Augmented Reality Guided Retrosigmoid Approach

While medical imaging data has traditionally been viewed on 2D displays, medical augmented reality (AR) allows physicians to project the medical imaging data on patient's bodies. An important application of medical AR is intra-operative surgical guidance by providing the physician with the ability to “see through” the patient's skin and locate important anatomy.

We present a medical AR application to support the retrosigmoid approach, an important approach to access the internal auditory canal. During the retrosigmoid approach, the craniotomy window is placed directly behind the sigmoid sinus, a large venous blood drainage running inside the posterior cranial fossa adjacent to the skull. The current standard is to use a surgical navigation system and anatomical surface landmarks to guide the surgeon during the procedure. However, surgical navigation systems require a long setup time and lack intuitiveness in presenting reformatted oblique planes to the surgeon while surface landmarks lack anatomical accuracy. As a simple and accurate alternative, we propose the use of an AR application that augments the surgeon's vision to guide the targeting procedure.

In this work, two surgeons performed a retrosigmoid approach 14 times on 8 cadaver heads. In each case the surgeon manually aligned a CT-derived virtual rendering of the sigmoid sinus on the real cadaveric heads using a see-through AR display, allowing the surgeon to plan and perform the craniotomy accordingly ([Fig. 1]). After the craniotomy, we performed repeat CT scans to measure the margins between the osteotomy border and the dural sinuses to see how accurately the surgeon performed the craniotomy with respect to its intended location.

We showed that the two surgeons had a mean margin of d_avg = 0.6 ± 4.7 mm and d_avg = 3.7 ± 2.3 mm over all their cases, respectively. For 12 of the 14 cases, the surgeons only had positive margins, successfully avoiding the sigmoid sinus during surgery. The relatively small and consistent margins found in this pilot study translate favorably for what may be expected at the time of actual surgery. These findings suggest that this approach has the potential to be a valuable tool to facilitate planning a variety of similar skull-base procedures.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
12 February 2021