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PubMed1995

[Adaptive algorithm for automatic measurement of retinal vascular diameter].

A new adaptive computer-aided method for the measurement of blood vessel diameters has been developed. Within areas of interest in the image, the algorithm detects, line-wise, the edges of the vessels, which are then used for image-wise approximation and noise filtration. A high level of adaptivity with respect to numerous measuring parameters ensures its use in a wide range of applications. Thus, it has been shown to significantly improve clinically relevant reproducibility in the area of follow-up observations. The standard deviation for vessel diameter was (2.2 +/- 0.7)% in the case of arteries and (1.8 +/- 0.5)% in the case of veins. Testing the algorithm in images of poor quality revealed its high level of reliability and sensitivity.

Algorithms↗
PubMed2006

Relation of QT interval measurements to evolving automated algorithms from different manufacturers of electrocardiographs.

QT-interval measurements have clinical importance for the electrocardiographic recognition of congenital and acquired heart disease and as markers of arrhythmogenic risk during drug therapy, but software algorithms for the automated measurement of electrocardiographic durations differ among manufacturers and evolve within manufacturers. To compare automated QT-interval measurements, simultaneous paired electrocardiograms were obtained in 218 subjects using digital recorders from the 2 major manufacturers of electrocardiographs used in the United States and analyzed by 2 currently used versions of each manufacturer's software. The 4 automated QT and QTc durations were examined by repeated-measures analysis of variance with post hoc testing. Significantly larger automated QT-interval measurements were found with the most recent software of each manufacturer (12- to 24-ms mean differences from earlier algorithms). Systematic differences in QT measurements between manufacturers were significant for the earlier algorithms (11-ms mean difference) but not for the most recent software (1.3-ms mean difference). Similar relations were found for the rate-corrected QTc, with large mean differences between earlier and later algorithms (15 to 26 ms). Although there was a <2-ms mean difference between the most recent automated QTc measurements of the 2 manufacturers, the SD of the difference was 12 ms. In conclusion, reference values for automated electrocardiographic intervals and serial QT measurements vary among electrocardiographs and analysis software. Technically based differences in automated QT and QTc measurements must be considered when these intervals are used as markers of heart disease, prognosis, or arrhythmogenic risk.

Algorithms↗
PubMed1994

[Computer system of electronystagmographic examination. Part I. Measuring equipment and algorithm of ENG test].

The work presents the computer system created by the author for automatic registration and analysing oculomotor response records evoked by the stimulation of the vestibular organ. The basis elements of the system had been described. It consists of microcomputer IBM PC/XT/AT, measurement and stimulatory apparatus, multimodular controlling and analytical software as well as the algorithm of system management.

Algorithms↗
PubMed1994

Evaluation of new algorithms for the interactive measurement of surface area and volume.

The maximum unit normal component (MUNC) method used for surface area measurement and the divergence theorem algorithm (DTA) used for volume measurement were evaluated. The accuracy and precision of these methods were investigated at varying signal-to-noise ratios (SNRs), sampling, spatial averaging, and orientation. The accuracy of the MUNC measured surface area, as indicated by the mean error, was 2.0% for seven spherical samples, with SNRs ranging from 5:1 to 39:1. The precision, as indicated by the percent coefficient of variation (% CV) for these samples, was less than 3.0%. Likewise, the accuracy and precision of the DTA measured volume for these samples were both less than 1.0%. MUNC surface area measurement from 23 samples of a computed tomography (CT) image of a wooden sphere (51.44-mm diameter) with x,y voxel size ranging from 1 to 10 mm and z voxel size ranging from 2 to 14 mm yielded an accuracy of 1.3% and a precision of 2.2%. The DTA volume measurements from 18 samples of the wooden sphere with x,y vowel size ranging from 1 to 8 mm and z size ranging from 2 to 14 mm provided an accuracy of 1.2% and a precision of 1.8%. Measurement of surface area for a cylindrical rod scanned by CT in five different orientations, ranging from along each axis to between all three axes, yielded an accuracy of 3.7% and a precision of 2.0%. The volume of the cylindrical rod measured by the DTA method for these orientations produced an accuracy of 4.0% and a precision of 3.7%. The volume measured by DTA compared well with the volume measured by a modified voxel counting method. The MUNC surface area method was superior to counting surface voxels. The accuracy and precision for five interactive surface area and volume measurements, using paired cut planes to select subsets of a computer-generated sphere with radius 25 pixels, were both less than 1.0%.

Algorithms↗
PubMed2004

Comparing stage of change measures in adolescent smokers.

This study compared stage of change measures among adolescent smokers. Participants were 56 adolescents who had received smoking tickets. They filled out an assessment packet including readiness to change measures [i.e., algorithm, Crittenden's measure, University of Rhode Island Change Assessment (URICA), and Ladder], smoking history, a 30-day calendar, Fagerstrom, self-efficacy measures, locus of control, and a problem screen. The Crittenden algorithm was correlated with the Ladder and URICA motivation scores as well as with decreased frequency/amount of smoking and past quit attempts. Ladder scores were correlated with less cigarettes smoked, self-efficacy, and fewer adolescent problems. Readiness to change was unrelated to nicotine dependence and locus of control. The classification of participants into stages by the Crittenden algorithm was associated with a significant MANOVA (Wilks' Lambda F=1.56, P<.025), with group differences on reported quit attempts, abstinence self-efficacy, and adolescent problems. The Crittenden measure and the URICA motivation score were sensitive to a MET intervention.

Adolescent↗
PubMed2006

Quantitative myocardial infarction on delayed enhancement MRI. Part I: Animal validation of an automated feature analysis and combined thresholding infarct sizing algorithm.

PURPOSE: To develop a computer algorithm to measure myocardial infarct size in gadolinium-enhanced magnetic resonance (MR) imaging and to validate this method using a canine histopathological reference. MATERIALS AND METHODS: Delayed enhancement MR was performed in 11 dogs with myocardial infarction (MI) determined by triphenyltetrazolium chloride (TTC). Infarct size on in vivo and ex vivo images was measured by a computer algorithm based on automated feature analysis and combined thresholding (FACT). For comparison, infarct size by human manual contouring and simple intensity thresholding (based on two standard deviation [2SD] and full width at half maximum [FWHM]) were studied. RESULTS: Both in vivo and ex vivo MR infarct size measured by the FACT algorithm correlated well with TTC (R = 0.95-0.97) and showed no significant bias on Bland Altman analysis (P = not significant). Despite similar correlations (R = 0.91-0.97), human manual contouring overestimated in vivo MR infarct size by 5.4% of the left ventricular (LV) area (equivalent to 55.1% of the MI area) vs. TTC (P < 0.001). Infarct size measured by simple intensity thresholdings was less accurate than the proposed algorithm (P < 0.001 and P = 0.007). CONCLUSION: The FACT algorithm accurately measured MI size on delayed enhancement MR imaging in vivo and ex vivo. The FACT algorithm was also more accurate than human manual contouring and simple intensity thresholding approaches.

Algorithms↗
PubMedDate not supplied

Acute lower respiratory infections among children hospitalized in Bangui, Central African Republic: toward a new case-management algorithm.

To measure the performance of the current WHO algorithm in identifying children at higher risk of death, children aged 2-59 months who presented with cough and/or difficult breathing and were admitted into the paediatric hospital of Bangui (Central African Republic) during a 1-year period (1996/97) were investigated. Among children with subcostal indrawing, mortality and severity of oxygen desaturation were identical whether or not they also had tachypnoea. Among children with a 'severe pneumonia', those who also fulfilled the 'very severe disease' definition had a higher risk of death (31/132, 23.5%) than those who did not (12/106, 11.3%, P = 0.02). However, this 'very severe disease' definition did not predict death when used in children who did not have severe pneumonia. To identify variables that would better predict death, combinations of symptoms and signs were examined among the subgroup of children with indrawing. Nine combinations had both a sensitivity and specificity over 60%. 'Grunting and/or nasal flaring' had a sensitivity of 72% and a specificity of 66% in predicting death, and might be easier to use by primary health care personnel than other combinations. A new algorithm is proposed for the management of children aged 2-59 months presenting with cough and/or difficult breathing. The definition of pneumonia would be unchanged (tachypnoea). Severe pneumonia would remain defined on indrawing regardless of respiratory rate, except that indrawing should be lower chest wall and/or intercostal. In health facilities where intravenous antibiotics, chloramphenicol and/or oxygen are available, entry into a 'very severe pneumonia' category would be based on 'grunting and/or nasal flaring' among children with indrawing. In our study population, the mortality rates in the categories based on these definitions were 0.8% (1/127) in children with no pneumonia, 0.9% (1/116) in children with pneumonia, 7.7% (12/156) in children with severe pneumonia and 31.1% (33/106) in children with very severe pneumonia.

Acute Disease↗
PubMed2005

Simple algorithm for the measurement of absorption coefficients of a two-layered medium by spatially resolved and time-resolved reflectance.

An inversion procedure for the recovery of absorption coefficients of a two-layered semi-infinite diffusive medium by use of time-resolved reflectance measured at two different source-detector distances is proposed. The inversion procedure is based on the property of the photon diffusion equation; i.e., the solution of the diffusion equation for the time-resolved reflectance measured at a longer source--detector distance coincides with that measured at a shorter one by a proper temporal, spatial, and intensity transformation. This inversion procedure, used together with the results of one set of Monte Carlo simulations, is validated as working well when the values of the scattering coefficients of the two layers and the thickness of the first layer are within a range of interest in tissue optics.

Absorption↗
PubMed1986

Algorithms for morphometric measurements on cancer cells in electron microscopy. Pilot tests.

Automated procedures were designed for handling quantitative data derived from a morphometric study of neoplastic cells on electron micrographs. Pilot studies were carried out on 3 breast carcinomas. Each tumor cell was coded by the sequence of 30 stereological parameters that described the general organization of subcellular constituents. Wide standard deviations, as large as 90% of the mean, were observed in some parameters. The practical application of correlation analysis between stereological parameters turned out to be of limited value, since only parameters related to the same subcellular structure showed correlation.

Adenocarcinoma, Mucinous↗
PubMed2005

Mass distributed clustering: a new algorithm for repeated measurements in gene expression data.

The availability of whole-genome sequence data and high-throughput techniques such as DNA microarray enable researchers to monitor the alteration of gene expression by a certain organ or tissue in a comprehensive manner. The quantity of gene expression data can be greater than 30,000 genes per one measurement, making data clustering methods for analysis essential. Biologists usually design experimental protocols so that statistical significance can be evaluated; often, they conduct experiments in triplicate to generate a mean and standard deviation. Existing clustering methods usually use these mean or median values, rather than the original data, and take significance into account by omitting data showing large standard deviations, which eliminates potentially useful information. We propose a clustering method that uses each of the triplicate data sets as a probability distribution function instead of pooling data points into a median or mean. This method permits truly unsupervised clustering of the data from DNA microarrays.

Algorithms↗
PubMedDate not supplied

[Non-invasive blood pressure measuring device].

Algorithms have been developed for the Russian non-invasive blood pressure measuring monitor MPK-01 that applies a frequency excess pressure transducer. The monitor uses oscillometry. A preliminary estimate of the accuracy of blood pressure measurement for its conformity to the ANSI/AAMI (USA) and BHS (UK) standards has indicated the legitimacy of the algorithm proposed for processing if there are hardware restrictions inherent in this monitor.

Algorithms↗
PubMed2005

A new simple iterative reconstruction algorithm for SPECT transmission measurement.

This paper proposes a new iterative reconstruction algorithm for transmission tomography and compares this algorithm with several other methods. The new algorithm is simple and resembles the emission ML-EM algorithm in form. Due to its simplicity, it is easy to implement and fast to compute a new update at each iteration. The algorithm also always guarantees non-negative solutions. Evaluations are performed using simulation studies and real phantom data. Comparisons with other algorithms such as convex, gradient, and logMLEM show that the proposed algorithm is as good as others and performs better in some cases.

Algorithms↗
PubMed1995

Classification-algorithm evaluation: five performance measures based on confusion matrices.

OBJECTIVE: The objective of this paper is to introduce, explain, and extend methods for comparing the performance of classification algorithms using error tallies obtained on properly sized, populated, and labeled data sets. METHODS: Two distinct contexts of classification are defined, involving "objects-by-inspection" and "objects-by-segmentation." In the former context, the total number of objects to be classified is unambiguously and self-evidently defined. In the latter, there is troublesome ambiguity. All five of the measures of performance here considered are based on confusion matrices, tables of counts revealing the extent of an algorithm's "confusion" regarding the true classifications. A proper measure of classification-algorithm performance must meet four requirements. A proper measure should obey six additional constraints. RESULTS: Four traditional measures of performance are critiqued in terms of the requirements and constraints. Each measure meets the requirements, but fails to obey at least one of the constraints. A nontraditional measure of algorithm performance, the normalized mutual information (NMI), is therefore introduced. Based on the NMI, methods for comparing algorithm performance using confusion matrices are devised. CONCLUSIONS: The five performance measures lead to similar inferences when comparing a trio of QRS-detection algorithms using a large data set. The modified NMI is preferred, however, because it obeys each of the constraints and is the most conservative measure of performance.

Algorithms↗
PubMed2001

Ground reaction: intrinsic and extrinsic variability assessment and related method for artefact treatment.

Ground reaction (GR) components measured by a dynamometric platform represent the dynamic interaction of the moving human body with the ground and depend on the subject-platform relative position and orientation. The observed variability among the GR measurements of the walking trials of an individual is either due to variability in the motor performance (intrinsic variability) or due to changes in the direction of walking and in the position and orientation of the striking foot relative to the platform (extrinsic variability). A method, based on the median operator, is presented here which lets us quantify the two components of variability. The application of the method to a large data set of normal subjects evidenced changes in progression direction/foot orientation (95th percentile value is 6.9 degrees ), which can dramatically change the patterns of GR components. This result warns about improper analysis of ground reaction measurement. An algorithm for restoring GR measurements affected by artefact was derived from the above method. This tool can be of valuable aid in clinical practice where patients' conditions suggest to not insist on repetition of trials even if the required number of correct foot placements has not been achieved. The artefact correction algorithm has been applied to a large data set artificially corrupted to evaluate its robustness.

Adult↗
PubMed1990

A comparison of the noise sensitivity of nine QRS detection algorithms.

The noise sensitivities for nine different QRS detection algorithms were measured for a normal, single-channel lead II, synthesized ECG corrupted with five different types of synthesized noise. The noise types were electromyographic interference, 60 Hz powerline interference, baseline drift due to respiration, abrupt baseline shift, and a composite noise constructed from all of the other noise types. The percentage of QRS complexes detected, the number of false positives, and the detection delay were measured. None of the algorithms were able to detect all QRS complexes without any false positives for all of the noise types at the highest noise level. Algorithms based on amplitude and slope had the highest performance for EMG-corrupted ECG. An algorithm using a digital filter had the best performance for the composite noise corrupted data.

Algorithms↗
PubMed2003

Eye feature extraction for diagnosing the facial phenotype associated with fetal alcohol syndrome.

Victims of fetal alcohol syndrome (FAS) exhibit a unique facial phenotype that is emphasised in diagnosis. Among the characteristic facial features, several occurring in the region of the orbits can be evaluated quantitatively using distance measurements. An algorithm is described for automatic extraction and measurement of eye features from stereo photographs. The algorithm was applied to photographs of 46 six-seven-year-old children. The approach relies on peak and valley maps and integral projection functions, to locate the eyes and extract the iris, and genetic algorithms to fit cubic splines to the upper and lower eyelids. Measurements obtained automatically using this algorithm were compared with measurements obtained manually from the photographs. Mean absolute differences between automatic and manual measurements were less than 1 mm for palpebral fissure length (PFL) and interpupillary distance (IPD). Absolute differences were less than 1 mm for 80.4% of PFLs and 100% of IPDs. Inner canthal distance and outer canthal distance did not compare favourably with manual measurements.

Algorithms↗
PubMed2005

Algorithm for accurate similarity measurements of peptide mass fingerprints and its application.

We present a simple algorithm which allows accurate estimates of the similarity between peptide fingerprint mass spectra from matrix assisted laser desorption/ionization (MALDI) spectrometers. The algorithm, which is a combination of mass correlation and intensity rank correlation, was used to cluster similar spectra and to generate consensus spectra from a data store of more than 100,000 spectra. The resulting first spectra library of 1248 unambiguously identified different protein digests was used to search for missed cleavage patterns that have not been reported so far and to shed light on some peptide ionization characteristics. The findings of this study could be directly implemented in peptide mass fingerprint search algorithms to decrease the false positive error rate to <0.25%. Furthermore, the results contribute to the understanding of the peptide ionization process in MALDI experiments.

Algorithms↗