Age-related decrease in collagen proton fraction in tibial tendons estimated by magnetization transfer modeling of ultrashort echo time magnetic resonance imaging (UTE-MRI)

Jiang Du,Yajun Ma,Aria Ashir,Mei Wu,Behnam Namiranian,Saeed Jerban,Hoda Shirazian,Eric Y. Chang,Zhao Wei,Zhenyu Cai,Nicole Le

doi:10.1038/s41598-019-54559-3

Abstract

Clinical magnetic resonance imaging (MRI) sequences are not often capable of directly visualizing tendons. Ultrashort echo time (UTE) MRI can acquire high signal from tendons thus enabling quantitative assessments. Magnetization transfer (MT) modeling combined with UTE-MRI—UTE-MT-modeling—can indirectly assess macromolecular protons in the tendon. This study aimed to determine if UTE-MT-modeling is a quantitative technique sensitive to the age-related changes of tendons. The legs of 26 young healthy (29 ± 6 years old) and 22 elderly (75 ± 8 years old) female subjects were imaged using UTE sequences on a 3T MRI scanner. Institutional review board approval was obtained, and all recruited subjects provided written informed consent. T1 and UTE-MT-modeling were performed on anterior tibialis tendons (ATT) and posterior tibialis tendons (PTT) as two representative human leg tendons. A series of MT pulse saturation powers (500–1500°) and frequency offsets (2–50 kHz) were used to measure the macromolecular fraction (MMF) and macromolecular T2 (T2MM). All measurements were repeated by three independent readers for a reproducibility study. MMF demonstrated significantly lower values on average in the elderly cohort compared with the younger cohort for both ATT (decreased by 16.8%, p = 0.03) and PTT (decreased by 23.0%, p < 0.01). T2MM and T1 did not show a significant nor a consistent difference between the young and elderly cohorts. For all MRI parameters, intraclass correlation coefficient (ICC) was higher than 0.98, indicating excellent consistency between measurements performed by independent readers. MMF serving as a surrogate measure for collagen content, showed a significant decrease in elderly leg tendons. This study highlighted UTE-MRI-MT techniques as a useful quantitative method to assess the impact of aging on human tendons.

Highlights

Clinical magnetic resonance imaging (MRI) sequences are not often capable of directly visualizing tendons
intraclass correlation coefficient (ICC) between the three independent measurements are presented in Table 1 for T1, macromolecular fraction (MMF), and T2MM values
Ultrashort echo time (UTE)-Magnetization transfer (MT) modeling as an orientation-insensitive MRI technique and a noninvasive tool to detect collagen fraction changes throughout aging may potentially help in the detection of weakened tendons and in prediction of potential tears or injuries

Summary

Introduction

Clinical magnetic resonance imaging (MRI) sequences are not often capable of directly visualizing tendons. Ultrashort echo time (UTE) MRI can acquire high signal from tendons enabling quantitative assessments. This study highlighted UTE-MRI-MT techniques as a useful quantitative method to assess the impact of aging on human tendons. Ultrashort echo time (UTE) MRI sequences are capable of detecting considerable signal of tendons before decay to background levels occurs[8]. UTE-MRI has provided quantitative MRI-based assessments of tendons, such as apparent relaxation time of transverse magnetization (T2*), relaxation time of longitudinal magnetization (T1), and magnetization transfer (MT) measurements such as MT ratio (MTR)[6,7,8,10,11,12,13,14,15,16]. Earlier studies have reported that over 200% of change observed in MR properties of normal tendons and cartilage measured at 3T only resulted from differing orientations of the tissue relative to B019–22

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