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Quantification of left ventricular kinetic energy using 4D flow MRI
Journal of Cardiovascular Magnetic Resonance volume 12, Article number: O94 (2010)
Introduction
Three-dimensional, three-component, time-resolved (4D) intracardiac flow can be visualized and quantified with velocity encoded phase contrast (PC) MRI. The kinetic energy content of the blood in the left ventricle (LV) during the cardiac cycle has previously not been described.
Purpose
To develop a method to calculate the kinetic energy during the cardiac cycle of the LV from 4D PC-MRI.
Methods
Six healthy volunteers age 32 ± 11 (mean ± SD), 4 men, were imaged in a 1.5 and 3 T Philips scanner, i.e. two scans per subject in one day. A 4D PC TFE-sequence with retrospective ECG-triggering and respiratory navigator, 3 mm isotropic voxels and a temporal resolution of 25 ms interpolated to 40 phases was used to quantify intraventricular flow. Typical sequence parameters: 1.5 T SENSE factor 2, TE/TR/flip (3.7/6.3 ms/8°). 3 T, SENSE factor 2, TE/TR/flip (3.7/6.2 ms/8°). Cine images from a SSFP sequence (TE/TR/flip, 1.5/2.9 ms/60°) with spatial resolution 1.48 × 1.48 mm, slice thickness 8 mm and a temporal resolution of 30 heart phases, covering the LV in short axis view was used to delineate the endocardial contours. 4D-flow data was post-processed using an in-house developed software including linear background phase correction. PC images were reconstructed from the 4D-data in the short axis view and the endocardial contours were imported and manually corrected when needed. The kinetic energy was calculated as the squared velocity times the mass divided by two for all voxels within the LV for each time point. LV energy values are presented as mean ± SEM and results from the 1.5 T and 3 T measurements were compared according to Bland-Altman analysis (mean ± SD).
Results
Three distinct kinetic energy peaks during the cardiac cycle was seen in all subjects (Figure 1), one in systole, the largest in early diastole, and one smaller in late diastole corresponding to the atrial contraction. Mean kinetic energy LV energy values were: systolic peak 3.8 ± 0.7 mJ, early diastolic peak 5.5 ± 0.8 mJ and late diastolic peak 1.1 ± 0.1 mJ. Bias between the two MRI scanners were 0.9 ± 1.1, -0.5 ± 1.2 and 0.1 ± 0.2 mJ for the three peaks respectively.
Conclusion
It is feasible to calculate LV kinetic energy using 4D PC MRI. The method showed a low interstudy variability and studies in patients are ongoing.
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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Wåxnäs, T.A., Heiberg, E., Togert, J. et al. Quantification of left ventricular kinetic energy using 4D flow MRI. J Cardiovasc Magn Reson 12 (Suppl 1), O94 (2010). https://doi.org/10.1186/1532-429X-12-S1-O94
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DOI: https://doi.org/10.1186/1532-429X-12-S1-O94
Keywords
- Short Axis View
- Endocardial Contour
- Diastolic Peak
- Intraventricular Flow
- Interstudy Variability