title: Comparison of apparent diffusion coefficients and distributed diffusion coefficients in high-grade gliomas.
abstract: OBJECTIVE
  To compare apparent diffusion coefficients (ADCs) with distributed diffusion coefficients (DDCs) in high-grade gliomas.
  
  
  METHODS
  Twenty patients with high-grade gliomas prospectively underwent diffusion-weighted MRI. Traditional ADC maps were created using b-values of 0 and 1000 s/mm(2). In addition, DDC maps were created by applying the stretched-exponential model using b-values of 0, 1000, 2000, and 4000 s/mm(2). Whole-tumor ADCs and DDCs (in 10(-3) mm(2)/s) were measured and analyzed with a paired t-test, Pearson's correlation coefficient, and the Bland-Altman method.
  
  
  RESULTS
  Tumor ADCs (1.14 +/- 0.26) were significantly lower (P = 0.0001) than DDCs (1.64 +/- 0.71). Tumor ADCs and DDCs were strongly correlated (R = 0.9716; P < 0.0001), but mean bias +/- limits of agreement between tumor ADCs and DDCs was -0.50 +/- 0.90. There was a clear trend toward greater discordance between ADC and DDC at high ADC values.
  
  
  CONCLUSIONS
  Under the assumption that the stretched-exponential model provides a more accurate estimate of the average diffusion rate than the mono-exponential model, our results suggest that for a little diffusion attenuation the mono-exponential fit works rather well for quantifying diffusion in high-grade gliomas, whereas it works less well for a greater degree of diffusion attenuation.
authors.affiliation: Department of Radiology, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Kwee
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Galbán
authors.forename: Christina
authors.initials: C
authors.lastname: Tsien
authors.forename: Larry
authors.initials: L
authors.lastname: Junck
authors.forename: Pia C
authors.initials: PC
authors.lastname: Sundgren
authors.forename: Marko K
authors.initials: MK
authors.lastname: Ivancevic
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Johnson
authors.forename: Charles R
authors.initials: CR
authors.lastname: Meyer
authors.forename: Alnawaz
authors.initials: A
authors.lastname: Rehemtulla
authors.forename: Brian D
authors.initials: BD
authors.lastname: Ross
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Chenevert
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001932:Brain Neoplasms / Q000473:pathology* / Q000503:physiopathology*; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005910:Glioma / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity