Measuring T 2 and T 1, and imaging T 2 without spin echoes

G. Wang, A. M. El-Sharkawy, W. A. Edelstein, M. Schär, P. A. Bottomley

Research output: Contribution to journalArticle

Abstract

During adiabatic excitation, the nuclear magnetization in the transverse plane is subject to T 2 (spin-spin) relaxation, depending on the pulse length τ. Here, this property is exploited in a method of measuring T 2 using the ratio of NMR signals acquired with short and long-duration self-refocusing adiabatic pulses, without spin-echoes. This Dual-τ method is implemented with B 1-insensitive rotation (BIR-4) pulses. It is validated theoretically with Bloch equation simulations independent of flip-angle, and experimentally in phantoms. Dual-τ T 2 measurements are most accurate at short T 2 where results agree with standard spin-echo measures to within 10% for T 2 ≤ 100 ms. Dual-τ MRI performed with a long 0° BIR-4 pre-pulse provides quantitative T 2 imaging of phantoms and the human foot while preserving desired contrast and functional properties of the rest of the MRI sequence. A single 0° BIR-4 pre-pulse can provide T 2 contrast-weighted MRI and serve as a "T 2-prep" sequence with a lower B 1 requirement than prior approaches. Finally, a Tri-τ experiment is introduced in which both τ and flip-angle are varied, enabling measurement of T 2, T 1 and signal intensity in just three acquisitions if flip-angles are well-characterized. These new methods can potentially save time and simplify relaxation measurements and/or contrast-weighted NMR and MRI.

Original languageEnglish (US)
Pages (from-to)273-280
Number of pages8
JournalJournal of Magnetic Resonance
Volume214
DOIs
StatePublished - Jan 1 2012

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Keywords

  • Adiabatic pulses
  • MRI
  • Measurement
  • Spin-lattice relaxation
  • Spin-spin relaxation
  • T
  • T

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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