Research On Electromagnetic Tracking Method For Surgical Navigation Based On Rotor Search

Minimally invasive is an important concept in modern clinical medicine. It is well received by both doctors and patients as having various advantages such as fewer traumas, less suffering, faster recovery, and easier operation. Interventional operation is a kind of surgical procedure to introduce surgical instruments to lesions under the guidance of medical imaging systems. As an important subdiscipline of minimally invasive medicine, it has made great progress in recent years. The navigation provided by medical imaging system during procedure is one of the key issues in the progressing of intervetional operation. As the conventional X-ray navigation method has drawbacks like high radiation doses, only2dimensions, and needs of contrast medium, the novel navigation method ultilizing electromagnetic tracking method has a great prospect.This paper mainly studies the electromagnetic tracking method for interventional navigation. As most of the electromagnetic tracking methods in the prior art are based on magnetic models and iterative algorithm, the complexity of these methods is increased while the stability and accuracy are reduced. In this paper, on the basis of reviewing of the prior methods and analyzing of the characteristic of the magnetic sources, a new concept of electromagnetic tracking based on rotation-and-search with magnetic coils is proposed. By ultilizing algorithms that are non-iterative and geometrical, the complexity of electromagnetic tracking method can be greatly reduced, and the stability can be well improved. Besides, as these methods are less-model-based or non-model-based, the tracking error introduced by the differences between the real distribution of the magnetic field and the estimated distribution calculated by using magnetic models are fundamentally eliminated. So the tracking performance can be greatly improved.In this paper, two kinds of methods based on rotation-and-search concept that ultilizing orthogonal coils and two indepantance coils are firstly proposed. Two kinds of rotation realization methods, mechanical scan and electrical scan, are proposed, and the basic embodiments of the methods are discussed. Secondly, two key issues of position and orientation algorithm as well as search strategy are studied. Non-iterative geometrical algorithms and optimized search strategy are proposed. A detailed simulation of the proposed methods is carried out, and a prototype system based on mechanical scanning method with two independent coils is developed and used in experiments to validate the method. In the end, some Preliminary thoughts on methods using changeable rotation axes are presented based on simulation results.The simulation results show that the proposed method can meet the requirement of electromagnetic navigation for minimally invasive therapy effectively. The methods can greatly decrease the complexity of algorithm compared with conventional methods, meanwhile increase stability and tracking accuracy. The experiments based on the procotype system give a preliminary validation of feasibility of the methods. Considering the simulation results, with accurate calibration, the proposed methods can be used for navigation in minimally invasive therapy and improve the performance of the navigation system greatly.