3D Echocardiography

3D Echocardiography

1. 3D Echocardiography Just fancy pictures or added value ?

2. Other Side of Picture

3. Why 3D Echocardiography? 3D structure of the heart and relation of various structures Easier to demonstrate to those who are echo-challenged No need to rely on geometric assumptions when quantifying volumes, mass, function Potentially faster image acquisition Presentation of realistic views of heart valves Volumetric evaluation of regurgitant lesions and shunts with 3DE color Doppler imaging 3DE stress imaging

4. Fully Sampled Matrix-Array Transducers Development of fully sampled matrix-array transducers in 2000. Currently, 3DE matrix-array transducers are composed of nearly 3,000 piezoelectric elements Frequencies TTE 2-4 MHZ TEE 5-7 MHz Single transducer to acquire both 2D and 3DE studies.

5. . Modes

6. Narrow angle/Zoomed • Valves • Inter-atrial septum • Inter-ventricular septum Wide angle/Multi-beat • LV • RV • Whole heart What Acquisition Mode To Choose?

7. Single Beat •Advantage –Overcomes limitations from rhythm disturbances and respiratory motion •Disadvantage –Limited by poor temporal resolution Multi-beat •Advantage –Images with higher temporal resolution •Disadvantage –Gated images are susceptible to artifacts from respiratory motion or cardiac arrhythmias Single or Multi-beat?

8. Multiplane Mode (X-Plane) Not true 3D modality Dual screen to simultaneously display two real-time images. Rreference plane Lateral plane 30 to 150 degrees from the reference plane. Multiplane imaging in the elevation plane is also available. Color flow Doppler imaging can also be superimposed onto the 2D images.

9. Real-Time 3D Mode—Narrow Sector Real-time display of a 30 x 60 degrees pyramidal volume. Narrow sector --- insufficient to visualize the entirety of a single structure in any one imaging plane Superior spatial and temporal resolution Easy to use Better for valves and small structures

10. 3D ZOOM ( Focused,Wide Sector) Focused to area of interest Wide sector view of cardiac structures Better for valves and IAS Decreased spatial and temporal resolution relative to real-time 3DE Used to cardiac interventions Best to visualize valves

11. Full Volume—Gated Acquisition Largest acquisition sector possible (up to 100° x 100°) Optimal spatial resolution High temporal resolution (30 Hz). Similar to the real-time 3D and the focused wide sector—“ZOOM” modalities Cropping and off-line analysis.                                                             ( Top ) Example of electrocardiographically trigger ed multiple-beat 3DE data acquisition from a trans thoracic apical window . Narrow pyramidal volumes from four cardiac cycles ( top left ) are stitched together to form a single volumetric data set ( top right ). ( Bottom ) Real-time or live 3DE single-beat acquisition of the whole heart ( bottom left ) and the left ventricle ( bottom right ) from the trans thoracic apical windo w.

12. Full Volume—Gated Acquisition Multiple-beat 3D echocardiography Higher temporal resolution Multiple acquisitions of narrow volumes of data over several heartbeats that are subsequently stitched together to create a single volumetric data set Prone to imaging artifacts created by patient or respiratory motion or irregular cardiac rhythms.

13. Full Volume with Color Flow Doppler 3D plus Color Initially only for Full volume mode with 7-14 beats volume stitched together. Currently 3D color full volume can be acquired with as low as single beats but at the cost of temporal resolution. Used for quantification of regurgitant jets

14. Limitations Poor spatial and temporal resolution Currently, live 3DE color Doppler acquisition is limited to small color Doppler volumes, usually with limited temporal resolution of 10 to 15 voxels/sec. Alternatively, multiple-beam full-volume acquisition of color Doppler providing larger color Doppler volumes and volume rates (up to 40 voxels/sec) are limited by stitching artifacts.

15. Challenges with 3DE Acquisition Temporal Versus Spatial Resolution The main trade-off in 3DE imaging is between volume rate (i.e., temporal resolution) and spatial resolution . Fortunately, imaging volumes can be adjusted in size (i.e., made smaller) to increase volume rate while maintaining spatial resolution.

16. Gated data sets are most challenging in patients with arrhythmias and/or respiratory difficulties. ECG tracing needs to be optimized to obtain a distinct R wave Stitching artifacts Challenges with 3DE Acquisition ECG Gating and Breath Hold

17. “ suboptimal 2D images result in suboptimal 3DE data sets .” 3D Optimization

18. 3D Optimization

19. Offline Analysis

20. 3DE Image Display: Cropping Cropping is inherent to 3D echocardiography. Different from Tomography From difficult cross sectional views to surgical views Cropping can be performed either during procedure or later Advantages of cropping during procedure

21.                                                       Multiplanar re construction of a rheumat ic, stenotic mitral valve imaged with zoomed, transesophageal 3D echocardiography ( bottom right ). Orthogonal cut planes through the narrowes t mitr al valve orifice in mid-diastole ( top left and right ) with a perpendicular plane providing an en face image for mitral valve area (MVA) measurement ( bottom left ).

22. Post-Acquisition Display Once a 3DE data set is acquired, it can be viewed interactively using a number of 3D visualization and rendering software packages. Display of 3DE images can be divided into three broad categories: volume rendering surface rendering (including wireframe display 2D tomo - graphic slices The choice of the display technique is generally determined by the clinical application.

23. Volume Rendering Volume rendering is a technique that uses different types of algorithms to preserve all 3DE information and project it, after processing, onto a 2D plane for viewing. Volume-rendered 3DE data sets can be electronically segmented and sectioned. To obtain ideal cut planes, the 3D data set can be manipulated, cropped, and rotated. Volume rendering provides complex spatial relationships in a 3D display that is particu - larly useful for evaluating valves and adjacent anatomic structures.

24.                                                   From a trans thoracic 3DE data set of the left ventricle ( left ), the LV endocardium can be tra ced ( middle, top ) to obtain the LV volume throughout the cardiac cycle ( right, top ). As well, the LV endocardium can be divided according to the 17-segment model ( middle, top ), and the time each segment requires to attain minimal volume in the cardiac cycle can be identified ( right, bottom ).

25. Surface Rendering Visualization technique that shows the surfaces of structures or organs in a solid appearance. Select structure (LV, RV, Atria) Trace Manually or automated Construction and display (Wire frame or 3D) Mostly volume and surface rendering are combined to get full details

26.                                 The R V volume can be determined from 3D echocardiographic data sets by the method of disks ( left ). Other methods include dynamic endocardial tra cking with end-diastolic volumes presented by the mesh shell and end-systolic volumes presented by the solid shell ( middle ). The RV endocardial shell can be segmented for r egional analy sis ( right ).

27. 2D Tomographic Slices The volumetric data set is sliced or cropped to obtain multiple simultaneous 2D Multiple levels and unique cuts Different planes like orthogonal or parallel planes Uniformly spaced cuts Accurate assessment of dimensions of chambers, valves or defect Simultaneous orthogonal slides in ONE cardiac cycle

28. Just fancy pictures or Added value ?

29. Thanks for your patience

30. Limitations Although RT3DTEE represents an important step in perioperative imaging, significant imitations remain. First, while 3D zoom and live 3D are indeed real-time modes, the acquisition of a 3D full volume as well as a 3D color full volumes are based on automatic reconstruction from subvolumes and are therefore prone to artifacts from arrhythmias, and ventilation – the socalled stitch artifacts. Second, as 3D echo obeys the same physical laws as 2D, poor 2D image quality will likely translate in similarly poor 3D image quality. Unlike the mitral valve, other structures in the far field like the aortic and tricuspid valves are more difficult to visualize using current technology. Third, direct measurements (e.g. caliper, trace) cannot be performed directly in 3D images and require the use of time-consuming software. Fourth, although the built-in software features quantitative assessment of the mitral valve and left ventricle, it would benefit from a more user-friendly interface. Finally, as with most new technology, RT3DTEE will prolong a comprehensive TEE examination, especially when quantitative techniques are employed. However, in the future and with further improvements in technology, RT3DTEE may help to Fig 4: 3D TEE en -face view of a mechanical bileaflet prosthesis in the mitral position with an Amplatzer occluding device positioned to seal a paravalvular leak (arrow). Page 6 of 6 even expedite a comprehensive TEE examination by using a single 3D view of the mitral valve rather than the five conventional 2D views.

31. • Live 3D: displays a pyramidal dataset with dimensions of approximately 50° x 30° that can be used to display cardiac structures located in the near field. •.

32. • Full Volume: that allows the inclusion of a larger cardiac volume. The wide angle data set is compiled by merging four to seven narrower RT-3D pyramidal wedges obtained over four to seven heartbeats. Imaging artifacts may be avoided in the anesthetized patient by suspending ventilation and avoiding electrocautery use during acquisition of the full volume sequence. Therefore, it is desirable to acquire full volume loops at the beginning of the comprehensive TEE-exam in the operating room prior to the start of surgery. A full volume loop of the left ventricle is based on the 2D midesophageal four chamber view. When selected, the full volume mode displays a biplane image with the four chamber view and the (perpendicular plane) corresponding orthogonal image. The 3D-volume is displayed as a 50% cropped volume mirroring the four chamber view. This is necessary since the full volume image at the outset will not display intraventricular structures like valves, papillary muscles etc. Resetting the crop plane however, allows the whole pyramidal dataset to be displayed. The full volume can be further processed offline by rotating and cropping to visualize specific intracardiac structures. Cropping can be performed by either using one of six available cropping planes selected from a 3D cropping box or by using a freely adjustable plane. Acquired full volumes can also be used for volumetric quantification of the LV using available built-in software (QLAB, Philips Medical Systems, Andover, MA).

33. • 3D Color Full Volume: Similar to the acquisition of a full volume the wide angle data set is compiled by merging 7 to 14 narrower RT-3D pyramidal wedges and is similarly prone to artifacts introduced by arrhythmias, movement, or electrocautery. For this mode it is essential to place the area of interest, for example, the regurgitant jet, in the center of the sector. The remainder of the acquisition is identical to that used for full volume acquisition. In the newer software release, the color full volume may be acquired using 1, 2, 4 or 6 separate slices. Once again, one must balance the need for optimal frame rates (more slices) with the tendency for stitch artifacts.