title: Effect of diffusion-sensitizing gradient timings on the exponential, biexponential and diffusional kurtosis model parameters: in-vivo measurements in the rat thalamus.
abstract: OBJECTIVE
  To investigate whether spacing (Delta) and duration (delta) of the diffusion-sensitizing gradient pulses differentially affect exponential (D'), biexponential (D (slow), D (fast) and f (slow)) and diffusional kurtosis (D and K) model parameters.
  
  
  METHODS
  Measurements were performed in the rat thalamus for b = 200-3,200 s mm(-2), sweeping Delta between 20 and 100 ms at delta = 15 ms, and delta between 15 and 50 ms at Delta = 60 ms. Linear regressions were performed for each model parameter vs. Delta or delta.
  
  
  RESULTS
  Increasing Delta from 20 to 100 ms increases D' (from 0.64 to 0.70 x 10(-3) mm(2)s(-1)) and D (slow) (from 0.26 to 0.33 x 10(-3) mm(2)s(-1)), reduces K (from 0.57 to 0.53), and has no effects on D (fast), f (slow) or D. Increasing delta from 15 to 50 ms increases D (from 0.80 to 0.88 x 10(-3) mm(2)s(-1)), and has no effects on the other parameters.
  
  
  CONCLUSIONS
  The parameters of the biexponential and diffusional kurtosis models are more sensitive than the exponential model to Delta and delta; however, observed effects are too small to account for the discrepancies found in literature.
authors.affiliation: Scientific Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, via Celoria 11, Milan, Italy. lminati@istituto-besta.it
authors.forename: Ludovico
authors.initials: L
authors.lastname: Minati
authors.forename: Ileana
authors.initials: I
authors.lastname: Zucca
authors.forename: Gabriella
authors.initials: G
authors.lastname: Carcassola
authors.forename: Michele
authors.initials: M
authors.lastname: Occhipinti
authors.forename: Roberto
authors.initials: R
authors.lastname: Spreafico
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Bruzzone
mesh_terms: D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008959:Models, Neurological; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013788:Thalamus / Q000033:anatomy & histology*