Regional differences in anterior cruciate ligament imaging biomarkers: T2 and T* Values

Introduction: Imaging biomarkers such as T2 and T2* relaxation times have been used in a variety of tissues as surrogates of structural components. Before using such techniques to assess ACL tissue, healthy values must be established. The purpose of this study was to characterize T2 and T2* ACL relaxation times in clinically relevant sub-regions in healthy ACLs. Methods: Healthy males (n=20) and females (n=20) were assessed via 3T magnetic resonance imaging. T2 weighted structural imaging was performed to obtain ACL volume. T2 and T2* relaxation imaging were then performed. The ACL was sub-divided into proximal, middle and distal thirds where regional T2 and T2* relaxation times were calculated. A 1 between (sex) and 3 within (sub-region) RMANOVA compared T2 and T2* relaxation times. Results: For the T2 relaxation analysis, the middle sub-region was greater than the proximal sub-region, and males had greater distal sub-region relaxation times than females. T2* relaxation times were significant greater in the distal than proximal and middle sub-regions in males and females. Conclusion: This is the first report of in vivo T2 and T2* ACL relaxation times in healthy individuals. Relaxation times were generally less in proximal portions of the ligament suggesting a nonuniform ligamentous structure. Level of evidence: IV.