Optimized, unequal pulse spacing in multiple echo sequences improves refocusing in magnetic resonance.
Abstract
A recent quantum computing paper (G. S. Uhrig, Phys. Rev. Lett. 98, 100504 (2007))
analytically derived optimal pulse spacings for a multiple spin echo sequence designed
to remove decoherence in a two-level system coupled to a bath. The spacings in what
has been called a "Uhrig dynamic decoupling (UDD) sequence" differ dramatically from
the conventional, equal pulse spacing of a Carr-Purcell-Meiboom-Gill (CPMG) multiple
spin echo sequence. The UDD sequence was derived for a model that is unrelated to
magnetic resonance, but was recently shown theoretically to be more general. Here
we show that the UDD sequence has theoretical advantages for magnetic resonance imaging
of structured materials such as tissue, where diffusion in compartmentalized and microstructured
environments leads to fluctuating fields on a range of different time scales. We also
show experimentally, both in excised tissue and in a live mouse tumor model, that
optimal UDD sequences produce different T(2)-weighted contrast than do CPMG sequences
with the same number of pulses and total delay, with substantial enhancements in most
regions. This permits improved characterization of low-frequency spectral density
functions in a wide range of applications.
Type
Journal articleSubject
AnimalsContrast Media
Health Care Reform
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Mice
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https://hdl.handle.net/10161/3315Published Version (Please cite this version)
10.1063/1.3263196Publication Info
Jenista, Elizabeth R; Stokes, Ashley M; Branca, Rosa Tamara; & Warren, Warren S (2009). Optimized, unequal pulse spacing in multiple echo sequences improves refocusing in
magnetic resonance. J Chem Phys, 131(20). pp. 204510. 10.1063/1.3263196. Retrieved from https://hdl.handle.net/10161/3315.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Elizabeth Jenista
Research Scholar
Warren S. Warren
James B. Duke Distinguished Professor of Chemistry
Our work focuses on the design and application of what might best be called novel
pulsed techniques, using controlled radiation fields to alter dynamics. The heart
of the work is chemical physics, and most of what we do is ultrafast laser spectroscopy
or nuclear magnetic resonance. It generally involves an intimate mixture of theory
and experiment: recent publications are roughly an equal mix of pencil- and-paper
theory, computer calculations with our workstations, and experiments. Collabo
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