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At least 703 records · Page 39Linked to original sources
PubMed1988

A new method for determining cross-sectional shape and area of soft tissues.

Assessment of the mechanical properties of soft tissues requires accurate measurement of the cross-sectional area. To date, techniques for determining cross-sectional areas of ligaments and tendons have been less than ideal due to the tissues' complex geometries and the fact that they deform easily under an applied external load. A new procedure has been developed for determining the cross-sectional area by means of an image reconstruction technique based on measurements from collimated laser beams. Using this procedure, the actual shape of the specimen cross-section can also be determined. The results are demonstrated to be highly accurate, and this methodology does not require mechanical contact with the specimen.

Algorithms↗
PubMed2002

Monitor unit calculation for tangential breast treatments: verification in an anthropomorphic phantom.

This paper presents an anthropomorphic phantom study of dose delivered to a specific point during tangential breast irradiation to verify monitor unit calculations. Measurements were made using a 0.6 cc Farmer type cylindrical ionization chamber in the phantom and compared to calculations made on a three-dimensional radiotherapy treatment planning system using single digitized contour through to multi slice CT data. A large breast phantom was used for a single field size with a combination of open and wedged fields for three different energies (4, 6, and 18 MV). Solid flat phantom measurements were also performed for comparison. Results showed a lower calculated dose than the dose measured for a fixed number of monitor units where the variations were within a range of 0.8% to 4.5%. Differences were larger for the anthropomorphic phantom than the flat phantom. We conclude that little accuracy is gained from CT based monitor unit calculations compared to those based on digitised contours for this breast treatment but that the dose distributions will be affected. This type of test is recommended as one of a large set, in the commissioning and testing procedures for treatment planning systems.

Breast Neoplasms↗
PubMed2003

Anomalous somatosensory cortical localization in schizophrenia.

OBJECTIVE: Schizophrenia has been reported to be associated with altered localization of regions responding to sound in the auditory cortex, suggesting possible cortical reorganization accompanying the disorder, but it is not clear whether such disturbances are present in any primary sensory cortex other than the auditory. This study examines magnetoencephalographic localization of field sources evoked by tactile stimulation generated in area 3b of the primary somatosensory cortex in patients with schizophrenia compared with normal subjects. METHOD: A total of 29 subjects participated; 14 were patients with schizophrenia, and 15 were normal comparison subjects. Equivalent current dipole generators in both hemispheres were used to model the sources of the 50-msec latency somatosensory evoked field (M50) components produced by contralateral tactile mechanoreceptor stimulation of the tip of the index finger. RESULTS: Compared with normal subjects, patients with schizophrenia demonstrated reversed asymmetry (left anterior to right) and relatively anterior and inferior displacement of the M50 equivalent current dipole location in the left hemisphere. CONCLUSIONS: Cerebral lateralization and localization of the M50 distinguished patients with schizophrenia from normal subjects. These findings suggest the possibility of anatomical displacement and/or disturbed organization of the primary sensory cortex in schizophrenia.

Adult↗
PubMed2005

SpectralNET--an application for spectral graph analysis and visualization.

BACKGROUND: Graph theory provides a computational framework for modeling a variety of datasets including those emerging from genomics, proteomics, and chemical genetics. Networks of genes, proteins, small molecules, or other objects of study can be represented as graphs of nodes (vertices) and interactions (edges) that can carry different weights. SpectralNET is a flexible application for analyzing and visualizing these biological and chemical networks. RESULTS: Available both as a standalone .NET executable and as an ASP.NET web application, SpectralNET was designed specifically with the analysis of graph-theoretic metrics in mind, a computational task not easily accessible using currently available applications. Users can choose either to upload a network for analysis using a variety of input formats, or to have SpectralNET generate an idealized random network for comparison to a real-world dataset. Whichever graph-generation method is used, SpectralNET displays detailed information about each connected component of the graph, including graphs of degree distribution, clustering coefficient by degree, and average distance by degree. In addition, extensive information about the selected vertex is shown, including degree, clustering coefficient, various distance metrics, and the corresponding components of the adjacency, Laplacian, and normalized Laplacian eigenvectors. SpectralNET also displays several graph visualizations, including a linear dimensionality reduction for uploaded datasets (Principal Components Analysis) and a non-linear dimensionality reduction that provides an elegant view of global graph structure (Laplacian eigenvectors). CONCLUSION: SpectralNET provides an easily accessible means of analyzing graph-theoretic metrics for data modeling and dimensionality reduction. SpectralNET is publicly available as both a .NET application and an ASP.NET web application from http://chembank.broad.harvard.edu/resources/. Source code is available upon request.

Algorithms↗
PubMed2006

MathDAMP: a package for differential analysis of metabolite profiles.

BACKGROUND: With the advent of metabolomics as a powerful tool for both functional and biomarker discovery, the identification of specific differences between complex metabolite profiles is becoming a major challenge in the data analysis pipeline. The task remains difficult, given the datasets' size, complexity, and common shifts in migration (elution/retention) times between samples analyzed by hyphenated mass spectrometry methods. RESULTS: We present a Mathematica (Wolfram Research, Inc.) package MathDAMP (Mathematica package for Differential Analysis of Metabolite Profiles), which highlights differences between raw datasets acquired by hyphenated mass spectrometry methods by applying arithmetic operations to all corresponding signal intensities on a datapoint-by-datapoint basis. Peak identification and integration is thus bypassed and the results are displayed graphically. To facilitate direct comparisons, the raw datasets are automatically preprocessed and normalized in terms of both migration times and signal intensities. A combination of dynamic programming and global optimization is used for the alignment of the datasets along the migration time dimension. The processed datasets and the results of direct comparisons between them are visualized using density plots (axes represent migration time and m/z values while peaks appear as color-coded spots) providing an intuitive overall view. Various forms of comparisons and statistical tests can be applied to highlight subtle differences. Overlaid electropherograms (chromatograms) corresponding to the vicinities of the candidate differences from any result may be generated in a descending order of significance for visual confirmation. Additionally, a standard library table (a list of m/z values and migration times for known compounds) may be aligned and overlaid on the plots to allow easier identification of metabolites. CONCLUSION: Our tool facilitates the visualization and identification of differences between complex metabolite profiles according to various criteria in an automated fashion and is useful for data-driven discovery of biomarkers and functional genomics.

Biomarkers↗
PubMed1998

Biomechanical differential equations of variables of the arterial pulse based on vessel wall and blood flow features.

A dynamic arterial vessel model with an associated flow resistance is deduced in Laplace-transformed form based on a linear dynamic muscle model and a laminar-instationary blood stream with accompanying parameters (such as elasticity, actin myosin overlap, movement resistances, blood stream resistance and blood mass). In addition, a flow resistance is connected at the outlet of the vessel. With the pulse pressure course as the given input, the Laplace-transformed definition enables, in a clearly arranged manner, the derivation of differential equations of several variables of the arterial pulse process--the changes of blood inflow, outflow, storage flow or volume, of the internal vessel pressure, of the output pressure, of the various pressure differences over the vessel, of the vessel wall tension, of the vessel radius and the vessel wall thickness. The derivations yield the order and the structures of these differential equations. The coefficients of these equations are complicated functions (sums and products) of the smooth-muscle, blood-flow and geometrical parameters. Only in special cases--with an open or the closed vessel at the outlet--are the coefficients simple functions of the vessels parameters.

Biomechanical Phenomena↗
PubMedDate not supplied

Towards computer assisted evaluation of plagiocephaly.

Plagiocephaly is a common asymmetry of the skull giving the impression that the subject, usually a neonate, has suffered a compressive force acting unilaterally. Normally innocuous, it is a postural deformity that can be suggestive of other significant abnormalities, e.g. joint dysplasia. Although intuitive measurements of plagiocephaly appear in the literature there is little evidence of analytical evaluation. This paper describes a measurement methodology based on black and white photography. A flat-bed scanner and a personal computer facilitated the transformation of the prepared photograph to standard tagged image file format at 256 grey scale. A utility was used to convert the file scan to a monochrome bitmap image which was displayed on the screen and subjected to an algorithm to compute the centroid of the cranial profile. Radials that emerge from the centroid to the cranial circumference at five degree intervals map to a signal display that represents the plagiocephaly.

Cephalometry↗
PubMed2001

An on-line exact small-sample test of significance for extended matching tasks.

An extension of the traditional matching paradigm that enables researchers to test a variety of new experimental hypotheses is outlined. An on-line computer program that provides an exact small-sample test of hypotheses in the extended matching paradigm is described. The program, which has an intuitive graphical interface, may be accessed and executed via the Internet by using an ordinary browser.

Computer Graphics↗
PubMed1999

Naive Bayesian-based nomogram for prediction of prostate cancer recurrence.

This paper introduces a schema with naive-Bayesian classifier and patient weighting technique to develop a prostate cancer recurrence prediction model from patient data. We propose the graphical presentation of naive-Bayesian classifier with a nomogram, which can be used both for prediction or can provide means to data analysis. The resulting model was experimentally evaluated; the results were favorable both in terms of interpretability and predictive accuracy.

Bayes Theorem↗
PubMed2001

3-D simulation of craniofacial surgical procedures.

An integrated system for simulating craniofacial surgical procedures is presented. The system computes nonlinear soft-tissue deformation due to bone realignment. It is capable of simulating bone cutting and bone realignment with integrated interactive collision detection. Furthermore, soft-tissue deformation and cutting due to surgical instruments can be visualized. The system has been tested with several individual patient data sets. Simulation processes are based on a 3-D model of a patient's preoperative bone structure of the skull derived from a computer tomography scan and on a 3-D, photorealistic model of the patient's preoperative appearance obtained by a laser range scanner. The multi-layer soft-tissue model is represented by nonlinear springs. Very fast and robust prediction of nonlinear soft-tissue deformation is computed by optimizing a nonlinear cost function.

Cephalometry↗
PubMed2002

[Evaluating scar development with objective computer-assisted viscoelastic measurement].

In a prospective study we compared the subjective scar assessment by the Vancouver Scar Scale with an objective viscoelastic measurement. Donor sites from the thigh primarily dressed with vaseline gauze (F), biobrane or occlusive dressing(O) were evaluated 0.5 years postoperatively by VSS and with the Cutometer (Courage and Khazaka). VSS of donor sites was 2.74 +/- 0.91 (F), 4.25 +/- 0.77 (B) and 2.57 +/- 0.72(O) (mean +/- sem). All ratings were significant compared to normal mirror-sided skin. Viscoelastic measurements by the Cutometer were near normal compared to uninjured skin. No correlation was found between subscale VSS pliabilty rating and Cutometer readings.

Bandages↗
PubMed2002

Effect of age and gender on the condition of bone tissue of stomatognathic system.

The 240 patients, with the mean age 50.3 year for males and 54.4 years for females treated in the Department of Dental and Maxillofacial Surgery Medical University and Institute of Rural Medicine in Lublin had radiovisiographically tested premolar teeth area on the left hand body side. Digital radiovisiographical picture was developed using computer software Radiograph Workshop, and obtained factors of bone mineral density and mandible bone structure were reviewed with regard to gender and age of the treated. It was concluded that relative density, mineral density and bone mineral contents is significantly greater with male than female patients, and is deteriorating significantly with age. Age and gender of the treated in a lesser degree influences on radiological structure factors resulting from radiovisiographical picture analysis using Radiograph Workshop.

Absorptiometry, Photon↗
PubMed1991

Algorithms for Bayesian belief-network precomputation.

Bayesian belief networks provide an intuitive and concise means of representing probabilistic relationships among the variables in expert systems. A major drawback to this methodology is its computational complexity. We present an introduction to belief networks, and describe methods for precomputing, or caching, part of a belief network based on metrics of probability and expected utility. These algorithms are examples of a general method for decreasing expected running time for probabilistic inference. We first present the necessary background, and then present algorithms for producing caches based on metrics of expected probability and expected utility. We show how these algorithms can be applied to a moderately complex belief network, and present directions for future research.

Algorithms↗