Medical Image Watermarking
Authors: B. Planitz
Date: July 2006
Abstract:
Increasingly widespread communication of medical images across multiple user systems raises concerns for image security, for which digital image watermarking offers one solution. While digital image watermarking methods have been widely studied, much less attention has been paid to their application in medical imaging situations, due partially to speculations on loss in viewer performance due to degradation of image information. Loss of image quality occurs when medical images are subject to image manipulations which change pixel intensity values. Such losses could lead to incorrect clinical outcomes if they influence image analysis computations, or affect the perception of viewers reading the images. Image quality degradation is thus a necessary consideration when applying watermarks to medical images for security purposes. Here we report on the results of experiments to establish the extent of image quality degradation which occurs for typical application of various watermark, across two important medical imaging modalities: MR and CT. The watermarking methods applied range from very fragile (Least Significant Bit watermarking) to more robust (Code-Division Multiple Access watermarking). Fragility describes the ease of removal, either intentionally or unintentionally, of a watermark from the medical image data in which it was embedded. We report on the visual degradation caused by watermarking MR and CT images using watermarking methods of varying fragility, and examine whether greater watermark robustness results greater visual degradation.
© 2006 CSIRO
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