title: Highly localized positive contrast of small paramagnetic objects using 3D center-out radial sampling with off-resonance reception.
abstract: In this article, we present a 3D imaging technique, applying center-out RAdial Sampling with Off-Resonance reception, to accurately depict and localize small paramagnetic objects with high positive contrast while suppressing long T(2) (*) components. The center-out RAdial Sampling with Off-Resonance reception imaging technique is a fully frequency-encoded 3D ultrashort echo time acquisition method, which uses a large excitation bandwidth and off-resonance reception. By manually introducing an offset, Δf(0), to the central reception frequency (f(0)), the typical radial signal pileup observed in 3D center-out sampling caused by a dipolar magnetic field disturbance can be shifted toward the source of the field disturbance, resulting in a hyperintense signal at the magnetic center of the small paramagnetic object. This was demonstrated both theoretically and using 1D time domain simulations. Experimental verification was done in a gel phantom and in inhomogeneous porcine tissue containing various objects with very different geometry and susceptibility, namely, subvoxel stainless steel spheres, a puncture needle, and paramagnetic brachytherapy seeds. In all cases, center-out RAdial Sampling with Off-Resonance reception was shown to generate high positive contrast exactly at the location of the paramagnetic object, as was confirmed by X-ray computed tomography.
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands. p.seevinck@umcutrecht.nl
authors.forename: Peter R
authors.initials: PR
authors.lastname: Seevinck
authors.forename: Hendrik
authors.initials: H
authors.lastname: de Leeuw
authors.forename: Clemens
authors.initials: C
authors.lastname: Bos
authors.forename: Chris J G
authors.initials: CJ
authors.lastname: Bakker
mesh_terms: D000465:Algorithms; D005547:Foreign Bodies / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity