A simple geometrical description of the TrueFISP ideal transient and steady-state signal

Peter Schmitt, M. A. Griswold, V. Gulani, A. Haase, M. Flentje, P. M. Jakob

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

An intuitive approach is presented for assessment of the TrueFISP signal behavior in the transient phase and the steady state, based on geometrical considerations in combination with the Bloch equations. Short formulations are derived for the zenith and phase angle determining the direction of the magnetization vector for which a smooth monoexponential decay is obtained even at considerable off-resonance frequencies, thus compactly defining the target of various preparation schemes proposed in literature. A pictorial explanation is provided to illustrate how the interplay between RF excitation and relaxation governs the TrueFISP transient phase and steady state. Closed form expressions are developed that describe the signal evolution, accounting for the influence of T1, T2, flip angle, and resonance frequency offset in agreement with recently published studies. These results are obtained directly from basic assumptions, without the need for abstract mathematical treatment or further approximations. The validity of the conceptual framework and the analytical description is verified by simulations based on the Bloch equations as well as with MR phantom experiments. The theory may be used for contrast calculations and has the potential to facilitate improved parameter quantification with magnetization prepared TrueFISP experiments accounting for off-resonance effects.

Original languageEnglish
Pages (from-to)177-186
Number of pages10
JournalMagnetic Resonance in Medicine
Volume55
Issue number1
DOIs
StatePublished - Jan 2006
Externally publishedYes

Keywords

  • Balanced SSFP
  • Decay rate
  • Off-resonance
  • Steady state
  • Transient phase
  • TrueFISP

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