Electromagnetic tracking systems

Note that the majority of modern image-guided systems utilize optical tracking. Electromagnetic tracking systems are also sometimes utilized however, these systems typically have lower accuracy than optical systems. 

The motion of the needle tip was measured experimentally and compared with predictions of the analytical model. The tip motion is measured with a magnetic position sensor (miniBIRD model 80 from Ascension Technology). This electromagnetic tracking system measures the three positions and three orientations of a small sensor (1.3 mm in diameter, 6.5 mm in length) with RMS accuracies of 1.4 mm and 0.5°. The sensor is small compared to the manipulator and does not affect its performance. 

C.L. Koerhuis, J.C. Winters, F.C. van der Helm, A.L. Hof. (2003) Neck mobility measurement by means of the Flock of Birds electromagnetic tracking system. Clin Biomech (Bristol, Avon) 18(1) 14-8. 

In principle, tracking is suitable for any technology. Thus, the three-dimensional position tuid orientation of an object can be determined as free of delay and reliable. Electromagnetic, kinematics, acoustic, optical, image work processing, and inertial procedures find use for tracking tasks. Currently available body-tracking systems fall into two classes (Bryson 1993) ... 

In this section we will discuss three of the more common methods used to collect human movement data electrogoniometers, electromagnetic tracking devices, and optoelectronic measuring systems. Of these distinctly different measuring tools, optoelectronic systems are the most common registration method, and therefore most of this section will focus on video-based motion analysis. 

To achieve accurate 3D reconstruction, electromagnetic interference must be minimized, the transmitter must be close to the receiver, and there should be no ferrous or highly conductive metals in the vicinity (Downey et al. 2000 Kelly et al. 1994). Magnetic field tracking systems can be used with standard and endocavitary transducers. These systems have been used successfully for fetal (Kelly et al. 1994 Pretorius and Nelson 1994) and vascular (Hodges et al. 1994) 3D imaging. Recently, there has been some development with a miniature magnetic position sensor suitable for use with intra-vascular transducers. 

Fig. 28.3. Close-up of biopsy experiment a robot (the IBM/ JHU LARS) holds the ultrasound probe and a second robot is used for positioning a needle guide. On both, an electromagnetic (EM) tracking system (Flock of Birds, model 6D FOB, Ascension Technology, Inc.) interfaces with the robot workstation. [Reprinted with permission from Boctor et al. (2004)]...

In addition, we present a practical concept to accurately track an object s position and orientation in 3D space. Our approach overcomes the disadvantages associated with the most popular tracking systems used in image-guided surgery, e.g., optical and electromagnetic trackers. Our tracker can be used in environments with metallic... 

The CMS experiment—one of the four large LHC experiments— is a general-purpose detector designed to optimally exploit the physics potential of the LHC. Located inside the superconducting solenoid, which provides a 3.8 Tesla held, are the hadronic and electromagnetic calorimeters as well as the tracking system. The latter is based on silicon pixels and silicon strip detectors, with a total sUicon area of 210 m. A multi-layer muon system embedded in the return yoke outside the solenoid completes the CMS detector. 

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