National Alliance for Medical Image Computing http://na-mic.org

Ising Prior in fMRI detection

• Junmo Kim

• John Fisher

• Eric Cosman

• Wanmei Ou

• Polina Golland

National Alliance for Medical Image Computing http://na-mic.org

GLM / Ising

Exact MAP Activity Detection in fMRI Using a GLM with an Ising

Spatial Prior

Eric Cosman, Jr., Wanmei Ou, John Fisher, William Wells

National Alliance for Medical Image Computing http://na-mic.org

GLM / Ising…

• Alternative model for noise reduction

• Ising MRF prior model

• In GLM / Hypothesis Test

• Fast exact solution: Portius, Grieg

• Result is F-statistic (threshold at)

National Alliance for Medical Image Computing http://na-mic.org

National Alliance for Medical Image Computing http://na-mic.org

GLM / Ising Results

Eric Cosman, Jr., Wanmei Ou

National Alliance for Medical Image Computing http://na-mic.org

GLM / Ising…

• Wanmei Ou– MIT MS Project with Polina Golland– Empirical Characterization of fMRI

detectors• Larry Panych data• GLM / MI• MARKOV spatial models

– Exact– Approximate

National Alliance for Medical Image Computing http://na-mic.org

GLM / Ising: Empirical Results

Eric Cosman, Jr., Wanmei Ou

•ROC analysis on realistic synthetic data

•Low SNR regime: Gaussian Blur is Better

•High SNR regime: Ising Prior is Better

National Alliance for Medical Image Computing http://na-mic.org

GLM Combined with Ising Model

• Eric Cosman et al. MICCAI 04

• Extends GLM hypothesis testing approach to include Ising Prior model on activations

National Alliance for Medical Image Computing http://na-mic.org

Synthetic Comparison with Gaussian Smoothing

National Alliance for Medical Image Computing http://na-mic.org

MI-Based fMRI Activation Detection

• Standard Modeling Assumptions (GLM):– Activating Voxel intensities are proportional

to protocol with added Gaussian Noise

• MI approach:– A Voxel is declared active if it is not

statistically independent of protocol• As Measured by MI

– Andy Tsai

National Alliance for Medical Image Computing http://na-mic.org

Kim MS: MI with Ising Prior on Activations

• Demonstrate that MI is optimal test statistic for Likelihood Ratio Test of independence

• Use Likelihood to facilitate combination with Ising prior model on activation

• Show that estimator can be solved in polynomial time

National Alliance for Medical Image Computing http://na-mic.org

Verb-Association Test Results

Provided by Eric Cosman,Jr.

National Alliance for Medical Image Computing http://na-mic.org

Representative Voxels

Provided by Eric Cosman,Jr.

NA-MICNational Alliance for Medical Image Computing http://na-mic.org

Bayesian Population Inference for the Multivariate Autoregressive Process

Eric Cosman

1/19/05

IPMI 05?, PhD 05

National Alliance for Medical Image Computing http://na-mic.org

•The end