A simulator for advanced analysis of a 5-DOF EM tracking systems in use for image-guided surgery (original) (raw)
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A novel electromagnetic tracking system for surgery navigation
Computer Assisted Surgery
Objective: This paper proposes the development of a novel electromagnetic tracking system for navigation surgery. Main objective is to provide a system able to operate in a wide tracking volume to make easier and efficient the surgical procedures by assuring high measurement accuracy. Methods: A new field generator consisting in five transmitting coils excited with Frequency Division Multiplexing technique has been developed. Attention is devoted to designing and arrangement of the coils to assure high sensitivity, system scalability and a homogeneous magnetic field inside working volume. A suitable technique based on Look-Up-Table is applied for sensor position calculation and an anthropomorphic robot is used for table calibration. Results: Experimental tests highlight a good repeatability of the measurement data and a negligible noise influence for the proposed system. The obtained tracking volume is wider with respect to the commercial tracking device used in surgical applications and seem promising. Conclusion: The main characteristic of the developed system consists of: scalable and modular configuration of Field Generator, high measured sensitivity due to the increased number of transmitting coils with respect to the classical configuration and large tracking volume. The development of the proposed magnetic tracking systems with high accuracy and wide working volume allows to promote broader utilization of advantaged techniques in surgery procedures for both improving the effectiveness and decreasing the invasiveness of medical interventions.
Sensors
In this paper we present a study of the repeatability of an innovative electromagnetic tracking system (EMTS) for surgical navigation, developed to overcome the state of the art of current commercial systems, allowing for the placement of the magnetic field generator far from the operating table. Previous studies led to the development of a preliminary EMTS prototype. Several hardware improvements are described, which result in noise reduction in both signal generation and the measurement process, as shown by experimental tests. The analysis of experimental results has highlighted the presence of drift in voltage components, whose effect has been quantified and related to the variation of the sensor position. Repeatability in the sensor position measurement is evaluated by means of the propagation of the voltage repeatability error, and the results are compared with the performance of the Aurora system (which represents the state of the art for EMTS for surgical navigation), showing...
A robust electromagnetic tracking system for clinical applications
2015
Electromagnetic tracking systems (EMTS) are utilized to track surgical instruments during navigated interventions. Compared to optical tracking technologies, the non-line-of-sight feature is the biggest advantage of EMTS. However, significant distortions due to nearby metallic objects and a small working volume are serious drawbacks preventing ETMS from being widely used. We worked on developing new methods to improve the accuracy of EMTS even in the vicinity of large metal objects while speeding up the position estimation frame rate. Therefore, we proposed a method to realize frequency deviation multiplexing (FDM) for EMTS in order to speed up the frame rate, and a quadratic-rectangular (QR) excitation method to remove the distorted voltage induced by the nearby conductive distorter. The results show that the measurement speed and robustness to nearby metal objects of our EMTS were improved by the FDM and QR method. Keyword: Electromagnetic Tracking, Image-guided Interventions, Nav...
Method for estimating dynamic EM tracking accuracy of surgical navigation tools
Medical Imaging 2006: Visualization, Image-Guided Procedures, and Display, 2006
Optical tracking systems have been used for several years in image guided medical procedures. Vendors often state static accuracies of a single retro-reflective sphere or LED. Expensive coordinate measurement machines (CMM) are used to validate the positional accuracy over the specified working volume. Users are interested in the dynamic accuracy of their tools. The configuration of individual sensors into a unique tool, the calibration of the tool tip, and the motion of the tool contribute additional errors. Electromagnetic (EM) tracking systems are considered an enabling technology for many image guided procedures because they are not limited by line-of-sight restrictions, take minimum space in the operating room, and the sensors can be very small. It is often difficult to quantify the accuracy of EM trackers because they can be affected by field distortion from certain metal objects. Many high-accuracy measurement devices can affect the EM measurements being validated. EM Tracker accuracy tends to vary over the working volume and orientation of the sensors. We present several simple methods for estimating the dynamic accuracy of EM tracked tools. We discuss the characteristics of the EM Tracker used in the GE Healthcare family of surgical navigation systems. Results for other tracking systems are included.
Electromagnetic tracking in the clinical environment
Medical Physics, 2009
When choosing an Electromagnetic Tracking System (EMTS) for image-guided procedures several factors must be taken into consideration. Among others these include, the system's refresh rate, the number of sensors that need to be tracked, the size of the navigated region, system interaction with the environment, can the sensors be embedded into the tools and provide the desired transformation data, and tracking accuracy and robustness. To date, the only factors that have been studied extensively, are the accuracy and the susceptibility of electromagnetic tracking systems to distortions caused by ferromagnetic materials. In this paper we provide an analysis based on these factors as assessed in three clinical environments. We evaluate two commercial tracking systems, the Aurora system from Northern Digital Inc., and the 3D Guidance system with three different field generators, from Ascension Technology Corp.. We show that these systems are applicable to specific procedures and specific environments, but that currently, no single system configuration provides a comprehensive solution across procedures and environments.
International journal of computer assisted radiology and surgery, 2017
Electromagnetic tracking systems (EMTS) have achieved a high level of acceptance in clinical settings, e.g., to support tracking of medical instruments in image-guided interventions. However, tracking errors caused by movable metallic medical instruments and electronic devices are a critical problem which prevents the wider application of EMTS for clinical applications. We plan to introduce a method to dynamically reduce tracking errors caused by metallic objects in proximity to the magnetic sensor coil of the EMTS. We propose a method using ramp waveform excitation based on modeling the conductive distorter as a resistance-inductance circuit. Additionally, a fast data acquisition method is presented to speed up the refresh rate. With the current approach, the sensor's positioning mean error is estimated to be 3.4, 1.3 and 0.7 mm, corresponding to a distance between the sensor and center of the transmitter coils' array of up to 200, 150 and 100 mm, respectively. The sensor p...
A buyer's guide to electromagnetic tracking systems for clinical applications
Medical Imaging 2008: Visualization, Image-guided Procedures, and Modeling, 2008
When choosing an Electromagnetic Tracking System (EMTS) for image-guided procedures, it is desirable for the system to be usable for different procedures and environments. Several factors influence this choice. To date, the only factors that have been studied extensively, are the accuracy and the susceptibility of electromagnetic tracking systems to distortions caused by ferromagnetic materials. In this paper we provide a holistic overview of the factors that should be taken into account when choosing an EMTS. These factors include: the system's refresh rate, the number of sensors that need to be tracked, the size of the navigated region, system interaction with the environment, can the sensors be embedded into the tools and provide the desired transformation data, and tracking accuracy and robustness. We evaluate the Aurora EMTS (Northern Digital Inc., Waterloo, Ontario, Canada) and the 3D Guidance EMTS with the flat-panel and the short-range field generators (Ascension Technology Corp., Burlington, Vermont, USA) in three clinical environments. We show that these systems are applicable to specific procedures or in specific environments, but that, no single system is currently optimal for all environments and procedures we evaluated.
Electromagnetic Tracker Characterization and Optimal Tool Design (With Applications to Ent Surgery)
2006
Electromagnetic tracking systems prove to have great potential for serving as the tracking component of image guided surgery (IGS) systems. However, despite their major advantage over other trackers in that they do not require line-of-sight to the sensors, their use has been limited primarily due to their inherent measurement distortion problem. Presented here are methods of mapping the measurement field distortion and results describing the distortion present in various environments. Further, a framework for calibration and characterization of the tracking system’s systematic error is presented. The error maps are used to generate polynomial models of the distortion that can be used to dynamically compensate for measurement errors. The other core theme of this work is related to optimal design of electromagnetically tracked tools; presented here are mathematical tools for analytically predicting error propagation and optimally configuring sensors on a tool. A software simulator, us...
Electromagnetic Tracking in Medicine—A Review of Technology, Validation, and Applications
IEEE Transactions on Medical Imaging, 2014
Object tracking is a key enabling technology in the context of computer-assisted medical interventions. Allowing the continuous localization of medical instruments and patient anatomy, it is a prerequisite for providing instrument guidance to subsurface anatomical structures. The only widely used technique that enables real-time tracking of small objects without line-of-sight restrictions is electromagnetic (EM) tracking. While EM tracking has been the subject of many research efforts, clinical applications have been slow to emerge. The aim of this review paper is therefore to provide insight into the future potential and limitations of EM tracking for medical use. We describe the basic working principles of EM tracking systems, list the main sources of error, and summarize the published studies on tracking accuracy, precision and robustness along with the corresponding validation protocols proposed. State-of-the-art approaches to error compensation are also reviewed in depth. Finally, an overview of the clinical applications addressed with EM tracking is given. Throughout the paper, we report not only on scientific progress, but also provide a review on commercial systems. Given the continuous debate on the applicability of EM tracking in medicine, this paper provides a timely overview of the state-of-the-art in the field.
Quality assurance for clinical implementation of an electromagnetic tracking system
Medical Physics, 2009
The Calypso® Medical 4D localization system utilizes alternating current electromagnetics for accurate, real-time tumor tracking. A quality assurance program to clinically implement this system is described here. Testing of the continuous electromagnetic tracking system ͑Calypso Medical Technologies, Seattle, WA͒ was performed using an in-house developed four-dimensional stage and a quality assurance fixture containing three radiofrequency transponders at independently measured locations. The following tests were performed to validate the Calypso system: ͑a͒ Localization and tracking accuracy, ͑b͒ system reproducibility, ͑c͒ measurement of the latency of the tracking system, and ͑d͒ measurement of transmission through the Calypso table overlay and the electromagnetic array. The translational and rotational localization accuracies were found to be within 0.01 cm and 1.0°, respectively. The reproducibility was within 0.1 cm. The average system latency was measured to be within 303 ms. The attenuation by the Calypso overlay was measured to be 1.0% for both 6 and 18 MV photons. The attenuations by the Calypso array were measured to be 2% and 1.5% for 6 and 18 MV photons, respectively. For oblique angles, the transmission was measured to be 3% for 6 MV, while it was 2% for 18 MV photons. A quality assurance process has been developed for the clinical implementation of an electromagnetic tracking system in radiation therapy.