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Preprints & Reprints THREE-DIMENSIONAL REMOTE IMAGING OF SURGERY (Implications of new technology for the training, supervision and audit of tomorrow's surgeons) Summary Introduction Methods and Materials To enable comfortable viewing of a three dimensional image it is necessary that the recording and replay geometry be accurately matched to the human visual system. The system used in this experiment was built around the desire to replay the image on a 17" monitor, with a viewing distance of 0.75 metres. Accordingly a pair of 1/3 inch diameter video cameras fitted with 6 mm focal length lenses were mounted on a base with a spacing of 40 mm. An adjustment system enabled them to be aligned optimally to view an object positioned at arms length. The complete camera assembly was itself mounted on a headband system, positioned in the centre of the wearer's forehead. To provide the data link, a pair of ISDN (Integrated Services Digital Network) codecs were used in loop-back mode with one codec dedicated to each of the cameras. This allowed various data rates to be evaluated during the course of the trial. Audio communication was provided using a loudspeaker and microphone at each end. Careful positioning removed the need for more sophisticated echo-cancellation techniques. Initially a simulated state was designed to replicate an operative procedure. A freshly sacrificed animal model was used and the operative procedure was carried out in one room while being directed from an adjacent room with no direct visual or verbal contact except through the ISDN line. A junior hospital doctor carried out an operative procedure under instruction from his senior colleague in an adjacent room. At a later date we tested the system in an operating theatre with two patients undergoing anterior cruciate ligament reconstruction. Each patient gave their consent to the operative procedure and the conferencing. A Senior Surgical Registrar (operating surgeon) carried out the surgical procedures under direction by the Consultant Surgeon (surrogate surgeon) who was located in a room adjacent to the operating theatre. The Senior Registrar was familiar with the surgical technique and had frequently carried out the procedure both under direction and independently. The purpose of this trial was to assess the view of the surgical procedure being provided in the distant location and not its value as a training tool in this first instance. However it was also hoped that the contact with the senior colleague who was more experienced with the operative technique might help the surgical technique of his junior partner. Results In the simulated surgical situation the initial use of tripod mounted cameras was found to be much inferior to the head mounted camera. Among the problems encountered were frequent obstruction of the field of view by the operating surgeon hands and problems with shadowing across the field of view. Despite the benefit of a 3D view in the distant location the tripod mounted set-up failed to create the unity of vision subsequently achieved by cameras mounted on a headband worn by the operating surgeon. Head mounted cameras on the operating surgeon conveyed a much better feeling of depth to the surrogate surgeon. They also ensured that both surgeons were focused on the same field of view. Initially the head mounted cameras were fixed on a headband and could not be controlled from the adjacent room. It was found that some degree of individual control by the surrogate surgeon was required for situations where the operating surgeon approaches and moves back from the operative site. The effect of movement of the operating surgeon's head besides was not regarded as a significant problem. In the true surgical setting a complex approach to the knee joint was carried out under full view of the surrogate surgeon in the adjacent room. During the operative procedure the surrogate surgeon was able to direct the precise movement of surgical instruments by the operating surgeon and could advise on the best surgical technique throughout. Although this surgical procedure was carried out through a rather restricted incision the view of the operative field transmitted to the surrogate surgeon was most satisfactory. The surrogate surgeon found the 3D view realistic and much superior to the view available to an observer in theatre. The only difficulty again encountered was the tendency for the centre of attention of the remote picture to change when the operating surgeon moved his head closer or further away from the operative field. Both surgeons felt very comfortable with the relationship throughout the operative procedure, in particular the junior surgeon felt that he had more operative freedom than would be provided by the actual presence of the surrogate surgeon within the operating area. The surrogate surgeon in the peripheral location also felt that he was not interfering unnecessarily with the operative procedure being carried out by his junior colleague yet he had a high degree of control over the procedure. Overall the operative procedure using the surrogate three dimensional video-imaging was regarded as a most useful technique in both observing and supervising the operation. Discussion References 2] May M, Korzec K R, Mester SJ. Video telescopic sinus surgery techniques for teaching. Transactions - Pennsylvania Academy of Ophthalmology & Otolaryngology. 1990, 42: 1037-9. 3] Smeak D D, Beck M L, Shaffer C A, Gregg CG. Evaluation of video tape and a simulator for instruction of basic surgical skills. Veterinary Surgery. 1991, 20(1): 30-6. 4] Wenzl R, Lehner R, Vry U, Pateisky N, Sevelda P, Husslein P. Three-dimensional video-endoscopy: clinical use in gynaecological laparoscopy. The Lancet. 1994, 244: December 10; 1621-2 |