Left and right ventricular kinetic energy using time-resolved versus time-average ventricular volumes.

PURPOSE: To measure the effects of using time-resolved (TR) versus time-averaged (TA) ventricular segmentation on four-dimensional flow-sensitive (4D flow) magnetic resonance imaging (MRI) kinetic energy (KE) calculations.

MATERIALS AND METHODS: Right (RV) and left (LV) ventricular KE was calculated from 4D flow MRI data acquired at 3.0T in 10 healthy volunteers and five subjects with cardiac disease using TR and TA segmentation. KE was calculated from the mass of blood within the ventricles multiplied by the velocities squared. Differences in TR and TA KE and interobserver variability were quantified with Bland-Altman analysis.

RESULTS: In healthy volunteers, peak systolic RV KE (KERV ) were 4.89 ± 1.49 mJ using TR and 5.53 ± 1.62 mJ using TA segmentation (P = 0.016); peak systolic LV KE (KELV ) were 3.29 ± 0.96 mJ and 4.16 ± 1.26 mJ (P = 0.005). Peak diastolic KERV were 3.33 ± 0.90 mJ (TR) and 3.61 ± 1.12 mJ (TA) (P = 0.082), while peak diastolic KELV were 4.90 ± 1.49 mJ and 5.31 ± 1.59 mJ (P = 0.044). In patient volunteers, peak systolic KERV were 4.34 ± 3.78 mJ using TR and 4.88 ± 3.98 mJ using TA segmentation (P = 0.26); peak systolic KELV were 4.39 ± 4.21 mJ and 4.36 ± 3.84 mJ (P = 0.91). Peak diastolic KERV were 3.34 ± 2.08 mJ (TR) and 4.05 ± 1.12 mJ (TA) (P = 0.08), while peak diastolic KELV were 4.34 ± 5.11 mJ and 4.06 ± 3.47 mJ (P = 0.75). Interobserver differences in KELV were greater for TR than TA calculations; bias ranged from 3 ± 30% for TA peak systolic KELV to 36 ± 30% for TR peak diastolic KELV .

CONCLUSION: Although qualitatively similar, KE values calculated through TA segmentation were consistently greater than TR KE, with differences more pronounced during systole and in the LV.

LEVEL OF EVIDENCE: 2 J. Magn. Reson. Imaging 2017;45:821-828.