title: Weighted Mean of Signal Intensity for Unbiased Fiber Tracking of Skeletal Muscles: Development of a New Method and Comparison With Other Correction Techniques.
abstract: The aim of this study was to investigate the origin of random image artifacts in stimulated echo acquisition mode diffusion tensor imaging (STEAM-DTI), assess the role of averaging, develop an automated artifact postprocessing correction method using weighted mean of signal intensities (WMSIs), and compare it with other correction techniques.
  
  
  
  Institutional review board approval and written informed consent were obtained. The right calf and thigh of 10 volunteers were scanned on a 3 T magnetic resonance imaging scanner using a STEAM-DTI sequence.Artifacts (ie, signal loss) in STEAM-based DTI, presumably caused by involuntary muscle contractions, were investigated in volunteers and ex vivo (ie, human cadaver calf and turkey leg using the same DTI parameters as for the volunteers). An automated postprocessing artifact correction method based on the WMSI was developed and compared with previous approaches (ie, iteratively reweighted linear least squares and informed robust estimation of tensors by outlier rejection [iRESTORE]). Diffusion tensor imaging and fiber tracking metrics, using different averages and artifact corrections, were compared for region of interest- and mask-based analyses. One-way repeated measures analysis of variance with Greenhouse-Geisser correction and Bonferroni post hoc tests were used to evaluate differences among all tested conditions. Qualitative assessment (ie, images quality) for native and corrected images was performed using the paired t test.
  
  
  
  Randomly localized and shaped artifacts affected all volunteer data sets. Artifact burden during voluntary muscle contractions increased on average from 23.1% to 77.5% but were absent ex vivo. Diffusion tensor imaging metrics (mean diffusivity, fractional anisotropy, radial diffusivity, and axial diffusivity) had a heterogeneous behavior, but in the range reported by literature. Fiber track metrics (number, length, and volume) significantly improved in both calves and thighs after artifact correction in region of interest- and mask-based analyses (P < 0.05 each). Iteratively reweighted linear least squares and iRESTORE showed equivalent results, but WMSI was faster than iRESTORE. Muscle delineation and artifact load significantly improved after correction (P < 0.05 each).
  
  
  
  Weighted mean of signal intensity correction significantly improved STEAM-based quantitative DTI analyses and fiber tracking of lower-limb muscles, providing a robust tool for musculoskeletal applications.
authors.affiliation: From the *High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna; †Orthopedic Department, Evangelisches Krankenhaus Wien, Vienna, Austria; ‡Siemens Healthcare GmbH, Erlangen, Germany; §Center of Anatomy and Cell Biology, Vienna General Hospital, and ∥Christian Doppler Laboratory for Clinical Molecular MR Imaging, Medical University of Vienna, Vienna, Austria.
authors.forename: Chiara
authors.initials: C
authors.lastname: Giraudo
authors.forename: Stanislav
authors.initials: S
authors.lastname: Motyka
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Christoph
authors.initials: C
authors.lastname: Resinger
authors.forename: Feiweier
authors.initials: F
authors.lastname: Thorsten
authors.forename: Hannes
authors.initials: H
authors.lastname: Traxler
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bogner
mesh_terms: D000328:Adult; D000818:Animals; D016477:Artifacts; D002417:Cattle; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007866:Leg / Q000000981:diagnostic imaging; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D011446:Prospective Studies; D013848:Thigh / Q000502:physiology