Prediction-Based Reversible Watermarking of CT Scan Images for Content Authentication and Copyright Protection

In the application of teleradiology, radiologists located at different geographical locations around the globe, exchange Computed Tomography (CT) scan images along with relevant patient information for diagnosis as well as therapeutic measures. However, when these images are exchanged over public networks like the Internet, two important issues are created: content authentication and copyright protection. In this paper, a novel high capacity reversible watermarking scheme for CT Scan images is presented which is based on the region of interest (ROI) and region of non-interest (RONI) watermarking. The scheme embeds and extracts the secret data into the input CT scan image as well as restores the image to its pristine state at the receiving end. After segmenting the host image into the ROI and RONI regions, the scheme implants a fragile watermark (FW) into the ROI to check the integrity of the ROI and a robust watermark (RW) into the RONI for copyright protection. The novelty of the proposed system is in two fold. First, it takes advantage of the segmentation algorithm to avoid the additional overhead of information about the vertices usually required at the receiving end in order to select the ROI. Secondly, it takes advantage of the prediction-based reversible watermarking to avoid additional overhead of location map, which is usually required for reversibility in most of the reversible medical image watermarking techniques. Experimental results show that the proposed system outperforms medical image watermarking techniques recently reported in the literature in terms of embedding capacity and imperceptibility of watermarked image.