title: Non-Gaussian diffusion-weighted imaging for assessing diurnal changes in intervertebral disc microstructure.
abstract: OBJECTIVE
  To investigate the use of non-Gaussian diffusion-weighted imaging (q-space imaging [QSI]) to estimate diurnal changes in intervertebral disc (IVD) microstructure.
  
  
  METHODS
  IVDs of 15 male subjects (mean age, 27.3 years; mean body mass index, 22.50 kg/m(2) ) were investigated once in the morning, less than 30 min after rising, and a second time in the evening after at least 10 h of normal physical activity, using 3 Tesla (T) MR imaging. T2 mapping and QSI data values (apparent diffusion coefficient [ADC], root mean square displacement [RMSD], and apparent kurtosis coefficient [AKC]) were calculated and compared between the morning and evening imaging sessions.
  
  
  RESULTS
  The T2, ADC, and RMSD values showed a significant decrease in the evening (175.8 ± 49.5 ms, 1.56 ± 0.32 10(-3) mm(2) /s and 40.0 ± 3.0 μm, respectively; P < 0.05 for all values; paired t-test), when compared with the morning values (226.5 ± 83.8 ms, 1.69 ± 0.29 10(-3) mm(2) /s and 45.2 ± 2.9 μm, respectively). The AKC value showed a significant increase in the evening (0.67 ± 0.08), when compared with the morning value (0.58 ± 0.04; P < 0.05).
  
  
  CONCLUSIONS
  The RMSD and AKC values obtained from QSI analysis may be biomarkers for IVD diurnal microstructural changes.
authors.affiliation: Department of Radiology Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Katsura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Junichi
authors.initials: J
authors.lastname: Hata
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hori
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sasaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Akai
authors.forename: Harushi
authors.initials: H
authors.lastname: Mori
authors.forename: Akira
authors.initials: A
authors.lastname: Kunimatsu
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Masutani
authors.forename: Shigeki
authors.initials: S
authors.lastname: Aoki
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007403:Intervertebral Disc / Q000648:ultrastructure*; D008297:Male; D016011:Normal Distribution; D012016:Reference Values; D012984:Software
keywords: diurnal changes; intervertebral disc; non-Gaussian diffusion-weighted imaging; q-space imaging