A real-time freehand 3D ultrasound system for image-guided surgery

Current freehand 3D ultrasound techniques separate the scanning or acquisition step from the visualization step. The process leads to a single image volume dataset that can be rendered for viewing later. While satisfactory for diagnostic purposes, the method is not useful for surgical guidance where the anatomy must be visualized in real time. The Image Guidance Laboratories are currently developing a freehand 3D ultrasound system that will allow real-time updates to the scanned volume data as well as the capability to simultaneously view cross-sections through the volume and a volume-rendered perspective view. The equipment used is not unlike other freehand 3D ultrasound systems: an optical tracking system for locating the position and orientation of the ultrasound probe, a video frame grabber for capturing ultrasound frames, and a high-performance computer for performing real-time volume updates and volume rendering. The system incorporates novel methods for inserting new frames into, and removing expired frames from, the volume dataset in real time. This paper reports on current work in progress, and focuses on methods unique to achieving real-time 3D visualization using freehand 3D ultrasound.