### 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) |
---|---|

Pages (from-to) | 273-280 |

Number of pages | 8 |

Journal | Journal of Magnetic Resonance |

Volume | 214 |

DOIs | |

State | Published - Jan 2012 |

### Fingerprint

### Keywords

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

### ASJC Scopus subject areas

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

### Cite this

*Journal of Magnetic Resonance*,

*214*, 273-280. https://doi.org/10.1016/j.jmr.2011.11.016

**Measuring T 2 and T 1, and imaging T 2 without spin echoes.** / Wang, G.; El-Sharkawy, A. M.; Edelstein, W. A.; Schar, Michael; Bottomley, Paul A.

Research output: Contribution to journal › Article

*Journal of Magnetic Resonance*, vol. 214, pp. 273-280. https://doi.org/10.1016/j.jmr.2011.11.016

}

TY - JOUR

T1 - Measuring T 2 and T 1, and imaging T 2 without spin echoes

AU - Wang, G.

AU - El-Sharkawy, A. M.

AU - Edelstein, W. A.

AU - Schar, Michael

AU - Bottomley, Paul A

PY - 2012/1

Y1 - 2012/1

N2 - 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.

AB - 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.

KW - Adiabatic pulses

KW - Measurement

KW - MRI

KW - Spin-lattice relaxation

KW - Spin-spin relaxation

KW - T

KW - T

UR - http://www.scopus.com/inward/record.url?scp=84855667502&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84855667502&partnerID=8YFLogxK

U2 - 10.1016/j.jmr.2011.11.016

DO - 10.1016/j.jmr.2011.11.016

M3 - Article

VL - 214

SP - 273

EP - 280

JO - Journal of Magnetic Resonance

JF - Journal of Magnetic Resonance

SN - 1090-7807

ER -