Cluster analysis of quantitative MRI T2 and T1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T

U D Monu; C D Jordan; B L Samuelson; B A Hargreaves; G E Gold; E J McWalter

doi:10.1016/j.joca.2016.09.015

Cluster analysis of quantitative MRI T₂ and T_1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T

Osteoarthritis Cartilage. 2017 Apr;25(4):513-520. doi: 10.1016/j.joca.2016.09.015. Epub 2016 Oct 5.

Authors

U D Monu¹, C D Jordan², B L Samuelson³, B A Hargreaves⁴, G E Gold⁵, E J McWalter⁶

Affiliations

¹ Department of Radiology, Stanford University, Stanford, CA, USA; Department of Electrical Engineering, Stanford University, Stanford, CA, USA. Electronic address: udmonu@stanford.edu.
² Department of Radiology and Biomedical Imaging, University of California San Francisco, CA, USA. Electronic address: cjordan@alumni.stanford.edu.
³ Department of Human Biology, Stanford University, Stanford, CA, USA. Electronic address: bonbon41@alumni.stanford.edu.
⁴ Department of Radiology, Stanford University, Stanford, CA, USA; Department of Electrical Engineering, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA. Electronic address: bah@stanford.edu.
⁵ Department of Radiology, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA; Department of Orthopaedic Surgery, Stanford University, Stanford, CA, USA. Electronic address: gold@stanford.edu.
⁶ Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK, Canada. Electronic address: emily.mcwalter@usask.ca.

Abstract

Purpose: To identify focal lesions of elevated MRI T₂ and T_1ρ relaxation times in articular cartilage of an ACL-injured group using a novel cluster analysis technique.

Materials and methods: Eighteen ACL-injured patients underwent 3T MRI T₂ and T_1ρ relaxometry at baseline, 6 months and 1 year and six healthy volunteers at baseline, 1 day and 1 year. Clusters of contiguous pixels above or below T₂ and T_1ρ intensity and area thresholds were identified on a projection map of the 3D femoral cartilage surface. The total area of femoral cartilage plate covered by clusters (%CA) was split into areas above (%CA+) and below (%CA-) the thresholds and the differences in %CA(+ or -) over time in the ACL-injured group were determined using the Wilcoxon signed rank test.

Results: %CA+ was greater in the ACL-injured patients than the healthy volunteers at 6 months and 1 year with average %CA+ of 5.2 ± 4.0% (p = 0.0054) and 6.6 ± 3.7% (p = 0.0041) for T₂ and 6.2 ± 7.1% (p = 0.063) and 8.2 ± 6.9% (p = 0.042) for T_1ρ, respectively. %CA- at 6 months and 1 year was 3.0 ± 1.8% (p > 0.1) and 5.9 ± 5.0% (p > 0.1) for T₂ and 4.4 ± 4.9% (p > 0.1) and 4.5 ± 4.6% (p > 0.1) for T_1ρ, respectively.

Conclusion: With the proposed cluster analysis technique, we have quantified cartilage lesion coverage and demonstrated that the ACL-injured group had greater areas of elevated T₂ and T_1ρ relaxation times as compared to healthy volunteers.

Keywords: ACL-injury; Cartilage; Cluster analysis; Knee; Projection maps; Quantitative MRI.

Publication types

Research Support, Non-U.S. Gov't
Research Support, N.I.H., Extramural

MeSH terms

Adult
Anterior Cruciate Ligament Injuries / diagnostic imaging*
Cartilage, Articular / diagnostic imaging*
Case-Control Studies
Cluster Analysis
Female
Humans
Magnetic Resonance Imaging
Male
Young Adult

Abstract

Publication types

MeSH terms

Grants and funding