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Results for “Software Validation”

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At least 109 records · Page 6Linked to original sources

PubMed1995

A computer program linking physiologically based pharmacokinetic model with cancer risk assessment for breast-fed infants.

The risk assessment process predicts the chances of adverse health effects that the toxicant possibly can do to the target organism under expected conditions of exposure. Regulators chose among several mathematical approaches to estimate the risk, but in each case it is necessary to link the dosemetrics of the toxicant with its predicted health effect. In this paper, a computer program is described that allowed us to link a physiologically based pharmacokinetic (PBPK) model for tetrachloroethylene (PCE) in the lactating mother with the estimate of extra cancer risk for breast-fed infants, according to the U.S. Environmental Protection Agency (EPA) methodology. When inhaled by a lactating woman, PCE may partition into breast milk and may be transferred to the breast-fed infant. We have developed and validated experimentally a PBPK model for lactational transfer of PCE in rats, including a quantitative description of a milk compartment and the nursing pup. Subsequently, the model has been scaled to describe human physiology, and was validated with literature data for human cases of PCE exposure. Finally, we linked the dosage predictions of the PBPK model with equations used by EPA to estimate the cancer risk from PCE. The model predictions are in good agreement with both the measured values and those reported in the literature for exposure to PCE. This comparison confirms the usefulness of PBPK modeling in risk assessments.

Air Pollutants↗

PubMed1997

Computerized scoring of abnormal human sleep: a validation.

A computerized assessment of sleep staging, arousals, premature ventricular contractions (PVCs), and respiratory events in sleep, was developed. Performance of the computerized system was assessed using epoch-by-epoch comparison and two human scorers across 30 consecutive patients. Percentages of agreement and Cohen's kappa coefficients were used for comparison. All agreements between all scorers for sleep staging, arousals, PVCs and respiratory events in sleep were significant (p < 0.001). The ratios of computer-human agreement descriptors to human-human agreement descriptors indicate that computerized analysis of abnormal human sleep offers reasonable results with savings in technologist time and work, but not in physician time and work.

Electroencephalography↗

PubMed1989

A computer-based interview system for patients with back pain. A validation study.

A microcomputer-based system has been designed to interview patients with a view to investigating and establishing common syndromes of back and leg pain. In a randomized crossover validation study, 50 consecutive outpatients were interviewed by the computer and had a conventional clerking by a doctor. The conventional clerking made minor errors in 3.75% of questions answered and major errors in 0.90%. The computer made minor errors in 6.75% of questions and major errors in 5.45%. The majority of the computer errors were due to inadequate question design. These have been corrected, and it is anticipated that the computer will now have an overall rate of 94% correct answers and be sufficiently accurate to pursue the aim of clinical syndrome identification.

Back Pain↗

PubMed1995

Computer analysis of monophasic action potentials: manual validation and clinically pertinent applications.

Monophasic action potential (MAP) recordings are increasingly being used in a variety of clinical and experimental situations but their manual measurement is cumbersome, especially when hundreds or thousands of beats must be analyzed to monitor the exact time course of action potential duration (APD) changes following heart rate alterations, during surveillance of APD alternans, or during the onset and stabilization of Class III drug effects. To facilitate this task we developed a computer program that automates programmed electrical stimulation, digitizes at 1-kHz sampling frequency MAP recordings up to 8 channels simultaneously, analyzes all APDs at repolarization levels from 10%-90% in 10% decrements (APD10-90), and automatically outputs the analyzed numerical data into spreadsheets for graphical display or statistical analysis. To validate the computer algorithm, two independent observers manually analyzed 585 concurrent MAP recordings at a paper speed of 100 mm/s. Cycle length measurements by the computer were precise to 0.4 +/- 0.5 ms as compared to the computer determined paced cycle length. Computer measurements of APD20, 50, and 90 differed from manual measurements by 2.0 +/- 8.8 ms, 0.7 +/- 7.9 ms, and 0.2 +/- 8.5 ms, respectively, for observer 1; and by 12.2 +/- 8.3 ms, 5.8 +/- 7.5 ms, and 1.4 +/- 10.1 ms, respectively, for observer 2. Inter-observer variability (IOV) was 10.3 +/- 11.1 (APD20), 5.1 +/- 9.0 ms (APD50), and 1.2 +/- 7.8 ms (APD90), which was similar to computer/observer-2 differences and significantly greater (0.001) than computer/observer-1 differences. This indicates that the computer analysis was at least as precise as manual measurements when compared to IOV, and more precise when comparing computer/observer-1 differences to IOV. While providing equal or greater precision, computer-aided analysis of 100 MAP signals took approximately 1 minute while manual analysis of the same data set took between 2.5 and 4 hours. The pacing and analysis software was subsequently applied to experiments that mimic clinically pertinent examples of MAP recordings: (1) automatic generation, analysis, and graphical display of electrical restitution curves at multiple ventricular sites simultaneously; (2) evaluation of myocardial pharmacokinetics by monitoring the progression of Class III antiarrhythmic drug effects by continuous MAP recordings, and displaying differences in drug action between multiple sites; (3) depiction of the adaptation time course of APD to abrupt changes in paced cycle length; and (4) quantitative analysis of APD alternans during myocardial ischemia. The results show that our computerized algorithm greatly facilitates the generation of cardiac electrophysiological, and clinically important, data.

Action Potentials↗

PubMed1999

Validating a decision support system for anti-epileptic drug treatment. Part II: adjusting anti-epileptic drug treatment.

A model of expertise for monitoring antiepileptic drug treatment was implemented in a decision support system. We validated the advice of the system regarding treatment decisions at first follow-up with 265 paper cases based on patient records. The reference for comparison is based on the opinions of neurologists. We found considerable variation among the decisions of five neurologists. It could be shown that the system agreed with (groups of) neurologists at least as often as individual neurologists did. The correctness of the system was consistently higher than that of each of the neurologists, when the majority decision of the remaining neurologists constituted the standard.

Anticonvulsants↗

PubMed1998

Detecting errors in a scoring program: a method of double diagnosis using a computer-generated sample.

This paper discusses a new method for locating errors in diagnostic computer scoring programs for structured clinical interviews. It was proposed as a test of the accuracy of the scoring program for the Composite International Diagnostic Interview, version 1.1. The proposal was to create an independent scoring program in a different computer language but serving the same criteria. Both programs were then applied to the same large set of valid (i.e., logically consistent) computer-generated test cases, and differences in diagnostic assignments reviewed. The method described can identify the program steps that account for the sources of the errors. Corrections can be made and the programs run again on new sets of test cases until discrepancy-free results are achieved. While this method cannot discover errors that are repeated in the two programs, it does discover more of the errors in a scoring program than we have previously been able to identify. This technique provides a systematic and rigorous approach to assuring the accuracy of scoring programs based on established algorithms.

Algorithms↗

PubMedDate not supplied

Machine learning for an expert system to predict preterm birth risk.

OBJECTIVE: Develop a prototype expert system for preterm birth risk assessment of pregnant women. Normal gestation involves a term of 40 weeks, but because 8-12% of the newborns in the United States are delivered prior to 37 weeks' gestation, problems associated with prematurity continue to plague individuals, families, and the health care system. DESIGN: A knowledge-base development methodology used machine learning, statistical analysis, and validation techniques to analyze three large datasets (18,890 subjects and 214 variables). The dependent (i.e., decision) variable studied was weeks of gestation at delivery, with dichotomous coding of preterm delivery (prior to 37 weeks) and full-term delivery (37+ weeks). RESULTS: Machine learning with a program named Learning from Examples using Rough Sets (LERS) induced 520 usable rules that were entered into a prototype expert system. The prototype expert system was 53-88% accurate in predicting preterm delivery for 9,419 patients. CONCLUSION: The prototype expert system was more accurate than traditional manual techniques in predicting preterm birth.

Adult↗

PubMedDate not supplied

Low-energy imaging with high-energy bremsstrahlung beams: analysis and scatter reduction.

The contrast and zero spatial frequency signal-to-noise ratio produced by a method for radiation therapy portal imaging known as low-energy imaging with high-energy bremsstrahlung beams have been mathematically analyzed. The analysis makes extensive use of Monte Carlo techniques and incorporates the detector, the spectrum, phantom, and geometry. The analysis is validated through comparison with measured data including subject contrast measurements and the attenuation of the beam with lead. Scatter reduction is found to be potentially the most effective method to improve contrast and SNR for a film based system. A large fraction of the scatter detected is of a much higher energy than that found in diagnostic radiology. Hence, traditional antiscatter grids, such as those used in diagnostic radiology, are ineffective. The analysis and theory from the literature are applied to design a new grid which is more appropriate for this application. The grid produces a modest improvement according to a contrast-detail study.

Humans↗

PubMed1991

Validation, clinical trial, and evaluation of a radiology expert system.

The PHOENIX Radiology Consultant is a rule-based expert system which assists physicians in planning radiological work-up strategies. This article describes the methods used to create and validate the system's knowledge base. The feasibility and acceptability of PHOENIX were tested for two years in a clinical trial. During this period, the system was used 1,421 times, an average of 13.7 times per week, primarily by medical students and nonradiologist physicians. Much of the system's use occurred at night and on weekends, when the radiology department was not fully staffed. Several physicians were enlisted to further evaluate the utility of the system. The results of their evaluation indicate that an expert system that helps physicians select diagnostic-imaging studies can serve as a useful and informative component of a radiology information system, and is particularly useful for medical students and physicians in training.

Algorithms↗

PubMed1993

TopFit: a PC-based pharmacokinetic/pharmacodynamic data analysis program.

The program TopFit was developed and validated within the European pharmaceutical industry. It provides both pharmacokinetic data analysis support for international regulatory submissions of new drugs, and sophisticated techniques for model-based kinetic/dynamic evaluation during drug development. TopFit features are: (1) non-compartmental methods; (2) standard compartment models assembled from input and disposition modules; (3) a potentially unlimited number of linear user-defined models that accommodate metabolites, effects, and absorption profiles; (4) a library of 24 non-linear models. No user programming is required. A well-defined file structure allows ready exchange of data with other programs such as SAS. TopFit version 2.0 is now commercially available, with comprehensive documentation, in the form of an MS-DOS application for the PC.

Data Interpretation, Statistical↗

PubMed1997

Geriatric patient simulations for dental hygiene.

The rapidly increasing number of this country's elderly requires that dental hygiene students practice the clinical problem-solving skills of information gathering, assessment, and treatment applied to geriatric patients. Computer-based simulations are purported to provide this experience, but little research has been completed with simulations in the education of dental hygienists. This paper summarizes the process used to design, develop, and evaluate a series of eighteen computer-based geriatric simulated patients. It contains a brief description of the simulations and a description of the design, validation, authoring, and formative evaluation phases. The paper also describes the summative evaluation, provides implementation suggestions, and summarizes future directions. The summative evaluation, conducted at four institutions, suggests that computer-based simulations are an effective instructional method as measured by pre/post-tests. The results suggest that simulations can provide a standardized set of geriatric patient experiences. These simulations may prove especially valuable at institutions that are unable to provide clinical geriatric experiences or lack the expertise to conduct a didactic course in geriatrics.

Aged↗

PubMed1994

Medical data and knowledge management by integrated medical workstations: summary and recommendations.

The health care professional workstation will function as an interface between the user and the patient data as well as an interface pertinent medical knowledge. Appropriate knowledge focus will require the workstation to recognize the concepts and structure of patient data, and understand the scope and access methods of knowledge sources. Issues are organized around five major themes: (i) structure, (ii) reliability and validation, (iii) views, (iv) location, and (v) ethical and legal. Conventional database representations can effectively address data structure and format variations that will inevitably persist in local data stores. The reliability of data and the validation of knowledge are critical issues that may determine the ultimate utility of clinical workstations. Alternative views of patient information and knowledge sources represent the true power of an intelligent data portal, represented by a well-designed clinical workstation. Both data and knowledge are optimally represented in decentralized information networks, although the confidentiality and ownership of this information must be respected. Evolutionary progress toward consistent representations of knowledge and patient data will be facilitated by the establishment of self-documentation standards for the developers of data encoding systems and knowledge sources, perhaps extended from the preliminary model afforded by the Unified Medical Language System (UMLS).

Computer Security↗

PubMed1998

Reproducibility of polar map generation and assessment of defect severity and extent assessment in myocardial perfusion imaging using positron emission tomography.

The purpose of this study was to determine the reliability of new software developed for the analysis of cardiac tomographic data. The algorithm delineates the long axis and defines the basal plane and subsequently generates polar maps to quantitatively and reproducibly assess the size and severity of perfusion defects. The developed technique requires an initial manual estimate of the left ventricular long axis and calculates the volumetric maximum myocardial activity distribution. This surface is used to map three-dimensional tracer accumulation onto a two-dimensional representation (polar map), which is the basis for further processing. The spatial information is used to compute geometrical and mechanical properties of a solid model of the left ventricle including the left heart chamber. A new estimate of the axis is determined from this model, and the previously outlined procedure is repeated together with an automated definition of the valve plane until differences between the polar maps can be neglected. This quantitative analysis software was validated in phantom studies with defects of known masses and in ten data sets from normals and patients with coronary artery disease of various severity. We investigated the reproducibility of the maps with the introduction of a similarity criterion where the ratio of two corresponding polar map elements lies within a 10% interval. The maps were also used to measure intra-and interobserver variability in respect of defect size and severity. In the phantom studies, it was possible to reliably assess mass information over a wide range of defects from 5 to 60 g (slope: 1.02, offset -0.68, r = 0.972). Patient studies revealed a statistically significant increase in the reproducibility of the automatic technique compared with the manual approach: 54%+/-19% (manual) compared with 88%+/-9% (automatic) for observer 1 and 61%+/-20% vs 82%+/-5% for observer 2, respectively. The intervariability analysis showed a significant improvement from 59%+/-14% to 83%+/-7% in similar polar map elements and a significantly improved correlation in the calculation of severity (from r = 0.908 to 0.989) and extent (from r = 0.963 to r = 0.992) of the perfusion defects when the automated procedure was applied. It is concluded that, assuming a constant wall thickness and tissue density, absolute defect mass can be reliably estimated. Furthermore, the proposed software demonstrates a significant improvement in the generation of volumetric polar maps for the quantitative assessment of perfusion defects.

Algorithms↗

PubMed1997

An automatic approach to the analysis, quantitation and review of perfusion and function from myocardial perfusion SPECT images.

UNLABELLED: We have developed a software suite that automatically selects, analyses, quantitates and displays all the key image data in a myocardial perfusion SPECT study. METHODS: The files automatically selected (upon specification of the patient name) are rest and stress projections, rest and stress short axis and gated short axis files, and all 'snapshot' files. The projection data sets are presented in cine mode for evaluation of patient motion, while the lung/heart ratio at rest and stress is calculated from regions of interest (ROIs) that are automatically derived and overlayed on the LAO 45 images. Left ventricular (LV) cavity volumes at rest and stress are calculated from the short axis data sets, and the related transient ischemic dilation (TID) ratio derived and displayed. Quantitative measurements of global (ejection fraction) and regional function parameters are performed from the gated short axis dataset. All algorithms use the C++, X-Windows and OSF-Motif standards. The overall suite executes in less than 1 minute on a SunSPARC5 with 32 Mb of RAM and no proprietary hardware. RESULTS: The software was validated on 144 patients (118 rest 201T1/post-stress 99mTc-sestamibi, 18 post-stress 99mTC-sestamibi, 8 rest 201Tl) acquired on a 90 degrees dual detector (ADAC Vertex, 91 patients) and a triple detector camera (Picker Prism 3000, 53 patients). Overall, the individual algorithms for the analysis of projection, short axis and gated short axis images were successful in 622/660 (94.2%) of the images. In 80.5% of the patients (73/91 + 43/53) all algorithms executed successfully, without significant difference in success rates for 201Tl versus 99mTc-sestamibi images. CONCLUSION: Our automated approach to myocardial perfusion SPECT analysis and review is highly successful, intrinsically reproducible, and can produce time and cost savings while improving accuracy in a clinical or teleradiology-type environment.

Algorithms↗

PubMed1994

Validation of the medical expert system RENOIR.

RENOIR is an expert system developed to assist the diagnosis of 37 diseases of connective tissue and inflammatory arthropathies. Precise diagnosis of rheumatic diseases implies great uncertainty and there is no gold standard with which to compare the expert system output. To overcome this problem a set of clinical cases was submitted to RENOIR and its diagnoses were compared with those of clinicians. Medical records of 81 patients with rheumatic diseases were interpreted by RENOIR and by 12 clinicians at three different expertise levels in rheumatology. Distances between the likelihoods of the 37 considered diseases provided by clinicians and RENOIR were computed as a disagreement measure. Mahalanobis distance was used to correct the collinearity between the possibilities of each pair of diseases. Using the resulting matrices of distances between experts, cluster analyses were carried out to classify RENOIR among human experts. Greater differences between RENOIR and clinicians than among clinicians themselves were not found.

Cluster Analysis↗

PubMed1994

Automatic detection of wave boundaries in multilead ECG signals: validation with the CSE database.

This paper presents an algorithm for automatically locating the waveform boundaries (the onsets and ends of P, QRS, and T waves) in multilead ECG signals (the 12 standard leads and the orthogonal XYZ leads). Given these locations, features of clinical importance (such as the RR interval, the PQ interval, the QRS duration, the ST segment, and the QT interval) may be measured readily. First, a multilead QRS detector locates each beat, using a differentiated and low-pass filtered ECG signal as input. Next, the waveform boundaries are located in each lead. The leads in which the detected electrical activity is of longest duration are used for the final determination of the waveform boundaries. The performance of our algorithm has been evaluated using the CSE multilead measurement database. In comparison with other algorithms tested by the CSE, our algorithm achieves better agreement with manual measurements of the T-wave end and of interval values, while its measurements of other waveform boundaries are within the range of the algorithm and manual measurements obtained by the CSE.

Algorithms↗

PubMed1991

Analysis of brain and cerebrospinal fluid volumes with MR imaging. Part I. Methods, reliability, and validation.

A computerized system was developed to process standard spin-echo magnetic resonance (MR) imaging data for estimation of brain parenchyma and cerebrospinal fluid (CSF) volumes. In phantom experiments, the estimated volumes corresponded closely to the true volumes (r = .998), with a mean error less than 1.0 cm3 (for phantom volumes ranging from 5 to 35 cm3), with excellent intra- and interobserver reliability. In a clinical validation study with actual brain images of 10 human subjects, the average coefficient of variation between observers for the measurement of absolute brain and CSF volumes was 1.2% and 6.4%, respectively. The intraclass correlations for three expert operators is greater than .99 in the measurement of brain and ventricular volumes and greater than .94 for total CSF volume. Therefore, the authors believe that their technique to analyze MR images of the brain performed with acceptable levels of accuracy and reliability and that it can be used to measure brain and CSF volumes for clinical research. This technique could be helpful in the correlation of neuroanatomic measurements to behavioral and physiologic parameters in neuropsychiatric disorders.

Algorithms↗

PubMed1995

Toward an intelligent wound assessment system.

There is general agreement regarding the need for pressure ulcer assessment methodology which more discretely reflects relevant aspects of wound status than does the commonly used staging system. The Pressure Sore Status Tool (PSST) is one such instrument which was developed with consensual expert input. While the psychometric properties of the PSST have been reported in the literature, the instrument was validated using ET nurses, highly trained wound care specialists, and existed only in manual form. This paper reports results from attempts to establish reliability estimates for healthcare practitioners without extraordinary wound care training or experience. The paper further describes the automation of the PSST and provides examples of pressure ulcer profiles tracked over time. Results indicate that inter-rater reliability with general healthcare practitioners was .78 and intra-rater reliability was .89. The practitioners were able to use the PSST for over six months and the automated system allowed analysis of wound healing profiles that would have been difficult using a manual system. These results imply that movement toward an automated system which makes discriminations regarding the effects of various treatment and intervention strategies is possible and practical.

Aged↗