Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Medicine and Health Sciences
Covariate-Adjusted Nonparametric Analysis Of Magnetic Resonance Images Using Markov Chain Monte Carlo, Haley Hedlin, Brian S. Caffo, Ziyad Mahfoud, Susan Spear Bassett
Covariate-Adjusted Nonparametric Analysis Of Magnetic Resonance Images Using Markov Chain Monte Carlo, Haley Hedlin, Brian S. Caffo, Ziyad Mahfoud, Susan Spear Bassett
Johns Hopkins University, Dept. of Biostatistics Working Papers
Permutation tests are useful for drawing inferences from imaging data because of their flexibility and ability to capture features of the brain that are difficult to capture parametrically. However, most implementations of permutation tests ignore important confounding covariates. To employ covariate control in a nonparametric setting we have developed a Markov chain Monte Carlo (MCMC) algorithm for conditional permutation testing using propensity scores. We present the first use of this methodology for imaging data. Our MCMC algorithm is an extension of algorithms developed to approximate exact conditional probabilities in contingency tables, logit, and log-linear models. An application of our non-parametric …
Nonlinear Tube-Fitting For The Analysis Of Anatomical And Functional Structures, Jeff Goldsmith, Brian S. Caffo, Ciprian Crainiceanu, Daniel Reich, Yong Du, Craig Hendrix
Nonlinear Tube-Fitting For The Analysis Of Anatomical And Functional Structures, Jeff Goldsmith, Brian S. Caffo, Ciprian Crainiceanu, Daniel Reich, Yong Du, Craig Hendrix
Johns Hopkins University, Dept. of Biostatistics Working Papers
We are concerned with the estimation of the exterior surface of tube-shaped anatomical structures. This interest is motivated by two distinct scientific goals, one dealing with the distribution of HIV microbicide in the colon and the other with measuring degradation in white-matter tracts in the brain. Our problem is posed as the estimation of the support of a distribution in three dimensions from a sample from that distribution, possibly measured with error. We propose a novel tube-fitting algorithm to construct such estimators. Further, we conduct a simulation study to aid in the choice of a key parameter of the algorithm, …
Group Comparison Of Eigenvalues And Eigenvectors Of Diffusion Tensors, Armin Schwartzman, Robert F. Dougherty, Jonathan E. Taylor
Group Comparison Of Eigenvalues And Eigenvectors Of Diffusion Tensors, Armin Schwartzman, Robert F. Dougherty, Jonathan E. Taylor
Harvard University Biostatistics Working Paper Series
No abstract provided.