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Tracking and Calibration
Published in Terry M. Peters, Cristian A. Linte, Ziv Yaniv, Jacqueline Williams, Mixed and Augmented Reality in Medicine, 2018
Magnetic tracking systems represent another type of spatial measuring technology commonly used in computer-assisted intervention. The physical principle of magnetic tracking is the generation of an artificial magnetic field in which the strength and the orientation of the magnetic field can be detected using either a search coil (for an alternating current driven field) or a fluxgate coil (for a direct current driven field) [5]. Magnetic tracking systems are sensitive to the presence of ferromagnetic objects. Due to the small size of these coils, a magnetic tracking system is particularly suitable in a scenario in which optical DRF is too large to be integrated into the surgical instrument or within flexible instruments such as transesophageal echocardiography ultrasounds.
Medical Devices and Systems Exposure and Dosimetry
Published in James C. Lin, Electromagnetic Fields in Biological Systems, 2016
Magnetic tracking systems determine the location of objects (e.g., a catheter) that contain a magnetic sensor or marker. This requires a magnetic field of known geometry generated by orthogonal field coils. In spite of the use of magnetic fields, due to widespread unfortunate habit, this technique is frequently called electromagnetic tracking (EMT). In contrast to an optical tracking system, this approach does not need line of sight and hence allows tracking of intracorporal objects. When an object is placed inside the magnetic field, voltages are induced in the sensor, which are indicating the position and orientation of the object. Sensors might be coils in which signals are induced either by 8–12 kHz AC fields or by switched DC fields. Another solution is tracking the position of a permanent magnet or transponder incorporated in the medical device. Inaccuracies might occur if the tracking field is disturbed by the presence of metallic objects or EMI (Zhang et al. 2006; Wagner et al. 2002).
Positioning and Tracking Approaches and Technologies
Published in Hassan A. Karimi, Advanced Location-Based Technologies and Services, 2016
Dorota Grejner-Brzezinska, Allison Kealy
Magnetic tracking systems are subject to error, primarily due to distortions of their magnetic fields by conducting objects or due to other electromagnetic fields in the environment, and generally, the error increases with the transmitter–receiver distance. If there is a metal object in the vicinity of the magnetic tracker’s transmitter or receiver, the transmitter signals are distorted and the resulting position/orientation measurements will contain errors. One possible solution is the system calibration based on a map of distortions (calibration table) from which a correction term can be derived. More details on magnetic tracking can be found in Allen et al. (2001), Raab et al. (1979), and Livingston (2002).
Magnetic tracking using a modular C++ environment for image-guided interventions
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2021
Marco Cavaliere, Conor Walsh, Herman Alexander Jaeger, Kilian O’Donoghue, Pádraig Cantillon-Murphy
Magnetic tracking, or electromagnetic tracking (EMT), enables instrument tracking and navigation during image-guided interventions with no line of sight limitation (Peters and Cleary 2008; Cleary and Peters 2010). EMT is used during clinical diagnosis or therapy using flexible bronchoscopy and in orthopaedic procedures (Franz et al. 2014; Herman Alexander Jaeger et al. 2019). The technology finds also application in robotic surgical devices for guidance and navigation in the absence of a line of sight (Schwein et al. 2017, 2018), as well as in Virtual and Augmented Reality in surgery (Halabi et al. 2020). Magnetic tracking can also be used in multi-modal imaging applications combining traditional radiological imaging such as CT, with ultrasound and other local imaging modalities (Franz et al. 2019), for example for percutaneous hepatic intervention (Lee 2014; Akhtar et al. 2021).
Localization strategies for robotic endoscopic capsules: a review
Published in Expert Review of Medical Devices, 2019
Federico Bianchi, Antonino Masaracchia, Erfan Shojaei Barjuei, Arianna Menciassi, Alberto Arezzo, Anastasios Koulaouzidis, Danail Stoyanov, Paolo Dario, Gastone Ciuti
The typical components of a magnetic tracking system are one or more magnetic sources (transmitters), and one or more sensor modules (receivers). Therefore, based on the relative position between transmitters and receivers, two main approaches are defined for robotic capsule localization. The first approach consists in positioning the magnetic sources inside the capsule and the sensing modules outside the patient’s body (Section 2.1.1), while the second approach consists in positioning the sensing module inside the capsule and the magnetic sources outside of the patient’s body (Section 2.1.2).