Hongfu Sun1, Mahesh Kate2, Laura C Gioia2, Derek J Emery3, Kenneth Butcher2, Alan H Wilman1. 1. Department of Biomedical Engineering, University of Alberta, Edmonton, Canada. 2. Division of Neurology, Department of Medicine, University of Alberta, Edmonton, Canada. 3. Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Canada.
Abstract
PURPOSE: To investigate gradient-echo phase errors caused by intracranial hemorrhage (ICH) of low signal magnitude, and propose methods to reduce artifacts from phase errors in quantitative susceptibility mapping (QSM) of ICH. METHODS: Two QSM methods are proposed: (1) mask-inversion that masks the phase of low signal magnitude regions, and (2) ICH magnetic dipole field isolation followed by susceptibility superposition using multiple boundaries for background field removal. The reconstruction methods were tested in eight subjects with ICH using standard single-echo susceptibility-weighted imaging at 1.5 Tesla with 40 ms echo time. Different phase unwrapping algorithms were also compared. RESULTS: Significant phase errors were evident inside ICHs with low signal magnitude. The mask-inversion method recovered susceptibility of ICH in numerical simulation and minimized phase error propagation in patients with ICH. The additional superposed dipole inversion process substantially suppressed and constrained streaking artifacts in all subjects. Using the proposed superposition method, ICH susceptibilities measured from long and short echo times were similar. Laplacian based phase unwrapping substantially underestimated the ICH dipole field as compared to a path-based method. CONCLUSION: The proposed methods of mask-inversion as well as ICH isolation and superposition can substantially reduce artifacts in QSM of ICH. Magn Reson Med 76:781-791, 2016.
PURPOSE: To investigate gradient-echo phase errors caused by intracranial hemorrhage (ICH) of low signal magnitude, and propose methods to reduce artifacts from phase errors in quantitative susceptibility mapping (QSM) of ICH. METHODS: Two QSM methods are proposed: (1) mask-inversion that masks the phase of low signal magnitude regions, and (2) ICH magnetic dipole field isolation followed by susceptibility superposition using multiple boundaries for background field removal. The reconstruction methods were tested in eight subjects with ICH using standard single-echo susceptibility-weighted imaging at 1.5 Tesla with 40 ms echo time. Different phase unwrapping algorithms were also compared. RESULTS: Significant phase errors were evident inside ICHs with low signal magnitude. The mask-inversion method recovered susceptibility of ICH in numerical simulation and minimized phase error propagation in patients with ICH. The additional superposed dipole inversion process substantially suppressed and constrained streaking artifacts in all subjects. Using the proposed superposition method, ICH susceptibilities measured from long and short echo times were similar. Laplacian based phase unwrapping substantially underestimated the ICH dipole field as compared to a path-based method. CONCLUSION: The proposed methods of mask-inversion as well as ICH isolation and superposition can substantially reduce artifacts in QSM of ICH. Magn Reson Med 76:781-791, 2016.
Authors: Yi Wang; Pascal Spincemaille; Zhe Liu; Alexey Dimov; Kofi Deh; Jianqi Li; Yan Zhang; Yihao Yao; Kelly M Gillen; Alan H Wilman; Ajay Gupta; Apostolos John Tsiouris; Ilhami Kovanlikaya; Gloria Chia-Yi Chiang; Jonathan W Weinsaft; Lawrence Tanenbaum; Weiwei Chen; Wenzhen Zhu; Shixin Chang; Min Lou; Brian H Kopell; Michael G Kaplitt; David Devos; Toshinori Hirai; Xuemei Huang; Yukunori Korogi; Alexander Shtilbans; Geon-Ho Jahng; Daniel Pelletier; Susan A Gauthier; David Pitt; Ashley I Bush; Gary M Brittenham; Martin R Prince Journal: J Magn Reson Imaging Date: 2017-03-10 Impact factor: 4.813