MRI contrasts in high rank rotating frames

Timo Liimatainen, Hanne Hakkarainen, Silvia Mangia, Janne M.J. Huttunen, Christine Storino, Djaudat Idiyatullin, Dennis Sorce, Michael Garwood, Shalom Michaeli

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

Purpose: MRI relaxation measurements are performed in the presence of a fictitious magnetic field in the recently described technique known as RAFF (Relaxation Along a Fictitious Field). This method operates in the 2nd rotating frame (rank n=2) by using a nonadiabatic sweep of the radiofrequency effective field to generate the fictitious magnetic field. In the present study, the RAFF method is extended for generating MRI contrasts in rotating frames of ranks 1≤n≤5. The developed method is entitled RAFF in rotating frame of rank n (RAFFn).

Theory and Methods: RAFFn pulses were designed to generate fictitious fields that allow locking of magnetization in rotating frames of rank n. Contrast generated with RAFFn was studied using Bloch-McConnell formalism together with experiments on human and rat brains.

Results: Tolerance to B0 and B1 inhomogeneities and reduced specific absorption rate with increasing n in RAFFn were demonstrated. Simulations of exchange-induced relaxations revealed enhanced sensitivity of RAFFn to slow exchange. Consistent with such feature, an increased grey/white matter contrast was observed in human and rat brain as n increased. Conclusion: RAFFn is a robust and safe rotating frame relaxation method to access slow molecular motions in vivo.

Original languageEnglish (US)
Pages (from-to)254-262
Number of pages9
JournalMagnetic resonance in medicine
Volume73
Issue number1
DOIs
StatePublished - Jan 1 2015

Keywords

  • Brain
  • Contrast
  • Grey matter
  • MRI
  • Rotating frames
  • White matter

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