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At least 343 records · Page 19Linked to original sources

PubMed2004

Dynamic echo-planar MR imaging of the diaphragm for a 3D dynamic analysis.

The purpose of this study was to prove the feasibility of 3D reconstructions of the diaphragm during the respiratory cycle using EPI sequences (EPI acquisition, 270 ms/image, on a healthy subject breathing spontaneously and at 0.1 Hz). Continuously recorded respiratory signal allowed for retrospective synchronization with respiratory phases for reconstruction of successive diaphragm surfaces using a specifically designed software. Displacements, area and volume changes of the diaphragm were quantified. Our measurements were comparable with the data in the literature. Reconstructed surfaces allowed in vivo diaphragm dynamic evaluation in terms of displacements, area and volume variations. EPI has adequate spatial and temporal resolution for studying diaphragm dynamics during natural breathing.

Diaphragm↗

PubMed2005

The dimensional accuracy for preparation of the femoral cavity in HIP arthroplasty. A comparison between manual- and robot-assisted implantation of hip endoprosthesis stems in cadaver femurs.

INTRODUCTION: The aim of the study was to determine the precision of the preparation of the femoral cavity in cementless hip arthroplasty. We compared the bone-prosthesis interface after manual- and robot-assisted implantation of the stems. MATERIAL AND METHODS: After plastination the specimens were cut to slices of 2.5 mm and documented by microradiography. The interface between prosthesis and bone was measured digitally with a specially designed software. RESULTS: The manually implanted prostheses showed an average full-contact area of 60% and an average area of gaps of 40% with an average height of 0.8 mm. The robot-assisted implanted stems had a significantly higher bone-prosthesis interface area of 93% and gap areas of less than 0.2 mm depth. Destructions of the spongeous bone were seen with the manually implanted stems but not after robot-assisted implantations. There was one stem fracture during the manual preparation of a stem. Microradiographic examination showed microfractures in the region of the lesser trochanter in two femora after robot-assisted implantation CONCLUSION: The robot-assisted technique highly increased the fitting area at the bone-prosthesis interface. The main reason for the fractures might be the absence of a robot done marker for the ideal implantation height with the applied type of prosthesis.

Arthroplasty, Replacement, Hip↗

PubMed2003

Bugs in computational chemistry software and their consequences: the importance of the source code.

The increase in computer power and the development of new mathematical concepts implemented in software have allowed computational chemistry to emerge as a new research field. Although programs were freely distributed during the "golden age" of this discipline, today they are usually copyrighted and have become easier and easier to use through sophisticated graphical interfaces. This "democratization" is a vector of success for this discipline. Nowadays, non-theoreticians can use such programs more easily and solve chemistry-related problems with the computer. The number of program offerings has rapidly grown and private companies specialized in molecular modeling have appeared and compete to sell their products. Thus, numerous software packages, often presenting similar capabilities, are now available on the market. Within this context, the availability of the program source code remains, in our opinion, an important criterion for program selection.

Chemistry↗

PubMed2002

Progress in maize gene discovery: a project update.

The Maize Gene Discovery Project (MGDP) is a 5-year NSF-funded plant genome initiative that began in 1998. The MGDP collaboration involves researchers at six universities from diverse disciplines with the common goal of discovering new maize genes and developing tools for the phenotypic characterization of maize mutants. The project utilizes several approaches: EST sequencing, cDNA microarray production, and the discovery of gene function and genomic sequence through the use of a recombinant Mu1 transposon ( RescueMu). Current achievements of the MGDP (NSF 98-72657) include the sequencing of over 120,000 maize ESTs from diverse cDNA libraries, and over 70,000 RescueMu flanking sequences, as well as the cataloguing of mutant seed and cob phenotypes of 23,000 maize ears, 6,200 families of maize seedlings, and 4,000 families of adult maize plants carrying MuDR/Mu and RescueMu insertion alleles. A consolidation of over 24,000 unique sequences from 19 libraries has been made into the first two of the planned set of four "Unigene" microarray slides. In addition, slides for four EST libraries have been produced. These microarray slides, EST clones, library plates of immortalized RescueMu bacterial cultures, and seed are all available online (http://www.zmdb.iastate.edu). The ZmDB website posts periodic assemblies of all maize EST and genomic sequences available from GenBank. ZmDB is also a portal for sequence analysis software designed to aid in gene discovery: MuSeqBox, GeneSeqer, and SplicePredictor. In addition, ZmDB contains links to other plant and genetics websites.

Alleles↗

PubMed1988

Development and validation of an automated method of the Selvester QRS scoring system for myocardial infarct size.

The Selvester QRS score for estimation of myocardial infarct (MI) size from the standard 12-lead electrocardiogram (ECG) has not yet achieved wide recognition as a valuable tool in the routine assessment of the MI patient, primarily because of the practical limitations inherent to manual application. This study examined the ECGs of 438 patients (105 normal subjects, 161 with "possible" MI and 172 with "definite" MI based on data from cardiac catheterization) to develop software for an automated method of the Selvester system in attempts to overcome the manual constraints. After a comprehensive validation process involving extensive interactions between the manual scorer and the software developer, an automated method of the Selvester system was generated that had a high correlation with manual application (r = 0.94) and was superior regarding time, training, reader bias, reproducibility and precision of measurement. These results indicate that an automated version of the Selvester QRS scoring system would resolve many of the limitations of manual application and would provide a reliable, technically accurate estimate of MI size that could be incorporated into ECG diagnostic programs and used in standard digital ECG machines.

Cardiac Catheterization↗

PubMed1993

Noninvasive computerized assessment of left ventricular performance and systemic hemodynamics by study of aortic root pressure and flow estimates in healthy men, and men with acute and healed myocardial infarction.

Aortic root pressure and flow data can be used to assess left ventricular (LV) performance and properties of the systemic arterial tree. The calibrated subclavian arterial pulse trace was combined with echocardiographic imaging and Doppler velocity recordings to obtain noninvasive estimates of aortic root pressure and flow in 8 healthy subjects (group A), 12 patients with recent myocardial infarction (group B), and 8 with healed myocardial infarction and a dilated left ventricle (group C). The pressure and flow data were transferred to a computer and processed in specially designed software, including a new procedure for estimation of 3-element windkessel model parameters. There were no significant group differences for either aortic root pressure estimates or heart rate. In groups B and C, stroke and cardiac indexes were lower and total peripheral resistance higher than in group A. There were no group differences in the model estimates of total arterial compliance, whereas the characteristic impedance was greater in group C than in A, indicating a less compliant aorta in C. Both LV total and steady power were less in groups B and C than in A, whereas no group difference was found for percent oscillatory power. The reproducibility for recording was good for the aortic root pressure estimates, and lower for the derived parameters (stroke and cardiac indexes, windkessel model parameters and LV power), whereas that for interpretation was generally good. This method provides a unique noninvasive access to important parameters of LV function and the systemic circulation.

Adult↗

PubMed1987

A microcomputer system for on-line collection of blood flow and related physiological data.

A multi-disciplinary approach is described for the development of a microcomputer based on-line data collection system for blood flow experiments. Well designed software provides a flexible approach to data collection, which is particularly suited to blood flow research laboratories. The choice of well supported hardware ensures ease of development with minimum time and cost.

Blood Circulation↗

PubMed1988

The Gemini conundrum--a problem of unpairable data: statistical comparison of ratios each derived from two separately estimated parameters.

In biological studies it may be necessary to compare ratios of two separately estimated parameters under test and control conditions. Since it is not always possible technically to obtain paired data for the two parameters, how does one take account of their variances? By extending previously described approximations in a modified t-test we present a BASIC computer program which may be used to solve this problem.

Algorithms↗

PubMed1993

An algorithm for measurement of expiratory flow rate parameters on the partial expiratory flow-volume curve.

Partial expiratory flow-volume (PEFV) curves are a useful tool in airway challenge studies, but unlike the maximal expiratory flow-volume (MEFV) curve, lung function parameters require manual calculation from the flow-volume tracing. We describe an algorithm written in QuickBASIC that analyzes a PEFV curve superimposed on a MEFV curve by (1) identifying the PEFV curve, (2) locating the maximal expiratory flow at the point on the PEFV curve that corresponds to 60% of the baseline forced vital capacity (FVC) below total lung capacity (TLC), termed MEF40%(P), and (3) identifying the size of the PEFV curve along the TLC axis. A report of these parameters is also provided. This algorithm was validated using flow-volume curves from a clinical study in which eight subjects performed two sets of MEFV and PEFV curves separated by approximately 1 hr. Paired comparison of MEF40%(P) determined by the algorithm and two independent manual calculations correlated strongly and yielded no statistically significant differences between the two methods. We conclude that this algorithm provides rapid and accurate determinations of PEFV parameters.

Algorithms↗

PubMed1996

Dynamic circular buffering: a technique for equilibrium gated blood pool imaging.

We have devised a software technique called "dynamic circular buffering" (DCB) with which we create a gated blood pool image sequence of the heart in real time using the best features of LIST and FRAME mode methods of acquisition/processing. The routine is based on the concept of independent "agents" acting on the timing and position data continuously written into the DCB. This approach allows efficient asynchronous operation on PC-type machines and enhanced capability on systems capable of true multiprocessing and multithreading.

Gated Blood-Pool Imaging↗

PubMed1988

Computer aided design and evaluation of limiting and serial dilution experiments.

Two computer programs are presented which can be used for the determination of the design and the statistical evaluation of data in the context of limiting and serial dilution analysis. The first program (DESIGN) gives the experimenter the opportunity to set up different designs, to improve a design according to several suggestions, to make a picture of a design and to evaluate the results of artificial data, obtained from a random experiment corresponding with the chosen design, until (s)he is convinced of having a suitable design for a particular experiment. The second program (EVALUATE) evaluates the experimental data. The design method and the statistical methods used in the programs have been chosen on practical and theoretical grounds.

Colony Count, Microbial↗

PubMed1993

Regression imputation of missing values in longitudinal data sets.

A stand-alone, menu-driven PC program, written in GAUSS, which can be used to estimate missing observations in longitudinal data sets is described and male available to interested readers. The program is limited to the situation in which we have complete data on N cases at each of the planned times of measurement t1, t2,..., tT; and we wish to use this information, together with the non-missing values for n additional cases, to estimate the missing values for those cases. The augmented data matrix may be saved in an ASCII file and subsequently imported into programs requiring complete data. The use of the program is illustrated. Ten percent of the observations in a data set consisting of mandibular ramus height measurements for N = 12 young male rhesus monkeys measured at T = 5 time points are randomly discarded. The augmented data matrix is used to determine the lowest degree polynomial adequate to fit the average growth curve (AGC); the regression coefficients are estimated and confidence intervals for them are determined; and confidence bands for the AGC are constructed. The results are compared with those obtained when the original complete data set is used.

Animals↗

PubMed1994

New opportunities for processing the OSI-7 layer protocols using parallel processing (transputers).

The attractiveness of the OSI-7 layer model is closely dependent upon a highly ambitious intent to promote a series of quasi-universal standards to coordinate the communication between heterogeneous applications, whatever the distributed architectures might be. However, a major criticism of the OSI-model is the performance and the handling of the presentation layer. This paper deals with the evaluation of parallel processing techniques operating at the upper levels of the OSI-model using transputers in a parallel co-processor. It is shown that the performance problem is highly dependent on the structure of the protocol stack and its implementation. With the object-oriented modularization of the protocol stack, an architecture of a possible co-processor using transputers is considered and its performance is considered adequate. An ideal configuration is briefly presented. A final performance appraisal of the parallelism effect is discussed with some insight into the future.

Computer Communication Networks↗

PubMed1996

A Dutch medical language processor.

This paper describes the current state of a medical language processor for Dutch. The goal is to implement a language specific front-end compatible with some existing applications that aim at the intelligent extraction and processing of information from patient discharge summaries. A complete chain for processing and understanding Dutch medical documents will be the ultimate result. The text focuses mainly on the language specific aspects of the language processing chain. Evaluation results of the already functioning components are given as well as an outline for future developments and enhancements. A short theoretical background is provided (cf. also [1-3]: Rossi Mori et al., Proc. SCAMC 90, 1990, pp. 185-189; Wingert, in: Informatics and Medicine, an advanced course, Springer-Verlag. 1977, pp. 579-646; Wingert, Proc. MEDINFO 80, 1980, pp. 1321-1331) before the description of each component in order to familiarise the non-experienced reader with the basic notions of computational linguistics.

Artificial Intelligence↗

PubMed1988

A personal computer-based arrhythmia generator based on mathematical models of cardiac arrhythmia.

A personal computer-based arrhythmia generator has been developed based upon mathematical models of modulated parasystole and the related equations. A system of nonlinear difference equations is used to generate the time series of RR intervals of ECG that contain normal as well as ectopic QRS waves. The ECG waveform is synthesized according to the computed RR interval and the type of QRS wave and output via DA converter in a real-time base. Various types of ECGs with ventricular ectopic beats and those with very long periods were generated by selecting values for a small number of model parameters. This method requires neither large RAM nor external memory for storing a library of arrhythmic ECGs. The theory, hardware design, software implementation on a personal computer, and experimental reconstruction of clinical ECGs based on the model are discussed.

Arrhythmias, Cardiac↗

PubMed1988

The evaluation of quantitative autoradiogram processing systems for cerebrovascular research.

The development of an image processing system for quantitative autoradiography (QAR) is described, with emphasis on the evaluation of image digitization systems independent of hardware or software design. Each step of converting the autoradiographic image to a functional image of a physiological variable such as local cerebral blood flow (LCBF) or local cerebral glucose utilization rate (LCGU) is evaluated. The autoradiograms are digitized, aligned, transformed to a tissue tracer concentrations image based on the gray value (GV) of calibrated 14C standards, subtracted from each other as required in double tracer QAR, and converted to an LCBF or LCGU image using the proper tracer kinetic model. Geometric size, mean and standard deviation of the LCBF, LCGU, and tracer concentration can be measured in regions of interest. These steps are evaluated separately for their contribution to the accuracy and precision of the final, functional image. The qualities important in the final image are spatial resolution, intensity linearity, and intensity sensitivity, as well as the noise level. Techniques for evaluating the LCBF image include: (1) optimization of the input linearity and dynamic range of the video camera to maximize relative intensity sensitivity of the final functional image; (2) visual inspection of the curves used to fit various functions that are important in the conversion of the GV image to an image of physiological interest; (3) consideration of the noise introduced by the input devices and during the image conversion; and (4) above all, the integration of the various parts of the system to produce an accurate image useful in cerebrovascular research.

Autoradiography↗

PubMed1995

Computer assisted pulse oximetry for detecting children with obstructive sleep apnea syndrome.

A prospective study was carried out on 110 children undergoing tonsillectomy or adenotonsillectomy to evaluate the usefulness of computer assisted pulse oximetry (POM) as a screening tool for nocturnal obstructive sleep apnea episodes. Twenty-one healthy age-matched children served as a control group. A self-designed software (CAPO version 1.0) was used to analyse collected oximetric data. Pre-operatively up to 25% of children showed a characteristic pattern of repeated oxygen desaturations related to partial or complete airway obstruction, which was not seen in the matched group. Thirty-one percent had an oxygen desaturation index (ODI) of more than 2 phases/h, being significantly higher than in the matched group. These children could not be identified from history or clinical examination with an acceptable sensitivity. A second monitoring has been performed in 32 patients 5 days after surgery. The nocturnal cyclic oscillations of oxygen saturation resolved in almost all cases. Computer assisted POM is useful in predicting and grading nocturnal obstruction and adds decision making data for the treatment in children suspected of suffering from obstructive sleep apnea.

Adenoidectomy↗

PubMedDate not supplied

An object-based architecture for biomedical expert database systems.

Objects play a major role in both database and artificial intelligence research. In this paper, we present a novel architecture for expert database systems that introduces an object-based interface between relational databases and expert systems. We exploit a semantic model of the database structure to map relations automatically into object templates, where each template can be a complex combination of join and projection operations. Moreover, we arrange the templates into object networks that represent different views of the same database. Separate processes instantiate those templates using data from the base relations, cache the resulting instances in main memory, navigate through a given network's objects, and update the database according to changes made at the object layer. In the context of an immunologic-research application, we demonstrate the capabilities of a prototype implementation of the architecture. The resulting model provides enhanced tools for database structuring and manipulation. In addition, this architecture supports efficient bidirectional communication between database and expert systems through the shared object layer.

Database Management Systems↗