Single- and Bicomponent Analyses of T2⁎ Relaxation in Knee Tendon and Ligament by Using 3D Ultrashort Echo Time Cones (UTE Cones) Magnetic Resonance Imaging.

Yajun Ma,Jin Liu,Yinghua Zhao,Quan Zhou,Amin Nazaran,Haimei Chen,Shaolin Li,Jiang Du,Yanchun Zhu

doi:10.1155/2019/8597423

Abstract

The collagen density is not detected in the patellar tendon (PT), posterior cruciate ligament (PCL), and anterior cruciate ligament (ACL) in clinic. We assess the technical feasibility of three-dimension multiecho fat saturated ultrashort echo time cones (3D FS-UTE-Cones) acquisitions for single- and bicomponent T2⁎ analysis of bound and free water pools in PT, PCL, and ACL in clinic. The knees of five healthy volunteers and six knee joint samples from cadavers were scanned via 3D multiecho FS-UTE-Cones acquisitions on a clinical scanner. Single-component fitting of T2⁎M and bicomponent fitting of short T2⁎ (T2⁎S), long T2⁎ (T2⁎L), short T2⁎ fraction (Frac_S), and long T2⁎ fraction (Frac_L) were performed within tendons and ligaments. Our results showed that biexponential fitting was superior to single-exponential fitting in PT, PCL, and ACL. For knee joint samples, there was no statistical difference among all data in PT, PCL, and ACL. For volunteers, all parameters of bicomponent fitting were statistically different across PT, PCL, and ACL, except for T2⁎S, T2⁎L, and T2⁎M resulting in flawed measurements due to the magic angle effect. 3D multiecho FS-UTE-Cones acquisition allows high resolution T2⁎ mapping in PT, PCL, and ACL of keen joint samples and PT and PCL of volunteers. The T2⁎ values and their fractions can be characterized by bicomponent T2⁎ analysis that is superior to single-component T2⁎ analysis, except for ACL of volunteers.

Highlights

Many of the degenerate tendons and ligaments from cadavers and biopsies from patients had a decreased collagen concentration and this change may predispose the tendons and ligaments to rupture, as a reduction in the collagen density has been correlated with the tensile strength of tendons and ligaments
Biexponential fits were significantly different from singleexponential fits for patellar tendon (PT) and posterior cruciate ligament (PCL) (P = 0.01 in both cases), while there was no statistical significance between the single- and biexponential fits for anterior cruciate ligament (ACL) (P = 0.29) in volunteer
2D Ultrashort echo time (UTE) sequences have been employed for bicomponent analysis of bound and free water components in various knee joint tissues [14]. 3D UTE Cones sequences have many advantages over 2D UTE sequences. 3D UTE cones sequences are much less prone to eddy current artifact compared with 2D UTE sequences with half-pulse excitation, where mapping of bound and free water components may suffer from errors due to outof-slice signal contaminations [18]

Summary

Introduction

Many of the degenerate tendons and ligaments from cadavers and biopsies from patients had a decreased collagen concentration and this change may predispose the tendons and ligaments to rupture, as a reduction in the collagen density has been correlated with the tensile strength of tendons and ligaments. If we can detect the reduction in the collagen density in the degenerate patellar tendon (PT), posterior cruciate ligament (PCL), and anterior cruciate ligament (ACL) in clinic, some medical methods might be used to prevent PT, PCL, and ACL from being ruptured. Tendons and ligaments typically have very short transverse relaxation times (T2s or T2∗s) and remain “invisible” with conventional clinical MRI sequences. Early stages of tendon and ligament degeneration may not be detected by traditional MRI. Ultrashort echo time (UTE) techniques, which use nominal TEs about 10-200 times shorter than those of conventional clinical MR sequences, can directly detect signal from short T2 tissues and might be used for diagnosis of these diseases at early stages [1, 2]. Previous studies showed that at the early stages of ligaments and tendons degeneration, fat-suppressed UTE T2∗ mapping could potentially reflect the biological composition and structural integrity in ligaments and tendons, which are BioMed Research International

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