A simple and rapid method for electromagnetic field distortion correction when using two Fastrak sensors for biomechanical studies

Hagemeister, Nicola; Parent, G.; Husse, Sabine; Guise, Jacques A. de

doi:10.1016/j.jbiomech.2008.02.030

Cited by 7 publications

(9 citation statements)

References 7 publications

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“…While magnetic tracking has advantages such as low system cost [13] and operation under conditions with occluded line-of-sight, the Fastrak system suffers from inaccuracies in the presence of magnetic field distortions, e.g., from metal. Distortions may be identified and corrected for by time-consuming on-site calibration (the calibration object must be sampled at, e.g., 24 positions [10] or moved through the measurement space for approximately 3 min [13]). Nevertheless, after these corrections, errors still exceed 10 mm for distances between sensor and emitter of beyond 1.20 m [10].…”

Section: Introductionmentioning

confidence: 99%

Automatic camera-based identification and 3-D reconstruction of electrode positions in electrocardiographic imaging

Schulze¹,

Mackens²,

Potyagaylo³

et al. 2014

Biomedical Engineering / Biomedizinische Technik

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Electrocardiographic imaging (ECG imaging) is a method to depict electrophysiological processes in the heart. It is an emerging technology with the potential of making the therapy of cardiac arrhythmia less invasive, less expensive, and more precise. A major challenge for integrating the method into clinical workflow is the seamless and correct identification and localization of electrodes on the thorax and their assignment to recorded channels. This work proposes a camera-based system, which can localize all electrode positions at once and to an accuracy of approximately 1 ± 1 mm. A system for automatic identification of individual electrodes is implemented that overcomes the need of manual annotation. For this purpose, a system of markers is suggested, which facilitates a precise localization to subpixel accuracy and robust identification using an error-correcting code. The accuracy of the presented system in identifying and localizing electrodes is validated in a phantom study. Its overall capability is demonstrated in a clinical scenario.

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Section: Introductionmentioning

confidence: 99%

Automatic camera-based identification and 3-D reconstruction of electrode positions in electrocardiographic imaging

Schulze¹,

Mackens²,

Potyagaylo³

et al. 2014

Biomedical Engineering / Biomedizinische Technik

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“…Sensor PnO during the data collection process is determined through application of the estimated sensor 0 PnO to the relative PnO developed in (16) and (17). The position of sensor n at time step k is the relative position of sensor n (rP n ) rotated by the sensor 0 orientation, i.e., QtoT(q 0 k ), summed with the sensor 0 position r 0 k (18).…”

Section: B Mapping Fixturementioning

confidence: 99%

“…Hagemeister et al [16] used multiple sensors in a known geometry to measure errors for real-time PnO corrections. Their technique generated correction factors by comparing the known distance between sensors with the measurements to correct PnO by more than 50% without a formal mapping.…”

Section: Introductionmentioning

confidence: 99%

Interpolation Volume Calibration: A Multisensor Calibration Technique for Electromagnetic Trackers

Himberg¹,

Motai

Bradley

2012

IEEE Trans. Robot.

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AC electromagnetic trackers are well suited for head tracking but are adversely affected by conductive and ferromagnetic materials. Tracking performance can be improved by mapping the tracking volume to produce coefficients that correct position and orientation (PnO) measurements caused by stationary distorting materials. The mapping process is expensive and time consuming, requiring complicated high-precision equipment to provide registration of the measurements to the source reference frame. In this study, we develop a new approach to mapping that provides registration of mapping measurements without precision equipment. Our method, i.e., the interpolation volume calibration system, uses two simple fixtures, each with multiple sensors in a rigid geometry, to determine sensor PnO in a distorted environment without mechanical measurements or other tracking technologies. We test our method in a distorted tracking environment, constructing a lookup table of the magnetic field that is used as the basis for distortion compensation. The new method compares favorably with the traditional approach providing a significant reduction in cost and effort.Index Terms-AC magnetic tracking, magnetic tracker calibration, position and orientation measurements. NOMENCLATURE SymbolDefinition ARAugmented Reality. f D (r)Dipole Formula for the signal matrix at field point r. f I (r)A function that determines the secondary field of field point r in the interpolation volume. f S (r)The estimated signal matrix measured at field point r inside the interpolation volume. f STS (S) A function that computes the product of the signal matrix S transpose and the signal matrix. r A field point position vector (3 × 1).

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“…For some applications, electromagnetic (EM) motion capture sensors 1 are a practical alternative to the more commonly used optoelectronic (OE) sensors. Although EM sensors have some disadvantages [1], including a small sensing volume [2] (a sphere with radius on the order of 4ft) and susceptibility to electromagnetic interference from ferromagnetic materials [2][3][4][5][6][7][8] and electrical equipment [8], they have some advantages over optoelectronic sensors. EM sensors: do not require a direct line of sight; output six degrees of freedom per sensor; sample at relatively high frequencies (between 40 and 360 samples/s); and are relatively low-cost.…”

Section: Introductionmentioning

confidence: 99%

Tracking Joint Angles During Whole-Arm Movements Using Electromagnetic Sensors

Clark

Dickinson

Loaiza

et al. 2020

Journal of Biomechanical Engineering

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Electromagnetic (EM) motion tracking systems are suitable for many research and clinical applications, including in vivo measurements of whole-arm movements. Unfortunately, the methodology for in vivo measurements of whole-arm movements using EM sensors is not well described in the literature, making it difficult to perform new measurements and all but impossible to make meaningful comparisons between studies. The recommendations of the International Society of Biomechanics (ISB) have provided a great service, but by necessity they do not provide clear guidance or standardization on all required steps. The goal of this paper was to provide a comprehensive methodology for using EM sensors to measure whole-arm movements in vivo. We selected methodological details from past studies that were compatible with the ISB recommendations and suitable for measuring whole-arm movements using EM sensors, filling in gaps with recommendations from our own past experiments. The presented methodology includes recommendations for defining coordinate systems (CSs) and joint angles, placing sensors, performing sensor-to-body calibration, calculating rotation matrices from sensor data, and extracting unique joint angles from rotation matrices. We present this process, including all equations, for both the right and left upper limbs, models with nine or seven degrees-of-freedom (DOF), and two different calibration methods. Providing a detailed methodology for the entire process in one location promotes replicability of studies by allowing researchers to clearly define their experimental methods. It is hoped that this paper will simplify new investigations of whole-arm movement using EM sensors and facilitate comparison between studies.

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A simple and rapid method for electromagnetic field distortion correction when using two Fastrak sensors for biomechanical studies

Cited by 7 publications

References 7 publications

Automatic camera-based identification and 3-D reconstruction of electrode positions in electrocardiographic imaging

Automatic camera-based identification and 3-D reconstruction of electrode positions in electrocardiographic imaging

Interpolation Volume Calibration: A Multisensor Calibration Technique for Electromagnetic Trackers

Tracking Joint Angles During Whole-Arm Movements Using Electromagnetic Sensors

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