Spatial compounding of trans-esophageal echo volumes using X-ray probe tracking

The use of ultrasound imaging for image guidance of cardiac procedures is limited by the small field of view of the ultrasound volume. A larger view can be created by image-based registration of partially overlapping volumes, but automatic registration often fails unless the volume alignment is initialised close to the volumes´ correct alignment. In this paper, we use X-ray images to track a trans-esophageal probe, which provides the required position estimates for the ultrasound volumes. The tracking is possible using multiple X-rays or just one X-ray at each probe position. We test the method in a phantom experiment and find that with at least 50% volume overlap, 98% of ultrasound volume pairs are correctly registered when tracked using three X-rays per volume, and 95% using single X-rays.