Quantification of left ventricular volumes, mass, and ejection fraction using cine displacement encoding with stimulated echoes (DENSE) MRI

Abstract

Purpose: To test the hypothesis that magnitude images from cine displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging (MRI) can accurately quantify left ventricular (LV) volumes, mass, and ejection fraction (EF).

Materials and methods: Thirteen mice (C57BL/6J) were imaged using a 7T ClinScan MRI. A short-axis stack of cine T2-weighted black blood (BB) images was acquired for calculation of LV volumes, mass, and EF using the gold standard sum-of-slices methodology. DENSE images were acquired during the same imaging session in three short-axis (basal, mid, apical) and two long-axis orientations. A custom surface fitting algorithm was applied to epicardial and endocardial borders from the DENSE magnitude images to calculate volumes, mass, and EF. Agreement between the DENSE-derived measures and BB-derived measures was assessed via coefficient of variation (CoV).

Results: 3D surface reconstruction was completed on the order of seconds from segmented images, and required fewer slices to be segmented. Volumes, mass, and EF from DENSE-derived surfaces matched well with BB data (CoVs ≤11%).

Conclusion: LV mass, volumes, and EF in mice can be quantified through sparse (five slices) sampling with DENSE. This consolidation significantly reduces the time required to assess both mass/volume-based measures of cardiac function and advanced cardiac mechanics.

Keywords: DENSE; heart; magnetic resonance imaging; ventricular volume and mass.

Figure 1

Overview of image processing steps: cine data were acquired from mice using either black blood (top row) or DENSE (bottom row) algorithms in both short- and long-axes. A) shows the number and orientation of these slices with respect to a 4-chamber view. For end diastolic phases, the endo- and epicardial surfaces were segmented, as shown in B) and C) for 2-chamber and short axis images, respectively. However, it is noted that the long-axis black blood images were not used for slice area summation. At end systole, only the endocardium was segmented (D). Finally, the endo- and epicardial valve points at their intersection with the myocardium were marked on the long-axis images (E) for definition of the valve plane in the 3D surface model.

Figure 2

Components of the 3D surface reconstruction: A) The valve boundary (in pink) calculated from the specified points (in blue), as shown in Figure 1E; B) Posterior lateral view of the endocardial surface (shown in yellow) with valve boundary intersection used for calculation of ventricular volumes; C) Posterior lateral view of the epicardial surface (dark green) encompassing the endocardium, used for calculation of ventricular mass; D) The valve boundary extruded through the epicardial and endocardial surfaces.

Figure 3

Bland-Altman plots comparing the left ventricular (LV) A) end diastolic volume, B) end systolic volume, C) ejection fraction, and D) mass results between the 3D surface model and segmented area summation method both derived from the black blood image stack. The blue markers denote measurements taken from the mice on a low fat diet, while the red markers correspond to the high fat diet mice.

Figure 4

Bland-Altman plots comparing the left ventricular (LV) A) end diastolic volume, B) end systolic volume, C) ejection fraction, and D) mass results between the 3D surface model from DENSE magnitude images and the area summation method using the black blood image stack. The blue markers denote measurements taken from the mice on a low fat diet, while the red markers correspond to the high fat diet mice.