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Results for “Error minimization”

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PubMedDate not supplied

The Alzheimer's Disease Assessment Scale: evaluation of psychometric properties and patterns of cognitive decline in multicenter clinical trials of mild to moderate Alzheimer's disease.

PURPOSE: To evaluate the psychometric properties and patterns of decline on the total score and item scores of the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-Cog) in patients with Alzheimer Disease (AD). METHODS: We analyzed data from 536 AD outpatients randomized to the placebo group in two identical 26-week multicenter drug trials. RESULTS: Mean deterioration at week 26 on the ADAS-Cog total score for subjects with moderate dementia was 84% greater than that for those with milder severity ( p < 0.001). After adjusting for this effect, age ( p = 0.015) and educational level ( p = 0.01) also predicted cognitive decline. In a model, absolute change for most individual ADAS items was less than 10% of the possible change, and it was generally smaller than one-third of the standard deviation of the measure. Measurement error variability was greatest for word recognition and the "placebo" effect was greatest for word recall. Variability increased with trial duration in a model. CONCLUSIONS: There is a relationship between baseline severity and magnitude of cognitive decline. In 6-month trials, measurement error makes a substantial contribution to the variance in ADAS-Cog change scores. Sensitivity to intervention effects will therefore depend both on the variability and magnitude of change. Such data must be considered when designing future trials to minimize measurement error variability and increase sensitivity for specific populations.

Aged↗

PubMed1990

Long-term survivorship analysis of cruciate-sparing versus cruciate-sacrificing knee prostheses using meniscal bearings.

A comprehensive, interchangeable, low-contact-stress, mobile-bearing knee prosthesis system was developed and used over a 12-year period with both cemented and cementless fixation. Individual components of the system included a bicruciate-retaining meniscal bearing, a posterior cruciate-retaining meniscal bearing, and a cruciate-sacrificing, rotating-platform tibial component mated to the same femoral and rotating patellar components. Survivorship analysis of each implant type was performed to identify specific failure modes and trends for long-term survival of the implants in a wide variety of primary knee arthroplasties. Clinically, there were 46 prostheses of the bicruciate type followed for up to 12 years, 57 prostheses of the posterior-cruciate type followed for up to six years, and 108 prostheses of the rotating-platform type followed for up to ten years. All knees in this study had rotating-bearing patellar prostheses. Cumulative survivorship analysis using an end point of implant revision or a poor knee score revealed a small early failure rate of each implant in the first three years, associated with technical positioning or undersizing errors. This study indicates a predictable long-term survival of both cruciate-retaining and cruciate-sacrificing mobile-bearing knee prostheses as well as rotating-bearing patellar prostheses when used in primary knee arthroplasties that minimized technical errors of insertion.

Adult↗

PubMed1986

Experimental errors in digital image processing for the determination of geometrical parameters of the human eye.

A new method is presented for measuring geometrical parameters of the anterior segment of human eye. A digital imaging technique is employed in conjunction with a slit lamp and TV camera. A method was developed to analyze images and the problem of minimizing measuring errors was studied. The method was tested using a contact lens to simulate the anterior corneal surface.

Electronic Data Processing↗

PubMed2005

Model-based color halftoning using direct binary search.

In this paper, we develop a model-based color halftoning method using the direct binary search (DBS) algorithm. Our method strives to minimize the perceived error between the continuous tone original color image and the color halftone image. We exploit the differences in how the human viewers respond to luminance and chrominance information and use the total squared error in a luminance/chrominance based space as our metric. Starting with an initial halftone, we minimize this error metric using the DBS algorithm. Our method also incorporates a measurement based color printer dot interaction model to prevent the artifacts due to dot overlap and to improve color texture quality. We calibrate our halftoning algorithm to ensure accurate colorant distributions in resulting halftones. We present the color halftones which demonstrate the efficacy of our method.

Algorithms↗

PubMed1990

Optimal interelectrode distance with the method of source density analysis.

Three error sources which contribute to the total error of the second space derivative (SSD) used with the method of current source density analysis (CSD) were examined. The approximate formula usually used with CSD was the first error source. Another error originated from the finite interelectrode distance. The measurement error of the device with which the potential was recorded was the third error source herein considered. A relative SSD error was determined to estimate the effect of the errors examined. The experimental data (a section from the three-dimensional potential profile in annuran cerebellum produced by parallel fiber activation) were fitted by polynomials, Fourier expansion and cubic splines. Then a preferable interelectrode distance was obtained corresponding to the minimal relative error.

Animals↗

PubMed2002

Nosocomial infections in intensive care patients.

Facilities must manage core system processes to minimize medication errors and other adverse outcomes, such as nosocomial infections. Characterization of specific risk factors for the development of nosocomial infections and efficacious evidence-based care interventions are expanding. Health care providers need to evaluate their patient populations and systems of care to minimize lack of knowledge, slips. and lapses in care and other system issues to assure that successful care practices are consistently used to minimize nosocomial infections.

Cross Infection↗

PubMed2000

Prostate biopsy grading errors: a sampling problem?

Potential reasons for discordance between the Gleason score in biopsies and surgical specimens are: 1) pathological interpretation bias, and 2) sampling effects. The importance of sampling effects in grading errors was examined in a series where the number of biopsy cores obtained was high. Biopsies were obtained using a technique whereby 18 directed cores were systematically obtained and mapped out within the gland. Gleason scores from biopsies and matched prostatectomy specimens were compared among 28 consecutive patients with localized prostate cancer. A pooled database from 10 series (n = 2,687) served as a baseline for comparison in the accuracy of Gleason score grading. With the present biopsy technique, an exact Gleason score match was achieved in 57% of cases, compared with the pooled database (PD) mean of 42% (P = 0.055), and was within 1 point in 93% of cases compared with 78% (PD) (P = 0.029). Upgrading of biopsies was seen in 35% of cases, compared with 43% (PD) (P = 0.19). With respect to Gleason score 7, an exact match was present in 78% of cases, compared with 63% (PD) (P = 0.17), and upgrading was 0%, compared with 20% (PD) (P = 0.07). The data suggest a significant reduction in grade errors by minimizing sampling effects, one that it is of the same order of magnitude as the reduction achieved from consensus pathologic evaluation. In our study, seven patients (25%) would have had their cancers missed altogether with sextant biopsies. Sampling effects may contribute significantly to grading errors in prostate needle biopsies, although a larger study is needed to confirm this. A methodology which adopts a higher number of cores combined with a consensus pathologic evaluation could potentially reduce grading errors substantially. The optimal number of cores remains to be determined in a larger study. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 326-330 (2000).

Biopsy, Needle↗

PubMed1995

Synthesis, analysis, and optimization of cam-link prosthetic knee mechanism.

This paper presents the design of three-bar cam-link prosthetic knee mechanism using the instant centers of a natural knee measured experimentally obtained from literature. The cam in this mechanism is approximated as a nth order polynomial form. The instant centers generated by the mechanism are compared with those of the natural knee and the error is minimized using random search optimization techniques. Also, a tangents-merge method is used to develop the cam profile. Normals to the corresponding instant center radii of the cam are found and merged with suitable radii to get a continuous cam profile with no error at prescribed instant centers. The design gives a prosthesis with fewer links and greater accuracy. Results in the form of cam profiles, transmission angles and radius of curvatures are presented.

Biomechanical Phenomena↗

PubMed2000

Errors in histological grading by prostatic needle biopsy specimens: frequency and predisposing factors.

Sampling error is an inherent problem of prostate biopsy. Consequently, there are problems in determining whether a given carcinoma is clinically significant on the basis of biopsy results. This study assesses the factors that predispose to errors in biopsy grading, as well as the dimensions of sampling error due to these factors. Among 187 cases, biopsy grading error was retrospectively related to grade heterogeneity in the prostate and to biopsy-related factors. Clinically relevant biopsy grading errors occurred in a quarter of the cases. Of all grading errors, at least 17% resulted from misinterpretation by the pathologist only. Overall, prostates with grade heterogeneity revealed grading errors twice as frequently as specimens without grade heterogeneity. In most cases, however, grading error resulted from multiple factors, such as the number and length of cores obtained (p<0.05). This was an important finding because the mean core length was only 9.4 mm, whereas the biopsy needle is designed to obtain cores of 15 mm. Moreover, clinically relevant biopsy grading error had occurred in almost half of the cases when the Gleason score was based on a tumour deposit measvring less than 0.5 mm (p<0.05). The clinical consequences of these findings are important. Clinicians should try to obtain at least six biopsies, each 15 mm in length, to minimize grading error. Pathologists should be cautious in reporting Gleason scores based on tumour lesions smaller than 400x total magnification field. Interpretation could be refined, when necessary, by warning the urologist of the Limitations of the biopsy report.

Aged↗

PubMed1990

Estimation of relative mRNA content by filter hybridization to a polythymidylate probe.

We have developed an accurate and sensitive method for the quantitation of relative mRNA in RNA samples. This procedure is especially applicable for normalizing numerous RNA samples which are to be analyzed by dot blot hybridization. The method entails hybridization of a polythymidylate probe with RNA bound to filters. The relative hybridization of polythymidylate probe to RNA is proportional to the polyadenylate RNA content of the RNA samples. Hybridization of polythymidylate probe to RNA is not dependent on any cell treatment or growth condition that we have observed, and experimental variation is minimized. Therefore, the relative hybridization to polythymidylate probe is a better method for standardizing the amount of mRNA in RNA samples than is relative hybridization to cDNA probes such as actin or beta 2-microglobulin, whose transcript levels may vary according to cell treatment. Furthermore, since experimental variation and errors are minimized, this procedure is suitable for normalizing RNA samples in which there are only small changes in the levels of particular transcripts.

Animals↗

PubMed1993

Cryotherapy precision. Clinician's estimate of cryosurgical iceball lateral spread of freeze.

OBJECTIVE: To examine physicians' ability to estimate the lateral spread of freeze (LSF) of a cryosurgical iceball using three techniques. DESIGN: A nonrandomized control trial of in vitro nitrous oxide cryosurgical procedures. SETTING: Primary care residency training programs. PARTICIPANTS: A convenience sample of 80 resident and faculty physicians from four family practice residency programs and one obstetrics and gynecology residency program. INTERVENTIONS: After performing cryosurgery with standard naked-eye and colposcopic-assisted techniques, subjects used a new experimental cryosurgical iceball gauge (CIG) to estimate the LSF during cryotherapy. MAIN OUTCOME MEASURES: LSF estimations reported physicians were compared simultaneously with those measured by an observer. RESULTS: The mean (+/- SD) LSF estimation errors at the termination of freeze were as follows: 2.62 +/- 2.42 mm for the colposcopy technique, 2.00 +/- 2.16 mm for the naked-eye method, and 1.28 +/- 0.87 mm for the CIG technique. The range of maximum error was 6.5 to 11 mm for the colposcopic technique, 5.5 to 12.5 mm for the naked-eye method, and 3.0 to 4.0 mm for the CIG technique. CONCLUSIONS: Overestimation of the LSF, which increases the risk of undertreatment and residual disease, was more common than underestimation. The CIG minimized perceptual error and provided the best cryosurgical precision.

Calibration↗

PubMed2006

Slice profile optimization in arterial spin labeling using presaturation and optimized RF pulses.

OBJECTIVE: An important source of error in arterial spin labeling (ASL) is incomplete static tissue subtraction due to imperfect slice profiles. This effect can be reduced by saturating the spins in the imaging area prior to labeling. In this study, the use of optimized presaturation is compared with the use of optimized RF pulses for minimizing this error. MATERIALS AND METHODS: Different methods for optimizing presaturation were simulated by numerical solution of the Bloch equation. Presaturation was optimized by changing the number of presaturation pulses, their position in the pulse sequence and the area of the crusher gradients following each saturation pulse. It was also investigated whether the use of optimized presaturation could reduce the tag gap needed to ensure complete static tissue subtraction. Simulation results were verified using phantom and in vivo studies at 3T. RESULTS: In proximal inversion with control for off-resonance effects, optimized presaturation could reduce the necessary tag gap to 15% of the imaging slab for experiments using standard RF pulses, while c-FOCI RF pulses could reduce it to 11%. In flow-sensitive alternating inversion recovery, a single presaturation pulse could reduce the inversion width to 122% of the imaging slab and neither multiple presaturation pulses nor optimized RF pulses could reduce it further. CONCLUSION: Optimized presaturation can reduce the necessary inversion width to the same level as if using optimized RF pulses and can, therefore, be used to optimize ASL sensitivity. Furthermore, optimized presaturation can reduce the B(1)-dependent sensitivity in static tissue subtraction.

Adult↗

PubMed2006

UF6 enrichment measurements using TDLS techniques.

The objective of this work was investigation of possibility of tunable diode laser spectroscopy (TDLS) technique application for gaseous uranium hexafluoride (UF6) isotope measurement. Spectra of uranium hexafluoride gas mixture were investigated using two different Fourier Transform Spectrometers Vector 22 and Bruker 66v. Observed spectral features were identified and model spectra of different gas mixture components were developed. Optimal spectral range for measurements was determined near maximum of UF6 combination band nu1+nu3. Laboratory prototype of multi-channel instrument under consideration based on tunable diode lasers was built and algorithms were developed to measure gaseous UF6 isotopic ratios. Diode laser used operated at the wavelengths near lambda=7.68 microm. It was placed in a liquid nitrogen cooled cryostat. Three instrument channels were used for laser frequency calibration and spectra recording. Instrument was tested in measurements of real UF6 gas mixtures. Measurement accuracy was analyzed and error sources were identified. The root-mean-square random error in the 235U isotopic content is characterized by a spread of about 0.27% for quick measurements (at times less than 1 min) and 1% for periods of more than an hour. It was estimated that the measurement accuracy could be improved by at least an order of magnitude by minimizing the error sources.

Algorithms↗

PubMed2026

Hotgenes: an R package for reducing bottlenecks in bulk omics data exploration and collaboration.

SUMMARY: A critical part of omics analysis is the transition from early data exploration to final interpretation, often including different analytical platforms and the proliferation of figures, tables, and files. To minimize potential errors and delays that can occur during this process, we have developed an R package called "Hotgenes" that contains a wide range of flexible utilities available in a single modular Shiny application. With Hotgenes, differential expression results generated from bulk omics platforms can be imported and shared among collaborators with minimal coding. Furthermore, the modular Hotgenes user interface can be customized by advanced users to fit the needs of their evolving pipelines. AVAILABILITY AND IMPLEMENTATION: Hotgenes is implemented in R and is freely available at https://github.com/pfizer-opensource/Open-Hotgenes. A permanent archived version is available at https://doi.org/10.5281/zenodo.20129460.

Software↗

PubMed1992

Vision in the "good" eye of children treated for unilateral congenital cataract.

PURPOSE: The authors examined linear acuity and contrast sensitivity in the "good" (fellow) eye of children treated for unilateral congenital cataract to determine (1) whether there were subtle deficits like those described for the good eye of patients with strabismic amblyopia and (2) whether any deficits were related to the degree to which the good eye had been patched. METHODS: The authors tested patients treated for unilateral congenital cataract who had a well-documented history of patching. The good eye was physically normal with minimal refractive error. The measures were linear acuity at far (n = 15) and contrast sensitivity (n = 9). RESULTS: Compared with age-matched control subjects, the good eyes of patients had subtle deficits in linear acuity and in contrast sensitivity at high spatial frequencies. These deficits occurred even in eyes that had received minimal patching, and their severity was not related systematically to the duration of patching, which varied widely across the group. CONCLUSION: The visual sensitivity of the good eye of children treated for unilateral congenital cataract is, on average, slightly reduced, even in cases of minimal patching. Consequently, any deficits discovered after aggressive patching may not have been caused by occlusion amblyopia.

Adolescent↗

PubMed2006

Zeus robot-assisted laparoscopic cholecystectomy in comparison with conventional laparoscopic cholecystectomy.

BACKGROUND: The robotic surgical system overcomes many technological obstacles of conventional laparoscopic surgery, and possesses enormous clinical applied potential. The aim of this study was to compare the efficacy of Zeus robot-assisted laparoscopic cholecystectomy with conventional laparoscopic cholecystectomy. METHODS: Forty patients undergoing elective cholecystectomy were randomly divided into two groups. Patients in group A (n=20) underwent Zeus robot-assisted laparoscopic cholecystectomy, and patients in group B (n=20) received conventional laparoscopic cholecystectomy. The parameters on operative field, operative time, the number of actions, the rate of operative errors and minimal trauma were evaluated and compared between the two groups. RESULTS: The number of clearing camera (1.1+/-1.0 times) and the time of adjusting the operative field (2.2+/-0.7 minutes) in group A were significantly less than those (4.5+/-1.5 times) and (7.5+/-1.2 minutes) in group B. The number of dissection actions (337+/-86 times) and the rate of operative errors (10%) in group A were less than those (389+/-94 times), (25%) in group B. The total operation time (104.9+/-20.5 minutes) and setup time (29.5+/-9.8 minutes) in group A were significantly longer than those (78.6+/-17.1 minutes), (12.6+/-2.5 minutes) in group B. Blood loss and postoperative hospitalization were similar. No postoperative complications occurred in both groups, and open cholecystectomy was performed in each group. CONCLUSIONS: Zeus robot-assisted cholecystectomy inherits the benefits of minimally invasive surgery. The Zeus robotic surgical system is better than conventional laparoscopic technique in controlling the operative field and can be manipulated precisely and stably though it requires more operative time.

Adult↗

PubMed2005

The relationship between initial errorless learning conditions and subsequent performance.

This experiment explores a suggestion by [Maxwell, J.P., Masters, R.S.W., Kerr, E., Weedon, E. (2001). The implicit benefit of learning without errors. Quarterly Journal of Experimental Psychology A 54, 1049-1068] that an initial bout of implicit motor learning confers beneficial performance characteristics, such as robustness under secondary task loading, despite subsequent explicit learning. Participants acquired a complex motor skill (golf putting) over 400 trials. The environment was constrained early in learning to minimize performance error. It was predicted that in the absence of explicit instruction, reducing error would prevent hypothesis testing strategies and the concomitant accrual of declarative (explicit) knowledge, thereby reducing dependence on working memory resources. The effect of an additional cognitive task on putting performance was used to assess reliance on working memory. Putting performance of participants in the Implicit-Explicit condition was unaffected by the additional cognitive load, whereas the performance of Explicit participants deteriorated. The relationship between error correction and episodic verbal reports suggested that the explicit group were involved in more hypothesis testing behaviours than the Implicit-Explicit group early in learning. It was concluded that a constrained, uninstructed, environment early in learning, results in procedurally based motor output unencumbered by disadvantages associated with working memory control.

Adult↗

PubMed1986

[Determination of the distribution of ventilation-perfusion ratios: technic of elimination of multiple inert gases].

The multiple inert gas elimination technique (MIGT) facilitates the estimation of the distributions of ventilation-perfusion (VA/Q) ratios in the experimental and clinical setting. The most relevant technical aspects and equipment and operational requirements needed to measure a mixture of inert gases in both the gas phase and the blood phase using gas chromatography are overviewed with detail. Results obtained in 3 dogs and 4 syringe-homogeneous lung models were entirely consistent with data formerly reported in the literature. Particular attention is paid to the linearity of the gas chromatograph detectors, reproducibility of inert gases sampling, and analysis of brands of heparin to detect acetone content. The errors of measurement (coefficients of variation) in blood were: 1.4 for sulfur hexafluoride; 1.8% for ethane; 2% for cyclopropane and halothane, each; 2.4% for diethyl ether; and, 3.6% for acetone. Important practical points are also emphasized in order to draw attention to potential problems and issues that should be concentrated upon to minimize the error in the measurements. It is concluded that the setting up of the MIGT is well established and validated.

Animals↗