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Spatial excitation using variable‐density spiral trajectories
Author(s) -
Schröder Christoph,
Börnert Peter,
Aldefeld Bernd
Publication year - 2003
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.10334
Subject(s) - excitation , spiral (railway) , imaging phantom , signal (programming language) , pulse (music) , excited state , physics , optics , computational physics , materials science , nuclear magnetic resonance , atomic physics , computer science , mathematics , mathematical analysis , quantum mechanics , detector , programming language
Purpose To examine the usefulness of variable‐density k‐space trajectories for the design of multi‐dimensional spatially selective RF pulses. Materials and Methods Experimental phantom and in vivo studies were performed and confirmed by simulations. Two‐dimensional spatially selective magnetization patterns were excited using variable‐density spiral trajectories and analyzed with respect to the signal excitation outside the excitation field of view (FOX). Results By using variable‐density trajectories, signal excitation outside the FOX was drastically reduced compared to trajectories with a uniform density, while maintaining fairly short pulse durations. Conclusion A main advantage of the method is that unwanted signal excitation outside the nominal FOX can be reduced without significantly increasing the duration of the RF excitation pulse. The variable‐density approach is useful for all applications that require a well‐defined spatial excitation profile, e.g., to perform imaging in a reduced field of view (FOV), for spatial saturation pulses, for curved slice imaging or in MR spectroscopy. J. Magn. Reson. Imaging 2003;18:136–141. © 2003 Wiley‐Liss, Inc.