Atrial septal defect tracking in 3D cardiac ultrasound.

We are working to develop beating-heart atrial septal defect (ASD) closure techniques using real-time 3-D ultrasound guidance. The major image processing challenges are the low image quality and the high frame rate. This paper presents comparative results for ASD tracking in sequences of 3D cardiac ultrasound. We introduce a block flow technique, which combines the velocity computation from optical flow for an entire block with template matching. Enforcing similarity constraints to both the previous and first frames ensures optimal and unique solutions. We compare the performance of the proposed algorithm with that of block matching and optical flow on six in-vivo 4D datasets acquired from porcine beating-heart procedures. Results show that our technique is more stable and has higher sensitivity than both optical flow and block matching in tracking ASDs. Computing velocity at the block level, our technique is much faster than optical flow and comparable in computation cost to block matching.