Search

As the importance and prevalence of electromagnetic tracking in medical and industrial applications increases, the need for customized sensor design has escalated. This work focuses on AC-based electromagnetic tracking systems where off-the-shelf inductive sensors may not be optimal for many medical instruments or tracking applications. We present a repeatable approach for the design, optimisation and implementation of air-core and ferrite-core inductive sensors suitable for AC-based electromagnetic tracking. Coil-based sensors were designed and tested to investigate the effect of the usual coil parameters such as turn count, geometry and core material on sensor tracking accuracy and precision. Our methodologies were experimentally validated using the Anser EMT system which enabled rapid experimental deployment. Experimental performance is reported compared to off-the-shelf sensors. Static tracking errors of less than 2mm were achieved and close correlation with theoretical design sensitivity and precision was observed. This work may represent a valuable tool in the design of bespoke sensors for electromagnetic tracking where customize sensitivity and form factor are critical. [ABSTRACT FROM AUTHOR]

This paper evaluates the use of planar magnetic shielding with electromagnetic (EM) tracking systems to prevent field distortion from ferromagnetic objects below a magnetic-field transmitter. A comparison of the shielding performance of MuMetal, ferrite, aluminum, and steel is presented over a frequency range of 1 Hz to 1 MHz. Both simulation and experimental results show the merits of each shield material. MuMetal and ferrite were found to give excellent shielding performance over a wide frequency range. The use of a ferrite and MuMetal shield is also demonstrated in a full 5 degree of freedom EM tracking system and is shown to successfully operate with position errors of 1.8 and 2.3 mm, respectively, in a volume of 25~cm\times 25~cm \times 25 cm. This is compared with a mean position error 67.3 mm without shielding. The orientation error for each shield was found to be 1.9° and 2.1° for the ferrite and MuMetal, respectively, in comparison with an error of 115.1° without shielding. [ABSTRACT FROM PUBLISHER]

We present a novel method for demodulating multiple frequency components of an ac magnetic field for use in electromagnetic tracking systems. Our undersampling method allows for a low sampling rate to acquire signals of interest in a range of 20–30 kHz without significant loss of precision. Lower sample rates give additional computation time between each sample, allowing for real-time demodulation without expensive high speed data acquisition and processing hardware. This also allows the use of low speed high precision analog-to-digital converters (ADCs) for sampling high frequency signals. The presented system demodulates 16 frequency components from two signals using an Arduino Due microcontroller and a two channel 16-bit ADC. The demodulated signals are then used to accurately determine the position of a magnetic sensor to within 1 mm in a volume 25 cm \times 25~cm \times 25 cm. The system accuracy compares well with both commercial and research systems in terms of accuracy, but at a dramatically lower cost. [ABSTRACT FROM PUBLISHER]

This paper presents an electromagnetic system for five degrees of freedom position and orientation sensing with application in a virtual bronchoscopy system. Planar magnetic source coils were manufactured on printed circuit boards for reproducibility and low-cost manufacturing. The exact magnetic field of each coil is calculated using a filament-based approach. A constant ac current amplifier is used to drive each coil at an independent frequency and a synchronous demodulator calculates each associated magnetic field component using the current waveform as a reference signal. Commercially available search coil sensors are used and a comparison between shielded and unshielded probes is presented. Extensive testing with two separate methods has shown the accuracy of the system to be between 1 and 2 mm. The use of a novel closed loop coil driver has been found to offer excellent magnetic field stability and significant reduction in crosstalk interference. [ABSTRACT FROM PUBLISHER]