title: Image registration improves human knee cartilage T1 mapping with delayed gadolinium-enhanced MRI of cartilage (dGEMRIC).
abstract: OBJECTIVE
  To evaluate the effect of automated registration in delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of the knee on the occurrence of movement artefacts on the T1 map and the reproducibility of region-of-interest (ROI)-based measurements.
  
  
  METHODS
  Eleven patients with early-stage knee osteoarthritis and ten healthy controls underwent dGEMRIC twice at 3 T. Controls underwent unenhanced imaging. ROIs were manually drawn on the femoral and tibial cartilage. T1 calculation was performed with and without registration of the T1-weighted images. Automated three-dimensional rigid registration was performed on the femur and tibia cartilage separately. Registration quality was evaluated using the square root Cramér-Rao lower bound (CRLB(σ)). Additionally, the reproducibility of dGEMRIC was assessed by comparing automated registration with manual slice-matching.
  
  
  RESULTS
  Automated registration of the T1-weighted images improved the T1 maps as the 90% percentile of the CRLB(σ) was significantly (P < 0.05) reduced with a median reduction of 55.8 ms (patients) and 112.9 ms (controls). Manual matching and automated registration of the re-imaged T1 map gave comparable intraclass correlation coefficients of respectively 0.89/0.90 (patients) and 0.85/0.85 (controls).
  
  
  CONCLUSIONS
  Registration in dGEMRIC reduces movement artefacts on T1 maps and provides a good alternative to manual slice-matching in longitudinal studies.
authors.affiliation: Biomedical Imaging Group Rotterdam, Departments of Medical Informatics and Radiology, Erasmus MC, P.O. Box 2040, 3000, CA, Rotterdam, The Netherlands. e.bron@erasmusmc.nl
authors.forename: Esther E
authors.initials: EE
authors.lastname: Bron
authors.forename: Jasper
authors.initials: J
authors.lastname: van Tiel
authors.forename: Henk
authors.initials: H
authors.lastname: Smit
authors.forename: Dirk H J
authors.initials: DH
authors.lastname: Poot
authors.forename: Wiro J
authors.initials: WJ
authors.lastname: Niessen
authors.forename: Gabriel P
authors.initials: GP
authors.lastname: Krestin
authors.forename: Harrie
authors.initials: H
authors.lastname: Weinans
authors.forename: Edwin H G
authors.initials: EH
authors.lastname: Oei
authors.forename: Gyula
authors.initials: G
authors.lastname: Kotek
authors.forename: Stefan
authors.initials: S
authors.lastname: Klein
mesh_terms: D016477:Artifacts; D002358:Cartilage, Articular / Q000473:pathology*; D016022:Case-Control Studies; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D010147:Pain Measurement; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA