Fig. 7 The overall spectra for the three models considered in the text.
For individual points the averaging is over a smaller subset of the possible individual spectra so that the spectra from individual points show some variation. In the low field, high diffusion case, the pixel spectra are all very similar, varying primarily in normalization and break frequency but not in shape---they are simply shifted relative to each other. The intermediate case spectra are also similar. The spectra in the high field, low diffusion case show a much greater variation. This is consistent with the behaviour noted for the images, in which individual points in the high field strength simulation fade at very different rates.