title: Test-retest reliability of diffusion tensor imaging of the liver at 3.0 T.
abstract: OBJECTIVE
  This study was done to evaluate test-retest reliability of liver diffusion tensor imaging (LDTI).
  
  
  METHODS
  Ten healthy volunteers (median age 23 years) underwent two LDTI scans on a 3.0 T magnet during two imaging sessions separated by 2 weeks (session-1/-2, respectively). Fifteen gradient directions and b values of 0-1,000 s/mm(2) were used. Two radiologists in consensus assessed liver apparent diffusion coefficient (ADC) and fraction of anisotropy (FA) values on ADC and FA maps at four reference levels, namely: right upper level (RUL), right lower level (RLL), left upper level (LUL) and left lower level (LLL). We then assessed (a) whether ADC and FA values overlapped when measured on different levels within the same imaging session or between different imaging sessions; (b) the degree of variability on an intra-session and inter-session basis, respectively, using the coefficient of variation (CV).
  
  
  RESULTS
  In sessions 1 and 2, the ADC/FA values were significantly larger in the left liver lobe (LUL/LLL) compared to right liver lobe (RUL/RLL) (p < 0.05/6). Intra-session CVs were 9.51 % (session 1) and 9.73 % (session 2) for ADC, and 12.93 % (session 1) and 11.82 % (session 2) for FA, respectively. When comparing RUL, RLL, LUL and LLL on an inter-session basis, CVs were 6.52, 8.20, 6.52 and 11.06 % for ADC, and 15.42, 15.80, 15.42 and 6.80 % for FA, respectively.
  
  
  CONCLUSIONS
  LDTI provides consistent and repeatable measurements. However, since larger left lobe ADC/FA values can be attributed to artefacts, right lobe values should be considered the most reliable measurements of water diffusivity within the liver.
authors.affiliation: Department of Medical and Biological Sciences, Institute of Diagnostic Radiology, University of Udine, Via Colugna n. 50, 33100, Udine, Italy, rgirometti@sirm.org.
authors.forename: Rossano
authors.initials: R
authors.lastname: Girometti
authors.forename: Marta
authors.initials: M
authors.lastname: Maieron
authors.forename: Giovanni
authors.initials: G
authors.lastname: Lissandrello
authors.forename: Massimo
authors.initials: M
authors.lastname: Bazzocchi
authors.forename: Chiara
authors.initials: C
authors.lastname: Zuiani
mesh_terms: D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008099:Liver / Q000033:anatomy & histology*; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results