Visualization and Quantification of Quantitative MRI Cartilage Changes in the Knee

Cluster analysis, our proposed tool for identifying quantitative changes occurring across the cartilage plate that is not synonymous with changes expected within a normal population, may help tease out significant differences in healthy vs. at-risk populations. Difference maps over a 1 year period (a & e) are reduced to contiguous sets of pixels (clusters) above an intensity threshold ( b & f) and size threshold (c & g), yielding the final cluster map (d & h) used for further analysis.

Osteoarthritis (OA) is a degenerative joint disease that should ideally be detected earlier on in the disease process when treatments will likely be more effective. An early characteristic of OA is the depletion and disorganization of the articular cartilage extracellular matrix macromolecules. MRI techniques have been developed to detect these changes. Most work to date has reported mean changes or general heterogeneity in quantitative MRI data of cartilage; however, there is very little directed at identifying focal lesions in the tissue. This is important because we know that later in the OA disease process both general cartilage thinning and focal defects are observed. Applying intensity and size thresholds on the difference maps created from longitudinal acquisitions, the cluster analysis method is able to identify focal cartilage lesions and evaluate potential differences that are important and different from those observed within healthy individuals. 



Monu UD, Kogan F, Walter EJ, Hargreaves BA, Gold GE. A Method to Quantitatively Compare Bone and Cartilage Changes: Initial Results. In Proceedings of the 24thInternational Society for Magnetic Resonance in Medicine (ISMRM) Annual Meeting, Singapore, Singapore, 2016.

Monu UD, Hargreaves, BA, Jordan CD, Garry, GE, McWalter EJ. Longitudinal Evaluation of T2 and T1rho Relaxation Times using projection Maps and Cluster Analysis in the Femoral Condyles of Healthy and ACL-injured Populations. IIn Proceedings of the 8th International Workshop on Osteoarthritis Imaging (IWOAI), Pacific Grove, CA, 2015.

Monu UD, Hargreaves BA, Jordan CD, Garry GE, McWalter EJ. Cluster Analysis for T2 and T1rho Relaxation Times using 3D Projection Maps of the Femoral Condyle in a Healthy and ACL-injured Population. In Proceedings of the 23rd International Society for Magnetic Resonance in Medicine (ISMRM) Annual Meeting, Toronto, Canada, 2015.

Monu UD, Walter EJ, Jordan CD, Hargreaves BA, Gold GE. 3D Visualization of Quantitative T2 Relaxation Times in the Femoral Condylar Cartilage in Healthy and ACL-injured Individuals.  In Proceedings of the 22nd International Society for Magnetic Resonance in Medicine (ISMRM) Annual Meeting, Milan, Italy, 2014.

Monu UD, Walter EJ, Hargreaves BA, Gold GE. An Angular WearMap of 3D Knee Cartilage T2 Relaxation Times. 5th Annual Center for Biomedial Imaging at Stanford (CBIS) Symposium, Stanford, CA, 2013.