title: Selective averaging for the diffusion tensor measurement.
abstract: The multishot echo planar imaging sequence was often used in the high-resolution diffusion measurements. However, it is susceptible to motion artifacts because of the requirements of combining the raw data from different acquisitions into one complete k-space data set. Conventional solutions used cardiac gating but greatly extended the total acquisition time. Here we propose a selective averaging algorithm based on the information in the navigator echoes. The data were sampled continuously without cardiac gating. Contributions contaminated by motion were detected by a thresholding algorithm and were discarded during postprocessing. The data were then averaged in the modulus or complex format. Diffusion tensor imaging (DTI) data with isotropic spatial resolution were acquired in phantom as well as from two normal volunteers. The information in the navigator echoes proved to be a good indicator for the extent of motion contamination. Differences were noticed between modulus and complex averaging in DTI quantification, but both showed reduced artifact and improved signal-to-noise ratio.
authors.affiliation: Department of Medical Imaging and Radiological Sciences, ChangGung University, TaoYuan county 333, Taiwan. jwang@mail.cgu.edu.tw
authors.forename: Jiun-Jie
authors.initials: JJ
authors.lastname: Wang
authors.forename: Ralf
authors.initials: R
authors.lastname: Deichmann
authors.forename: IngTsung
authors.initials: I
authors.lastname: Hsiao
authors.forename: HoLing
authors.initials: H
authors.lastname: Liu
authors.forename: YauYau
authors.initials: Y
authors.lastname: Wai
authors.forename: YungLiang
authors.initials: Y
authors.lastname: Wan
authors.forename: Robert
authors.initials: R
authors.lastname: Turner
authors.forename: Roger
authors.initials: R
authors.lastname: Ordidge
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D008297:Male; D009038:Motion; D019047:Phantoms, Imaging