![]() This simplest technique, shown in Figure 1, is called streamline or deterministic tractography. We can then change to this new direction and carry on until the entire pathway is traced. In its simplest form, this consists of starting at a seed location and following the preferred direction until we reach a new measurement. Once we know the orientation of fibers at every point in the brain, we can join these directions up to reconstruct entire pathways and hence brain connections. The white line shows the streamline obtained by connecting up a set of pixels based on their preferred directions and is an example of deterministic tractography. The color is a complementary way of coding the preferred direction where red denotes left-right, green denotes back-front and blue up-down (out of the image plane). Hence, by measuring diffusion along many directions and observing that it is faster in one direction than in others, we can deduce the direction of the fiber bundles at every point in the brain.įigure 1: Preferred diffusion directions are shown as the long axes of diffusion ellipsoids. Crucially, it is more hindered across than along such bundles. it progresses more slowly than it would in water. In such tissue diffusion is "hindered", i.e. In brain white matter, tissue consists of bundles of myelinated axons. The extent of this spread depends on the diffusivity of the medium. Why is diffusion useful?ĭiffusion is the spread of molecules in a fluid due to constant thermal motion. At the same time, we are investing significant effort into optimizing data acquisition strategies and tractography algorithms to maximize accuracy and minimize errors in the diffusion tractography data. The Human Connectome Project is capitalizing on the key strengths of diffusion imaging. Furthermore, connections can be compared with other in-vivo measures such as functional connectivity and behavior across individuals. Hence, areal connections may be compared in humans across many cortical and sub-cortical sites. In particular, brain connections can be measured in living human subjects, and measurements can be made simultaneously across the entire brain. However, their non-invasive nature and ease of measurement mean that tractography studies can address scientific questions that cannot be answered by any other means. By comparison with invasive techniques, tractography measurements are indirect, difficult to interpret quantitatively and error-prone. Tractography is the only available tool for identifying and measuring these pathways non-invasively and in-vivo. These connections form the substrate for information transfer between remote brain regions and are therefore central to our understanding of brain function. Excuse me for the delay in my reply (very busy with clinical stuffs in this period).MR diffusion tractography is a method for identifying anatomical connections in the living human brain. Thanks for your kind reply and for the post in the blog. ![]() The only real problem of the software is the total lack of a manual that is very disappointing. Recently I discovered Fiber Navigator and it seems able to satisfy my needs,ġ) I can use the scalars and tensor I already created with FSL or Camino Ģ) It's great in visualization of deterministic tractography ģ) It's the only softare I found able to visualizing the probabilistic tractography I created in FSL. In MedInria it seems also impossible visualising probabilistic tractography. The only problem I found is a difficult use of ROIs for the selection of the tract of my interest. In any case MedInria create good deterministic tractography and it is also good in visualization. MedInria forces me to start from the beginning and re-calculate scalar maps and tensor, It's impossible using the scalars and tensor I have already created with FSL. In any case I'm happy to have learned more about this software. Unfortunately In my personal opinion MedInria is a DTI tool not so complete and rich of option as FSL or Camino and in visualization it is not at same level of Trackvis. Thanks for your advice, I tried MedInria and I found the software is rather compatible with FSL and Camino beeing all based on NIFTI format.
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