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

To evaluate the feasibility of diffusion tensor imaging (DTI) using quantitative ultrashort echo time double-echo steady-state (qUTE-DESS) MRI in short T₂ 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 T₁, T₂, 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 T₁, T₂, or diffusivity and their concentrations (R² > 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 T₂ 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 T₂ 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 T₂ tissues, offering potential benefits in clinical diagnosis and research. Further studies should assess its diagnostic utility in larger cohorts with musculoskeletal pathologies.