Multiple embedding using robust watermarks for wireless medical images

Abstract

Within the expanding paradigm of medical imaging and wireless communications there is increasing demand for transmitting diagnostic medical imagery over error-prone wireless communication channels such as those encountered in cellular phone technology. Medical images must be compressed with minimal file size to minimize transmission time and robustly coded to withstand these wireless environments. It has been reinforced through extensive research that the most crucial regions of medical images must not be degraded and compressed by a lossless or near lossless algorithm. This type of area is called the Region of Interest (ROI). Conversely, the Region of Backgrounds (ROB) may be compressed with some loss of information to achieve a higher compression level. This type of hybrid coding scheme is most useful for wireless communication where the 'bit-budget' is devoted to the ROI. This paper also develops a way for this system to operate externally to the Joint Picture Experts Group (JPEG) still image compression standard without the use of hybrid coding. A multiple watermarking technique is developed to verify the integrity of the ROI after transmission and in the situation where there may be incidental degradation that is hard to perceive or unexpected levels of compression that may degrade ROI content beyond an acceptable level. The most useful contribution in this work is assurance of ROI image content integrity after image files are subject to incidental degradation in these environments. This is made possible with extraction of DCT signature coefficients from the ROI and embedding multiply in the ROB. Strong focus is placed on the robustness to JPEG compression and the mobile channel as well as minimizing the image file size while maintaining its integrity with the use of semi-fragile, robust watermarking.