title: Short- and midterm reproducibility of apparent diffusion coefficient measurements at 3.0-T diffusion-weighted imaging of the abdomen.
abstract: OBJECTIVE
  To test the hypothesis that there is no significant variability in apparent diffusion coefficients (ADCs) at assessment of the short- and midterm reproducibility of ADC measurements in a healthy population.
  
  
  METHODS
  Twenty healthy male volunteers were enrolled in this prospective institutional review board-approved study after they provided written informed consent. A 3.0-T magnetic resonance (MR) system was used to perform five axial diffusion-weighted (DW) abdominal acquisitions (session 1). A mean of 147 days +/- 20 (standard deviation) later, 16 of the 20 volunteers were imaged again with use of the same protocol and MR system (session 2). The mean ADCs for three regions of interest (ROIs) in five anatomic locations (right hepatic lobe, spleen, and head, body, and tail of pancreas) were calculated. The coefficient of variation (CV, equal to standard deviation divided by mean) was calculated for each subject, session, and anatomic location. The ADC and CV data were then analyzed by using repeated-measures analysis of variance.
  
  
  RESULTS
  There were significant differences (P < .001) in mean ADCs among the five anatomic locations. There were no significant differences in ADCs among the various repeated sequence acquisitions or the three ROIs. There were no significant differences in ADCs between imaging sessions 1 and 2. ADCs were fairly stable over the midterm within a given individual. Finally, there were no significant differences in resulting CVs between the imaging sessions or anatomic locations. The mean CV for ADC measurement reproducibility was 14% (95% confidence interval: 13%, 15%).
  
  
  CONCLUSIONS
  The mean CV for short- and midterm ADC reproducibility was 14% at abdominal DW imaging. Treatment effects of less than approximately 27% (change in ADC divided by pretreatment ADC) will not be clinically detectable with confidence with one acquisition in a single individual.
authors.affiliation: Department of Radiology, Duke University Medical Center, Erwin Rd, Durham, NC 27710, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Braithwaite
authors.forename: Brian M
authors.initials: BM
authors.lastname: Dale
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Boll
authors.forename: Elmar M
authors.initials: EM
authors.lastname: Merkle
mesh_terms: D000005:Abdomen / Q000033:anatomy & histology*; D000328:Adult; D000704:Analysis of Variance; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D011446:Prospective Studies; D015203:Reproducibility of Results