Eddy-current induction in extended metallic parts as a source of considerable torsional moment

Journal of Magnetic Resonance Imaging : JMRI
Hansjörg GrafFritz Schick

Abstract

To examine eddy-current-provoked torque on conductive parts due to current induction from movement through the fringe field of the MR scanner and from gradient switching. For both cases, torque was calculated for frames of copper, aluminum, and titanium, inclined to 45 degrees to B0 (maximum torque case). Conditions were analyzed in which torque from gravity (legal limit, ASTM F2213-02) was exceeded. Experiments were carried out on a 1.5 T and a 3 T scanner for copper and titanium frames and plates (approximately 50 x 50 mm2). Movement-induced torque was measured at patient table velocity (20 cm/second). Alternating torque from gradient switching was investigated by holding the specimens in different locations in the scanner while executing sequences that exploited the gradient capabilities (40 mT/m). The calculations predicted that movement-induced torque could exceed torque from gravity (depending on the part size, electric resistance, and velocity). Two experiments on moving conductive frames in the fringe fields of the scanners confirmed the calculations. For maximum torque case parameters, gradient-switching-induced torque was calculated to be nearly 100 times greater than the movement-induced torque. Well-conducting metal...Continue Reading

References

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Citations

Jan 29, 2011·Skeletal Radiology·Reza Hosseini GhomiMartin Torriani
Jan 20, 2007·European Radiology·Alfonso Di CostanzoTommaso Scarabino
Sep 3, 2010·International Journal of Computer Assisted Radiology and Surgery·Ningbo YuRobert Riener
May 30, 2008·Nihon Hoshasen Gijutsu Gakkai zasshi·Yuta MorishitaHiroyuki Hayashi
Apr 14, 2015·Journal of Magnetic Resonance Imaging : JMRI·Ellyce F StehlinDavid M Budgett
May 23, 2014·IEEE Transactions on Bio-medical Engineering·Karl-Johan Fredén JanssonMåns Eeg-Olofsson
Jun 7, 2017·Magnetic Resonance in Medicine : Official Journal of the Society of Magnetic Resonance in Medicine·Brian J LeeCraig S Levin
Oct 16, 2018·Journal of Magnetic Resonance Imaging : JMRI·Taiki YamaguchiToru Yamamoto
Oct 31, 2007·Journal of Magnetic Resonance Imaging : JMRI·Hansjörg GrafFritz Schick
Jun 7, 2019·Der Radiologe·O Kraff, H H Quick
May 26, 2017·Journal of Magnetic Resonance Imaging : JMRI·Lawrence P Panych, Bruno Madore

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