Cardiac MRI > Pathology > Coronary Artery Disease > Assessment of Cardiac Function and Volumetrics
Assessment of Cardiac Function and Volumetrics
Due to the superb delineation between blood pool and myocardium, Cardiac MRI is well suited for evaluation of both regional and global myocardial function. It has become the gold-standard for following ventricular volumetric indices.
Global myocardial function can be qualitatively as well as quantitatively assessed. From the horizontal long axis and vertical long axis view, ejection fraction (EF) can be visually estimated. Semi-quantitative measurements of the heart chambers are made from the horizontal long axis as follows:
|Left Ventricular End Diastolic Diameter (LVEDD)||
|Right Ventricular End Diastolic Diameter (RVEDD)||
|End Diastolic Thickness (EDT)||
|Right Atrial End Systolic Diameter (RAESD)||
|Left Atrial End Systolic Diameter (LAESD)||
These images shows 4 chamber views of the heart at end diastole and end systole to calculate various cardiac indices. The end diastole image is used to calculate LVEDD, RVEDD, and EDT. The end systole image is used to calculate RAESD and LAESD.
Cardiac MRI can quantify volumetric indices of the heart directly from the 3 dimensional dataset; an ability that sets it apart from other modalities. End-Diastolic Volume (EDV), End-Systolic Volume (ESV), Stroke Volume (SV), Ejection Fraction (EF), and Ventricular Mass can be obtained using Simpson’s rule (see next section). Cardiac MRI has the benefit of being able to determine these measurements in the right heart as well as the left.
Regional myocardial function is most often assessed visually, by evaluating wall thickening. However, quantitative assessment is possible by directly measuring wall thickening. Myocardial tagging can be used to calculate “strain”, a more accurate depicter of myocardial function. The downside of using myocardial tagging to calculate strain is that it requires significant time for post-processing. Researchers are working on several new techniques that would make calculating myocardial strain simpler including cine Displacement Encoded Stimulated Echo (DENSE) imaging.
This graphic is a schematic of myocardium contraction in the presence of tag lines. The first image is during diastole and the second during systole. The myocardium is thicker in the systolic image. The tag lines form regular squares in the diastolic image, but become deformed in the systolic image. The measurement of deformation of the tag line is used to calculate myocardial strain.
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