Reversible Watermarking for Enhancing the Security and Storage of ECG Signal and EPR in DICOM Images

Abstract

Hospital information system and picture archiving and communication system allow transfer of medical images via internet for sharing studies, getting second opinion from radiologist and physician etc. Storage and transmission of Medical Images is crucial as huge volumes are generated every day. Security of medical images is of greater concern for its role in clinical diagnostics. Digital image watermarking is a proven technique that addresses the security and storage issues concerned. The objective is to improve the storage of medical data by applying a reversible watermarking technique. This work presents a semi fragile watermarking technique which hides Electronic patient record and Electrocardiogram Signal (ECG) in the medical image. Embedding is done in discrete wavelet domain followed by singular value decomposition. Recursive dither modulation is used to embed the watermark consisting of EPR, ECG signal, Hash of Region of interest (ROI), vertices of ROI and Doctor Identification code (DIC). Security is provided by encrypting the watermark using Advanced Encryption Standard before embedding. Performance of the scheme is evaluated on DICOM images in different modalities using Peak Signal to noise ratio (PSNR), Mean Structural Similarity Index (MSSIM) and Normalized Cross Correlation (NCC). PSNR and MSSIM values obtained are above 57dB and 0.98 for the proposed technique. NCC value of 0.98 is obtained showing the robustness of the watermark. Thus the proposed work presents a technique for storing EPR and ECG signal in medical image offering better visual quality and security when compared to other techniques of this type.