Tuned SQUID-MRI System With Resonant Frequency Adjustment

Author

Seton, Hugh C. ; Rieger, Sebastian W. ; Hutchison, James M.S.

Author_Institution

Univ. of Aberdeen, Aberdeen

Volume

17

Issue

2

fYear

2007

fDate

6/1/2007 12:00:00 AM

Firstpage

850

Lastpage

853

Abstract

We describe a low field, bench-top MRI system for small samples, based on a permanent magnet. Signals are received at 830 kHz using a tuned SQUID magnetometer, cooled in a modified liquid helium cryostat. The SQUID input circuit has an intrinsic Q-factor of 28,000, so this is damped by flux-locking electronics and an additional feedback loop to give an effective Q of between 40 and 200 for imaging. The resonant frequency is adjusted by a control rod coupled to a trimmer capacitor mounted in the liquid helium volume. Images of a test object acquired using the cooled receiver exhibit up to two-fold SNR gains in regions close to the sensor, compared to an equivalent room temperature coil, with the noise level dominated by losses coupled from the magnet pole faces.

Keywords

Q-factor; SQUID magnetometers; biomedical MRI; permanent magnets; Q-factor; SQUID input circuit; SQUID magnetometer; SQUID-MRI system; bench-top MRI system; cooled receiver; feedback loop; flux-locking electronics; frequency 830 kHz; imaging; liquid helium volume; low field MRI system; magnet pole faces; modified liquid helium cryostat; noise level; permanent magnet; resonant frequency; resonant frequency adjustment; room temperature coil; trimmer capacitor; two-fold SNR gains; Coupling circuits; Feedback circuits; Feedback loop; Helium; Magnetic resonance imaging; Permanent magnets; Q factor; Resonant frequency; SQUID magnetometers; Temperature sensors; Magnetic resonance imaging; SQUID magnetometers;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/TASC.2007.898258

Filename

4277708