There are growing evidences of neuroinflammation (NI) in Obsessive-Compulsive Disorder (OCD). Initially, there were evidences in regards to the association of OCD onset following Group A Beta-hemolytic Streptococcus infection. More recently autoimmune processes has also been linked to OCD as well as the involvement of peripheral neuroinflammatory markers. Neuroimaging techniques, mainly using Positron Emission Tomography, allow the investigation of NI in vivo. However, this technique suffers bioavailability influence of biological compounds and in the most part generate complex images with difficult interpretation and cumbersome. Underpinned on this fragility, new imaging methods such as Free Water Imaging, which uses Diffusion Tensor magnetic resonance imaging (MRI), are emerging. This method offers a type of assessment more precise about the interference of water in brain tissue. This approach provides two parameters: the fractional volume of the free-water compartment (FW), important for estimate the extracellular volume and the diffusion tensor of the tissue compartment, measured by tissue- Fractional Anisotropy (FAT). The most important parameter for us, in this project is the FW. It quantifies the extracellular free water contribution that is altered when there is NI. This measure increases the sensitivity and is promissory for clinical application, with the potential to identify more subtle changes in OCD. The possibility of quantify NI in vivo in human brain of OCD patients using Diffusion Tensor MRI is extremely important and has not been done yet, which allows the measurement of white matter microstructures and pathological processes such as inflammation. The results of this study may shed light to the involvement of NI in the pathophysiology of OCD and help future studies to the identification of new target therapeutic. Therefore, the aim of this investigation is to compared 98 patients with OCD versus 59 healthy controls using Free Water Diffusion Tensor MRI.
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