A novel watermarking technique for medical image authentication

Medical images are stored in PACS (picture archiving and communication systems) that are accessed over the intranet by radiologists for diagnosis. These days the trend is shifting towards a Web based interface for accessing PACS (image) data. This calls for thorough security measures in the information system of the hospital to ensure integrity of medical image data that is being transferred over the public network. The paper analyses various watermarking techniques with a perspective of applying them to medical images stored on the PACS. It discusses the applicability of invertible watermarking technique for ensuring integrity of medical images. Any modification to the watermarked DICOM (digital imaging and communications in medicine) image can be detected with high reliability using invertible fragile watermarking system. A unique content based digital signature can be generated from the image data (pixel data) which would be embedded inside the image in an imperceptible way without increasing the data size that need to be transferred. This signature can be extracted at the radiologist viewer work stations and used for the authentication while the modified pixel data is restored back to original if the image is found to be authentic. This kind of distortion free (erasable) embedding procedure would ensure image retrieval without any modification to pixel data after the authentication process that caters to the unique need of medical images for diagnosis