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PubMed2003

[Antituberculous measures according to the results of Mantoux test].

Analyzing the results of Mantoux tests with 2 TE made 7 times for 5 years in 750-850 schoolchildren of the settlement of Sulak has demonstrated that the infection rates are on the increase on the one hand, and, due to material and transport problems, the proportion of examinees from a risk group decreases to 10-30% of those to be examined, on the other hand. The authors suggest that the remaining unexamined children should undergo chemotherapy with 2-3 antituberculosis drugs for 3 months so as to perform an examination when the first opportunity occurs. They propose to examine the coverage of children, except for children and adolescents with a hyperergic and increasing reactions and those with a highly positive (15-16 mm) Mantoux test. An algorithm for implementation of the above measures is offered.

Adolescent↗

PubMed1999

Scanning E-field sensor device for online measurements in annular phased-array systems.

PURPOSE: A measurement device for noninvasive and simultaneous control of antennas during regional radiofrequency (rf) hyperthermia and, subsequently, the estimation of the power distribution in the interior of patients are essential preconditions for further technological progress. Aiming at this, the feasibility of an electro-optical electric field sensor was investigated during clinical rf hyperthermia. MATERIAL AND METHODS: The electro-optical electric field (E-field) sensor is based on lithiumniobate crystals and the Mach-Zehnder interferometer structure, and was tested in an earlier phantom study. For this study, a mechanical scanning device was developed allowing the registration of the E-field during clinical application. Data were recorded along a curve in the water bolus of the SIGMA 60 applicator of the annular phased-array system BSD-2000 (BSD Medical Corp., Salt Lake City, UT) close to the base points of the flat biconical dipole antennas. The results were compared with modeling calculations using the finite-difference time-domain (FDTD) method. For the latter, different antenna models were assumed. For systematic registration of the E-field curves in amplitude and phase, we employed an elliptical lamp phantom with fat-equivalent ring (filled with saline solution) and an elliptical polyacrylamide phantom with acrylic glass wall. Further measurements were carried out during the treatment of 5 patients with 20 hyperthermia treatments. RESULTS: Data of both phantom and patient measurements can be satisfactorily described by the FDTD method, if the antenna model is refined by taking into account the conical form of the dipoles and the special dielectric environment of the feeding point. Phase deviations can be entered ex posteriori for correction in the calculation algorithm. A comparison of amplifier power measurement (forward and backward power) and bolus E-field scans near the antenna base points demonstrates that E-field measurements between antennas and patient are a necessity for the appropriate characterization of antenna radiation properties. These measurements are sensitive to variations of the lossy medium in position and shape, and can be correctly predicted with current models. However, the differences between different patients are moderate and unspecific in both calculations and measurements, with fluctuations at maximum of 30 degrees in phases and 40% in amplitudes. CONCLUSIONS: The measurement method presented here turned out to be a practical tool for online registration of E-fields in phases and amplitudes along arbitrary curves in a water bolus or phantom. It can be utilized to evaluate antenna design and modeling calculations and leads, thus, to a better understanding of complicated multiantenna systems. In clinical routine, it can be employed as input for patient-specific hyperthermia planning and, finally, for the realization of online control with subsequent optimization of the power distribution in the patient.

Algorithms↗

PubMed2003

Sensor data validation using gray models.

A new method based on the gray model is described for the online validation of measurements. A gray model is a differential equation describing the behavior of an accumulate generating operation (AGO) data sequence. First-order gray models are fitted to measuring data records using the recursive orthogonal least-squares algorithm. Predictions derived from the fitted gray model are then compared with the actual measurements to generate a prediction error sequence. The quality of the measured value is determined by the prediction errors and variance of the prediction error sequence. Experimental results for detecting the quality of measurements from a thermistor are presented.

Algorithms↗

PubMed2000

Eye care for the critically ill.

PURPOSE: To evaluate the effectiveness and efficiency of an algorithm in the prevention of ocular surface disease in sedated and unconscious patients in the intensive care unit (ICU). METHODS: The eyes of all sedated and unconscious patients admitted to an ICU between September and December 1998 were managed according to an eye care algorithm. The applications of the preventive measures were assessed by a single observer twice weekly. The lid position, the presence and degree of keratopathy, sedation score, and the treatment received were documented at every assessment. RESULTS: Thirty-four patients were recruited for management according to the eye care algorithm over a period ranging from 1 to 28 days. Four patients were excluded because of failure by staff to adhere to the protocol. In 18 patients no active treatment was required. Out of six patients who had conjunctival exposure and were given ocular lubricants, four maintained clear corneas. No corneal or conjunctival staining was noted in two of the four patients whose lids required closure with Micropore tape for corneal exposure. Use of lid taping and lubricants prevented corneal abrasion in two patients who were prone ventilated. The prevalence of ocular surface abnormalities was 8.7 % where the algorithm was properly followed (23 patients). CONCLUSION: The proposed eye care algorithm appears to be effective in preventing ocular surface abnormalities in the sedated and unconscious patients in the ICU, and efficient in that it may reduce the workload required for critically ill patients.

Adult↗

PubMed1996

Retrospective benzene and total hydrocarbon exposure assessment for a petroleum marketing and distribution worker epidemiology study.

A quantitative exposure-estimating algorithm for benzene and total hydrocarbons was developed for a case control study of petroleum marketing and distribution workers. The algorithm used a multiplicative model to adjust recently measured quantitative exposure data to past scenarios for which representative exposure measurement data did not exist. This was accomplished through the development of exposure modifiers to account for differences in the workplace, the materials handled, the environmental conditions, and the tasks performed. Values for exposure modifiers were obtained empirically and through physical/chemical relationships. Dates for changes that altered exposure potential were obtained from archive records, retired employee interviews, and from current operations personnel. Exposure modifiers were used multiplicatively, adjusting available measured data to represent the relevant exposure scenario and time period. Changes in exposure modifiers translated to step changes in exposure estimates. Though limited by availability of data, a validation exercise suggested that the algorithm provided accurate exposure estimates for benzene (compared with measured data in industrial hygiene survey reports); the estimates generally differed by an average of less than 20% from the measured values. This approach is proposed to quantify exposures retrospectively where there are sufficient data to develop reliable current era estimates and where a historical accounting of key exposure modifiers can be developed, but where there are insufficient historic exposure measurements to directly assess historic exposures.

Algorithms↗

PubMed1993

On-line determination of pulmonary blood flow using respiratory inert gas analysis.

An inert gas analysis method has been developed to perform on-line real time determination of pulmonary blood flow using a nonrebreathing approach. This technique is based on a mathematical model describing mass balance of two inert gases which are breathed using an open gas circuit. The measurements using this method are noninvasive, easy to peform, and do not disturb normal physiological processes. As well, since data are collected on a breath-by-breath basis, it is possible to estimate other respiratory, cardiopulmonary, and metabolic parameters simultaneously in a breath-by-breath manner. Special consideration was given to developing effective data processing algorithms to minimize the influence of measurement noise and respiratory variations. Experimental studies to compare this method with other accepted techniques were conducted to validate the present technique.

Acetylene↗

PubMedDate not supplied

Performance of an adaptive MIMO controller for a multiple-element ultrasound hyperthermia system.

A prototype adaptive automatic control algorithm was implemented to regulate temperatures measured at several points in a tumour by adjusting the power applied to several ultrasound transducers. The goal was to control the temperatures under the elements of a mosaic applicator individually without any priori knowledge of which probes are under which elements. The control algorithm was devised for clinical applications where the position of each probe with respect to the heat sources is difficult to determine precisely. Instead, the program 'learns' the relationship between the inputs (power levels) and the outputs (temperatures) automatically. Based on the observed transfer function relating the power at m sources to the temperatures n probes, where n and m are not necessarily the same, a new method was used to implement a feedback controller. This method simplifies the design of the controller for a multiple-input/multiple-output (MIMO) system, while taking into account the coupling that may exist between the various elements of the system. As a result of using an adaptive scheme, the regulator continuously tracks changes in the system, such as blood flow variations or patient motion, by modifying its control parameters. The algorithm performance has been tested in simulations as well as experiments in dog thigh and a perfused kidney model.

Algorithms↗

PubMed1993

Validation of arterial oxygen saturation measurements in utero using pulse oximetry.

The noninvasive measurement of fetal arterial oxygen saturation using pulse oximetry could be of potential use in assessing fetal well-being in utero during labor. In this study, the accuracy and technical feasibility of reflectance pulse oximetry in utero was evaluated in acutely instrumented fetal sheep using a specially designed sensor. Following recalibration of the analysis algorithms, fetal arterial saturation could be measured by pulse oximetry in utero. Arterial oxygenation measurements obtained using pulse oximetry correlated well with simultaneous in vitro measurements over the range of 6 to 81%. We conclude that in utero pulse oximetry is technically feasible, appears useful and accurate, and merits further evaluation.

Algorithms↗

PubMed2004

Retrospective respiratory motion correction for navigated cine velocity mapping.

In general, high spatial and temporal resolutions in cine cardiac imaging require long scan times, making breath-hold acquisition impossible in many cases. To enable free-breathing cardiac imaging, methods such as navigator gating were developed to reduce image artifacts due to respiratory motion. Nevertheless, residual image blurring is seen in images acquired late in the cardiac cycle. Image blurring itself hampers accurate blood flow quantification, especially in vessels exhibiting high flows during diastole. In the present work, the navigator gating and slice tracking method was extended by using navigator information to correct for in-slice motion components throughout the cardiac cycle. For this purpose, a standard two-dimensional (2D) cine phase contrast sequence with navigator gating and slice position correction was used, and navigator information was recorded along with the raw k-space data. In postprocessing, in-plane motion components arising from respiration during the actual data acquisition were estimated and corrected according to the Fourier shift theorem. In phantom experiments, the performance of the correction algorithm for different slice angulations with respect to the navigator orientation was validated. In vivo, coronary flow measurements were performed in 9 healthy volunteers. The correction algorithm led to considerably improved vessel sharpness throughout the cardiac cycle in all measured subjects [increase in vessel sharpness: 16+/-11% (mean+/-SD)]. Furthermore, these improvements resulted in increased volume flow rates [16+/-13% (mean+/-SD)] after retrospective correction indicating the impact of the method. It is concluded that retrospective respiratory motion corrections for navigated cine two-dimensional (2D) velocity mapping can correct for in-plane motion components, providing better image quality for phases acquired late in the cardiac cycle. Therefore, this method holds promise in particular for free-breathing coronary flow quantification.

Blood Flow Velocity↗

PubMed1993

Ultrasonic measurements of breathing rate in rats and computer assisted analysis.

PURPOSE: An ultrasound breathing rate measurement technique and a computer analysis algorithm have been developed to reduce the amount of time needed to collect and analyze animal breathing rate data, as well as to improve the testing environment. The system is not airtight, therefore, acclimatization and collection time is not limited, and the technique makes use of a top loading apparatus to facilitate animal entry. METHODS AND MATERIALS: Breathing rate is measured using two ultrasound transducers housed directly above the rat thorax in the plexiglass jig. The breathing rate signal is stored and evaluated by computer. The ultrasound technique was tested using a loud speaker driven by a signal generator, over a range of 30 to 450 cycles/min. In addition, the ultrasonic breathing rate method was used to record the breathing rate response of Sprague Dawley rats, treated with graded single doses of radiation, over a period of 170 days. RESULTS: For the loud speaker tests, the measured frequency agreed with that of the input signal with a maximum deviation of 1%. For the animal irradiations, all breathing rate data were analyzed by both user and computer selection of regular breathing. The techniques gave the same results at the 95% confidence limit. Using the computer program to assess the traces, 240 breathing rates can be determined per hour, from previously measured data. CONCLUSION: A new technique for measuring breathing rate has been developed and enhances both the collection and analysis of data.

Algorithms↗

PubMed2002

Direct reconstruction of MR images from data acquired on a non-Cartesian grid using an equal-phase-line algorithm.

The equal-phase line (EPL) algorithm is proposed as a means of allowing rapid Fourier transform (FT) reconstruction of MR image data acquired on a non-Cartesian grid. The pixels on the image are grouped according to their positions. The pixels in a group have the same phase in the complex exponential function -exp[j2pi(xu + yv)] and receive the same contribution from a data point. Each group is related to an EPL in the image space. The contribution of a data point can then be distributed to the pixels along the EPLs. The described EPL algorithm enables a decrease of the reconstruction time to about 40% of the direct FT (DrFT) for the non-Cartesian data. A numerical phantom and two sets of in vivo spiral data were used to investigate an optimal number of the EPLs and to measure the reconstruction time. The EPL algorithm runs nearly as fast as the look-up table (LUT) method (Dale et al. IEEE Trans Med Imaging 2001;20:207-217), but it does not require a large memory to store the coefficients in advance, as is required in the LUT method. Thus, the EPL algorithm can be used to reconstruct images up to 512 x 512 pixels in size in a PC of limited memory, and may be more conveniently applied to a multiprocessor system.

Algorithms↗

PubMed2002

Electromagnetic impedance tomography (EMIT): a new method for impedance imaging.

We propose a new impedance imaging method, electromagnetic impedance tomography (EMIT), in which the boundary electric potential measurements in electrical impedance tomography (EIT) are augmented by measurements of the exterior magnetic field induced by the currents excited in the object by the standard EIT procedures. These magnetic measurements can be obtained reliably and inexpensively by simple pickup coils located around the imaged cross section. We derive expressions for the forward problem and for the Jacobian of the measurements, and propose an iterative reconstruction algorithm using a squared error cost function. The performance of EMIT and EIT is compared in numerical simulations using a finite-element model for the conductivity distribution of several phantoms. Evaluation of the rank and condition of the Jacobian demonstrates that the additional magnetic measurements provided by a few pickup coils in EMIT turn an underdetermined EIT problem into a well-posed one with reasonable condition, or significantly improve the conditioning of the EIT problem when it is already fully determined. Reconstructions of various phantoms reveal that EMIT provides particularly significant visual and quantitative improvement (threefold to tenfold reduction in the root-mean-squared error) in the sensitivity at the center of the object, which is the area most difficult to image using EIT.

Computer Simulation↗

PubMed2006

An approach for clustering gene expression data with error information.

BACKGROUND: Clustering of gene expression patterns is a well-studied technique for elucidating trends across large numbers of transcripts and for identifying likely co-regulated genes. Even the best clustering methods, however, are unlikely to provide meaningful results if too much of the data is unreliable. With the maturation of microarray technology, a wealth of research on statistical analysis of gene expression data has encouraged researchers to consider error and uncertainty in their microarray experiments, so that experiments are being performed increasingly with repeat spots per gene per chip and with repeat experiments. One of the challenges is to incorporate the measurement error information into downstream analyses of gene expression data, such as traditional clustering techniques. RESULTS: In this study, a clustering approach is presented which incorporates both gene expression values and error information about the expression measurements. Using repeat expression measurements, the error of each gene expression measurement in each experiment condition is estimated, and this measurement error information is incorporated directly into the clustering algorithm. The algorithm, CORE (Clustering Of Repeat Expression data), is presented and its performance is validated using statistical measures. By using error information about gene expression measurements, the clustering approach is less sensitive to noise in the underlying data and it is able to achieve more accurate clusterings. Results are described for both synthetic expression data as well as real gene expression data from Escherichia coli and Saccharomyces cerevisiae. CONCLUSION: The additional information provided by replicate gene expression measurements is a valuable asset in effective clustering. Gene expression profiles with high errors, as determined from repeat measurements, may be unreliable and may associate with different clusters, whereas gene expression profiles with low errors can be clustered with higher specificity. Results indicate that including error information from repeat gene expression measurements can lead to significant improvements in clustering accuracy.

Algorithms↗

PubMed1996

[Detection of rapid eye movement with rapidly adapting neuronal fuzzy systems in imprecise REM syntax].

Both living beings and artificial neuronal networks are capable of 'learning' and behavioural adaptation. But also the fuzzy program designed to detect rapid eye movements (REM) during sleep and described here, can be provided with a self-learning option that provides important information about REM sleep. The algorithm computes REM on the basis of horizontal and vertical EOG. EEG, EMG and actiography signals are employed to optimize the method and eliminate artefacts. In a second step, the fuzzy system learns to detect REM with the aid of a sample data set and a minimal set of syntax rules. From sample data and the actions and reactions of visual scorers, the program extracts additional rules and information, which are then used to build a complete fuzzy structure. Thereafter, the REM detection program optimizes the fuzzy logic structure, independently of visual monitoring, on its own. A direct comparison of the results of the algorithm in a 10-night analysis with those of two experienced visual scorers revealed a better than 95% agreement. Re-analysis with the algorithm showed a 100% concurrence. Complete visual measurement of the eye movements occurring in a single night requires several hours; this compares with only 15 minutes required by the algorithm.

Algorithms↗

PubMed1983

A computerized timing algorithm for determination of pulmonary tissue volume.

We developed a computerized method to measure pulmonary tissue volume (Vt) and capillary blood flow (Qc) that requires only a single interface for measurement of a soluble and an insoluble gas. The method uses a timing algorithm that replaces either a marker gas (C18O) or a volume signal. Gas concentrations are stored in digitized form. The data analysis consists of three parts: 1) initial and end-tidal samples found by using minima and maxima; 2) a timing algorithm derived from the end-tidal dead space method (ETDS, J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 782-795, 1978); and 3) calculations of Vt and Qc, also by the ETDS method. Both the timing and Vt and Qc agree well with the hand-calculated values, but the coefficient of variation of Vt is slightly improved (6 vs. 7% manually). We conclude that our computerized method is equivalent to the manual ETDS method, but it is faster and more accurate; in addition, it has the advantage of requiring only one interface without the use of expensive gases.

Capillaries↗

PubMed2006

Combined use of ESI-QqTOF-MS and ESI-QqTOF-MS/MS with mass-spectral library search for qualitative analysis of drugs.

The potential of the combined use of ESI-QqTOF-MS and ESI-QqTOF-MS/MS with mass-spectral library search for the identification of therapeutic and illicit drugs has been evaluated. Reserpine was used for standardizing experimental conditions and for characterization of the performance of the applied mass spectrometric system. Experiments revealed that because of the mass accuracy, the stability of calibration, and the reproducibility of fragmentation, the QqTOF mass spectrometer is an appropriate platform for establishment of a tandem-mass-spectral library. Three-hundred and nineteen substances were used as reference samples to build the spectral library. For each reference compound, product-ion spectra were acquired at ten different collision-energy values between 5 eV and 50 eV. For identification of unknown compounds, a library search algorithm was developed. The closeness of matching between a measured product-ion spectrum and a spectrum stored in the library was characterized by a value called "match probability", which took into account the number of matched fragment ions, the number of fragment ions observed in the two spectra, and the sum of the intensity differences calculated for matching fragments. A large value for the match probability indicated a close match between the measured and the reference spectrum. A unique feature of the library search algorithm-an implemented spectral purification option-enables characterization of multi-contributor fragment-ion spectra. With the aid of this software feature, substances comprising only 1.0% of the total amount of binary mixtures were unequivocally assigned, in addition to the isobaric main contributors. The spectral library was successfully applied to the characterization of 39 forensic casework samples.

Algorithms↗

PubMedDate not supplied

Recent advances in the estimation of population exposure to mobile source pollutants.

The U.S. Environmental Protection Agency (EPA) has developed several computer-based exposure models applicable to pollutants which are directly or indirectly linked to mobile sources. Probabilistic versions of the National Ambient Air Quality Standards (NAAQS) Exposure Model (pNEM) have been used to estimate the exposures of urban populations to carbon monoxide and ozone. An enhanced version of the Hazardous Air Pollutant Exposure Model (HAPEM-MS) has been used to develop city-specific estimates of exposure to benzene and other volatile organic compounds emitted by mobile sources. These models are similar in that each contains algorithms that simulate microenvironmental pollutant levels, time/activity patterns, and commuting patterns. The pNEM models also provide estimates of equivalent ventilation rate (EVR), defined as ventilation rate divided by body surface area. This paper summarizes the methods and results of selected research projects conducted since 1991 with the goal of improving pNEM, HAPEM-MS, and similar exposure models applicable to mobile source pollutants. The studies include: (1) the development of an improved algorithm for estimating EVR, (2) a field study to measure ozone levels near roadways and inside vehicles, (3) the development of an algorithm for estimating school commuting patterns, and (4) the construction of a comprehensive database containing time/activity data from ten activity diary studies.

Adult↗

PubMedDate not supplied

A useful algorithm for calculating central ray TAR and TMR values.

An algorithm utilizing a two-dimensional polynomial power functions least squares fit has been applied to the calculations of TAR in the case of CO-60 teletherapy and TMR in the case of an 8MV LS75/10 linear accelerator giving less than +/- 1/2% errors respectively between calculated and measured values. The TAR and TMR algorithms are used as subroutines in pocket sized and table top programmable calculators or computers and thus provide rapid calculation of treatment time or monitor units as well as given dose.

Cobalt Radioisotopes↗