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Repeatability of focal changes in knee cartilage T2 relaxation times with load and time
Kaitlin G Sofko1, Ibukunoluwa O Elebute1, Lumeng Cui2
1Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5B2, Canada.
Objective:
The purpose of this study is to assess the repeatability of focal changes in T2 relaxation time of knee articular cartilage with load and over time.
Design:
A short-term repeatability study was conducted in five healthy participants. Images were acquired of the knee in an unloaded position and in loaded flexion with a custom, quantitative Double Echo Steady State (qDESS) MRI sequence on a 3T scanner. The protocol was carried out three times within a one-week period. T2 relaxation maps of the tibial and femoral articular cartilage were created and focal areas of change were identified using a cluster-based analysis approach; the outcome measure was defined as the percentage area covered by a cluster of pixels that change with load or over time. Average T2 relaxation time within anatomical regions was also calculated. Repeatability of the cluster-based and regional approach was described as the root mean square standard deviation (SDrms) of the trials.
Results:
The SDrms of the percentage area of the entire cartilage surface covered by clusters when the knees were loaded was <9.5 %. The repeatability of the percentage area of the entire cartilage surface covered by clusters over time was <4.5 % for the unloaded knees and 7.4 % for the loaded knees. For the regional analysis, the average SDrms of the entire plate was <3.0 ms.
Conclusion:
Cluster analysis provides important information on focal changes in cartilage with the application of load and over time, but at the cost of repeatability compared to regional approaches.
