Ultrashort echo time imaging with bicomponent analysis

Biological tissues frequently contain different water compartments, and these often have distinct transverse relaxation times. Quantification of these may be problematic on clinical scanners because spin echo sequences usually have initial echo times that are too long to accurately quantify shorter relaxation time components. In this study, an ultrashort echo time pulse sequence was used together with bicomponent analysis to quantify both the short and long T2 components in tissues of the musculoskeletal system. Feasibility studies were performed using numerical simulation, and on phantoms and in vitro tissues including bovine cortical bone, ligaments, menisci, tendons, and articular cartilage. The simulation and phantom studies demonstrated that this technique can quantify T2* and fractions of the short and long T2 components. The tissues studies showed two distinct components with short T2*s ranging from 0.3 ms for bovine cortical bone to 2.1 ms for menisci, and long T2*s ranging from 2.9 ms for bovine cortical bone to 35.0 ms for articular cartilage. The short T2* fraction ranged from 18.5% for patella cartilage to 80.9% for ligaments. The results show that ultrashort echo time imaging with bicomponent analysis can quantify the short and long T2 water components in vitro in musculoskeletal tissues. Magn Reson Med, 2012. (c) 2011 Wiley Periodicals, Inc.