BMC Musculoskeletal Disorders (Sep 2019)
Abbreviated quantitative UTE imaging in anterior cruciate ligament reconstruction
Abstract
Abstract Background Existing ultrashort echo time magnetic resonance imaging (UTE MRI) methods require prohibitively long acquisition times (~ 20–40 min) to quantitatively assess the clinically relevant fast decay T2* component in ligaments and tendons. The purpose of this study was to evaluate the feasibility and clinical translatability of a novel abbreviated quantitative UTE MRI paradigm for monitoring graft remodeling after anterior cruciate ligament (ACL) reconstruction. Methods Eight patients who had Graftlink™ hamstring autograft reconstruction were recruited for this prospective study. A 3D double-echo UTE sequence at 3.0 Tesla was performed at 3- and 6-months post-surgery. An abbreviated UTE MRI paradigm was established based on numerical simulations and in vivo validation from healthy knees. This proposed approach was used to assess the T2* for fast decay component ( T2s∗ $$ {T}_{2s}^{\ast } $$) and bound water signal fraction (f bw ) of ACL graft in regions of interest drawn by a radiologist. Results Compared to the conventional bi-exponential model, the abbreviated UTE MRI paradigm achieved low relative estimation bias for T2s∗ $$ {T}_{2s}^{\ast } $$ and f bw over a range of clinically relevant values for ACL grafts. A decrease in T2s∗ $$ {T}_{2s}^{\ast } $$ of the intra-articular graft was observed in 7 of the 8 ACL reconstruction patients from 3- to 6-months (− 0.11 ± 0.16 ms, P = 0.10). Increases in T2s∗ $$ {T}_{2s}^{\ast } $$ and f bw from 3- to 6-months were observed in the tibial intra-bone graft ( ΔT2s∗ $$ {\varDelta T}_{2s}^{\ast } $$: 0.19 ± 0.18 ms, P < 0.05; Δf bw : 4% ± 4%, P < 0.05). Lower T2s∗ $$ {T}_{2s}^{\ast } $$ (− 0.09 ± 0.11 ms, P < 0.05) was observed at 3-months when comparing the intra-bone graft to the graft/bone interface in the femoral tunnel. The same comparisons at the 6-months also yielded relatively lower T2s∗ $$ {T}_{2s}^{\ast } $$ (− 0.09 ± 0.12 ms, P < 0.05). Conclusion The proposed abbreviated 3D UTE MRI paradigm is capable of assessing the ACL graft remodeling process in a clinically translatable acquisition time. Longitudinal changes in T2s∗ $$ {T}_{2s}^{\ast } $$ and f bw of the ACL graft were observed.
Keywords
