer scan techniques measure blood flow in multiple slices and in three directions.9 Fig. 10 shows an example of how these data can be used for assessing blood flow in the aorta.
Several techniques exist to provide quantitative measures of intramyocardial function. The phase contrast velocity encoding technique can also be used for myocardial tissue velocity mapping.10 MRI myocardial tagging is another technique where the signal in the myocardium is destroyed in a series of dark bands or tags, which are a material property of the tissue and can be seen to deform as the heart moves.. Tagged images provide insight into contracti-lity and myocardial mechanics, and can be processed to yield meaningful measures of myocardial strain.11
Displacement encoding with stimulated echoes (DENSE) MRI is a related technique which provides more accurate measures of myocardial displacement and strain.. The healthy tissue exhibits a strong contraction (blue) and the region of poor contractility (yellow) corresponds to the location of the fibrosis.
Although MRI coronary imaging has improved considerably over the past years, resulting in techniques such as volume imaging with respiratory navigator tagging, multidetector computed tomography (CT) is still the gold standard for coronary angiography. However, because thickening of the vessel wall precedes luminal narrowing, MRI has the ability to detect early coronary atherosclerosis.
CMR can also be used to evaluate aspects of valvular heart disease.7 Valvular function can, for example, be observed in cine gradient echo images. . Turbulent flow reduces the synchronicity of the protons being imaged and results in signal loss. A turbulent jet from an aortic valve regurgitation is evident in Fig. 9 as a characteristic dark streak in the otherwise bright blood (white arrow). This is commonly known as a flow void.
Phase contrast velocity encoded MRI allows one to obtain measures of blood velocity plotted over the cardiac cycle through the valves and the great vessels.8 This affords quantitative measures of blood flow which can, for example, be used to estimate the ejected blood volume during systole, or capture flow profiles proximal and distal to a stenosis. Newer scan techniques measure blood flow in multiple slices and in three directions.9 Fig. 10 shows an example of how these data can be used for assessing blood flow in the aorta.
Several techniques exist to provide quantitative measures of intramyocardial function. The phase contrast velocity encoding technique can also be used for myocardial tissue velocity mapping.10 MRI myocardial tagging is another technique where the signal in the myocardium is destroyed in a series of dark bands or tags, which are a material property of the tissue and can be seen to deform as the heart moves.. Tagged images provide insight into contracti-lity and myocardial mechanics, and can be processed to yield meaningful measures of myocardial strain.11
Displacement encoding with stimulated echoes (DENSE) MRI is a related technique which provides more accurate measures of myocardial displacement and strain.. The healthy tissue exhibits a strong contraction (blue) and the region of poor contractility (yellow) corresponds to the location of the fibrosis.
Although MRI coronary imaging has improved considerably over the past years, resulting in techniques such as volume imaging with respiratory navigator tagging, multidetector computed tomography (CT) is still the gold standard for coronary angiography. However, because thickening of the vessel wall precedes luminal narrowing, MRI has the ability to detect early coronary atherosclerosis.
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