title: Multi-parametric MRI characterization of enzymatically degraded articular cartilage.
abstract: Several laboratory and rotating frame quantitative MRI parameters were evaluated and compared for detection of changes in articular cartilage following selective enzymatic digestion. Bovine osteochondral specimens were subjected to 44 h incubation in control medium or in collagenase or chondroitinase ABC to induce superficial collagen or proteoglycan (glycosaminoglycan) alterations. The samples were scanned at 9.4 T for T1 , T1 Gd (dGEMRIC), T2 , adiabatic T1 ρ , adiabatic T2 ρ , continuous-wave T1 ρ , TRAFF2 , and T1 sat relaxation times and for magnetization transfer ratio (MTR). For reference, glycosaminoglycan content, collagen fibril orientation and biomechanical properties were determined. Changes primarily in the superficial cartilage were noted after enzymatic degradation. Most of the studied parameters were sensitive to the destruction of collagen network, whereas glycosaminoglycan depletion was detected only by native T1 and T1 Gd relaxation time constants throughout the tissue and by MTR superficially. T1 , adiabatic T1 ρ , adiabatic T2 ρ , continuous-wave T1 ρ , and T1 sat correlated significantly with the biomechanical properties while T1 Gd correlated with glycosaminoglycan staining. The findings indicated that most of the studied MRI parameters were sensitive to both glycosaminoglycan content and collagen network integrity, with changes due to enzymatic treatment detected primarily in the superficial tissue. Strong correlation of T1 , adiabatic T1ρ , adiabatic T2 ρ , continuous-wave T1 ρ , and T1 sat with the altered biomechanical properties, reflects that these parameters were sensitive to critical functional properties of cartilage. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1111-1120, 2016.
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.|Research Unit of Medical Imaging, Physics, and Technology, University of Oulu, Oulu, Finland.|Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.|Department of Radiology, CMRR, University of Minnesota, Minneapolis, Minnesota.|Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Mikko J
authors.initials: MJ
authors.lastname: Nissi
authors.affiliation: Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.|Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland.
authors.forename: Elli-Noora
authors.initials: EN
authors.lastname: Salo
authors.affiliation: Institute of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Virpi
authors.initials: V
authors.lastname: Tiitu
authors.affiliation: Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland.|Department of Biotechnology and Molecular Medicine, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Liimatainen
authors.affiliation: Department of Radiology, CMRR, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Shalom
authors.initials: S
authors.lastname: Michaeli
authors.affiliation: Department of Radiology, CMRR, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Silvia
authors.initials: S
authors.lastname: Mangia
authors.affiliation: Department of Radiology, CMRR, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Jutta
authors.initials: J
authors.lastname: Ellermann
authors.affiliation: Research Unit of Medical Imaging, Physics, and Technology, University of Oulu, Oulu, Finland.|Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.|Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland.
authors.forename: Miika T
authors.initials: MT
authors.lastname: Nieminen
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging*; D002417:Cattle; D002810:Chondroitinases and Chondroitin Lyases; D017364:Collagenases; D008279:Magnetic Resonance Imaging / Q000379:methods*
chemical_list: D017364:Collagenases; D002810:Chondroitinases and Chondroitin Lyases
keywords: MRI; biomechanics; cartilage; relaxation; rotating frame of reference