Rationale and objectives: Ejection fraction (EF) measurements obtained using conventional cine-magnetic resonance imaging (MRI) are accurate but time-consuming. With echoplanar imaging (EPI), these data can be acquired much faster. In this study, EF and cardiac output (CO) measurements based on EPI data are compared with those measurements based on cine-MRI images.
Methods: Twelve subjects were examined on a 1.5-T imager equipped with a special EPI gradient system. The entire heart was imaged with contiguous axial 10-mm sections using cine-MRI and EPI techniques. With cine-MRI, 20 frames were acquired over 256 cardiac cycles; with EPI, 24 frames were obtained over four RR intervals using an electrocardiogram-triggered four-shot acquisition strategy. Ejection fraction and CO were calculated based on the summation of the individual end-systolic and end-diastolic volumes. Ejection fraction and CO measurements based on the two different data sets were compared.
Results: Multishot EPI was 50 times faster than cine-MRI. The short acquisition time permitted breath-hold imaging. The high temporal (16 to 24 frames/RR interval) and spatial resolution (1.56 x 1.56 mm in plane) of the multishot EPI images enabled delineation of the ventricular lumen at end-systole and end-diastole in a fashion similar to cine-MRI. Echoplanar imaging EF and CO measurements correlated well with cine-MRI EF measurements, with correlation coefficients of 0.96 and 0.94, respectively. The 95% confidence interval of the EF measurement differences between the two techniques was narrow, ranging from -5.2 to 5.7 EF percentage points.
Conclusions: Accurate volumetric EF and CO measurements are possible based on ultrafast multishot EPI data sets as part of an integrated MRI-based cardiac evaluation.