ABSTRACT

The digital CT scan images are exchanged among the medical practitioners for their guidance or discussing in order to achieve the requirements of medical information. This transfer of medical information imposes two main constraints: (i) Content Authentication and (ii) Copyright protection. To address these issues, we have proposed a technique of watermarking for medical images which embeds two watermarks in the CT scan image. The binary pattern, which is embedded in region of interest (ROI) for content authentication and the composite watermark, which is inserted in the region of non-interest (RONI) for copyright protection. Initially CT Scan image is separated in ROI and RONI by segmentation process. The segmented ROI contains some holes which are first filled. The image morphology is then used and closing operation is applied on the resultant image which removes tiny holes and fulfills all the gaps in the contour. Thus, binary mask is obtained which is used to separate ROI from RONI. Before embedding the binary pattern in ROI for data authentication purpose the LSB information of ROI is extracted first and is saved in separate store. Before embedding the composite watermark, pixels in RONI are scrambled for providing the further security. The payload in both ROI and RONI is embedded with simple LSB substitution technique. The extraction procedure is the reverse of embedding process. However some steps of extraction procedure remain same as in embedding procedure. We have used CT scan image database obtained from Radiology department, Ackron University Ohio USA. The results show that proposed algorithm provides better security of medical information by addressing both issues of data authentication and copyright protection.