Research On Integration Of Optical And Inertial Positioning For Surgical Navigation System

Along with the development of stereotaxic and imaging techniques, surgical navigation system(SNS) has been more and more widely used in operations of orthopaedics, neurosurgery, otorhinolaryngology and other surgeries. SNS is a complex system, involving a variety of key technologies including positioning system which directly decides positioning accuracy and operation result. Currently used positioning systems can be divided into four types, mechanical positioning system, optical positioning system, ultrasonic positioning system and electromagnetic positioning system. However, these systems have limitations, and they are unable to achieve the unity of precision and robustness.Most of the currently used SNS employed optical positioning system. Optical positioning system relies on visible light or infrared light for positioning. It cannot provide positioning information when the light has been blocked, and it is difficult to ensure that the light is not blocked during operation. Thus, physicians have to pay attention to make the light unblocked when they are in use of other instruments. It brings a lot of inconvenience to doctors, and the loss of positioning information will also bring a lot of risk.In this paper, we proposed a novel positioning algorithm that integrating of optical positioning system and inertial positioning system to improve its performance. Inertial positioning system will be alternatively used when optical positioning system is blocked to make the positioning information uninterrupted and ensure the procedure of surgeries. Inertial positioning system belongs to autonomous positioning system, relying on inertial measurement device to detect motion. Inertial measurement devices exist inevitably drift phenomenon; it can’t be used in a long time. Here, extended Kalman filter was used in fusion of the data from two positioning systems. The fused data was used to predict the motion when optical positioning system is blocked.In this paper, the calculating method of inertial positioning system positioning information was studied, and the static and dynamic experiments were utilized to verify the feasibility and reliability of the calculating method. Finally the combination positioning method was used to verify the accuracy. Our results showed that the positioning error at x, y and z axis were 0.34 mm, 0.24 mm and 1.0 mm respectively and the angle error was 2.2。 during 0.2s blockade. So our strategy can compensate missed positioning information when the light is blocked, and meet the demand of clinical navigation.