4D Ultrasound Mosaicing and Visualization
Beating heart procedures eliminate the need for cardiopulmonary bypass and its associated morbidities, and allow the surgeon to evaluate the process under physiologic loading conditions. Real-time 4D ultrasound Atlanta (3DUS) imaging is usually the imaging modality of option for guiding these procedures. 3DUS is non-invasive, inexpensive, able to see through the blood, and can offer real-time diagnostic details of the anatomical area of interest. 3DUS additionally mitigates the problems in spatial perception associated with traditional 2DUS.
Intra-cardiac procedures usually involve geometrically complex and spatially extended moving anatomic structures. Real-time visual feedback of the moving structures is important to the success of these procedures. In order to understand the potential of 3DUS in guiding such procedures, 2 challenges should be addressed: high noise and narrow field of view. These limitations is mitigated with a real-time panoramic view of the area of interest.
Electrocardiograph (ECG) gating is popular in the 4D reconstruction of a time-series of 3DUS volumes. Efforts were reported in the reconstruction of gated 4DUS by mosaicing tracked 2DUS imaging. In this case, 2DUS frames are acquired at the same point in the motion cycle of the target and composited into 3D volumes first, which then are assembled into a time series for sequential display.
With the arrival of real-time 3DUS machines, 3DUS volumes is obtained directly and they provide improved spatial details compared to 2DUS, especially for geometrically complex targets with fast motion. Brekke et al developed an algorithm that assembles ECG gated 3D cardiac ultrasound sub volumes into a symmetric pyramidal without utilizing picture registration. They reported decreased
geometric distortions compared to the non-stitched 3D amount. 1 major limitation of such a program is the fact that it needs acquiring sub volumes at particular azimuth and elevation angles, and thus, users have limited control over probe location and orientation. Kutter et al presented a multi-modal 3DUS registration and mosaicing approach by incorporating info from co-registered CT. However, CT information isn’t usually available for clinical cases, especially for the non-intervention cases.