Diffusion Tensor Imaging of Short T 2 Tissues Using Quantitative Ultrashort Echo Time Double‐Echo Steady‐State: A Feasibility Study

ABSTRACT To evaluate the feasibility of diffusion tensor imaging (DTI) using quantitative ultrashort echo time double‐echo steady‐state (qUTE‐DESS) MRI in short T 2 musculoskeletal tissues, we validated it in phantoms, an ex vivo porcine hoof, and an in vivo human knee. The qUTE‐DESS sequence was implemented on a clinical 3 T MRI system, enabling simultaneous estimation of T 1 , T 2 , and diffusivity in tissues with rapid signal decay. Data were acquired with six diffusion‐weighting orientations (x, y, z, xy, yz, xz) to obtain mean diffusivity (MD) and fractional anisotropy (FA). Sucrose and agarose phantoms demonstrated linear relationships between T 1 , T 2 , or diffusivity and their concentrations ( R 2 > 0.88). A celery phantom demonstrated anisotropic diffusion by revealing elevated FA in fibrous structures. In experiments with the porcine hoof and healthy volunteers' knees, qUTE‐DESS generated high‐resolution parameter maps of MD and FA across various tissues, including cartilage, meniscus, tendon, ligament, and muscle, effectively capturing short T 2 components that conventional DTI could not visualize. By preserving ultrashort echo signals, qUTE‐DESS appeared to overcome the limitations of spin‐echo–based DTI, which suffers from longer echo times and subsequent signal loss in short T 2 tissues. Therefore, this approach may serve as a valuable quantitative imaging tool for assessing microstructural features in the musculoskeletal system, facilitating detection and evaluation of joint abnormalities or degenerative changes. The results suggest qUTE‐DESS can provide insight into both long and short T 2 tissues, offering potential benefits in clinical diagnosis and research. Further studies should assess its diagnostic utility in larger cohorts with musculoskeletal pathologies.