View source for Algorithm:MGH:DTI POIStats

= Path of Interest =

The goal of the POIStats (Path-of-Interest Statistics) algorithm is to calculate the highest probability path between two user-defined seed regions from magnetic resonance diffusion tensor data.  The best path is determined by minimizing the energy of the entire path through randomization of the position of the control points of a spline curve drawn through the data and of the position of the endpoints. The energy of each point in the path is given by the negative natural logarithm of the scaled orientation density function at that point.  The magnitude of the perturbation is time-step dependent – the magnitude is decreased exponentially with time step number.  A set of replicates are used to explore the path parameter space and minimization of the path energy is achieved using a Metropolis algorithm with a constant percentage reduction of the temperature.  The Metropolis algorithm accepts a path if its energy is less than that of the current lowest energy path; otherwise it accepts the path with a probability based on the difference in energy between the current path and the current best path normalized by the current temperature.  Replicates can be exchanged between temperature baths and the exchange is determined also using a Metropolis algorithm.

== Project Weeks ==
*[[Media:2007_Project_Half_Week_PoistatsSlicerItkIntegration.ppt| ITK/Slicer3 Implementation of POIStats, Progress at Project Half Week, Jan 2007 (4-Block PPT)]]
*[[Media:2007_Project_Half_Week_PoistatsImageFormatDartmouth.ppt| Supporting Dartmouth Data for POIStats, Progress at Project Half Week, Jan 2007 (4-Block PPT)]]

== Additional Links ==
* http://www.na-mic.org/Wiki/index.php/Algorithm:MGH
* http://www.na-mic.org/Wiki/index.php/AHM_2006:ProjectsDTIPathOfInterest