Figure 4.
Density plots showing change between co-registered control and experimental scans of stationary volunteer at 3T using MEMPRAGE (top row), T2SPACE (middle row), or T2SPACE FLAIR (bottom row). For each plot, volumes acquired in an experimental condition (one of: no vNavs; with vNavs; with vNavs and motion correction; with vNavs, motion correction, and reacquisition) were co-registered with a control volume produced by averaging three navigator-free acquisitions. Pairing each experimental volume with the control volume gave a set of voxel intensity-pairs describing change between control and experimental sequences; masking each volume for grey and white matter selected the voxels of interest that are plotted. The x-axis in all plots represents mean intensity in the control (without navigators) volume. The y-axis in each plot represents intensity in the experimental condition of interest. Color shows the relative number of WM and GM voxels at a given location in 2D space (color scale shown in bottom right); white regions had no voxels. Dashed grey lines represent 1.0 (i.e., no change in voxel intensity), +10%, +20%, −10%, −20%. Solid red line shows the mean ratio between white matter voxel intensities in the experimental and control conditions. Solid blue line shows the same for grey matter. The slope of these two lines are written in each plot.