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At least 1,801 records · Page 100Linked to original sources
PubMed2005

First order error propagation of the procrustes method for 3D attitude estimation.

The well-known Procrustes method determines the optimal rigid body motion that registers two point clouds by minimizing the square distances of the residuals. In this paper, we perform the first order error analysis of this method for the 3D case, fully specifying how directional noise in the point clouds affects the estimated parameters of the rigid body motion. These results are much more specific than the error bounds which have been established in numerical analysis. We provide an intuitive understanding of the outcome to facilitate direct use in applications.

Algorithms↗
PubMed2006

Keypoint recognition using randomized trees.

In many 3D object-detection and pose-estimation problems, runtime performance is of critical importance. However, there usually is time to train the system, which we will show to be very useful. Assuming that several registered images of the target object are available, we developed a keypoint-based approach that is effective in this context by formulating wide-baseline matching of keypoints extracted from the input images to those found in the model images as a classification problem. This shifts much of the computational burden to a training phase, without sacrificing recognition performance. As a result, the resulting algorithm is robust, accurate, and fast-enough for frame-rate performance. This reduction in runtime computational complexity is our first contribution. Our second contribution is to show that, in this context, a simple and fast keypoint detector suffices to support detection and tracking even under large perspective and scale variations. While earlier methods require a detector that can be expected to produce very repeatable results, in general, which usually is very time-consuming, we simply find the most repeatable object keypoints for the specific target object during the training phase. We have incorporated these ideas into a real-time system that detects planar, nonplanar, and deformable objects. It then estimates the pose of the rigid ones and the deformations of the others.

Algorithms↗
PubMedDate not supplied

Local histograms for design of transfer functions in direct volume rendering.

Direct Volume Rendering (DVR) is of increasing diagnostic value in the analysis of data sets captured using the latest medical imaging modalities. The deployment of DVR in everyday clinical work, however, has so far been limited. One contributing factor is that current Transfer Function (TF) models can encode only a small fraction of the user's domain knowledge. In this paper, we use histograms of local neighborhoods to capture tissue characteristics. This allows domain knowledge on spatial relations in the data set to be integrated into the TF. As a first example, we introduce Partial Range Histograms in an automatic tissue detection scheme and present its effectiveness in a clinical evaluation. We then use local histogram analysis to perform a classification where the tissue-type certainty is treated as a second TF dimension. The result is an enhanced rendering where tissues with overlapping intensity ranges can be discerned without requiring the user to explicitly define a complex, multidimensional TF.

Algorithms↗
PubMedDate not supplied

On histograms and isosurface statistics.

In this paper, we show that histograms represent spatial function distributions with a nearest neighbour interpolation. We confirm that this results in systematic underrepresentation of transitional features of the data, and provide new insight why this occurs. We further show that isosurface statistics, which use higher quality interpolation, give better representations of the function distribution. We also use our experimentally collected isosurface statistics to resolve some questions as to the formal complexity of isosurfaces.

Algorithms↗
PubMedDate not supplied

Artifacts caused by simplicial subdivision.

We review schemes for dividing cubic cells into simplices (tetrahedra) for interpolating from sampled data to IR3, present visual and geometric artifacts generated in isosurfaces and volume renderings, and discuss how these artifacts relate to the filter kernels corresponding to the subdivision schemes.

Algorithms↗
PubMedDate not supplied

Visualization of boundaries in volumetric data sets using LH histograms.

A crucial step in volume rendering is the design of transfer functions that will highlight those aspects of the volume data that are of interest to the user. For many applications, boundaries carry most of the relevant information. Reliable detection of boundaries is often hampered by limitations of the imaging process, such as blurring and noise. We present a method to identify the materials that form the boundaries. These materials are then used in a new domain that facilitates interactive and semiautomatic design of appropriate transfer functions. We also show how the obtained boundary information can be used in region-growing-based segmentation.

Algorithms↗
PubMed1977

Linking of medical records to form pedigrees.

The human pedigree provides a highly organized representation of historical family morbidity. In order to allow for careful analysis of large numbers of pedigrees, we have developed an interactive computer system for their storage, retrieval and statistical review. The system is capable of integration with our computerized medical record through the use of a common classification (ICHPPC) for patient morbidity. This linkage of pedigrees to clinical data may allow a richer utilization of the clinical experience within Family Practice for the support of research into disease patterns within the family.

Computers↗
PubMed2005

Feature selection and nearest centroid classification for protein mass spectrometry.

BACKGROUND: The use of mass spectrometry as a proteomics tool is poised to revolutionize early disease diagnosis and biomarker identification. Unfortunately, before standard supervised classification algorithms can be employed, the "curse of dimensionality" needs to be solved. Due to the sheer amount of information contained within the mass spectra, most standard machine learning techniques cannot be directly applied. Instead, feature selection techniques are used to first reduce the dimensionality of the input space and thus enable the subsequent use of classification algorithms. This paper examines feature selection techniques for proteomic mass spectrometry. RESULTS: This study examines the performance of the nearest centroid classifier coupled with the following feature selection algorithms. Student-t test, Kolmogorov-Smirnov test, and the P-test are univariate statistics used for filter-based feature ranking. From the wrapper approaches we tested sequential forward selection and a modified version of sequential backward selection. Embedded approaches included shrunken nearest centroid and a novel version of boosting based feature selection we developed. In addition, we tested several dimensionality reduction approaches, namely principal component analysis and principal component analysis coupled with linear discriminant analysis. To fairly assess each algorithm, evaluation was done using stratified cross validation with an internal leave-one-out cross-validation loop for automated feature selection. Comprehensive experiments, conducted on five popular cancer data sets, revealed that the less advocated sequential forward selection and boosted feature selection algorithms produce the most consistent results across all data sets. In contrast, the state-of-the-art performance reported on isolated data sets for several of the studied algorithms, does not hold across all data sets. CONCLUSION: This study tested a number of popular feature selection methods using the nearest centroid classifier and found that several reportedly state-of-the-art algorithms in fact perform rather poorly when tested via stratified cross-validation. The revealed inconsistencies provide clear evidence that algorithm evaluation should be performed on several data sets using a consistent (i.e., non-randomized, stratified) cross-validation procedure in order for the conclusions to be statistically sound.

Algorithms↗
PubMedDate not supplied

A portable system for monitoring physiological responses to hypoglycaemia.

Hypoglycaemia is the most common complication affecting people with Type 1 insulin dependent diabetes mellitus. Its onset is characterized by symptoms which include sweating, tremor, palpitations, loss of concentration and tiredness. As part of a research project to investigate the mechanisms of hypoglycaemia we have developed an ambulatory system to monitor and record pulsatile changes in blood flow, pulse interval, body temperature and skin impedance. The system uses a pocket computer (Atari Portfolio) to collect and store the data on a memory card. The analogue system consists of two thermocouples, an infrared photoplethysmograph and skin impedance monitoring circuit. To conserve power the system is programmed to make measurements for 2 min every 10 min: using this regimen over 16 h of data can be stored. Data collected during a spontaneous overnight hypoglycaemic episode are presented and also a comparison between continuous and intermittent data collection during a period of induced hypoglycaemia. The system is being used to investigate the physiological responses to hypoglycaemia but could easily be adapted for monitoring other physiological signals.

Arrhythmias, Cardiac↗
PubMed1998

A database for environmental contaminants in traditional food in northern Canada.

The potential health effects of environmental contaminants in traditional food on indigenous peoples in Northern Canada have been a growing concern. We have conducted an extensive literature review on contaminant levels in Northern Canada through searches of commercial, private, and government databases for the years 1986-1995, including MEDLine, Agricola, Biological Abstracts, Current Contents, Applied Science and Technology, Biosis, CABCD, Aquatic Sciences and Fisheries Abstracts, CRIS/ICAR, and the Northern Aquatic Food Chain Contaminant Database. More than 20,000 data items were identified in over 50 published articles, unpublished data, government reports, and review articles. Ranges of levels of 13 contaminants in major traditional food groups collected from four geographical regions (Yukon, MacKenzie, Keewatin, Baffin and Northern Quebec) were calculated. Exposure levels, particularly according to different dietary patterns, were estimated and discussed in relation to guideline levels.

Animals↗
PubMed2002

EDMS: what it was, is, and could be.

The decision to implement an Electronic Document Management System (EDMS) should not be made lightly. Such is the advice of a health are provider organization that pioneered the technology a decade ago. University Health Systems of Eastern Carolina's largest facility, Pitt County Memorial Hospital (PCMH), implemented an EDMS in February 1992 and converted to its current EDMS in December 1999. This article describes PCMH's transition from paper to automation, the many trials along the way, and the advantages an EDMS offers.

Electronic Data Processing↗
PubMed2001

Presentation of problem-specific, text-based medical knowledge: XML and related technologies.

Systematic reviews of the impact of clinical decision support systems on provider behavior and patient outcome have shown evidence of benefit. Knowledge-based functions for decision support or monitoring that are integrated in clinical information systems are a potentially effective way. But these concepts are restricted by the efforts required for development and maintenance of the information systems and the limited number of implemented medical rules. Physicians are familiar to get their information from text-based sources. It seems to be straight-forward to rely on a document-based solution in order to present problem-specific information at the point of care. We have developed a concept for context-sensitive retrieving and presentation of text-based medical knowledge (textbook of internal medicine) using the eXtensible Markup Language (XML) and related technologies. This concept can facilitate the electronic query and presentation of this resource. XML may replace narrative text as a storage format and allows to structure the data in a stepwise fashion. On the basis of structured data we are able to improve the search quality for clinical information and its presentation which forms a crucial pre-requisite for the use of the information and the implementation of evidence-based care in the clinical routine.

Decision Support Systems, Clinical↗
PubMed2003

Web-based submission, archive, and review of radiotherapy data for clinical quality assurance: a new paradigm.

PURPOSE: To report on the implementation of a web-based system (the Resource Center for Emerging Technologies [RCET] System) that provides immediate access to the patient radiotherapy planning and delivery data for clinical quality assurance (QA) by the experts. MATERIALS AND METHODS: An infrastructure of comprehensive tools required for preparation, submission, auto-archiving, web-based review, and retrieval of diagnostic images, treatment planning images, and radiation therapy objects has been developed. These tools represent approximately 1.1 million lines of computer code development in seven languages (V, C++, Visual Basic, Java, ASP, HTML, and SQL) and consist of a secure auto-anonymizing upload and auto-archiving patient database, a web-based secure object archiving network system, a web-based rapid review tool, a web-based upload/download tool, and a personal computer client data application for data object preparation, visualization, and submission, named NetSys. The RCET system enables users to share radiotherapy data in a secure environment. This paradigm of electronic data exchange makes remote peer review very efficient and convenient. RESULTS: The RCET system can help the radiation therapy community ensure consistent evaluation of its therapies. It will encourage proactive QA. An example of proactive clinical QA would be to provide atlases of target and critical structure definitions, to serve as class solutions, as well as dose prescription, specification, and reporting examples for guidance to the radiation oncologists in the community. The web-based clinical quality assurance is ideally suited for emerging technologies in radiation therapy that generate complex and voluminous multimodality imaging and planning data. CONCLUSIONS: The RCET system enables users to share multimodality imaging data, radiation therapy planning, and delivery data on demand. Our design paradigm will allow rapid peer review of radiotherapy data through a simple personal computer-based web browser.

Humans↗
PubMed1997

Using views for retrieving data from extremely heterogeneous databanks.

Information in molecular biology or biology in general is contained in a multitude of different databanks each specializing in a certain area. This specialization is useful since it improves the maintainability of the data and the flexibility of the overall structure which until now manages to exist without almost any standards. However, information gathering from these extremely heterogeneous sources is difficult since the desired data may be scattered over many databanks. This paper presents the concept of views implemented in the retrieval system SRS that uses links between databanks and a sophisticated parsing engine for information extraction to provide a flexible way of searching and obtaining data across databank boundaries. The implementation provides homogeneous access to all databanks using two types of views: the list-view which displays selected data-fields in their original format and the table-view available for HTML and plain ASCII text which tries to represent the data in a format independent from that of the source databank.

Amino Acid Sequence↗
PubMed1996

[Use of computer base MEDIP in retrieving information on occupational medicine and hygiene].

In order to provide easier access to the world literature through scientific journals collected in the Library at the Nofer Institute of Occupational Medicine, the computed MEDIP database has been set up. It contains 18,000 bibliographic documents in the areas of occupational medicine, toxicology and environmental hazards issued during the period 1990-1994. It is up-dated three times a year. It serves as the source of bibliographic data for researchers, industrial health services, sanitary and epidemiological services and all persons occupationally involved in issues pertaining to labour protection.

Databases, Bibliographic↗

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