Quantitative analysis of adiabatic fast passage for steady laminar and turbulent flows.
Magn Reson Med
; 47(4): 709-19, 2002 Apr.
Article
em En
| MEDLINE
| ID: mdl-11948732
ABSTRACT
Adiabatic fast passage (AFP) is used in noninvasive quantitative perfusion experiments to invert (or label) arterial spins. Continuous arterial spin labeling (CASL) experiments conducted in vivo often assume the inversion efficiency based on the labeling field and steady flow conditions, without direct verification. In practice, the labeling field used in CASL is often amplitude- and duty cycle-limited due to hardware or specific absorption rate constraints. In this study, the effects of the labeling field amplitude and duty cycle, and flow dynamics on the inversion efficiency of AFP were examined under steady flow conditions in a saline flow phantom. The experimental results were in general agreement with models based on Zhernovoi's theory except at high labeling field amplitudes, when the spin inversion times are at least half of the duration of the labeling pulse. The nonlinear relation observed between the inversion efficiency and the labeling duty cycle implies that the practice of linear derating the inversion efficiency with the labeling duty cycle may be prone to significant error. A secondary finding was that the T1 of the flowing fluid could be calculated based on the flow dynamics after varying the flow rate.
Buscar no Google
Base de dados:
MEDLINE
Assunto principal:
Marcadores de Spin
/
Imageamento por Ressonância Magnética
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
Magn Reson Med
Assunto da revista:
DIAGNOSTICO POR IMAGEM
Ano de publicação:
2002
Tipo de documento:
Article
País de afiliação:
Estados Unidos