Rotating frame relaxation during adiabatic pulses vs. conventional spin lock: simulations and experimental results at 4 T

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Abstract

Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse rotating frame relaxation rate constants (R and R). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R and R due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of rotating frame relaxation methods. Rotating frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.

Original languageEnglish (US)
Pages (from-to)1074-1087
Number of pages14
JournalMagnetic Resonance Imaging
Volume27
Issue number8
DOIs
StatePublished - Oct 1 2009

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Irradiation
Brain
Chemical shift
Magnetic resonance imaging
Rate constants

Keywords

  • Adiabatic pulses
  • Anisochronous exchange
  • Dipolar interactions
  • MR contrast
  • Rotating frame relaxations
  • Spin lock

Cite this

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title = "Rotating frame relaxation during adiabatic pulses vs. conventional spin lock: simulations and experimental results at 4 T",
abstract = "Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse rotating frame relaxation rate constants (R1ρ and R2ρ). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R1ρ and R2ρ due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of rotating frame relaxation methods. Rotating frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.",
keywords = "Adiabatic pulses, Anisochronous exchange, Dipolar interactions, MR contrast, Rotating frame relaxations, Spin lock",
author = "Silvia Mangia and Timo Liimatainen and Michael Garwood and Shalom Michaeli",
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T1 - Rotating frame relaxation during adiabatic pulses vs. conventional spin lock

T2 - simulations and experimental results at 4 T

AU - Mangia, Silvia

AU - Liimatainen, Timo

AU - Garwood, Michael

AU - Michaeli, Shalom

PY - 2009/10/1

Y1 - 2009/10/1

N2 - Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse rotating frame relaxation rate constants (R1ρ and R2ρ). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R1ρ and R2ρ due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of rotating frame relaxation methods. Rotating frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.

AB - Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse rotating frame relaxation rate constants (R1ρ and R2ρ). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R1ρ and R2ρ due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift δω≠0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of rotating frame relaxation methods. Rotating frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.

KW - Adiabatic pulses

KW - Anisochronous exchange

KW - Dipolar interactions

KW - MR contrast

KW - Rotating frame relaxations

KW - Spin lock

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