Holographic Display for Quantification of Mitral Annular Dynamics

Three-dimensional (3D) echocardiography with multiplanar reconstruction (MPR) is used clinically to quantify the mitral annulus. MPR images are, however, presented on a two-dimensional screen, calling into question their accuracy. An alternative to MPR is an autostereoscopic holographic display that enables in-depth visualization of 3D echocardiographic data without the need for special glasses. The aim of this study was to validate an autostereoscopic display using sonomicrometry as a gold standard.

Accurate assessment of mitral valve disease is pertinent when planning valve repair and increasingly important with the introduction of novel treatment strategies. Imaging modalities such as two-dimensional (2D) and three-dimensional (3D) echocardiography have important limitations in describing and quantifying the time-resolved 3D nature of the mitral valve apparatus.
Clinical data from patients and normal volunteers on mitral annular measurements have been acquired using 2D and 3D echocardiography and magnetic resonance imaging. Inconsistent data in the literature raise the question of how these mitral annular parameters are assessed. To ensure more reliable measurements, validation studies are needed, particularly when several commercial software packages allow the quantification of different mitral annular parameters on the basis of echocardiographic data.

The mitral valve area was calculated as follows: the coordinates of each crystal in 3D space were calculated. The center point of the mitral valve ring was found as the average position of the crystals around the mitral ring. The ring area was then segmented into triangles consisting of the three corners made up of two neighboring crystals and the center point. The mitral valve area was finally calculated as the sum of the areas of these triangles. This calculation was performed at each time frame throughout the cardiac cycle, providing the mitral valve area as a function of time.

The present study demonstrates that mitral annular dynamics can be quantified noninvasively using 3D echocardiography visualized on an autostereoscopic holographic screen. The mitral annular dimensions measured by 3D VSAS were validated against sonomicrometry and showed an excellent correlation. Furthermore, over a range of loading conditions, annular dimensions measured by 3D VSAS approximated those values obtained by sonomicrometry.