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De-identification of Facial Images by Use of Composites

This paper discusses the use of composites to de-identify facial images and examines their realism in appearance. The study found that subjects did not recognize composite faces unless they were primed to their presence.

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De-identification of Facial Images by Use of Composites

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  1. De-identification of Facial Images by Use of Composites *Mark E. Engelstad MD, DDS, MHI Oregon Health & Science University Dept of Oral and Maxillofacial Surgery Dept Medical Informatics & Clinical Epidemiology Genevieve B. Melton, MD, MA University of Minnesota Institute for Health Informatics Department of Surgery Medbiquitous Annual Symposium, Baltimore MD May 10, 2011

  2. Pre-op De-identification + = Original injury Periorbital area

  3. Post-op De-identification + =

  4. The Questions: Do composites de-identify faces? Even those that are well-known to an observer? Are facial composites realistic in appearance?

  5. Figure 2: A comparison of two techniques for facial image de-identification. The middle image (B) is the original image. (A) black boxes only. (C) a facial composite, altered in the area of eyes and eyebrows only.

  6. This is a PRE-operative patient This is a POST-operative patient I recognize this patient

  7. Faces Me Subjects viewed the composite faces twice—first unaware that the faces were composites, and then primed to the presence of composites.

  8. Subjects viewed 20 composite faces

  9. Test Face Test Face • Subjects viewed 20 composite faces • 10/20 had a third of a familiar face (test face)

  10. Results No subjects identified test faces unless they were primed to their presence (* p < 0.001).

  11. Table 2: Identification of Test faces after priming--compared by facial region. Percentages of subjects who correctly identified a familiar face when regions of that face were visible in the composite image are shown (true positives). In Test Face B, a significant difference (* p<0.01) in identification rate existed between Upper Face and Midface. Test Face A Midface was recognized correctly more often than Test Face B Midface (†p<0.01)

  12. Black Boxes Original Composite, Eyes only

  13. Making a Facial Composite 1: Photoshop 2: A Library

  14. Step 2,3: Remove Background, Change laterality

  15. 4: Size all images to a standard (800 x1200) 5: Align the facial features 6: Create a Layer Mask 7: Use a Brush to reveal deeper layer 8: Blend the edges between the two layers 9: Correct Color Tones

  16. Show Simulation/ Example

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