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

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.

Three‐dimensional Yarnball k‐space acquisition for accelerated MRI

“…A new center-out 3D k-space acquisition technique named "Yarnball" is introduced, which requires fewer trajectories to generate images free from aliasing artifact than the 3D-Cones technique presented by Gurney et al 2 The 3D-Cones technique was originally introduced within the context of ultrashort TE imaging of the human knee using T RO = 2 ms, and most of the 3D-Cones work that has followed has also focused on imaging in vivo tissues with short T * 2 . [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][28][29][30] Simulated imaging with T RO = 2 ms showed that 3D Cones required about 1.4 times more trajectories than Yarnball to produce images free from aliasing artifact for a sphere (Figure 7), and about 1.75 times more trajectories for a prolate spheroidal (head-like) object ( Table 1). Yarnball also exhibits less PSF and resolution-element smearing than 3D Cones in the presence of T * 2 decay and off-resonance ( Figure 6).…”

“…A practical implementation of 3D Cones was presented in 2006, 2 and lately this technique has found considerable use. Given its ultrashort TE capability and much greater sampling efficiency than 3D radial acquisition, 3D Cones has been used to measure proton density, T 1 , , susceptibility variation, and magnetization transfer in cortical bone 3‐15 as well as the short tissues of the knee including tendons, ligaments, and meniscus 16‐22 . Given its robustness to motion and flow artifacts, 3D Cones has also been considered for whole‐heart coronary MRA, 23,24 together with motion correction 25,26 and off‐resonance artifact correction, for pediatric body 27 .…”

Quantitative Ultrashort Echo Time (UTE) Magnetic Resonance Imaging of Bone: An Update

“…The lack of direct signal obtained from bone makes it impossible to quantify the MR relaxation times (e.g., T1 and T2 * ), magnetization transfer ratio (MTR) and volume concentration of various bone compartments. To address this shortcoming and take advantage of both MRI's safety profile and its excellent assessment of soft tissues such as tendon ( 27 ) and muscle, a benefit not available in x-ray-based techniques, a number of advanced MRI techniques have recently been developed to evaluate bone more effectively ( 14 , 28 – 30 ). Among recently developed MRI techniques, ultrashort echo time (UTE) sequences have emerged as a technique capable of directly imaging cortical bone and providing a number of quantitative measurements ( 14 , 28 – 30 ).…”

An Update in Qualitative Imaging of Bone Using Ultrashort Echo Time Magnetic Resonance

“…MRI-based techniques for bone evaluation avoid the potential harm associated with x-ray-based imaging techniques ( 5 , 6 , 16 , 22 ). MRI-based bone evaluation can also provide valuable evaluation of the surrounding soft tissues including tendons ( 23 ) and muscles, advantages that are not available in x-ray-based techniques. Bone has a short apparent transverse relaxation time (T2*) and is typically visualized with a void signal when using conventional clinical pulse sequences with echo times (TEs) of a several milliseconds or longer ( 24 , 25 ).…”