Patient movement compensation for 3D echocardiography fusion

Limited field of view (FOV) is a major problem for 3D real-time echocardiography (3DRTE), which results in an incomplete representation of cardiac anatomy. Various image registration techniques have been proposed to improve the field of view in 3DRTE by fusing multiple image volumes. However, these techniques require significant overlap between the individual volumes and rely on high image resolution and high signal-to-noise ratio. Changes in the heart position due to patient movement during image acquisition can also reduce the quality of image fusion. In this paper, we propose a multi-camera based optical tracking system which 1) eliminates the need for image overlap and 2) compensates for patient movement during acquisition. We compensate for patient movement by continuously tracking the patient position using skin markers and incorporating this information into the fusion process. We fuse volumes acquired during R-R wave peaks based on Electrocardiogram (ECG) data to account for retrospective image acquisition. The fusion technique was validated using a heart phantom (Shelley Medical Imaging Technologies) and on one healthy volunteer. The fused ultrasound volumes could be generated in within 2 seconds and were found to have complete myocardial boundaries alignment upon visual assessment. No stitching artefacts or movement related artefacts were observed in the fused image.