Starting the visualizer
The visualizer is started by clicking on an icon the looks like an eye. This icon can be found both on the 'Phantom scans' page and the list of studies associated with a post.
The 3D view in the visualizer presents an image of the phantom in scanner coordinates. The origin of the R-A-S coordinate system shown is at the isocenter of the scanner, and any displacement or rotation of the phantom relative to this coordinate system will show up in the image. The lower and upper thresholds that appear in the sidebar are the maximum and minimum distortions, in mm, of the 1cm diameter sphere positions.
The basic representation of the spheres is in grayscale. Spheres with distortions closest to and below the lower threshold are blacker and spheres with distortions closer to and above the upper threshold are whiter. As the lower threshold is raised, spheres with smaller distortions will darken. As the upper threshold is lowered spheres with larger distortions will brighten.
The 'Remove below /above threshold' checkboxes don't actually remove spheres from the image, but change their color in a binary fashion. When the 'Remove below threshold' box is checked, spheres with distortions below the lower threshold appear in green. When the 'Remove above threshold' checkbox is checked, spheres with distortions above the upper threshold appear in red. The thresholds can be changed by using the sliders or typing values in the boxes. Display of the larger spheres can be toggled on and off using the 'Large spheres' checkbox.
Scatter plots display sphere-by-sphere distortions in each coordinate direction, R-A-S, as a function of sphere position. The sphere positions are in scanner coordinates, relative to the isocenter, in mm. The distortions are in mm also. The vertical axis displays sphere position in each independent coordinate direction. The horizontal axis displays distortion.
For example, the first graph in the upper left hand corner shows Left-Right distortion as a function of Left-Right position. Each dot in the graph represents one sphere. The farther a dot is above the horizontal axis, the farther right the sphere is in the scanner. The farther a dot is below the horizontal axis the farther left the sphere is in the scanner. The farther a dot is to the right of the vertical axis, the greater the distortion of the sphere to the right. The farther to the left of the vertical axis a dot is, the greater the distortion of the sphere is to the left. Each of the nine plots can be analyzed in a similar way. The thresholding and control panel work as in the 3D view.