On the artifact of a subvoxel susceptibility deviation in spoiled gradient-echo imaging.
In MRI, susceptibility-based negative contrast amplifies the effect of objects that are too small to be detected by water displacement or intrinsic contrast properties. In this work, a simplified description of the susceptibility artifact of a subvoxel object in spoiled gradient-echo imaging is presented that focuses on the elimination of signal in its vicinity: the dephased-volume. The size and position of the dephased-volume are investigated using 3D time-domain simulations and in vitro experiments in which scan parameters and object magnetic moment are systematically varied. Overall signal loss is found to be linearly related to a dephasing parameter that contains the susceptibility difference with tissue, object volume, and echo time (TE), and thus allows the magnetic moment of the object to be assessed. Gradient strength, in-plane resolution, fractional echo, and slice orientation have limited influence. For the settings used, the center of mass of the artifact was always within 0.5 mm of the object's in-plane position.
Bos
Clemens
C
Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands. clemens@imf.u-bordeaux2.fr
Viergever
Max A
MA
Bakker
Chris J G
CJ
D016477:Artifacts; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging