Clinical Utility of Realtime Three-dimensional Echocardiography - A New and Emerging Standard

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Cardiac imaging has become fully integrated in the management of patients, with echocardiography being the most widely used modality. Two-dimensional echocardiography (2DE) offers a detailed assessment of ventricular function, valvular pathology, and hemodynamics, but its comprehensiveness is limited by the fact that images represent a single plane, and may thus inadequately represent a heart whose function is not uniform. For example, when evaluating 2-D images to calculate ventricular volumes, geometrical assumptions need to be made regarding the ventricular shape, which may not be valid in the presence of regional wall motion abnormalities. More than 15 years ago, 3DE was developed to provide a more accurate assessment of ventricular volume, mass, and function to enhance the ability to assess the spatial relations between cardiac structures and provide a more complete view of the valves. While multiple studies demonstrated the advantages of 3DE, it too had several limitations. 3-D images were actually reconstructed from multiplanar 2-D images taken over several cardiac cycles. This increased the risk of introducing artifact from patient respiration or motion. Analysis was performed off-line and required tedious manual tracing of endocardial borders. In addition, limited computer technology caused slow data processing. As a result, 3DE remained a research tool that was not used widely in the clinical arena.

The past years have seen significant developments in transducer technology, allowing pyramidal shaped blocks to be acquired in realtime. It is now possible to image an entire ventricle or valve and analyze it online, thus obviating the need for complicated and time-consuming reconstructions. Advances in computer technology have also contributed to streamlining and expediting data analysis. Realtime 3-D echocardiography (RT3DE) has thus greatly enhanced the potential clinical utility for the evaluation of left ventricular (LV) and valvular function. This article examines the technological improvements in RT3DE and the evidence to support its routine use in the clinical setting.

RT3DE Technology

Early models of RT3DE transducers used only 256 elements, which did not fire simultaneously, resulting in an image quality that was often inferior to that of 2DE. Displayed images still consisted of computer-generated 2-D cut planes obtained from the 3-D dataset, and the size of the pyramidal scan volume was incapable of accommodating larger ventricles. The recently developed matrix array transducer uses 3,000 simultaneously firing elements, and, as a result, contrast resolution and penetration has improved.