A Study of Block-Based Medical Image Watermarking Using a Perceptual Similarity Metric

Medical image watermarking has been proposed as an appropriate method for enhancing data security, content verification and numerical image fidelity. Due to the sensitive nature of the data, medical image watermarking requires that any additional information that is stored within an image must not affect the perceptual integrity of the image. In typical approaches, additional information is generally hidden in the entire image, or in the background regions of an image (so as not to affect the medical data). This paper presents a novel model whereby medical image regions are watermarked differently so that perceptual degradation due to watermarking is limited. The model partitions images into regions and characterises each region according to some feature(s). Each region is then watermarked with a particular watermark method and payload capacity such that perceptual degradation is limited. This paper presents the model in conceptual form and then uses one instance of it to demonstrate how it would be used in practise. Results on MR and CT images demonstrate that less visually sensitive areas on images can be watermarked using more robust techniques and more sensitive areas can be watermarked using lighter or no embedding.