CPL - Chalmers Publication Library
| Utbildning | Forskning | Styrkeområden | Om Chalmers | In English In English Ej inloggad.

Conductive shield for ultra-low-field magnetic resonance imaging: Theory and measurements of eddy currents

K. C. J. Zevenhoven ; S. Busch ; M. Hatridge ; Fredrik Öisjöen (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik) ; R. J. Ilmoniemi ; J. Clarke
Journal of Applied Physics (0021-8979). Vol. 115 (2014), 10, p. 12.
[Artikel, refereegranskad vetenskaplig]

Eddy currents induced by applied magnetic-field pulses have been a common issue in ultra-low-field magnetic resonance imaging. In particular, a relatively large prepolarizing field-applied before each signal acquisition sequence to increase the signal-induces currents in the walls of the surrounding conductive shielded room. The magnetic-field transient generated by the eddy currents may cause severe image distortions and signal loss, especially with the large prepolarizing coils designed for in vivo imaging. We derive a theory of eddy currents in thin conducting structures and enclosures to provide intuitive understanding and efficient computations. We present detailed measurements of the eddy-current patterns and their time evolution in a previous-generation shielded room. The analysis led to the design and construction of a new shielded room with symmetrically placed 1.6-mm-thick aluminum sheets that were weakly coupled electrically. The currents flowing around the entire room were heavily damped, resulting in a decay time constant of about 6ms for both the measured and computed field transients. The measured eddy-current vector maps were in excellent agreement with predictions based on the theory, suggesting that both the experimental methods and the theory were successful and could be applied to a wide variety of thin conducting structures. (C) 2014 AIP Publishing LLC.

Nyckelord: MRI

Denna post skapades 2014-05-21. Senast ändrad 2016-07-19.
CPL Pubid: 198392


Läs direkt!

Lokal fulltext (fritt tillgänglig)

Länk till annan sajt (kan kräva inloggning)

Institutioner (Chalmers)

Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik



Chalmers infrastruktur