title: Test-retest reliability and repeatability of renal diffusion tensor MRI in healthy subjects.
abstract: OBJECTIVE
  This study assessed test-retest reliability and repeatability of diffusion tensor imaging (DTI) in the kidneys.
  
  
  METHODS
  Seven healthy volunteers (age range, 19-31 years), were imaged three consecutive times on the same day (short-term reliability) and the same imaging protocol was repeated after a month (long-term reliability). Diffusion-weighted magnetic resonance imaging scans in the coronal-oblique projection of the kidney were acquired on a 1.5 T scanner using a multi-section echo-planar sequence; six contiguous slices each 5 mm thick, diffusion sensitisation along 20 non-collinear directions, TR=730 ms, TE=73 ms and 2 b-values (0 and 400 s mm(-2)). Volunteers were asked to hold their breath throughout each data acquisition (approx. 20 s). The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were obtained from maps generated using dedicated software MIStar (Apollo Medical Imaging, Melbourne, Australia).
  
  
  RESULTS
  Statistical analyses of both short- and long-term repeats were carried out from which the within-subject coefficient of variation (wsCV) was calculated. The wsCV obtained for both the ADC and FA values were less than 10% in all the analyses carried out. In addition, paired (repeated measures) t-test was used to measure the variation between the diffusion parameters collected from the two scanning sessions a month apart. It showed no significant difference and the wsCV obtained after comparing the first and second scans were found to be smaller than 15% for both ADC and FA.
  
  
  CONCLUSIONS
  Renal DTI produces reliable and repeatable results which make longitudinal investigation of patients viable.
authors.affiliation: Imaging and Biophysics Unit, University College London, Institute of Child Health, 30 Guilford Street, London WC1N1EH, United Kingdom. m.cutajar@ich.ucl.ac.uk
authors.forename: Marica
authors.initials: M
authors.lastname: Cutajar
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Clayden
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Clark
authors.forename: Isky
authors.initials: I
authors.lastname: Gordon
mesh_terms: D000293:Adolescent; D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007668:Kidney / Q000033:anatomy & histology*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult