Diffusion tensor imaging of the anterior cruciate ligament graft

Abstract

3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1423-1432.

Diffusion tractography of the rat knee at microscopic resolution

“…Ligaments and tendon have higher FA values, which should be more suitable for diffusion tractography, compared to low FA values in cartilage (~0.14 at b value of 1250 s/mm 2 ) and growth plate (~0.12 at b value of 1250 s/mm 2 ). However, the water relaxation time is much lower in these highly organized tissues, which may degrade the quality of the fiber tracking .…”

“…However, the water relaxation time is much lower in these highly organized tissues, which may degrade the quality of the fiber tracking . The TE value used in clinical MRI could be as high as 45 ms; more averages may need to achieve sufficient SNR . Recently, a novel stimulated echo readout‐segmented echo planar imaging DTI sequence was proposed to achieve a TE of 14 to 20 ms, which successfully detected the human Achilles tendon diffusion properties and tractography .…”

“…Dyck et al demonstrated that diffusion tractography of the anterior cruciate ligament (ACL) graft is feasible with clinical 3T MRI scanners, which provide a reliable estimation of quantitative DTI indices of the ACL graft . Recently, Achilles tendon diffusion properties of healthy participants and tendinopathy patients were investigated on a clinical MR scanner with the Achilles positioned at the magic angle (~55°) to main magnetic field for the maximum tendon MR signal .…”

Detection of maturity and ligament injury using magic angle directional imaging

“…The proposed magic angle directional imaging represents an alternative method to the DTI, which is a widely used technique for fiber tractography. The present study did not involve a direct comparison with DTI, although it would be useful to perform such an investigation in the future.…”

“…Diffusion tensor imaging is generally challenging for imaging of ligaments and tendons because of its very short T 2 (1‐2 ms) compared with the long TE (50‐90 ms) typically required for the diffusion‐encoding gradients, with a resulting low signal. This requires the subject to be positioned at or near the magic angle to increase T 2 sufficiently, whereas TE also needs to be reduced by using suitably modified imaging sequences, such as that in Wengler et al The recent DTI study by Van Dyck et al involved the anterior cruciate ligament graft, in which the specific tissue properties allowed the use of relatively long TE (45 ms).…”