title: Added value of high-b-value (b = 3000 s/mm2) diffusion-weighted imaging at 3 T in relation to fluid-attenuated inversion recovery images for the evaluation of cortical lesions in inflammatory brain diseases.
abstract: OBJECTIVE
  The purpose of this study was to determine how the gray-to-white matter contrast in healthy subjects changes on high-b-value diffusion-weighted imaging (DWI) acquired at 3 T and evaluate whether high-b-value DWI at 3 T is useful for the detection of cortical lesions in inflammatory brain diseases.
  
  
  METHODS
  Ten healthy volunteers underwent DWI at b = 1000, 2000, 3000, 4000, and 5000 s/mm(2) on a 3-T MRI unit. On DW images, 1 radiologist performed region-of-interest measurements of the signal intensity of 8 gray matter structures. The gray-to-white matter contrast ratio (GWCR) was calculated. Ten patients with inflammatory cortical lesions were also included. All patients underwent conventional MRI and DWI at b = 1000 and 3000 s/mm(2). Using a 4-point grading system, 2 radiologists independently assessed the presence of additional information on DW images compared with fluid-attenuated inversion recovery images. Interobserver agreement was assessed by κ statistics.
  
  
  RESULTS
  In the healthy subjects, the b value increased as the GWCR decreased in all evaluated gray matter structures. On DW images acquired at b = 3000 s/mm(2), mean GWCR was less than 1.0 in 7 of 8 structures. For both reviewers, DWI at b = 3000 s/mm(2) yielded significantly more additional information than did DWI at b = 1000 s/mm(2) (P < 0.05). Interobserver agreement for DWI at b = 1000 s/mm(2) and b = 3000 s/mm(2) was fair (κ = 0.35) and excellent (κ = 1.0), respectively.
  
  
  CONCLUSIONS
  At 3-T DWI, the gray-to-white matter contrast in most gray matter structures reverses at b = 3000 s/mm. In the evaluation of cortical lesions in patients with inflammatory brain diseases, 3-T DWI at b = 3000 s/mm was more useful than b = 1000 s/mm(2).
authors.affiliation: Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Koya
authors.initials: K
authors.lastname: Iwashita
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hirai
authors.forename: Mika
authors.initials: M
authors.lastname: Kitajima
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Shigematsu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Uetani
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Iryo
authors.forename: Minako
authors.initials: M
authors.lastname: Azuma
authors.forename: Eri
authors.initials: E
authors.lastname: Hayashida
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ando
authors.forename: Ryuji
authors.initials: R
authors.lastname: Murakami
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000033:anatomy & histology*; D001927:Brain Diseases / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D018709:Statistics, Nonparametric