title: Quantitative assessment of mobile protein levels in human knee synovial fluid: feasibility of chemical exchange saturation transfer (proteinCEST) MRI of osteoarthritis.
abstract: OBJECTIVE
  To establish the feasibility of chemical exchange saturation transfer (proteinCEST) MRI in the differentiation of osteoarthritis (OA) knee joints from non-OA joints by detecting mobile protein and peptide levels in synovial fluid by determining their relative distribution.
  
  
  METHODS
  A total of 25 knees in 11 men and 12 women with knee injuries were imaged using whole knee joint proteinCEST MRI sequence at 3 T. The joint synovial fluid was segmented and the asymmetric magnetization transfer ratio at 3.5 ppm MTR(asym) (3.5 ppm) was calculated to assess protein content in the synovial fluid. The 85th percentile of synovial fluid MTR(asym) (3.5 ppm) distribution profile was compared using the independent Student's t test. The diagnostic performance of the 85th percentile of synovial fluid MTR(asym) (3.5 ppm) in differentiating OA and non-OA knee joints was evaluated.
  
  
  RESULTS
  The 85th percentile of synovial fluid MTR(asym) (3.5 ppm) in knee joints with OA was 8.6%±3.4% and significantly higher than that in the knee joints without OA (6.3%±1.4%, P<.05). A knee joint with an 85th percentile of synovial fluid MTR(asym) (3.5 ppm) greater than 7.7% was considered to be an OA knee joint. With the threshold, the sensitivity, specificity and overall accuracy for differentiating knee joints with OA from the joints without OA were 54% (7/13), 92% (11/12) and 72% (18/25), respectively.
  
  
  CONCLUSIONS
  proteinCEST MRI appears feasible as a quantitative methodology to determine mobile protein levels in synovial fluid and identify patterns characteristic for OA disease.
authors.affiliation: Department of Radiology and Wright Center of Innovation in Biomedical Imaging, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Guang
authors.initials: G
authors.lastname: Jia
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Takayama
authors.forename: David C
authors.initials: DC
authors.lastname: Flanigan
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Kaeding
authors.forename: Jinyuan
authors.initials: J
authors.lastname: Zhou
authors.forename: Ajit
authors.initials: A
authors.lastname: Chaudhari
authors.forename: Daniel
authors.initials: D
authors.lastname: Clark
authors.forename: Steffen
authors.initials: S
authors.lastname: Sammet
authors.forename: Jiachao
authors.initials: J
authors.lastname: Liang
authors.forename: Seongjin
authors.initials: S
authors.lastname: Choi
authors.forename: Michael V
authors.initials: MV
authors.lastname: Knopp
mesh_terms: D000293:Adolescent; D000328:Adult; D003937:Diagnosis, Differential; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000378:metabolism* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000378:metabolism* / Q000473:pathology; D011506:Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013582:Synovial Fluid / Q000166:cytology / Q000378:metabolism*; D055815:Young Adult
chemical_list: D011506:Proteins