Reversible Region of Non-Interest (RONI) Watermarking for Authentication   of DICOM Images
  This paper introduces current watermarking techniques available from the literatures. Requirements for medical watermarking will be discussed. We then propose a watermarking scheme that can recover the original image from the watermarked one. The purpose is to verify the integrity and authenticity of DICOM images. We used ultrasound (US) images in our experiment. SHA-256 of the whole image is embedded in the least significant bits of the RONI (Region of Non-Interest). If the image has not been altered, the watermark will be extracted and the original image will be recovered. SHA-256 of the recovered image will be compared with the extracted watermark for authentication. 
Jasni Mohamad Zain, Malcolm Clarke
cs.CR