Blind Medical Image Watermarking Method Using Combined NSCT/2D-DCT Domains

This paper presents a novel blind watermarking framework that combines Non-Subsampled Contourlet Transform (NSCT) and 2D Discrete Cosine Transform (DCT) domains. The proposed method embeds the watermark’s data within low-frequency coefficients of sub-vectors extracted from a concatenated NSCT/2D-DCT transforms processing. The embedding procedure involves simple differential processing which ensures a straightforward watermark extraction. Extensive testing across medical imaging modalities (X-ray, CT, MRI, ultrasound) confirmed strong imperceptibility and robustness against attacks like JPEG compression, noise, filtering, and geometric manipulations. Compared to contemporary techniques, our NSCT/2D-DCT method shows stronger robustness against attacks without compromising diagnostic quality, proving its viability for medical image authentication in clinical settings.