To test the software and develop its capabilities, PET fluoro-18-deoxyglucose (FDG) images were analyzed and displayed for two major drug addiction studies. The first study included 30 subjects the second included 40 subjects both under baseline and drug conditions. Metabolic activity was measured for each subject as the average intensity signal for a given ROI defined manually by a trained medical doctor. ROI locations for the first study included 424 anatomically significant regions while the second study included 120 regions. Correlation matrices were generated for each of these ROI datasets. Three major statistical measures were subsequently generated given the correlation matrix for each study: 1) Principle Component Analysis, 2) ROI cluster analysis and 3) Factor Analysis. Visualization software was compiled using libraries for OpenGL, the Fast Light Toolkit (FLTK) and written in C++. Versions were compiled for Irix 6.4, Windows NT 4.0 and Linux and run on an SGI O2/R1000, a Pentium II class laptop and a Pentium 233 respectively. The visualization interface displayed a 3D MRI volume representative of Talairach coordinates which was sliced as three half planes of axial, coronal and saggital views. The slices were drawn using 2D texture mapping. The user could define the slice location along these three axis by dragging each slice with a mouse button. The surface of the brain was also displayed as a polygonal mesh generated from the Marching Cubes algorithm. ROIs were drawn as spheres but were obscured by the surface depending on the current slice locations. Correlation value was represented for each ROI as a color intensity in relation to a selected “root” ROI. A side window also displayed the current slice as either the Talairach atlas digitized or the MRI volume along with a 2D representation of the ROIs (circles). In addition, all objects could be rotated together with the mouse (trackball interface) to provide a viewpoint from any direction.
BrainMiner allows interactive exploration of both the 120×120 and 424×424 correlational data on many platforms. It is cuurently in use by a number of brain researchers and is being refined almost on an hourly basis.