Correction of susceptibility-induced GRE phase shift for accurate PRFS thermometry proximal to cryoablation iceball

Antje Kickhefel, Clifford Weiss, Joerg Roland, Patrick Gross, Fritz Schick, Rares Salomir

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Introduction The susceptibility contrast between frozen and unfrozen tissue disturbs the local magnetic field in the proximity of the ice-ball during cryotherapy. This effect should be corrected for in real time to allow PRFS-based monitoring of near-zero temperatures during intervention. Material and methods Susceptibility artifacts were corrected post-processing, using a rapid numerical algorithm. The difference in bulk magnetic susceptibility between frozen and non-frozen tissue was approximated to be uniform over the ice-ball volume and was determined from the isothermal principle applied to the phase-transition frontier of compartments. Subsequently, the magnetic perturbation field was calculated rapidly in 3D using a Fourier-convolution. Experimental studies were performed for two scenarios: tissue defrosting in a water bath and induction of an ice-ball by a MR-compatible cryogenic probe. Results The susceptibility artifacts yielded PRFS temperature errors as high as 10-12?C proximal to the ice-ball, positive or negative depending on the relative orientation of the position vector from the Bo direction. These effects were fully corrected for to within the noise range. The susceptibility-corrected PRFS temperature values were consistent with the phase-transition isothermal condition, irrespective of the local orientation of the position vector. Conclusion By implementing on-line the post processing algorithm, PRFS MRT may be used as a safety tool for noninvasive and accurate monitoring of near-zero temperatures during MR-guided clinical cryotherapy.

Original languageEnglish (US)
Pages (from-to)23-31
Number of pages9
JournalMagnetic Resonance Materials in Physics, Biology and Medicine
Issue number1
StatePublished - Feb 2012


  • Interventional
  • MR-guided cryoablation
  • Magnetic susceptibility
  • PRFS thermometry
  • Real-time correction
  • Safety

ASJC Scopus subject areas

  • Biophysics
  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging


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