Registration between 2D and 3D ultrasound images to track liver blood vessel movement

BACKGROUND

For the accurate positioning of surgical tools, conventional intraoperative navigation systems have been developed to recognize the relationship between target positions and the tools. However, since an internal organ is deformed during the operation, registratin between real-time two-dimensional (2D) ultrasound images and three-dimensional (3D) CT or MRI images is not always effective. Therefore, this study developed image registration between 2D and 3D ultrasound images considering deformation for tracking target vessel movement in the liver.

METHODS

3D ultrasound image was obtained in advance with 3D coordinates, including the target vessel. Then real-time 2D images and ultrasound probe position were simultaneously acquired using a 3D position sensor. We applied multiple image resolution registration, where rapid and fine optimizations can be expected in higher and lower levels, respectively. Meanwhile, gradient descent method was adopted for the optimization, which determines the relative arrangements to obtain maximum similarity between 2D and 3D images. We experimentally established resolution level parameters using a phantom before applying it to track liver blood vessel movements in a normal healthy subject.

RESULTS

Comparing between the 2D images and the registered images, although the approach has some limitations in tracking large displacement, we confirmed that the cross section of the target blood vessel was clearly visualized.

CONCLUSION

This method has a potential for an ultrasound therapy targeting blood vessels under natural respiration conditions.