3D echocardiography has evolved from a complicated and time-consuming research tool into a simple and fast imaging modality ready for everyday clinical use. During this interesting session, four experts shared their experience on how they use 3D echocardiography in various applications, and the future development of this technique in these different areas.
The first speaker, Dr. Ignatios Ikonomidis from Athens, showed the strengths and limitations of 3D echocardiography for assessing left ventricular (LV) function. The purpose of 3D imaging of the LV is to provide volume and ejection fraction measurements independent of geometric assumptions regarding LV shape. The landmarks used for this process are the mitral annulus and LV apex, which are used to initiate edge detection by semi-automated quantification software. He compared the validity of the various available softwares and underlined possible inconsistencies between systems.
On the other hand, he pointed out that the temporal resolution of single-beat modality appears insufficient to provide an accurate estimation of LV function and end-systolic volume calculations. Other anatomic features of importance are the LV trabeculae and papillary muscles, which should be included within the LV cavity for the calculation of LV volumes. The trabeculae are small structures that are often poorly visualized with 3D echo imaging, and the use of LV opacification with contrast is the best way to ensure that they are incorporated within the LV cavity. He also discussed the potential value of this new technique to evaluate dyssynchrony and LV mass.
The next speaker, Vlasis Ninios from Thessaloniki focused mainly on the use of 3D transoesophageal echocardiography (TEE) for the evaluation of valve morphology. He briefly discussed the feasibility and limitations of 3D echocardiography in this setting compared to 2D echocardiography for guiding treatment. He very nicely illustrated various pathological conditions in which 3D TEE provides true anatomic and functional images and can be particularly useful.
Dr. Thomas Buck from Essen, Germany presented how to use 3D echocardiography for flow quantification in mitral regurgitation. He underlined the limitations of 2D echocardiography using either the Proximal Isovelocity Surface Area (PISA) method or vena contracta width for the quantification of mitral regurgitation. He very nicely demonstrated how 3D echocardiography offers new opportunities for more accurate flow quantification especially using the vena contracta width method, even in asymmetrical regurgitation. He showed new methods of automated 3D PISA quantification and vena contracta. He concluded that to date, no method has yet been shown clinically robust enough to become a trusted standard.
The last talk, given by Roberto Lang from Chicago, addressed the very exciting and new field of image fusion. He has first defined what image fusion can be. Multiple images from a patient are registered and overlaid or merged. Fused images may be created from multiple images from the same imaging modality, or by combining information from multiple modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), positron-emission tomography (PET) and single-photon emission computed tomography (SPECT). The fusion can be performed through hardware using dedicated hybrid imaging systems or through software using image registration, spatial compounding and mosaicing. He illustrated various techniques with impressive examples of 3D echocardiography fused with computed tomography images of the coronary arteries and others with SPECT perfusion images. He also showed the combination of 3D echocardiography with cardiac magnetic resonance and fluoroscopy in patients receiving cardiac resynchronisation therapy devices.
The use of spatial compounding with multiple ultrasound images obtained from different transducer positions should improve the quality of the compounded image.