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Flow distortion and signal loss in spiral imaging
Author(s) -
Gatehouse P.D.,
Firmin D.N.
Publication year - 1999
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/(sici)1522-2594(199905)41:5<1023::aid-mrm22>3.0.co;2-1
Subject(s) - spiral (railway) , physics , distortion (music) , k space , turbulence , optics , signal (programming language) , trailing edge , phase (matter) , mechanics , mathematics , computer science , fourier transform , mathematical analysis , amplifier , optoelectronics , cmos , quantum mechanics , programming language
The effect of in‐plane motion on the point spread function (velocity PSF) in spiral imaging is studied experimentally and derived mathematically and is shown to consist of a smoothed, trailing edge and fringes around the leading edge. The velocity PSF remains largely in phase with the static PSF, consistent with the absence of signal loss by motion‐related phase shifts in central k space. However, single‐shot spiral imaging gives no clear improvement in complex and turbulent flow signal uniformity compared with echo‐planar imaging with early, central k ‐space acquisition, which requires explanation given the spiral's earlier coverage of central k space. Alternate leading‐edge fringes of the spiral's velocity PSF are in antiphase to the source, and cancellation may occur when these overlap other in‐phase signals. Phase variations toward peripheral k space in turbulent flow also cause distortion. It is concluded that spiral imaging may lose complex and turbulent flow signals because of complex PSF distortion. Magn Reson Med 41:1023–1031, 1999. © 1999 Wiley‐Liss, Inc.