Quick image deface

1. Create ROI encompassing face area (nose, eyes) but excluding as much of brain as feasible.
2. Use CropVolume module to crop based on the ROI.
3. Use Editor to select ALL intensity values creating labelmap of the whole ROI
4. Use MaskImage to grab just that ROI area as a new image
5. Subtract new image from original image.

The convoluted way is necessary because CropVolume rescales intensity; else could just subtract the cropped image.