Chapter 13 - Ultrashort echo time magnetic resonance imaging of knee joint components and correlation with biomechanics

Abstract

Knee osteoarthritis (OA) is recognized as a whole-organ disease; the failure of any single tissue component has the potential to affect those around it, contributing to failure of the joint as a whole. A truly comprehensive assessment of OA and knee biomechanics would rely on the essential ability to image all major components of the joint, but currently available clinical magnetic resonance imaging (MRI) sequences are only able to assess those tissues with relatively long T2 values such as the superficial layers of articular cartilage. Several knee joint tissues, including the deep layers of articular cartilage, menisci, ligaments, tendons, and bone, have short T2 values and consequently show little or no signal when imaged with conventional clinical MRI sequences. Newly developed ultrashort echo time (UTE) MRI sequences, on the other hand, are able to image these otherwise inaccessible “short T2” musculoskeletal tissues. Quantitative UTE MRI biomarkers, namely, T2*, T1, T1ρ, Adiabatic T1ρ, magnetization transfer ratio, and MT modeling of macromolecular proton fraction, have been developed for robust assessment of knee joint tissues. Their ability to evaluate the mechanical properties of imaged tissues and recognize signs of degeneration position them as potential tools in the detection of mechanical malfunction in early-stage OA knee joints.