ABSTRACT
Myocardial tissue tracking based on a threedimensional (3D) data set has been anticipated because the heart moves in a 3D space. Regional myocardial deformation was fi rst assessed on the basis of tissue velocity with tissue Doppler imaging.1 However, wall deformation can be accurately estimated only at regions parallel to the ultrasound beam owing to the use of the Doppler effect. Next, two-dimensional (2D) speckle tracking echocardiography (STE), which is based on tracking of speckle patterns created by interference of ultrasound beams in the myocardium, became available. This methodology is based on a B-mode image, so it is conceptually angle independent of the ultrasound beam. In the setting of 2D echocardiography, the heart moves through the 2D plane of interest, and in fact, a different myocardium appears in the 2D image frame by frame. This is called “throughplane or out-of-plane phenomenon.” Figure 18.1 illustrates the effect of 3D motion on the image of a cross-sectional image plane.2 Left ventricular (LV) translation and rotation might be perceived as being due to ventricular contraction on the 2D image and, therefore, might lead to either underestimation or overestimation of the segmental deformation. Especially, longitudinal shortening makes the LV base move toward the apex by approximately 10 mm during a systole in a healthy subject. As a result, this may cause no negligible effects on the accuracy of tissue tracking. In contrast, 3D fullvolume LV data overcome the limitation of plane dependency of the 2D image, and rotation, translation, and, myocardial contraction itself can be directly appreciated.
