Study on the development of augmented-reality navigation system for transsphenoidal surgery

Abstract

In this study, we developed an augmented-reality (AR) navigation system that can assist surgeons during transsphenoidal surgery, including identification of the tumor site. Since transsphenoidal surgery is performed by looking at an endoscopic image, thus requiring situational judgment on the image, transsphenoidal surgery poses greater challenges with regard to grasping the positional relationships between the tumor and the organs compared with normal operations. The proposed system is expected to help surgeons understand the conditions surrounding the operating field, by intraoperatively displaying a real-time overlaid 3D model based on preoperative MRI images of the patient. Markers were used to obtain the data necessary to view the overlaid images, which were attached to the operating table and to the end of the endoscope. The patient’s head was held in a fixed position during the surgery. The relative positions of the maker on the operating table and the feature point on the patient’s head were captured by a camera mounted on top of the operating table. Then, using this information, the positions of the tumor and the organs were estimated, and a 3D model was created using the patient’s MRI scans. Further, by obtaining the relative position of the markers attached to the end and tip of the endoscope, the position of the tip of the endoscope was estimated from the marker at the end even if it could not be seen from outside after inserting it into the patient’s body during surgery. The relative positions of the tip of the endoscope and the tumor site were calculated, and a 3D model was displayed using the MRI images in conjunction with the current endoscopic image. By constantly updating the positional information in accordance with the behavior of the endoscope, the overlaid image of the tumor and the organs could be viewed. In this study, we developed a prototype of the proposed system, and discussed the accuracy of its results.