Importance of ACL substructure composition for quantitative analysis using UTE

Motivation: Quantitative MR-imaging of ligaments needs special approaches like ultra-short echo-time (UTE) imaging. Most quantitative studies of the anterior cruciate ligament (ACL) regard it as a uniform structure and do not consider differences in ligament composition at different anatomical positions. Goal(s): This study is aimed to use UTE to evaluate anatomical position specific T1 and T2* parameters of the ACL. Approach: The region specific ACL T1 and T2* values of 10 healthy volunteers were investigated by quantitative UTE mapping. Results: Quantitative mapping revealed that T1 and T2* values decrease from the distal to the proximal ACL endings, due to different fractions of free water. Impact: This study reveals that the anterior cruciate ligament (ACL) shows severe differences in quantitative values between its proximal and distal ends. The ACL region plays an important role in quantitative analysis and should be considered for assessments of pathologies.