Page 437 - Biomedical Engineering and Design Handbook Volume 2, Applications

COMPUTER-INTEGRATED SURGERY AND MEDICAL ROBOTICS 415

FIGURE 14.16 (a) Typical screen display of a CIS navigation system for endoscopic surgery. The left windows show orthogonal cross-
sectional views of the CT data set and the endoscope image. The diagonal line (which is green in the original image) shows the position of
the endoscope. (b) The endoscope and the tracking plate. (Reproduced from Ref. 98.)

together with the preoperative images. The video stream can be shown side by side with a preop-
erative study, as shown in Fig. 14.16, or selected information from it can be inserted in the video
stream. The main advantage of these systems is that they allow surgeons to see beyond the surfaces
shown in the video and to obtain spatial location information that overcomes the narrow field of
view of the cameras. 96

Augmented Reality Navigation Systems. One of the drawbacks of the navigation systems
described above is that they require the surgeon to constantly shift attention from the patient to the
computer display and back. Augmented reality navigation systems attempt to overcome this draw-
back by bringing the display right where the surgeon needs it. The data is viewed through glasses
worn by the surgeon, projected directly on the patient, or displayed on a transparent screen standing
between the surgeon and the patient. The surgeon’s head is usually tracked, so that the data can be
displayed from the correct viewpoint.
97
Two examples of this type of system are the augmented reality CIS system for neurosurgery and
the CMU image overlay system 63 for orthopedics. The augmented reality CIS system for neuro-
surgery projects colored segmented volumetric data of brain tumors and other neural structures
directly on the patient’s skull (Fig. 14.17). This allows the surgeon to directly see where to start the
minimally invasive procedure. The HipNav navigation system was developed to assist orthopedic
surgeons in positioning the acetabular cup in total hip replacement surgery. In this system, a trans-
parent glass that serves as a projection screen is placed between the surgeon and the patient on the
operating table. After registration, the hip and pelvis models extracted from the preoperative CT data
are projected on the glass screen, thereby providing the surgeon with an x-ray-like view of what lies
beneath.
Virtual Reality Diagnosis Systems. The third type of information-enhancing system is virtual real-
ity diagnosis systems. These systems, typically used in diagnostic endoscopy and colonoscopy,