UTE imaging in the musculoskeletal system

Abstract

Tissues, such as bone, tendon, and ligaments, contain a high fraction of components with “short” and “ultrashort” transverse relaxation times and therefore have short mean transverse relaxation times. With conventional MRI sequences that employ relatively long echo times (TEs), there is no opportunity to encode the decaying signal of short and ultrashort T2/T2* tissues before it has reached zero or near zero. The clinically compatible ultrashort TE (UTE) sequence has been increasingly used to study the musculoskeletal system. This article will review the UTE sequence as well as various modifications that have been implemented since its introduction. These modifications have been used to improve efficiency or contrast as well as provide quantitative analysis. This article also reviews several clinical musculoskeletal applications of UTE.

Thickness of the Meniscal Lamellar Layer: Correlation with Indentation Stiffness and Comparison of Normal and Abnormally Thick Layers by Using Multiparametric Ultrashort Echo Time MR Imaging

“…However, the advent of ultrashort echo time (UTE) MR imaging enabled the selective imaging of tissues with short T2, which allows for acquisition of signal from these tissues and further provides high spatial and contrast resolution. This combination of imaging features allowed the anatomic structure of the menisci to be viewed in a noninvasive fashion (4)(5)(6)(7)(8). Additionally, quantitative MR imaging relaxation measurements have been used to interrogate changes in collagen matrix and water content and early proteoglycan depletion, including T2 and T2*, and T1r (6,9).…”

“…This combination of imaging features allowed the anatomic structure of the menisci to be viewed in a noninvasive fashion (4)(5)(6)(7)(8). Additionally, quantitative MR imaging relaxation measurements have been used to interrogate changes in collagen matrix and water content and early proteoglycan depletion, including T2 and T2*, and T1r (6,9). When acquired with a UTE sequence, these techniques can be applied to tissues with short T2, such as the menisci (9-13).…”

Feasibility of using an inversion-recovery ultrashort echo time (UTE) sequence for quantification of glenoid bone loss

“…The UTE sequence, which utilizes TEs short enough to capture lamellar bone signal, was first described nearly three decades ago [15], but only in recent years has advances in hardware and software technology allowed for high quality imaging in clinically compatible imaging times. UTE sequences have been successfully implemented on every major MRI vendor system [5], but have not yet been offered as a product sequence. We believe that demonstrating this exciting application for assessment of glenoid bone stock will be important in pushing the product into the clinics.…”

“…Conventional MRI techniques are fundamentally limited in their assessment of bone due to the extremely short T2/T2* of lamellar bone [5]. Using conventional MRI sequences with longer echo times (TEs), the signal of short T2/T2* structures has decayed to background levels prior to acquisition.…”

“…Rather, the contours of lamellar bone are inferred by visualizing fatty bone marrow or surrounding soft tissue, potentially resulting in imprecise localization. Techniques involving ultrashort echo time (UTE) can directly image lamellar bone, with newer methods incorporating fat and adjacent soft tissue suppression [5, 6]. These techniques produce images of cortical bone that are more similar in quality to that currently available by CT scan [7].…”