title: Validation and optimization of adiabatic T1ρand T2ρfor quantitative imaging of articular cartilage at 3 T.
abstract: The aim of the present work was to validate and optimize adiabatic T1ρand T2ρmapping for in vivo measurements of articular cartilage at 3 Tesla (T).
  
  
  
  Phantom and in vivo experiments were systematically performed on a 3T clinical system to evaluate the sequences using hyperbolic secant HS1 and HS4 pulses. R1ρand R2ρrelaxation rates were studied as a function of agarose and chondroitin sulfate concentration and pulse duration. Optimal in vivo protocol was determined by imaging the articular cartilage of two volunteers and varying the sequence parameters, and successively applied in eight additional subjects. Reproducibility was assessed in phantoms and in vivo.
  
  
  
  Relaxation rates depended on agarose and chondroitin sulfate concentration. The sequences were able to generate relaxation time maps with pulse lengths of 8 and 6 ms for HS1 and HS4, respectively. In vivo findings were in good agreement with the phantoms. The implemented adiabatic T1ρand T2ρsequences demonstrated regional variation in relaxation time maps of femorotibial cartilage. Reproducibility in phantoms and in vivo was good to excellent for both adiabatic T1ρand T2ρ.
  
  
  
  The findings indicate that sequences are suitable for quantitative in vivo assessment of articular cartilage at 3 T. Magn Reson Med 77:1265-1275, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.|Medical Research Center, University of Oulu and Oulu University Hospital, Oulu, Finland.
authors.forename: Victor
authors.initials: V
authors.lastname: Casula
authors.affiliation: Center for Life Science and Technologies, RIKEN, Kobe, Japan.
authors.forename: Joonas
authors.initials: J
authors.lastname: Autio
authors.affiliation: Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.|Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN.|Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.|Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Mikko J
authors.initials: MJ
authors.lastname: Nissi
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Auerbach
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN.
authors.forename: Jutta
authors.initials: J
authors.lastname: Ellermann
authors.affiliation: Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland.
authors.forename: Eveliina
authors.initials: E
authors.lastname: Lammentausta
authors.affiliation: Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.|Medical Research Center, University of Oulu and Oulu University Hospital, Oulu, Finland.|Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland.
authors.forename: Miika T
authors.initials: MT
authors.lastname: Nieminen
mesh_terms: D000328:Adult; D000465:Algorithms; D015415:Biomarkers / Q000378:metabolism; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D002809:Chondroitin Sulfates / Q000378:metabolism*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012685:Sepharose / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D002809:Chondroitin Sulfates; D012685:Sepharose
keywords: T1ρ; T2ρ; adiabatic; articular cartilage; in vivo; relaxation; spin lock