Open Collections

Sullivan, Emily

University of British Columbia

Introduction: Osteoarthritis (OA) is a debilitating disease caused by abnormal joint mechanics. There is a need for a non-invasive method to identify the specific mechanical changes that lead to OA. Magnetic resonance imaging (MRI) techniques such as T2 and T1ρ have shown sensitivity to mechanical changes in cartilage. However, the response is depth-dependent, and clinical MRI scanners with lower image resolutions cannot detect such specific changes. The magnetization transfer ratio (MTR) is a newer MRI metric that has shown promise as a measure of cartilage strain and stiffness. This research aimed to validate MTR as a robust method to measure loaded deformation and stiffness of knee cartilage. Methods: Three phases of work are described: first, an electropneumatic compressive loading device was developed and validated to apply step compressive forces to cartilage specimens in a high-resolution small-bore 9.4 Tesla MRI scanner. Second, bovine tibiofemoral osteochondral samples were compressed using this device while acquiring MTR and T2 data, and the correlations between cartilage strain and MTR/T2 were analyzed to determine any significant relationships. Finally, instantaneous stiffness maps were acquired across the same specimens via indentation testing. The relationship between local instantaneous modulus and local MTR/T2 were then assessed. Results: The loading device was successfully developed and validated to apply step compressive loads to cartilage samples in a small-bore MRI. Uniform MTR differences were observed through the cartilage thickness with increasing strain, whereas the T2 reaction to strain was regionally dependent. The relationship between MTR and strain was also found to be less specimen dependent (rrm = -0.25 to -0.36) than the relationship between T2 and strain (rrm = -0.28 iv to 0.21). When assessing correlations between local MTR/T2 and local instantaneous modulus, neither MRI metrics were found to be strong predictors of cartilage stiffness (rrm = 0.06 to 0.35). However, both measurements showed promise as indicators of mean cartilage stiffness when averaged across the cartilage plate. Conclusion: Our results suggest MTR could be useful in future in vivo cartilage studies in clinical MRI scanners, which may further our understanding of the mechanical changes that occur in cartilage during OA initiation and progression.

Text

2023-03-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84060

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/