2born (2born) wrote,

МРТ: последовательность SWIFT и артефакт бычьего глаза

Gap Cycling for SWIFT: http://arxiv.org/abs/1307.2926

Purpose: SWIFT (SWeep Imaging with Fourier Transformation) is a non- Cartesian MRI method with unique features and capabilities. In SWIFT, radiofrequency (RF) excitation and reception are performed nearly simultaneously, by rapidly switching between transmit and receive during a frequency-swept RF pulse. Because both the transmitted pulse and data acquisition are simultaneously amplitude-modulated in SWIFT (in contrast to continuous RF excitation and uninterrupted data acquisition in more familiar MRI sequences), crosstalk between different frequency bands occurs in the data. This crosstalk leads to a "bulls-eye" artifact in SWIFT images. We present a method to cancel this inter-band crosstalk by cycling the pulse and receive gap positions relative to the un-gapped pulse shape. We call this strategy "gap cycling."
Methods: We carry out theoretical analysis, simulation and experiments to characterize the signal chain, resulting artifacts, and their elimination for SWIFT.
Results: Theoretical analysis reveals the mechanism for gap-cycling's effectiveness in canceling inter-band crosstalk. We show phantom and in-vivo results demonstrating bulls-eye artifact free images.
Conclusion: Gap cycling is an effective method to remove bulls-eye artifact resulting from inter-band crosstalk in SWIFT data. Comments: Technical Note 2173 Words 5 figures version 130710 final draft, preprint submitted to MRM

Авторы определяют свой текст как технический отчет, и это верно: он представляет собой прекрасный пример реального рассчета параметров конкретной последовательности, чего так не хватает учебникам по ЯМР-томографии!
Tags: Мегаучебник или Что я читал и похвалил, медицинская физика, наука, образование, разгребая arXiv'ы, техника

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