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At least 1,711 records · Page 95Linked to original sources
PubMed2004

Assessing diabetic retinopathy using two-field digital photography and the influence of JPEG-compression.

OBJECTIVE: To study the effectiveness of two digital 50 degree photographic fields per eye, stored compressed or integrally, in the grading of diabetic retinopathy, in comparison to 35-mm colour slides. SUBJECTS AND METHODS: Two-field digital non-stereoscopic retinal photographs and two-field 35-mm retinal photographs were made at the same time from patients visiting a diabetic retinopathy outpatient clinic. The digital images were stored integrally (TIFF-file) and in a compressed way (JPEG-file). Two ophthalmologists assessed the photographs in a masked fashion. The results were compared. The sensitivity and specificity for the detection of vision-threatening diabetic retinopathy were calculated, using only the grading of the most affected eye. The differences between the retinopathy gradings of the two kinds of photographs were analysed. RESULTS: The agreement for the grading of DR compared to slides was good, both for the compressed and for the integrally stored images (kappa 0.63-0.68). The sensitivity for the detection of vision-threatening diabetic retinopathy using the JPEG-stored images was 0.72-0.74, specificity 0.93-0.98. The sensitivity for vision-threatening retinopathy detection using the integrally stored images was 0.86-0.92, specificity 0.93. CONCLUSIONS: Two-field digital retinal photography is effective in diabetic retinopathy grading and it can replace 35-mm retinal photography. Vision-threatening retinopathy can be detected on the images with reasonable to good sensitivity and specificity. An experienced grader should assess the images. The compression of the digital images seems to have some adverse effect on the detection of diabetic retinopathy.

Data Compression↗
PubMed1994

Real-time multichannel abdominal fetal ECG monitor using digital signal coprocessor.

A real-time multichannel fetal ECG monitor based on a personal computer (PC) and a MOTOROLA DSP56001 Digital Signal CoProcessor (DSP) is introduced. The DSP board is plugged into the PC, which functions as a HOST computer. An analog 8 Leads Interface and Analog to Digital circuits module is connected to the DSP through a synchronous, optical-isolated communication channel. The fetal ECG detection is based on a cross-correlation technique. An averaged maternal ECG waveform is generated using a cross-correlation alignment procedure and a user-defined template. The fetal ECG signals present in the maternal waveform is suppressed during the averaging procedure, since both are uncorrelated. The average maternal ECG waveform is then subtracted from the abdominal real time signals, and maternal-free fetal ECGs signals are obtained, including fetal QRS complexes that coincide with maternal ones. Using the abdominal ECGs signals after subtraction, an averaged fetal waveform is generated. The maternal and the fetal heart rate are calculated during the process. The algorithm described above can be performed in real time on up to eight abdominal ECG traces by the DSP, and the desired results are passed to the HOST PC, to be stored and displayed. Electrodes positioning procedures for detecting the fetal QRS complexes with the best signal to noise ratio are not needed. Using the multichannel system, the user can select the best channel for fetal QRS detection, and accurate results for the heart rate signal are obtained. Averaged fetal waveforms are obtained from all the leads.

Abdomen↗
PubMed2006

Internet communities for recruitment of cancer patients into an Internet survey: a discussion paper.

The purpose of this paper is to provide future directions for the usage of Internet communities (ICs) for recruitment of research participants based on issues raised in an Internet survey among 132 cancer patients. About 317 general and 233 ethnic-specific Internet Cancer Support Groups and 1588 ethnic-specific ICs were contacted to recruit cancer patients. Research staff recorded issues and wrote memos during the recruitment process. The written memos and records were later analyzed using content analysis. The issues included: (a) difficulty in identifying appropriate ICs and potential participants, (b) meta-tags, (c) dominant white and women groups, (d) dynamics inside ICs, (e) difficulty in trust building, and (f) potential selection bias. The findings suggest that researchers thoroughly review the ICs' information, be recognizant of potential gender and ethnic issues and current trends in Internet interaction, and consider potential selection bias.

Attitude to Computers↗
PubMed2005

MedView: an instrument for clinical research and education in oral medicine.

The etiology for many of the mucosal lesions we encounter in clinical practice is frequently uncertain or unknown and there is reason to believe that multicausality plays an important role. To detect multicausal relationships, the analysis must include multiple variables and large amounts of data. A traditional retrospective analysis is often based on a limited number of variables and frequently entails methodological errors where vital information may be missing. Prospective studies may be hampered by the fact that the prevalences of many conditions are relatively low. The search for new knowledge in oral medicine should therefore be facilitated by prospective use of formalized information gathered in multicenter studies. MedView is a computer program that is based on formalized input and registration of all clinical information. The output applications are focused on visualization and statistical analysis. MedView is aimed at clinical research and is well suited for multicenter studies. It also contains applications for education and distant consultations.

Causality↗
PubMed1998

Case-based reasoning for medical decision support tasks: the Inreca approach.

We describe an approach for developing knowledge-based medical decision support systems based on the new technology of case-based reasoning. This work is based on the results of the Inreca European project and preliminary results from the Inreca + project which mainly deals with medical applications. One goal was to start from case-based reasoning technology for technical diagnosis and 'scale-up' to more general non-technical decision support tasks as typically given in medical domains. Inreca technology has been used to build an initial decision support system at the Russian Toxicology Information and Advisory Center in Moscow for diagnosing poison cases caused by psychotropes.

Artificial Intelligence↗
PubMedDate not supplied

Computerized brain atlases as decision support systems: a methodological approach.

This paper deals with the development of computerized brain atlases addressing both research and clinical needs. The authors analyze in detail the potential of these systems and discuss the capabilities and limitations of the digital atlases currently being developed around the world. The authors propose to reconsider the concept of a brain atlas, regarding both its content, and the way it has to be used and managed in order to set up more effective cooperation between the user and the system. Particular emphasis is placed on extensibility and reuse issues. which are critical in this rapidly evolving field. These orientations result from both the authors' experience and the analysis of current trends in the field of neuroimaging. The general methodology is illustrated with examples related to computer aided surgical planning.

Artificial Intelligence↗
PubMedDate not supplied

A family of ring system-based structural fragments for use in structure-activity studies: database mining and recursive partitioning.

In earlier work from our laboratory, we have described the use of the ring system and ring scaffold as descriptors. We showed that these descriptors could be used for fast compound clustering, novelty determination, compound acquisition, and combinatorial library design. Here we extend the concept to a whole family of structural descriptors with the ring system as the centerpiece. We show how this simple idea can be used to build powerful search tools for mining chemical databases in useful ways. We have also built recursive partition trees using these fragments as descriptors. We will discuss how these trees can help in analyzing complex structure-activity data.

Drug Design↗
PubMed2002

Injury surveillance in the ED: design, implementation, and analysis.

Comprehensive, population-based surveillance for nonfatal injuries requires uniform methods for data collection from multiple hospitals. To show issues related to design and implementation of multihospital, emergency department (ED), injury surveillance, a city-wide system in the United States is discussed. From October 1, 1995 to September 30, 1996 all injury-related ED visits among District of Columbia residents <3 years of age were ascertained at the 10 hospitals where city children routinely sought care. Information was abstracted from 2,938 injury-related, ED visits (132.7 visits/1,000 person-years). Based on this experience, suggestions to facilitate design of multihospital, injury surveillance in other locations are offered. Importantly, injury-related visits were reliably ascertained from ED logs, and for most variables, a systematic sample of injury-related visits was representative of the total injured population. However, there is a need for more complete documentation of circumstances surrounding injuries and for standardization of data elements on ED logs and treatment records.

Child, Preschool↗
PubMed2005

An update on master's degrees in medical education.

Planning and implementing educational programs in medicine optimally requires a background in educational theory and practice. An avenue of training open to such practitioners is a master's degree in medical education. A single 1998 report lists the programs known at that time and information about them remains scarce. The authors have re-examined all current programs offering master's degrees in medical or health sciences education in the English-speaking world, including the Netherlands. The authors contacted the programs identified in the 1998 report to establish how many were still in operation. The search was extended using Pubmed and other search engines. A further verification targeted a selected sample of 10 prominent US medical schools. Twenty-one currently operating programs were identified: six in the US, eight in the UK, three in Canada, three in Australia and one in Holland. Seven of nine original master's programs were still in existence. URLs, website and other logistical information about each program are tabled. A master's degree in medical or health sciences education is the most specific method for medical faculty to obtain a credentialed grounding in educational theory and practice. The authors provide up-to-date contact information for current programs and summarize other related essential logistical data.

Curriculum↗
PubMed2002

Microarray data warehouse allowing for inclusion of experiment annotations in statistical analysis.

MOTIVATION: Microarray technology provides access to expression levels of thousands of genes at once, producing large amounts of data. These datasets are valuable only if they are annotated by sufficiently detailed experiment descriptions. However, in many databases a substantial number of these annotations is in free-text format and not readily accessible to computer-aided analysis. RESULTS: The Multi-Conditional Hybridization Intensity Processing System (M-CHIPS), a data warehousing concept, focuses on providing both structure and algorithms suitable for statistical analysis of a microarray database's entire contents including the experiment annotations. It addresses the rapid growth of the amount of hybridization data, more detailed experimental descriptions, and new kinds of experiments in the future. We have developed a storage concept, a particular instance of which is an organism-specific database. Although these databases may contain different ontologies of experiment annotations, they share the same structure and therefore can be accessed by the very same statistical algorithms. Experiment ontologies have not yet reached their final shape, and standards are reduced to minimal conventions that do not yet warrant extensive description. An ontology-independent structure enables updates of annotation hierarchies during normal database operation without altering the structure. AVAILABILITY AND SUPPLEMENTARY INFORMATION: http://www.dkfz.de/tbi/services/mchips

Algorithms↗
PubMed2005

An optimal nonlinear extension of linear filters based on distributed arithmetic.

Distributed arithmetic (DA)-based implementation of linear filters relies on the linear nature of this operation and has been suggested as a multiplication free solution. In this work, we introduce a nonlinear extension of linear filters optimizing under mean-square error criterion the memory function [(MF) multivariate Boolean function with not only binary output] which is in the core of DA based implementation. Such an extension will improve the filtering of noise which may contain non-Gaussian components without increasing the complexity of implementation. Experiments on real images have shown the superiority of the proposed filters over the optimal linear filters. Different versions of these filters are also considered for an impulsive noise removal, faster processing, and filtering using large input data windows.

Algorithms↗
PubMed2005

Transform and embedded coding techniques for maximum efficiency and random accessibility in 3-D scalable compression.

This study investigates random accessibility and efficiency enhancements in highly scalable video and volumetric compression. With the advent of interactive multimedia technology, random accessibility has emerged as an increasingly important consideration in the design and optimization process. In this paper, we assess the impact that the transform, embedded coding components, and code-block configurations have on the compression efficiency and accessibility of a scalable codestream. We develop performance bounds on techniques which exploit temporal redundancy within the confines of a feed-forward compression system. We also examine their random access properties to argue the significance of motion-adaptive subband transforms. When information-theoretic measures are used to determine the potential benefits of three-dimensional (3-D) context coding, we find that most of the coding gain is attributed to code-block extension, rather than interslice context modeling itself. To gain further insight into the tradeoffs that the coding part has to offer, we run a series of simulations to determine code-block partitioning strategies which maximize reconstruction quality and space-time localization. The LIMAT framework and EBCOT coding paradigm have laid a solid foundation for further progress in the development of highly scalable 3-D compression systems.

Algorithms↗
PubMed2006

Subsampling models and anti-alias filters for 3-D automultiscopic displays.

A new type of three-dimensional (3-D) display recently introduced on the market holds great promise for the future of 3-D visualization, communication, and entertainment. This so-called automultiscopic display can deliver multiple views without glasses, thus allowing a limited "look-around" (correct motion-parallax). Central to this technology is the process of multiplexing several views into a single viewable image. This multiplexing is a complex process involving irregular subsampling of the original views. If not preceded by low-pass filtering, it results in aliasing that leads to texture as well as depth distortions. In order to eliminate this aliasing, we propose to model the multiplexing process with lattices, find their parameters and then design optimal anti-alias filters. To this effect, we use multidimensional sampling theory and basic optimization tools. We derive optimal anti-alias filters for a specific automultiscopic monitor using three models: the orthogonal lattice, the nonorthogonal lattice, and the union of shifted lattices. In the first case, the resulting separable low-pass filter offers significant aliasing reduction that is further improved by hexagonal-passband low-pass filter for the nonorthogonal lattice model. A more accurate model is obtained using union of shifted lattices, but due to the complex nature of repeated spectra, practical filters designed in this case offer no additional improvement. We also describe a practical method to design finite-precision, low-complexity filters that can be implemented using modern graphics cards.

Algorithms↗
PubMed2006

An efficient content-adaptive motion-compensated 3-D DWT with enhanced spatial and temporal scalability.

We propose a novel, content adaptive method for motion-compensated three-dimensional wavelet transformation (MC 3-D DWT) of video. The proposed method overcomes problems of ghosting and nonaligned aliasing artifacts which can arise in regions of motion model failure, when the video is reconstructed at reduced temporal or spatial resolutions. Previous MC 3-D DWT structures either take the form of MC temporal DWT followed by a spatial transform ("t+2D"), or perform the spatial transform first ("2D + t"), limiting the spatial frequencies which can be jointly compensated in the temporal transform, and hence limiting the compression efficiency. When the motion model fails, the "t + 2D" structure causes nonaligned aliasing artifacts in reduced spatial resolution sequences. Essentially, the proposed transform continuously adapts itself between the "t + 2D" and "2D + t" structures, based on information available within the compressed bit stream. Ghosting artifacts may also appear in reduced frame-rate sequences due to temporal low-pass filtering along invalid motion trajectories. To avoid the ghosting artifacts, we continuously select between different low-pass temporal filters, based on the estimated accuracy of the motion model. Experimental results indicate that the proposed adaptive transform preserves high compression efficiency while substantially improving the quality of reduced spatial and temporal resolution sequences.

Algorithms↗
PubMed2004

Image restoration of arbitrarily warped documents.

We present a framework for acquiring and restoring images of warped documents. The purpose of our restoration is to create a planar representation of a once planar document that has undergone an arbitrary and unknown rigid deformation. To accomplish this restoration, our framework acquires and flattens the 3D shape of a warped document to determine a nonlinear image transform that can correct for image distortion caused by the document's shape. Our framework is designed for use in library and museum digitization efforts where very old and badly damaged manuscripts are imaged.

Algorithms↗
PubMed2006

Restoring warped document images through 3D shape modeling.

Scanning a document page from a thick bound volume often results in two kinds of distortions in the scanned image, i.e., shade along the "spine" of the book and warping in the shade area. In this paper, we propose an efficient restoration method based on the discovery of the 3D shape of a book surface from the shading information in a scanned document image. From a technical point of view, this shape from shading (SFS) problem in real-world environments is characterized by 1) a proximal and moving light source, 2) Lambertian reflection, 3) nonuniform albedo distribution, and 4) document skew. Taking all these factors into account, we first build practical models (consisting of a 3D geometric model and a 3D optical model) for the practical scanning conditions to reconstruct the 3D shape of the book surface. We next restore the scanned document image using this shape based on deshading and dewarping models. Finally, we evaluate the restoration results by comparing our estimated surface shape with the real shape as well as the OCR performance on original and restored document images. The results show that the geometric and photometric distortions are mostly removed and the OCR results are improved markedly.

Algorithms↗
PubMedDate not supplied

Reconstruction and visualization of planetary nebulae.

From our terrestrially confined viewpoint, the actual three-dimensional shape of distant astronomical objects is, in general, very challenging to determine. For one class of astronomical objects, however, spatial structure can be recovered from conventional 2D images alone. So-called planetary nebulae (PNe) exhibit pronounced symmetry characteristics that come about due to fundamental physical processes. Making use of this symmetry constraint, we present a technique to automatically recover the axisymmetric structure of many planetary nebulae from photographs. With GPU-based volume rendering driving a nonlinear optimization, we estimate the nebula's local emission density as a function of its radial and axial coordinates and we recover the orientation of the nebula relative to Earth. The optimization refines the nebula model and its orientation by minimizing the differences between the rendered image and the original astronomical image. The resulting model allows creating realistic 3D visualizations of these nebulae, for example, for planetarium shows and other educational purposes. In addition, the recovered spatial distribution of the emissive gas can help astrophysicists gain deeper insight into the formation processes of planetary nebulae.

Algorithms↗