Tuned SQUID-MRI system with resonant frequency adjustment

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

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)850-853
Number of pages4
JournalIEEE Transactions on Applied Superconductivity
Issue number2
Publication statusPublished - 2007


  • magnetic resonance imaging
  • SQUID magnetometers.
  • biomagnetic signals
  • magnetic-fields
  • amplifier
  • NMR
  • sensitivity
  • coil


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