title: Artifact quantification and tractography from 3T MRI after placement of aneurysm clips in subarachnoid hemorrhage patients.
abstract: BACKGROUND
  The application of advanced 3T MRI imaging techniques to study recovery after subarachnoid hemorrhage (SAH) is complicated by the presence of image artifacts produced by implanted aneurysm clips. To characterize the effect of these artifacts on image quality, we sought to: 1) quantify extent of image artifact in SAH patients with implanted aneurysm clips across a range of MR sequences typically used in studies of volumetry, blood oxygen level dependent signal change (BOLD-fMRI), and diffusion-weighted imaging (DW-MRI) and 2) to explore the ability to reconstruct white matter pathways in these patients.
  
  
  METHODS
  T1- and T2-weighted structural, BOLD-fMRI, and DW-MRI scans were acquired at 3T in two patients with titanium alloy clips in ACOM and left ACA respectively. Intensity-based planimetric contouring was performed on aligned image volumes to define each artifact. Artifact volumes were quantified by artifact/clip length and artifact/brain volume ratios and analyzed by two-way (scan-by-rater) ANOVAs. Tractography pathways were reconstructed from DW-MRI at varying distances from the artifacts using deterministic methods.
  
  
  RESULTS
  Artifact volume varied by MR sequence for length (p = 0.007) and volume (p < 0.001) ratios: it was smallest for structural images, larger for DW-MRI acquisitions, and largest on fMRI images. Inter-rater reliability was high (r = 0.9626, p < 0.0001), and reconstruction of white matter connectivity characteristics increased with distance from the artifact border. In both patients, reconstructed white matter pathways of the uncinate fasciculus and inferior fronto-occipital fasciculus were clearly visible within 2 mm of the artifact border.
  
  
  CONCLUSIONS
  Advanced 3T MR can successfully image brain tissue around implanted titanium aneurysm clips at different spatial ranges depending on sequence type. White matter pathways near clip artifacts can be reconstructed and visualized. These findings provide a reference for designing functional and structural neuroimaging studies of recovery in aSAH patients after clip placement.
authors.affiliation: The Vivian L. Smith Department of Neurosurgery and Mischer Neuroscience Institute, The University of Texas Medical School at Houston, Houston TX 77030, USA.
authors.forename: Faraz
authors.initials: F
authors.lastname: Khursheed
authors.forename: Fiona
authors.initials: F
authors.lastname: Rohlffs
authors.forename: Shuichi
authors.initials: S
authors.lastname: Suzuki
authors.forename: Dong H
authors.initials: DH
authors.lastname: Kim
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Ellmore
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D017542:Aneurysm, Ruptured / Q000175:diagnosis / Q000601:surgery*; D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D002532:Intracranial Aneurysm / Q000175:diagnosis / Q000601:surgery*; D008875:Middle Aged; D019736:Prostheses and Implants; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis / Q000601:surgery*; D014025:Titanium; D016896:Treatment Outcome
chemical_list: D014025:Titanium