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Research Papers

Automated Three-Dimensional Reconstruction of the Left Ventricle From Multiple-Axis Echocardiography

[+] Author and Article Information
Navaneetha Krishnan Rajan, Zeying Song

Department of Mechanical and
Aerospace Engineering,
University at Buffalo,
SUNY, Buffalo, NY 14260

Kenneth R. Hoffmann

Department of Neurosurgery,
University at Buffalo,
SUNY, Buffalo, NY 14214

Marek Belohlavek, Eileen M. McMahon

Division of Cardiovascular Diseases,
Department of Internal Medicine,
Mayo Clinic,
Scottsdale, AZ 85259

Iman Borazjani

Department of Mechanical and
Aerospace Engineering,
University at Buffalo,
SUNY, Buffalo, NY 14260
e-mail: iman@buffalo.edu

1Corresponding author.

Manuscript received April 3, 2015; final manuscript received October 30, 2015; published online November 23, 2015. Assoc. Editor: Alison Marsden.

J Biomech Eng 138(1), 011003 (Nov 23, 2015) (12 pages) Paper No: BIO-15-1146; doi: 10.1115/1.4031977 History: Received April 03, 2015; Revised October 30, 2015

Two-dimensional echocardiography (echo) is the method of choice for noninvasive evaluation of the left ventricle (LV) function owing to its low cost, fast acquisition time, and high temporal resolution. However, it only provides the LV boundaries in discrete 2D planes, and the 3D LV geometry needs to be reconstructed from those planes to quantify LV wall motion, acceleration, and strain, or to carry out flow simulations. An automated method is developed for the reconstruction of the 3D LV endocardial surface using echo from a few standard cross sections, in contrast with the previous work that has used a series of 2D scans in a linear or rotational manner for 3D reconstruction. The concept is based on a generalized approach so that the number or type (long-axis (LA) or short-axis (SA)) of sectional data is not constrained. The location of the cross sections is optimized to minimize the difference between the reconstructed and measured cross sections, and the reconstructed LV surface is meshed in a standard format. Temporal smoothing is implemented to smooth the motion of the LV and the flow rate. This software tool can be used with existing clinical 2D echo systems to reconstruct the 3D LV geometry and motion to quantify the regional akinesis/dyskinesis, 3D strain, acceleration, and velocities, or to be used in ventricular flow simulations.

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References

Figures

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Fig. 1

Echo cross sections of a pig heart are obtained over an entire cardiac cycle for standard projections. LA (apical) projections: (a) three-chamber, (b) two-chamber, and (c) four-chamber. SA projections: (d) apical, (e) mid, and (f) basal. All projections are shown for one time instant at end-diastole. Epicardial and endocardial borders are interactively delineated and automatically divided into standardized segments [40] by a commercial speckle tracking algorithm; however, only endocardial delineations are used in our study.

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Fig. 2

Overview of the steps for the developed method

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Fig. 3

LV segmentation, definition of angular orientation [40], and the spherical coordinate system. Standardized LA A2C, A3C, and A4C, as well as SA basal, mid, and apical sections of the LV are shown.

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Fig. 4

Extracted and smoothened boundaries at an instant of the A3C section

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Fig. 5

Overview of the steps for sectional scaling and the optimization of orientation and position (LA, long-axis and SA, short-axis)

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Fig. 6

Data transformation for the bivariate spatial interpolation: (a) long-axis (LAi) and short-axis (SAi) sectional data in cylindrical coordinates, (b) long-axis (LAi) and short-axis (SAi) sectional data on the z–θs plane, and (c) SA radial measurements transformed as scaling ratios (ei). Radius at the point P is evaluated as the product of radius interpolated from the LA sections (LAi) and scaling ratio interpolated from the SA sections (ei).

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Fig. 7

Surface points interpolated from the available cross-sectional data.

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Fig. 8

Generated triangular surface mesh—close up. The LV surface is divided into slices of fixed angular resolution, Δθs, and layers of fixed thickness, Δz.

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Fig. 9

Multiple views of the LV endocardial surface reconstructed at baseline. End-diastole: (a) longitudinal and (b) basal views and end-systole: (c) longitudinal and (d) basal views. In a healthy LV, the overall shape is preserved even under stress from contraction.

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Fig. 10

Volume (mL) of the LV during one cardiac cycle withvarying cutoff frequency, ns, for the temporal smoothing (number of time steps = 100)

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Fig. 11

Comparison of models reconstructed from three long-axis sections, and from six cross sections at (a) basal, (b) mid, and (c) apical locations at the same instant. Assuming the model reconstructed from six cross sections as reference, the difference between the curves shows the interpolation error.

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Fig. 12

Comparison of (a) volume, and (b) flow rate of models reconstructed from varying number of sections. (c) Percentage difference in volume and (d) absolute difference in flow rate, assuming the model with all the six sections as reference.

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Fig. 13

Sensitivity of (a) volume and (b) flow rate of reconstructed models with angular perturbation. Sensitivity of (c) volume and (d) flow rate of reconstructed models with longitudinal perturbation.

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Fig. 14

Volume change of models reconstructed based on different temporal resolution of the original echo data. In the models reconstructed at 100 and 2500 steps/cycle from the original high-resolution 46 fps echo data the volume curves are identical and all the cardiac phases can be distinctly identified. However, the model reconstructed from the echo data at 23 fps (by using every other frame of the original echo data) fails to capture the systolic peak and the diastasis (∼0.55–0.65 s) effectively.

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Fig. 15

Multiple views of the LV endocardial surface reconstructed after AMI. End-diastole: (a) longitudinal and (b) basal views and end-systole: (c) longitudinal and (d) basal views. Unlike the healthy LV in Fig. 9, the shape of the LV is not preserved when contracted due to the infarction. Notice the bulging anterior wall marked by the dotted line.

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Fig. 16

Comparison of (a) volume and (b) flow rate of an LV with acute myocardial infarction reconstructed from varying number of sections

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