title: Diffusion tensor tractography of normal facial and vestibulocochlear nerves.
abstract: OBJECTIVE
  Diffusion tensor tractography (DTT) is not adequately reliable for prediction of facial and vestibulocochlear (VII-VIII) nerve locations, especially relative to a vestibular schwannoma (VS). Furthermore, it is often not possible to visualize normal VII-VIII nerves by DTT (visualization rates were 12.5-63.6%). Therefore, DTT post-processing was optimized for normal VII-VIII nerve visualization with and without manual noise elimination.
  
  
  METHODS
  DTT examinations of ten patients were evaluated to assess the improvement in performance by modifying seed region of interest (ROI) and fractional anisotropy (FA) threshold. Seed ROI was placed at the porus of the internal auditory meatus, and FA threshold values were either fixed or variable for each patient. DTT visualization of cranial nerves VII-VIII was evaluated and the noise effect was measured.
  
  
  RESULTS
  Cranial nerves VII-VIII were visualized in 90% of patients without using manual noise elimination by modifying the seed ROI and FA threshold. The visualization rate with FA threshold of the upper limit in each patient (100%) was significantly higher than that with FA threshold of 0.1 (75%) (p = 0.02). The incidence rate of noise with FA threshold of the upper limit (10%) was not significantly different than the FA threshold of 0.1 (20%) (p = 0.66).
  
  
  CONCLUSIONS
  Seed ROI modification and FA thresholding can improve the visualization of cranial nerve VII-VIII locations in DTT. This technique is promising for its potential to determine the relationship of cranial nerves VII-VIII to VS.
authors.affiliation: Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan, ymasa-tky@umin.ac.jp.
authors.forename: Masanori
authors.initials: M
authors.lastname: Yoshino
authors.forename: Taichi
authors.initials: T
authors.lastname: Kin
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ito
authors.forename: Toki
authors.initials: T
authors.lastname: Saito
authors.forename: Daichi
authors.initials: D
authors.lastname: Nakagawa
authors.forename: Kyousuke
authors.initials: K
authors.lastname: Kamada
authors.forename: Harushi
authors.initials: H
authors.lastname: Mori
authors.forename: Akira
authors.initials: A
authors.lastname: Kunimatsu
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Nakatomi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Oyama
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Saito
mesh_terms: D000368:Aged; D016880:Anisotropy; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005154:Facial Nerve / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000159:Vestibulocochlear Nerve / Q000502:physiology*