selective excitation

selective excitation

An MRI term for controlling the frequency spectrum (bandwidth) of a radio frequency excitation pulse while imposing a gradient magnetic field on spins, so that only a desired region will have a suitable resonant frequency to be excited.
References in periodicals archive ?
In the latter approach, acid-base interactions in the substrate-catalyst complex will lead to a significant bathochromic absorption shift of the substrate, enabling a selective excitation within the complex and a subsequent enantioselective reaction pathway within a spatially defined chiral environment.
Frydman, "Longitudinal relaxation enhancement in 1H NMR spectroscopy of tissue metabolites via spectrally selective excitation," Chemistry, vol.
Macovski, "Parameter relations for the Shinnar-Le Roux selective excitation pulse design algorithm [NMR imaging," IEEE Trans.
PANalytical says the performance of the Epsilon 3 comes from selective excitation and careful matching of the x-ray tube output to the capabilities of the detection system, together with "advanced spectrum processing and unique correction and quantification algorithms".
For those sequences for which SAR does affect the pulse sequence, other solutions may be applied, including parallel imaging to shorten echo trains (with a small reduction in optimal SNR), (9-11) and tailored RF pulse shapes or flip angles (variable-rate selective excitation, hyperecho-turbo spin-echo, transition between pseudo steady-states).
Hence, the KR illumination leads to a strong selective excitation in close proximity to the metal surface.
While latest GaAs technology allows highest sensitivity, the novel 4kW peak power active Transmit/Receive switch provides full linearity in the transmit path of the spectrometer, delivering ultimate selective excitation performance for any NMR application.

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