A real-time pointer to a preoperative surgical planning index block of ultrasound images for image guided surgery

Ultrasound is a non-invasive, cheap and portable imaging system available in most hospitals. It would be beneficial to surgeons to use an ultrasound transducer as a real time intraoperative positional pointer to previously acquired surgical planning images. We have developed a system to link live intraoperative ultrasound images with pre-operative surgical planning images utilizing a 3-dimensional image index block, a multimedia database, and a graphical wire-frame model. An index block is created using a set of planning images, from which images in any plane can be interpolated. The new images created are ordered in a database using bandpassed spatial feature detection, from which a smaller set of images are selected by feature presence and position for faster matching to a live image. Preliminary testing of the system has evaluated the image matching accuracy and tolerances, and results show that in over 90% cases a 'good' match can be found from a database containing approximately 3000 images in only 30 seconds, with significant correlations found between the coordinates of the live and best match images, indicating the potential for live ultrasound to act as a near-real time positional pointer to planning data.