De-facing a Head Scan

Load the image to be de-faced into the Input image selection panel:

Panel for selecting the input image

Defacing involves reducing the intensity of pixel values in the region of the face towards zero, so that the subject becomes unrecognisable by their facial features. Selection of the face region is done by registering the scan to a template. Registration will be most effective if the correct template is used, and Jim has three templates to choose from:

  • T1-weighted
  • T2-weighted
  • Proton-density (PD) weighted

Select the image contrast that is closest to that of the input image in the Image Weighting Type panel:

Panel to select the type of image weighting

The result of the registration is an image of the probability that a voxel is non-face. The input image is masked by this probability map at a particular probability threshold, which is set using the Face threshold panel:

Panel to set the face probability threshold

Setting a lower threshold will result in more of the face region being removed.

Now click on the Button to do the de-facing button to deface the input image. The defaced image will be automatically saved with a file name taken from the input image, with the suffix "_defaced" appended.