Digital medical images are very easy to be modified for illegal purposes. For example, microcalcification in mammography is an important diagnostic clue, and it can be wiped off intentionally for insurance purposes or added intentionally into a normal mammography. In this paper, we proposed two methods to tamper detection and recovery for a medical image. A 1024 Â 1024 x-ray mammogram was chosen to test the ability of tamper detection and recovery. At first, a medical image is divided into several blocks. For each block, an adaptive robust digital watermarking method combined with the modulo operation is used to hide both the authentication message and the recovery information. In the first method, each block is embedded with the authentication message and the recovery information of other blocks. Because the recovered block is too small and excessively compressed, the concept of region of interest (ROI) is introduced into the second method. If there are no tampered blocks, the original image can be obtained with only the stego image. When the ROI, such as microcalcification in mammography, is tampered with, an approximate image will be obtained from other blocks. From the experimental results, the proposed near-lossless method is proven to effectively detect a tampered medical image and recover the original ROI image. In this study, an adaptive robust digital watermarking method combined with the operation of modulo 256 was chosen to achieve information hiding and image authentication. With the proposal method, any random changes on the stego image will be detected in high probability.
Interventions to help family caregivers manage the changes in persons with MCI can reduce caregiver burden. Our findings could provide a knowledge base for use by healthcare providers to develop and implement strategies to reduce caregiver burden for family caregivers of persons with MCI.
Silicon positive-intrinsic-negative (p-i-n) diodes have been used in plasma diagnostics by the Los Alamos and Lawrence Livermore National Laboratories (LANL and LLNL) since the early seventies. Since the response bandwidth of these detectors is relatively poor (typically, 5-ns FWHM for 1-cm2 sensitive area and 25O-m depletion depth), they are too slow for high-speed applications. GaAs photoconductive detectors (PCD) have been developed since the early eighties at LANL and later at LLNL, and can be tailored by judicious neutron damage to provide the required high-speed bandwidth. Unfortunately, for surface absorbed or non-penetrating radiation, we have discovered that the PCD sensitivity is not flat across its gap, where the incident radiation is perpendicular to the bias electric field. This response non-uniformity can lead to erroneous measurements in cases where the radiation is spatially varying. To overcome this problem, we re-oriented the GaAs chip to allow the radiation to be incident through the electrode and parallel to the bias electric field. Then to increase bandwidth, we doped the GaAs crystal with chromium to create trapping sites and provide large resistivity ( iO (i-cm), thus creating a semi-insulator detector (SID). We will present and discuss the merits of the SID versus PCD and p-i-n diode by showing pulse response data of each detector characterized with 16-MeV endpoint gamma and electron radiation created by the EG&G/EM linear accelerator (Linac) and 5-to 16.5-MeV proton radiation produced by the LLNL Tandem Van de Graaff (TVDG). Application of the SID in Compton electron spectrometry will also be discussed.
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