title: Systematic protocol for assessment of the validity of BOLD MRI in a rabbit model of inflammatory arthritis at 1.5 tesla.
abstract: BACKGROUND
  Blood-oxygen-level-dependent (BOLD) MRI has the potential to identify regions of early hypoxic and vascular joint changes in inflammatory arthritis. There is no standard protocol for analysis of BOLD MRI measurements in musculoskeletal disorders.
  
  
  OBJECTIVE
  To optimize the following BOLD MRI reading parameters: (1) statistical threshold values (low, r > 0.01 versus high, r > 0.2); (2) summary measures of BOLD contrast (percentage of activated voxels [PT%] versus percentage signal difference between on-and-off signal intensities [diff_on_off]); and (3) direction of BOLD response (positive, negative and positive + negative).
  
  
  METHODS
  Using BOLD MRI protocols at 1.5 T, arthritic (n = 21) and contralateral (n = 21) knees of 21 juvenile rabbits were imaged at baseline and on days 1, 14 and 28 after a unilateral intra-articular injection of carrageenan. Nine non-injected rabbits served as external control knees (n = 18). By comparing arthritic to contralateral knees, receiver operating characteristic curves were used to determine diagnostic accuracy.
  
  
  RESULTS
  Using diff_on_off and positive + negative responses, a threshold of r > 0.01 was more accurate than r > 0.2 (P = 0.03 at day 28). Comparison of summary measures yielded no statistically significant difference (P > 0.05). Although positive + negative (AUC = 0.86 at day 28) and negative responses (AUC = 0.90 at day 28) for PT% were the most diagnostically accurate, positive + negative responses for diff_on_off (AUC = 0.78 at day 28) also had acceptable accuracy.
  
  
  CONCLUSIONS
  The most clinically relevant reading parameters included a lower threshold of r > 0.01 and a positive + negative BOLD response. We propose that diff_on_off is a more clinically relevant summary measure of BOLD MRI, while PT% can be used as an ancillary measure.
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Ave., Toronto, Canada, M5G 1X8.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Chan
authors.forename: George
authors.initials: G
authors.lastname: Nathanael
authors.forename: Antonella
authors.initials: A
authors.lastname: Kis
authors.forename: Afsaneh
authors.initials: A
authors.lastname: Amirabadi
authors.forename: Anguo
authors.initials: A
authors.lastname: Zhong
authors.forename: Tammy
authors.initials: T
authors.lastname: Rayner
authors.forename: Ruth
authors.initials: R
authors.lastname: Weiss
authors.forename: Garry
authors.initials: G
authors.lastname: Detzler
authors.forename: Roland
authors.initials: R
authors.lastname: Jong
authors.forename: Harpal
authors.initials: H
authors.lastname: Gahunia
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.forename: Adrian
authors.initials: A
authors.lastname: Crawley
authors.forename: Andrea S
authors.initials: AS
authors.lastname: Doria
mesh_terms: D000818:Animals; D001171:Arthritis, Juvenile / Q000097:blood* / Q000175:diagnosis*; D004195:Disease Models, Animal; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007249:Inflammation / Q000097:blood* / Q000175:diagnosis*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000097:blood; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D010100:Oxygen