title: Pitfalls of 3D FLAIR brain imaging: a prospective comparison with 2D FLAIR.
abstract: OBJECTIVE
  To prospectively compare the image contrast of various brain lesions on two-dimensional (2D) and three-dimensional (3D) fluid-attenuated inversion-recovery (FLAIR) images and to highlight the pitfalls of 3D FLAIR.
  
  
  METHODS
  Institutional review board approval was obtained. We examined 94 brain lesions with 2D and 3D FLAIR at 3T. First, we optimized the repetition time and echo time of 3D FLAIR with a volunteer study. Then, we assessed the conspicuity and detection of the various lesions qualitatively, and the contrast ratio between the gray or white matter and lesions was calculated as a quantitative assessment. We also performed a phantom study to investigate the effects of different flow velocities on 2D and 3D FLAIR.
  
  
  RESULTS
  With regard to the conspicuity and detection of most lesions (multiple sclerosis, ischemic lesions or infarction, brain tumors, or chronic trauma), 3D FLAIR was equal or superior to 2D FLAIR. For these lesions, the mean contrast ratios were higher on 3D FLAIR than on 2D FLAIR images. In terms of lesion conspicuity in the patients with hippocampal sclerosis and leptomeningeal metastasis, however, 3D FLAIR was equal or inferior to 2D FLAIR. The ivy sign in patients with moyamoya disease was frequently obscured on 3D FLAIR. The phantom study demonstrated that the signal-intensity ratio on 3D FLAIR decreased more rapidly with increasing velocity than that on 2D FLAIR.
  
  
  CONCLUSIONS
  Although 3D FLAIR may replace 2D FLAIR images for most patients, radiologists should keep in mind that 3D has some pitfalls.
authors: Department of Radiology, University of Occupational and Environmental Health School of Medicine, Iseigaoka 1-1, Yahatanishi-ku, Kitakyushu 807-8555, Japan. kakeda@med.uoeh-u.ac.jp
authors: Shingo
authors: S
authors: Kakeda
authors: Yukunori
authors: Y
authors: Korogi
authors: Yasuhiro
authors: Y
authors: Hiai
authors: Norihiro
authors: N
authors: Ohnari
authors: Toru
authors: T
authors: Sato
authors: Toshinori
authors: T
authors: Hirai
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000473:pathology*; D001927:Brain Diseases / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity