Diffusion-tensor MRI methods to study and evaluate muscle architecture

The thesis describes the development of various approaches for measuring muscle architectural parameters using Diffusion Tensor MR Imaging (DTI). It also illustrates how to apply them to study changes in muscle architecture after an injury prevention program.
In Chapter 2, because manual segmentation of muscles is cumbersome, we validated a semi-automatic framework for estimating DTI indices in upper leg muscles. This method reduced segmentation time by a factor of three in a cross-sectional study design and can be used fully automatically in a longitudinal assessment of changes in DTI indices.
Chapter 3 was a feasibility study measuring fiber orientation changes with DTI in calf muscles and sub-compartments of the Soleus and Tibialis Anterior during plantarflexion and dorsiflexion. Differences in fiber orientations corresponded to the known agonist-antagonist function of the muscles. This shows that DTI can be utilized to assess changes in muscle orientation due to posture or training.
In Chapter 4, we compared DTI fiber tractography for Vastus Lateralis fiber architecture assessment with 3D ultrasonography (3D-US). We discovered that both methods have their advantages and disadvantages, with the agreement between the two techniques being moderate.
Finally, in Chapter 5, we examined the effects of a hamstring injury prevention exercise on the muscle architectural parameters of basketball players. DTI was employed to quantify changes in fiber orientation and length using tractography and fiber orientation maps. It was observed that the Semitendinosus fascicle length increased after the Nordics exercise, while the Biceps Femoris long head fiber orientation decreased following the Divers intervention.