Advanced tractography methods: Applied to patients with carpal tunnel syndrome

Sammanfattning: Introduction: Carpal tunnel syndrome (CTS) is a common condition especially for people with diabetes, obesity or women who are pregnant. Diagnosing CTS has primarily been performed using electroneuronography. In this thesis the aim was to use an advanced method of tractography to measure and evaluate diffusion tensor imaging (DTI) parameters between anatomical landmarks at the distal radioulnar joint to the hamate and trapezium through the median nerve to see if these parametric values were different between patients and healthy volunteers. Method and material: The amount of subjects which took part in this thesis was 20 in total, 10 patients and 10 healthy volunteers. The data acquisition was obtained with a SIEMENS MAGNETOM Prisma 3T scanner using a handwrist 16 channel coil. The sequence used to acquire these images was a single-shot echo planar imaging (EPI) with 38 transverse slices. The diffusion encoding was performed in 20 separate encoding directions using a bfactor of 1000 s/mm2. The tractogram created from the tractography algorithm was used as a segmentation tool, to find the voxels in each slice for different anatomical landmarks of the wrist which were between the anatomical landmarks at the distal radioulnar joint to the hook of hamate and trapezium. The DTI parameters fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and functional cross section area (FCSA) were then evaluated using MATLAB [1]. To evaluate the significance of these parameters the Mann-Whitney U-test between the patients and healthy volunteers. Result: The results of this thesis shows a significant difference between patients and healthy volunteers for the parameter FA, MD, AD and FCSA. The average parametric values for the significant parameters were larger for healthy volunteers than for patients. Discussion: The method used in this thesis could potentially have a better robustness than some previous methods used with the purpose of diagnosing CTS. The results of this thesis showed a difference between patients and healthy volunteers for the FCSA-parameter, which is a new parameter that has not been used in any previous wrist studies and should be tested more in future work to see if it was reproducible. The parameters FA, MD and AD showed some similarities with the values obtained from previous studies with the same purpose. Conclusion: The method used in this thesis was a valid method when evaluating the parametric DTI-values for patients with CTS. This thesis concluded that DTI can be useful as a supplementing tool to electroneuronography when diagnosing CTS. The results of the new parameter FCSA showed potential of differentiating between patients and healthy volunteers although more work is needed before it can be used on a individual level.