DIGITAL WATERMARKING OF 3D MEDICAL VISUAL OBJECTS

High resolution digital medical images are stored in DICOM (Digital Imaging and Communications in Medicine) format that requires high storage space in database. Therefore reducing the image size while maintaining diagnostic quality can increase the memory usage efficiency in PACS. In this study, diagnostic regions of interest (ROI) of pelvis radiographs marked by the radiologist are segmented and adaptively compressed by using image processing algorithms. There are three ROIs marked by red, blue and green in every image. ROI contoured by red is defined as the most significant region in the image and compressed by lossless JPEG algorithm. Blue and green regions have less importance than the red region but still contain diagnostic data compared to the rest of the image. Therefore, these regions are compressed by lossy JPEG algorithm with higher quality factor than rest of the image. Non-contoured region is compressed by low quality factor which does not have any diagnostic information about the patient. Several compression ratios are used to determine sufficient quality and appropriate compression level. Compression ratio (CR), peak signal to noise ratio (PSNR), bits per pixel (BPP) and signal to noise ratio (SNR) values are calculated for objective evaluation of image quality. Experimental results show that original images can approximately be compressed six times without losing any diagnostic data. In pelvis radiographs marking multiple regions of interest and adaptive compression of more than one ROI is a new approach. It is believed that this method will improve database management efficiency of PACS while preserving diagnostic image content.

Over the past 15 years Digital Imaging and Communications in Medicine (DICOM) has established itself as the international standard for medical image communication. Most medical imaging equipment uses DICOM network and media services to export image data, thus making this standard highly relevant for medical image processing. The first section of this chapter provides a basic introduction into DICOM with its more than 3,600 pages of technical documentation, followed by a section covering selected advanced topics of special interest for medical image processing. The introductory text familiarizes the reader with the standard’s main concepts such as information objects and DICOM media and network services. The rendering pipeline for image display and the concept of DICOM conformance are also discussed. Specialized DICOM services such as advanced image display services that provide means for storing how an image was viewed (“Softcopy Presentation States”) and how multiple images should be aligned on an output device (“Structured Display” and “Hanging Protocols”) are described. We further describe DICOM’s sophisticated approach (“Structured Reporting”) for storing structured documents such as CAD information, which is then covered in more detail. Finally, the last section provides an insight into a newly developed DICOM service called “Application Hosting”, which introduces a standardized plug-in architecture for image processing, thus permitting users to utilize cross-vendor image processing plug-ins in DICOM applications.

11 - Data Security and Protection for Medical Images

Digital CT Scan images are exchanged among the medical practitioners for consultative purposes or discussing diagnostic and therapeutic measures. This exchange of medical images imposes two main constraints for medical information: (i) the Content Authentication and (ii) Copyright protection. To address these two issues, we have proposed a technique of watermarking for medical images which embeds two watermarks in the CT scan image. The binary pattern is embedded in region of interest (ROI) for content authentication and the composite watermark is embedded in the region of non interest (RONI) for copyright protection. Initially CT Scan image is divided in ROI and RONI by segmentation process. The segmented ROI contains some holes which are first filled. The image morphology is then used and closing operation is applied on the resultant image which eliminates small holes and fills gaps in the contour. Thus binary mask is obtained which is used to separate ROI from RONI. Before embedding the binary pattern in ROI for data authentication purpose, the Least Significant Bit (LSB) information of ROI is extracted first and is saved in separate store. Also, before embedding the composite watermark, pixels in RONI are scrambled for providing the further security. The payload in both ROI and RONI is embedded with simple LSB substitution technique. The extraction procedure is the reverse of embedding process. However few steps of extraction procedure are same as embedding procedure. We have used CT scan image database obtained from Radiology Department, Ackron University Ohio USA. The experimental results show that the proposed algorithm provides better security of medical information during transmission by addressing both issues of data authentication and copyright protection.KeywordsMedical image watermarkingLeast significant bit techniqueImage morphologyImage segmentationData authenticationCopyright protectionRegion of interest (ROI)Region of non interest (RONI)

We present a new scheme for digital watermarking and secure copyright protection of digital images using non-negative matrix factorization and singular value de-composition approaches. The proposed method improves the performance of the data embedding system effectively, and it is resistant to a variety of intentional attacks and normal visual processes. The experimental results clearly illustrate the much improved performance of the proposed watermarking methodology in comparison with existing techniques.

This paper presents an objective MPEG-2 video quality measurement method based on fragile digital image watermarking. Based on the DWT-based watermarking scheme, this paper presents a fragile digital video watermarking scheme that can work as an automatic quality monitoring system. We embed watermark in the DWT domain of the I-frames of an original video, and the DWT coefficients for embedding are carefully selected so that the degradation of the watermark can reflect the degradation of the video quality. This scheme can track the change of the PSNR value and the Watson JND value. The Watson perceptual model is taken into account to weight the quality measurement according to the human visual system. The evaluations demonstrate the effectiveness of the proposed scheme against MPEG-2 compression and noise pollution

4 - Digital Imaging and Communications in Medicine

The aim of this work is to report our experience in contrast-enhanced magnetic resonance (MR) automatic analysis. This technique is usually used in our practice for the diagnosis of breast cancer. Study execution and semiautomatic data analysis require at least 1 hour of the radiologist. So, we decided to develop a tool that aids the radiologist in locating the regions of neoplastic angiogenesis and quickly plotting the enhancement curves. This is not a computer-aided diagnostic tool; of course, the curves are interpreting directly by the radiologist. We used a programmable graphical and calculus environment (Matlab, The Mathworks, Natick, MA) to develop a tool that interfaces directly with our picture archiving and communication system (PACS) via Digital Imaging and Communications in Medicine (DICOM), receives images, performs images subtraction, and shows some possible regions of interest (ROIs), each with an enhancement curve. The radiologist can also select other ROIs. The software shows a good performance (sensitivity, 100%). A low specificity (25%) is acceptable because the software allows the radiologist to save some time during each study.

In the past, many of the medical information produced by hospitals (such as medical records or imagery) have had trouble being transferred from place to place; the main reason for this being the fference in the many formats that are used by each and every brand. With the development of the ages, the need for exchange of medical information has increased. Thus, imagery medical information uses the DICOM (Digital Image and Communication in Medicine) standard. The goal of this study is to establish a reformatting interface using the DICOM file management system to transfer paper-based records into DICOM format. Once in DICOM format, these records can then be sent to the DICOM server so that they may be accessed via the DICOM Viewer cross hospitals. This study also aims to transform text information into DICOM format so that files may be exchanged with other hospitals through DICOM’s secure system so that medical records can be incorporated into hospitals’ image systems to form a congregation of hospital resources.

Fragile watermarking is designed to protect content integrity of digital data, meaning to detect any change in the content as well as localize areas that have been changed. In this paper, we propose a fragile watermarking scheme, which embeds dual watermarks (one is naturally fragile and the other is actually robust) in JPEG-2000 compressed images with ROI (region of interest) selection. In this scheme, the fragile watermark is embedded in ROI coefficients at the first decomposition layer, while the robust watermark embedded in ROB (region of backgrounds) coefficients at the third decomposition layer. The combinational working of them is not only capable of detecting malicious changes precisely and flexibly but also estimating the degree of alteration to discriminate intended attacks from unintended ones (e.g., such normal image processing as compression, low-pass filtering, sharpening, etc). Experiments show that our functionally fragile watermarking scheme is scalable in view of detecting attack's intension as well as accuracy in localizing the tampered areas.

A number of clinical specialties routinely use images in treating patients, for example ophthalmology, dentistry, cardiology, endoscopy, and surgery. These images are captured by a variety of commercial digital image acquisition systems. The US Department of Veterans Affairs has been working for several years on advancing the use of the Digital Imaging and Communications in Medicine (DICOM) Standard in these clinical specialties. This is an effort that has involved several facets: (1) working with the vendors to ensure that they satisfy existing DICOM requirements, (2) developing interface software to the VistA hospital information system (HIS), (3) field testing DICOM systems, (4) deploying these DICOM interfaces nation-wide to all VA medical centers, (5) working with the healthcare providers using the system, and (6) participating in the DICOM working groups to improve the standard. The VA is now beginning to develop clinical applications that make use of the DICOM interfaces in the clinical specialties. The first of these will be in ophthalmology to remotely screen patients for diabetic retinopathy.

Security is one of the important characteristics while transmitting the data particularly medical images and patient information over cyberspace without any loss of information. In the proposed method LWT, DCT and SHA-256 hashing techniques are used to provide security to the patient data and to detect tampers in ROI of the medical images. In this paper, medical image is segmented into three regions, region of interest (ROI), region of non interest (RONI) and BORDER regions. ROI is an area that has an important impact on diagnosis, whereas RONI has less or no significance in diagnosis. This paper proposed ROI based tamper detection that embeds hash value of ROI into RONI for authentication and also embed the patient information into RONI for providing security. The experimental results of the proposed method on various medical image databases proved to identify the tampers in medical images. Compared with the existing technique, the proposed method offered high Peak Signal to Noise Ratio (PSNR) approximately 59db for watermarked medical images.

Over the last decade, the specification of a standard format for digital (medical) images has received a great deal of attention. The yearly meetings of the ACC (95 and 96) and ESC (95) were used to promote the DICOM (Digital Imaging and Communications in Medicine) format, the result of a joined effort by the ACC, ACR, NEMA and ESC. At the moment, one of the most interesting questions is: how will the introduction of the DICOM standard affect the daily practice in the catheterization laboratory (cath lab) in the near future?

Digital Imaging and Communications in Medicine (DICOM) has standardized structure reports (SR) to fully support conventional free-text reports, images, and structured information, thus enhancing the precision, clarity, and value of clinical documents. The SR standard provides the capacity to link key images, region of interest within images, and measurement as result of Computer-Aided Diagnosis (CAD) process. Accordingly, SR bridges the traditional gap between CAD and PACS. Last year we presented an open and universal CAD-PACS integration toolkit that could seamlessly integrate standalone Computer-Aided Diagnosis (CAD) workstations with a clinical PACS based on Structure Report (SR) and IHE Post-Processing. In this presentation, we illustrate the workflow and procedures of CAD-PACS integration by showing examples from some available CAD applications using the toolkit. This proper integration will improve usage of the CAD applications for more accurate analysis and faster assessment in the clinical decisionmaking process.

In medical devices, nonconformance with Digital Imaging and Communications in Medicine (DICOM) standard is a serious risk. DICOM nonconformance radiology devices could cause undetected image loss, increasing examination time, and costs in health centers and could even result in the wrong patient treatment. However, there is a rich literature on medical standards that identify the best practices for producing safe and effective medical software. However, these standards do not expressly provide tools to deal with all the relevant DICOM compatibility issues in a specific case. This study aims to introduce a systematic software development workflow that complies with medical standards and ensures DICOM conformance of a new or upgraded radiology software project. In this approach, DICOM conformance gets the highest priority, and the whole software project is organized around it. Software requirement analysis, risk evaluation, and test management tasks are arranged systematically to make the final device DICOM conformant. This conceptual framework was developed during the R&D work towards a novel radiography device, and it could be employed as a roadmap in other medical imaging software projects. The proposed methodology controls the DICOM compatibility risk of the final software, and its systematic evaluation complied with medical standards.