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Related Experiment Videos

Encoding to the longitudinal magnetization for MR imaging and flow velocity mapping.

Jung-Jiin Hsu1, Irving J Lowe

  • 1Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA. jjhsu@stanford.edu

Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|August 15, 2006
PubMed
Summary

This study introduces phase-encoding to longitudinal magnetization for improved MRI. It details methods to separate and remove spin-lattice relaxation effects, enabling clearer spatial MRI and flow velocity mapping.

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Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

  • Phase-encoding in NMR pulse sequences is crucial for spatial information.
  • Spin-lattice relaxation (T1) can introduce artifacts in phase-encoded data.
  • The 90-degree pulse's partial transformation of transverse to longitudinal magnetization affects phase encoding.

Purpose of the Study:

  • To implement and analyze phase-encoding to longitudinal magnetization.
  • To investigate the impact of spin-lattice relaxation and develop methods for its removal.
  • To demonstrate the application in spatial MRI and flow velocity mapping using RUFIS.

Main Methods:

  • Implementing phase-encoding by adding gradient pulses in the NMR pulse sequence (90°x-τ-90°x).
  • Theoretical analysis to separate phase information from spin-lattice relaxation effects.

Related Experiment Videos

  • Data acquisition using the rotating ultra-fast imaging sequence (RUFIS).

    • Main Results:

    • Spin-lattice relaxation effects are separable and identical in repeated measurements.
    • Relaxation artifacts can be eliminated by data subtraction or polarity alternation.
    • Partial phase information leads to mirror aliasing in Fourier reconstruction, which can be addressed with orthogonal data or may be acceptable.

    Conclusions:

    • Phase-encoding to longitudinal magnetization is feasible and effective for MRI applications.
    • Spin-lattice relaxation can be successfully compensated for, improving image quality.
    • RUFIS enables phase-encoding for spatial MRI and flow velocity mapping, with potential for artifact management.