PACS Model Based On Digital Watermarking And Its Key Algorithms

With the development of information technology, digital information management system is playing a more and more important role in the modern medical system, and picture archiving and communication system (PACS) based on digital medical imaging and communication (DICOM) standards has become a research hotspot. With wide application of PACS, the information security problems are being gradually exposed recently. Compared to traditional film image, if the medical image as diagnostic materials encounter anomalies, such as Counterfeiting, tampering and information disorder, it would not only be used as strong evidence of medical malpractice cases, but also delay the best time for diagnosis and treatment. When encryption and access control has been difficult to meet the safety requirements of PACS, the new information security technology measures are imminent. At present, the digital watermarking technology for medical image is still in the exploratory stage, and research achievements are very limited at home and abroad. From the point of the information security, this paper designs a new PACS model based on digital watermarking and two medical image digital watermarking algorithms through analyzing security requirements of PACS and characteristics of medical image; Because of specificity lesion area of medical image, this paper proposed to embed watermark in the non- region of interest (NROI).The main research contents of this dissertation are recapitulated as follows:(1) Summarize the literature at home and abroad, analyze information security deficiencies of existing PACS model, and then design a novel PACS model based on digital watermarking.(2) On basic of analyzing characteristics of medical image, it is pointed out that "over-flowing" of "light region" and "under-flowing" of "dark region" may happen among existing watermarking algorithms for medical image; In order to ensure the authenticity and integrity of lesion area, it is presented to embed watermark into the NROI of medical image. (3) In order to enhance the robustness of algorithms, especially the capable of anti-compression attacks, and realize the authenticity of certification, this paper designs a new detrimental digital watermarking based on block-mean of wavelet domain and NROI. Multi-resolution of wavelet transform provides a good way for protecting the region of interest of images, and introduction of block-mean approach a good scheme to enhance the anti-attack capability. The experiment results proved that this algorithm has good effectiveness and superiority.(4) In order to achieve the integrity authentication of medical image, the paper designs a new invertible watermarking scheme based on margin-expansion and NROI. This fragile watermarking algorithm is simple, and has a good capacity, and can realize tamper localization effectively. Experimental results show that this algorithm has good transparency and tamper positioning function.(5) On basic of two novel watermarking algorithms in this paper, study the operation processes of digital watermarking server and watermark processing module, and then discuss the possibility of image retrieval based on watermarking.