3-D Transthoracic and Transesophageal Image Acquisition
Windows and Views
Reconstruction of the Mitral Annulus

Building a 3-D model of any chamber is done by gathering images in a systematic way, and ensuring they are registered in 3-D space relative to each other. Sweeping the left ventricle in the longitudinal and axial direction gives two intersecting sets of tomographic images, while a magnetic locator device attached to the moving probe, or the angle and pitch information from a stationary probe, allow the image planes to be reassembled in 3-D.

(Reproduced courtesy of Florence Sheehan MD, Division of Cardiology, University of Washington.)

Starting from the sternum, sweeping the transducer along the 4th or 5th rib space gives a set of transverse images of the LV.

Intersecting sets of oblique longitudinal images are obtained by tilting the transducer in one or more rib spaces in the parasternal position.

Rotating the probe at the apical window gives a set of true longitudinal images perpendicular to those obtained parasternally This completes the orthogonal image acquisition for 3-D TTE. An analogous image set is obtained in TEE study by rotating the probe element through 180 degrees and capturing images every 5 to 7 degrees.

The mitral annulus can be reconstructed as a 3-D object across several points in the cardiac cycle. Using high density TEE data, the mitral annulus is marked in the images offline, then registered in 3-D. The resultant ring of annular markers is reconstructed and smoothed to create a moving cine loop of the annulus as it moves towards the apex during systole. Changes in its shape and elongation occur with myocardial action. When LV function is compromised, the ring's movement is abnormal.
(Reproduced courtesy of Florence Sheehan MD, Division of Cardiology, University of Washington.)