The magnetic resonance Diffusion Tensor Imaging (DTI) is a powerful extension of Diffusion Weighted Imaging (DWI) utilizing multiple bipolar gradients, allowing for the evaluation of the microstructural environment of the highly anisotropic tissues. DTI was predominantly used for the assessment of the central nervous system (CNS), but with the advancement in magnetic resonance (MR) hardware and software, it has now become possible to image the peripheral nerves which were difficult to evaluate previously because of their small caliber. This study focuses on the assessment of the human median peripheral nerve ex vivo by DTI microscopy at 9.4 T magnetic field which allowed the evaluation of diffusion eigenvalues, the mean diffusivity and the fractional anisotropy at 35 μm in-plane resolution. The resolution was sufficient for clear depiction of all nerve anatomical structures and therefore further image analysis allowed the obtaining of average values for DT parameters in nerve fascicles (intrafascicular region and perineurium) as well as in the surrounding epineurium. The results confirmed the highest fractional anisotropy of 0.33 and principal diffusion eigenvalue of 1.0 × 10⁻⁹ m²/s in the intrafascicular region, somewhat lower values of 0.27 and 0.95 × 10⁻⁹ m²/s in the perineurium region and close to isotropic with very slow diffusion (0.15 and 0.05 × 10⁻⁹ m²/s) in the epineurium region.

Background: Quantitative magnetic resonance imaging (MRI) techniques such as T₂ mapping may detect early tendon changes following biologic therapies. This study aimed to assess the structural remodeling of the supraspinatus tendon using mean T₂ values and T₂ distribution profiles after an ultrasound (US)-guided single platelet-rich plasma (PRP) injection. Methods: Twenty-six patients with symptomatic supraspinatus tendinopathy were divided into tendinosis (n = 9) and partial tear (n = 13) groups. T₂ mapping and clinical evaluations (shoulder pain and disability index questionnaire (SPADI), Constant-Murley score) were conducted at baseline and 6 months post-PRP. Mean T₂ values were measured in three tendon segments (lateral, middle, and medial), and T₂ profiles were compared to asymptomatic controls. Results: Clinical outcomes showed significant improvement in both the tendinosis and partial tear groups at the 6-month follow-up. Although no significant changes were observed in the mean T₂ relaxation times across tendon segments following PRP treatment, T₂ distribution profiling revealed statistically significant alterations in both groups. In the tendinosis group, post-treatment T₂ profiles approached those of the asymptomatic controls, suggesting structural remodeling consistent with tendon healing. Conclusions: T₂ mapping is an effective tool for detecting tendon remodeling following PRP therapy. Structural improvements indicative of tissue healing were observed in cases of tendinosis, but not in partial tendon tears. These findings support the use of T₂ mapping—particularly the T₂ distribution profiling—as a quantitative biomarker for assessing treatment response to PRP.