POSSUM

Overview

POSSUM is a simulation project that produces realistic simulated images and FMRI time series given a gradient echo pulse sequence, a segmented object with known tissue parameters, and a motion sequence. The way the Bloch equations are solved, by tracking and updating the magnetisation vector through time for every object voxel, allows the changes that occur during the acquisition of one TR to be modelled and then carried through to the acquisition of the next TR, making it possible to simulate spin history effects, motion during the readout periods and interactions that these have with Bo inhomogeneities.

The simulator has the capability to turn on or off various subject- and scanner- related effects, which is not possible in real scanning and therefore has a wide range of applications. These applications include the simulation and removal of various artifacts, both in MRI and FMRI. Furthermore, by generating the "ground truth", the FMRI simulator can be used for evaluation and validation of software tools for FMRI analysis methods (e.g. motion correction, registration, statistical analysis of images, etc.).

Papers

1. I Drobnjak, D Gavaghan, E Süli, J Pitt-Francis and M Jenkinson.
   Development of an FMRI Simulator for Modelling Realistic Rigid-Body Motion Artifacts
   Magnetic Resonance in Medicine, 2006, 56(2), 364-380, August 2006.
   
2. I Drobnjak and M Jenkinson.
   FMRI simulation and its application in modelling the interaction of motion and B0-inhomogeneities
   In Proceedings of the 10th International conference for Fuctional Mapping of the Human Brain, Budapest (Hungary), 2004.

For a few examples of the applications of POSSUM see a slideshow. For all the examples presented here the object model was digital brain phantom, developed for the BrainWeb simulator.

Software

POSSUM was released as part of the FSL software package in 2007.