Influence of External and Internal Parameters on the Accuracy of a Mobile Tracking System Based on an IPhone

Abstract

For the determination of a fitting rod during pedicle screw surgery, a measuring system consisting of an iPhone 7 and retroreflective markers was developed. In addition to intraoperative use, the system is also applied to track an ultrasound probe for preoperative determination of the Pelvic Tilt. For the intraoperative use of this system it is important to keep a distance of at least 1.5 m from the nonsterile iPhone 7 to the patient. Under operating conditions, the mobile tracking system has to cope with very bright lighting conditions, which makes it difficult to detect the retroreflective markers on the rigid bodies. The influence of the light condition and the distance of the markers to the camera are analyzed in an operating theatre with the possibility of controlling the operating lights to a defined light intensity. In addition to the external settings, the ISO and exposure time settings are changed internally in the mobile tracking system software. In this paper the influence of external and internal parameters on the accuracy of the tracking system is investigated.