## 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 language | English (US) |
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Pages (from-to) | 273-280 |

Number of pages | 8 |

Journal | Journal of Magnetic Resonance |

Volume | 214 |

DOIs | |

State | Published - Jan 2012 |

## 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