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Estimation of the left ventricular ejection fraction using a novel multiphase, dark-blood, breath-hold MR imaging technique.

OBJECTIVE
In this paper, we evaluate a recently proposed dual-phase dark-blood MR sequence for estimating the left ventricular ejection fraction, compare Simpson's method of estimation of ejection fraction with a model based on the biplane method, assess the reproducibility of both methods, and finally, test a semiautomated method for contouring the endocardial border.


SUBJECTS AND METHODS
An MR pulse sequence was implemented to acquire cardiac images in both diastolic and systolic phases within a single breath-hold. A special magnetization preparation scheme rendered blood dark while a segmented acquisition allowed breath-hold scan times. Five healthy volunteers and five patients with cardiac disease were imaged. Ejection fractions were estimated using (1) long-axis and four-chamber biplane views with an ellipsoid model and (2) a series of short-axis views in combination with Simpson's model. These values of ejection fractions were then compared with values obtained from echocardiography.


RESULTS
Estimates of ejection fractions obtained using biplane ellipsoid volume and Simpson's rule methods varied by 14% in healthy volunteers. However, for patients with severe cardiomyopathy, differences between the values of ejection fraction obtained with the two methods varied by as much as 150%. Ejection fraction estimates obtained from MR images with the biplane ellipsoid method and from echocardiography varied by approximately 14% for all subjects. Ejection fraction estimates obtained with the semiautomated algorithm agreed well with estimates obtained with manual contours made by experienced radiologists. Intraobserver variability was low for both the short-axis (3%) and biplane (4%) methods. However, interobserver variability of the biplane method (12%) exceeded that of the short-axis method (4%). Interexamination variability (9%) was the largest factor in determining the reproducibility of the ejection fraction estimates.


CONCLUSION
Breath-hold dark-blood MR imaging technique with simultaneous acquisition of a series of short-axis views during systolic and diastolic phases permits rapid and accurate estimates of ejection fractions in healthy subjects and in patients. Model based biplane MR imaging methods are less reliable in patients with global cardiomyopathy. The estimation of ejection fractions can be automated using the proposed contouring algorithm and the dark-blood short-axis views.