title: Evaluating the accuracy of diffusion MRI models in white matter.
abstract: Models of diffusion MRI within a voxel are useful for making inferences about the properties of the tissue and inferring fiber orientation distribution used by tractography algorithms. A useful model must fit the data accurately. However, evaluations of model-accuracy of commonly used models have not been published before. Here, we evaluate model-accuracy of the two main classes of diffusion MRI models. The diffusion tensor model (DTM) summarizes diffusion as a 3-dimensional Gaussian distribution. Sparse fascicle models (SFM) summarize the signal as a sum of signals originating from a collection of fascicles oriented in different directions. We use cross-validation to assess model-accuracy at different gradient amplitudes (b-values) throughout the white matter. Specifically, we fit each model to all the white matter voxels in one data set and then use the model to predict a second, independent data set. This is the first evaluation of model-accuracy of these models. In most of the white matter the DTM predicts the data more accurately than test-retest reliability; SFM model-accuracy is higher than test-retest reliability and also higher than the DTM model-accuracy, particularly for measurements with (a) a b-value above 1000 in locations containing fiber crossings, and (b) in the regions of the brain surrounding the optic radiations. The SFM also has better parameter-validity: it more accurately estimates the fiber orientation distribution function (fODF) in each voxel, which is useful for fiber tracking.
authors: Department of Psychology, Stanford, Stanford, California, United States of America.
authors: Ariel
authors: A
authors: Rokem
authors: Department of Psychology, Stanford, Stanford, California, United States of America; Institute for Learning and Brain Sciences, University of Washington, Seattle, Washington, United States of America.
authors: Jason D
authors: JD
authors: Yeatman
authors: Department of Psychology, Stanford, Stanford, California, United States of America; Department of Psychological and Brain Sciences, Program in Neuroscience, Indiana University, Bloomington, Indiana, United States of America.
authors: Franco
authors: F
authors: Pestilli
authors: Department of Psychology, Stanford, Stanford, California, United States of America; Department of Psychology, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors: Kendrick N
authors: KN
authors: Kay
authors: Department of Psychology, Stanford, Stanford, California, United States of America; Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Givat Ram, Jerusalem, Israel.
authors: Aviv
authors: A
authors: Mezer
authors: Division of Applied Mathematics, Stellenbosch University, Stellenbosch, South Africa.
authors: Stefan
authors: S
authors: van der Walt
authors: Department of Psychology, Stanford, Stanford, California, United States of America.
authors: Brian A
authors: BA
authors: Wandell
mesh_terms: D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D066127:White Matter / Q000473:pathology*