This leads to failure of the model, as demonstrated in our work. It assumes the previously mentioned Gaussian diffusion profile and, consequently, that there can only be a single fiber population per voxel. Brainvoyager uses streamline fiber tracking, one of the simplest possible approaches, to estimate the major eigenvector of the tensor ( 15). All the programs used in this study are based on a deterministic fixed step tracking algorithm. Two families of algorithms exist for tractography: deterministic (which uses the directional information described by the diffusion tensor) and probabilistic (which uses probability density functions (pdfs) of fiber orientation to quantify the resultant uncertainty in tracking). crossing fibers) can produce P with highly non-ellipsoidal contours which can lead to serious failings of the tensor model, as seen in our phantom experiments and as previously reported ( 2, 3) and cannot be easily resolved. The shape of P in white matter depends strongly on the configuration of the axon fibers. DTI models the probability distribution ( P) of tensors with ellipsoidal contours as a Gaussian distribution with a mean of zero. Furthermore, the StealthViz tool, which is designed for neurosurgical neuronavigation, could not satisfactorily show the crossing of the tensors. The least accurate tracts were presented by a tool developed for physicians to qualitatively assess neural tracts anatomy (Neuro-3D). Only one program (MedInria) could satisfactorily model the crossing of the tensor fibers in the axial plane and thus, in our opinion, it is adequate for clinical use (Fig. The interpretation of water diffusion in complex biological tissue, such as neural white matter, remains a highly debated research topic ( 3). To start with, for stopping criterion the following parameters were used: seeding threshold FA, 0.10 step size, 0.5 mm stopping criteria for tracking FA, 0.10 and deflection angle, 60°. If the resulting tracts did not appear as expected, we modified the settings and location and number of seed points to optimize the results. Initially, the manufacturers’ recommended default settings for FA analysis and tractography were employed. For tractrography, Neuro-3D, Brainvoyager, MedInria, and a neuronavigation tool StealthViz (Medtronic Minneapolis, MN, USA) were employed. Data transformation from DICOM to NifTi format was performed with MRIcroN (Neuropsychology Lab Columbia, SC, USA) which is freely available. All subjects Allied Health Cardiology & Cardiovascular Medicine Dentistry Emergency Medicine & Critical Care Endocrinology & Metabolism Environmental Science General Medicine Geriatrics Infectious Diseases Medico-legal Neurology Nursing Nutrition Obstetrics & Gynecology Oncology Orthopaedics & Sports Medicine Otolaryngology Palliative Medicine & Chronic Care Pediatrics Pharmacology & Toxicology Psychiatry & Psychology Public Health Pulmonary & Respiratory Medicine Radiology Research Methods & Evaluation Rheumatology Surgery Tropical Medicine Veterinary Medicine Cell Biology Clinical Biochemistry Environmental Science Life Sciences Neuroscience Pharmacology & Toxicology Biomedical Engineering Engineering & Computing Environmental Engineering Materials Science Anthropology & Archaeology Communication & Media Studies Criminology & Criminal Justice Cultural Studies Economics & Development Education Environmental Studies Ethnic Studies Family Studies Gender Studies Geography Gerontology & Aging Group Studies History Information Science Interpersonal Violence Language & Linguistics Law Management & Organization Studies Marketing & Hospitality Music Peace Studies & Conflict Resolution Philosophy Politics & International Relations Psychoanalysis Psychology & Counseling Public Administration Regional Studies Religion Research Methods & Evaluation Science & Society Studies Social Work & Social Policy Sociology Special Education Urban Studies & Planning BROWSE JOURNALSįA values were computed using two commercially available software packages (Neuro-3D and BrainVoyager QX v2.1 ) and two free software packages (MedInria v.1.9.0 and FSL ).
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