3-D VISION TECHNOLOGY APPLIED TO ADVANCED MINIMALLY INVASIVE SURGERY SYSTEMS

Current-generation vision for laparoscopic surgery involves flat two-d imensional display on a video monitor; this approach makes it difficul t to accurately place the tip of a surgical instrument in the three-di mensional real space of the patient. The surgeon must rely on motion p arallax, monocular cues, and other indirect evidence of depth to judge accurately the correct spatial relationship of objects in the field o f view. Stereoscopic video can return accuracy to the surgeon. Critica l elements in creating stereovision are the biophysical laws governing field of view, focal point, depth of field, accommodation, and conver gence. In addition, engineering constraints must be followed, such as fitting a 10-mm port, which are compatible with current systems and ec onomic feasibility. There are two methods for 3-D vision under develop ment which are variations on the same theme of modifying standard lapa roscopes by using lenses, mirrors and prisms, and optical shuttering. One method uses two video cameras to simultaneous capture two separate images from a paired optical system. Each image is alternately transm itted to the video monitor (field sequential video) and viewed with el ectronic or polarizing glasses for a 3-D image. Another method uses a standard laparoscope, optically splits this one image into alternating right/left images, and reconstructs the image as above. A major chall enge for both systems is that the distance between the optical element s in the laparoscope is not greater than 10 mm apart and fixed, wherea s the human interpupillary distance is greater than 60 mm and can acco mmodate. The application of 3-D vision technology is critical to a new , minimally invasive surgical system under development: Telepresence s urgery. Using remote, dexterous, force feedback manipulators; 3-D visi on; and stereophonic sound, the image at the surgical site is projecte d to a ''computer workstation'' with such convincing realism that the surgeon feels as if he were actually at the operative site. The image could also be projected from a microscopic scale, allowing performance of procedures that are simply not possible today. Other 3-D visualiza tion techniques under development involve CT scanning, MRI, and ultras ound, any of which could be projected over the real-time video image t o enhance the surgeon's ability to perceive an operation. Methods of d isplaying 3-D vision beyond simple video monitors are high-definition TV (HDTV), head-mounded displays, and possibly holograms. Also, critic al patient information (vital signs and intraabdominal pressure) can o verlay the video image. The potential of 3-D vision technology has yet to be realized. In the future it will permit surgery with more accura cy, speed, dexterity, and safety than imaginable today.