------------------------------------------------------------

The partial volume effect in Positron Emission Tomography (PET) is a problem for quantitative adiotracer studies. These studies can be used to study of many well-known diseases such as Epilepsy but partial volume effects can cause misinterpretation of the data. The partial volume effect results from the limited spatial resolution of the imaging device (a few mm's) and results in a blurring of the data. Two factors are involved for pre-defined regions; spillover of radioactivity into neighboring regions and the underlying tissue inhomogeneity (mixed tissue types) of the particular region. Linear modelling methods are currently used to correct for this effect on a regional level, using tissue classification from higher resolution imaging modalities, e.g. Magnetic Resonance Imaging, and anatomically defined regions which are assumed to contain homogeneous tracer concentrations. We extend these methods to incorporate the underlying noise structure of the PET tomograph measurements, and develop fast tensor based algorithms to facilitate the computation of true tracer concentration estimates and their associated errors. This allows calculation of linear models in the case of massive data sets with inherent spatial correlation structure. We also investigate the possibility of using the developed noise models to infer whether the defined regions were homogenous using Krylov subspace based approximate estimates for the regional errors associated with the fits.

-------------------------------------------------------------

Title: BAYESIAN GROUP TESTING
Speaker: Professor Curtis Tatsuoka
Department of Statistics, The George Washington University
Date: October 4, 2002
Location: Funger Hall 323
Time: 11:00 a.m.

------------------------------------------------------------

A Bayesian formulation of group testing with testing error will be considered, where group testing is viewed as a sequential classification problem on lattices. Various response distribution formulations will be presented, including the case when testing error is a function of pool size. Results include describing experiment selection rules that attain optimal rates of convergence. Non-standard group testing problems also will be discussed.

------------------------------------------------------------

Title: The Value of Standardization - Software and Current Best Methods
Speaker: Dr. David Morganstein
WESTAT corporation
Date: October 18, 2002
Location: Funger Hall 323
Time: 11:00 a.m.

------------------------------------------------------------

In a private statistical organization, the amount of effort needed to plan and conduct a survey is a critical indicator of success in competing for government contracts. Westat, an employee owned survey organization, must be concerned about the staff time needed to do it's work. It must also be concerned about retaining high quality staff, so job satisfaction is also a critical measure of success. The statistical group of 55 statisticians is involved in dozens of surveys every year. Often a staff member is working on 3 or more surveys simultaneously. To reduce the effort needed to support the variety of surveys and to increase interest in the work, our statistical group has standardized in two areas: software and current best methods. In this talk, we'll describe why we choose to do this, how we do it and the benefits we have observed.

----------------------------------------------------------

Title: Modeling Compositional Data with Dirichlet Covariate Models
Speaker: Dr. Robert W. Jernigan
Department of Mathematics and Statistics
Date: November 1, 2002
Location: Funger Hall 323
Time: 11:00 a.m.

------------------------------------------------------------

We will examine compositional data, relative frequencies of objects classified into disjoint categories. The resulting data of non-negative proportions with unit sum make the elementary concepts of covariance and correlation misleading. Modeling of compositional data based on Dirichlet covariate models will be considered and compared to more traditional methods using log-ratios. Examples and some preliminary results of work with Rafiq Hijazi will be discussed.

----------------------------------------------------------

Title: Risk Assessment in the Office of Homeland Security
Speaker: Dr. James D. Morgeson
Office of Homeland Security
Date: December 6, 2002
Location: Tompkins Hall of Engineering, 203
Time: 5:00 p.m.
------------------------------------------------------------

Darrell Morgeson is the Director of Critical Infrastructure Assessment in the Office of Homeland Security. He is on detail in this assignment from the Institute for Defense Analyses. He has held this position since January 2002. Since being assigned to OHS, Mr. Morgeson has worked on developing an analytical framework for supporting the decision making process for homeland security policy, planning, budgeting, and crisis management decisions.

--------------------------------------------------------------------------------
The contact person is Reza Modarres at Reza@gwu.edu

or 202-994-6359.