Space Registration For Electromagnetic Navigation System Of Coronary Intervention

Cardiovascular disease is not only an increasingly common disease,but it also has become one of the leading causes of death from disease worldwide.In many counties,its mortality rate even exceeds the cancer.In recent years,with the continuous development of electromagnetic navigation technology,the navigation system for a specific cardiovascular disease has been constantly reported.However,among numerous cardiovascular-related navigation system,none of them can still play a role in navigation after the medical device enters the coronary artery due to the factors such as severe heartbeat.Firstly,thanks to the development of four-dimensional CT(Computed Tomography)technology,we can obtain the fourdimensional motion model of coronary artery accompanying ECG(electrocardiogram)signals from the beating heart.Except this,the existing techniques can well solve registration problem in time domain with the aid of ECG signals.Therefore,the challenge changed to a spatial registration problem after registration finished in time domain.However,most of the current electromagnetic navigation system use a spatial registration method based on externally fiducial markers,which will cause the spatial registration to fail when the catheter or the guide wire is entering the coronary artery due to the movement of coronary arteries,thus failing to complete the navigation function.In order to solve the problem of spatial registration in the electromagnetic navigation system for coronary intervention surgery,an innovative spatial registration method based on radiopaque markers attached to the catheter was proposed in this study.The intraoperative X-ray image was used as the intermediary to complete the registration of electromagnetic navigation space and the space of preoperative coronary artery model.The spatial registration method proposed in this paper for the electromagnetic navigation system of coronary intervention surgery mainly includes the following three aspects:Firstly,unlike the traditional spatial registration method of establishing fixed markers in vitro,we embedded radiopaque markers on the catheter that needed to enter the coronary artery.In addition,in order to obtain the position of the sensors in X-ray,we also placed the same radiopaque marker on the electromagnetic sensors.Secondly,time domain registration of intraoperative X-ray with two viewing angle and preoperative four-dimensional CT were carried out through electrocardiogram signals.Then,three-dimensional coordinates of the sensors and the coronary arteries’ centerlines were reconstructed by using X-ray in two directions at the corresponding moment.Finally,we registered the sensors’ coordinates in magnetic tracking navigation space to the sensors’ coordinates in X-ray reconstruction space.Based on the registration results of three-dimensional vascular centerline reconstructed by two viewing X-ray image and preoperative three-dimensional vascular centerline,the coordinates of the electromagnetic sensors were transformed into the preoperative vascular model to complete the spatial registration in the electromagnetic navigation system for coronary intervention surgery.In order to evaluate the spatial registration method proposed in this paper,two model experiments were designed to verify the feasibility of reconstructing the three-dimensional points from two viewing X-ray image and the accuracy of the complete spatial registration respectively.In the first experiment,the root mean square error of the Euclidean distance between the back projection points from three-dimensional reconstructed points using two viewing X-ray image and the original corresponding points on the X-ray image was 0.145 ± 0.059 mm.The RMS(root-mean-square)registration error of the reconstructed three-dimensional points using two viewing X-ray image and their real three-dimensional coordinates was 0.884 ± 0.06 mm.In the second experiment,the RMS error of the complete spatial registration measured on the model was 1.318 ±0.246 mm.The experimental results showed that the radiopaque marker proposed by this paper could be applied to electromagnetic navigation for coronary intervention surgery with highly accuracy and the registration error was within 1.5mm.The spatial registration method proposed in this paper is a key step in the electromagnetic navigation system for coronary intervention surgery.It is also of great significance for the improvement and development of the subsequent coronary navigation system and practical clinical application.