Short‐TR, Coherent, Gradient Echo Imaging

Yu‐Chung Norman Cheng1, E. Mark Haacke2

1 Case Western Reserve University, Cleveland, Ohio, 2 The MRI Institute for Biomedical Research, St. Louis, Missouri
Publication Name:  Current Protocols in Magnetic Resonance Imaging
Unit Number:  Unit B5.2
DOI:  10.1002/0471142719.mib0502s02
Online Posting Date:  November, 2001
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Abstract

When a spin system is repeatedly disturbed by a fast repetition of RF pulses, the transverse magnetization after each new RF pulse approaches a steady‐state value which is smaller than the thermal equilibrium value. The spin system takes a finite number of pulses before this steady‐state is reached in a time that depends on both the T1 of the tissue and the flip angle of the RF pulse. The focus of this unit is on understanding the build‐up of the magnetization to steady‐state and the practical implementation of the simplest forms of imaging in the steady‐state. Sequences utilizing a steady‐state approach can be broadly classified as steady‐state coherent (SSC) and steady‐state incoherent (SSI) sequences. The SSC behavior is the subject of this unit.

     
 
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Table of Contents

  • Overview
  • Technical Discussion
  • Key References
  • Figures
     
 
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Materials

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Figures

Videos

Literature Cited

Key References
   Bydder, G.M. and Young, I.R. 1985. Clinical use of the partial and saturation recovery sequences in MR imaging. J. Comput. Assist. Tomogr. 9:1020.
  This paper proposed different short TE, fast imaging methods.
   Ernst, R.R. and Anderson, W.A. 1966. Application of Fourier transform spectroscopy to magnetic resonance. Rev. Sci. Instrum. 37:93.
  This article covers both the coherent and incoherent steady‐states and gives expressions for flip angles which maximize the signal (hence the name “Ernst angle”).
   Haacke, E.M., Weilopolski, P.A., and Tkach, J.A. 1991. A comprehensive technical review of short TR, fast magnetic resonance imaging techniques. Rev. Magn. Reson. Med. 3:53.
  This article gives a modern review of the steady‐state, fast imaging methods.
   Haacke, E.M., Brown, R.W., Thompson, M.R., and Venkatesan, R. 1999. Magnetic Resonance Imaging: Physical Principles and Sequence Design. John Wiley & Sons, New York.
  This text covers the technical aspects presented here, but in more detail, and also discusses more advanced materials.
   Haase, A., Frahm, J., Matthei, D., Hannicke, W., and Merboldt, K.‐D. 1986. FLASH imaging: Rapid imaging using low flip angle pulses. J. Magn. Reson. 67:256.
  This article proposed different short TE, fast imaging methods.
   Hennig, J. 1991. Echoes—how to generate, recognize, use or avoid them in MR imaging sequences. Part I: Fundamental and not so fundamental properties of spin echoes. Concepts Magn. Reson. 3:125.
  This text gives a modern review of the steady‐state, fast imaging methods.
   Hennig, J. 1991. Part II: Echoes in imaging sequences. Concepts Magn. Reson. 3:179.
  This paper gives a modern review of the steady‐state, fast imaging methods.
   Oppelt, A., Graumann, R., Barfuss, H., Fischer, H., Hertl, W., and Schajor, W. 1986. FISP: A new fast MRI sequence. Electromedica 3:15.
  This paper proposed different short TE, fast imaging methods.
   van der Muelen, P., Croen, J.P., and Cuppen, J.J.M. 1985. Very fast MR imaging by field echoes and small angle excitation. Magn. Reson. Imaging 3:297.
  This article proposed different short TE, fast imaging methods.
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