Minimizing perspective error in gross photography.
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Photography↗
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Results for “Error minimization”
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[Preoperative and peroperative tactics and techniques for minimizing peroperative errors and technical mistakes].
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Endocrine Surgical Procedures↗
Acoustic absorption measurement of human hair and skin within the audible frequency range.
Utilizing the two-microphone impedance tube method, the acoustic absorption of human skin and hair is measured in the frequency range 1-6 kHz. Various locations on a number of human subjects are measured to determine if the presence of bone or an air pocket affects the acoustic absorption of human skin. The absorption coefficient of human hair is also measured. Additional techniques are utilized to minimize errors due to sample mounting methods. Techniques are employed to minimize potential errors in sensor and sample locations. The results of these measurements are compared to relevant historical papers on similar investigations. Results for skin measurements compare well with previous work. Measured hair absorption data do not agree with previous work in the area but do coincide with expected trends, which previous works do not.
Absorption↗
Patient safety in surgery: error detection and prevention.
Error in medicine is becoming a well recognized phenomenon. The U.S. Institute of Medicine's publication in 1999 included estimations that medical error is the eighth leading cause of death in the United States and results in up to 100,000 deaths annually. Retrospective studies and a few prospective studies are shedding more light on this challenging problem. Strategies to reduce error and increase patient safety have not been widely developed or embraced by surgeons for a variety of reasons. We provide a review on patient safety aimed at surgeons that includes definitions, incidence of errors including those in the surgical literature, causes of error, methods of error detection, and strategies to minimize errors and maximize patient safety.
Communication↗
Predicting forage indigestible NDF from lignin concentration.
We used chemical composition and in vitro digestibility data from temperate and tropical forages to develop relationships between indices of lignification and forage indigestible NDF. Neutral detergent fiber indigestibility increased nonlinearly as the lignin concentration of the NDF increased. Differences in estimated indigestible NDF using equations developed for a specific forage class (C3 and C4 grasses and legumes) were small and are probably not biologically significant when compared to those estimated from a common equation. Selected equations were compared with the Cornell Net Carbohydrate and Protein System (CNCPS) for the prediction of ADG. The linear equation (2.4 times NDF lignin content) used by the CNCPS and the Beef NRC had some of the largest errors due to mean bias. A log-log model [4.37 x (lignin/NDF)(.84)] provided the best combination of low total prediction error, low mean bias, and minimal error due to regression bias when permanganate lignin was used. A similar equation based on sulfuric acid lignin [6.17 x (lignin/NDF)(.77)] also met the above criteria. These equations then were evaluated with the CNCPS model against animal growth data from diets ranging in forage quality. Regardless of the equation used for predicting unavailable fiber, the CNCPS underpredicted daily gain, with mean biases ranging from -.10 to -.22 kg/d. Regression bias ranged from .13 to .14 kg/d and the coefficients differed from unity (P = .0001). The new equations gave numerically lower energy allowable ADG by steers compared to the linear equation currently used by the CNCPS model. The estimates were lower due to a higher predicted indigestible NDF, which resulted in a lower estimated forage energy value.
Animal Feed↗
Correction approaches for doubly labeled water in situations of changing background water abundance.
Doubly labeled water (DLW) is an accurate, portable method for measuring free-living energy expenditure. However, under certain conditions shifts in baseline abundance of deuterium and oxygen-18 tracers used in the method may produce errors in derivation of both turnover (k) rates and calculated energy expenditure. Present objectives were to examine during what experimental situations baseline errors arise and to address means of correcting for such baseline shifts so that consequent errors in energy expenditure calculations are minimized. Under conditions where shifts in baseline abundance for deuterium and oxygen-18 parallel abundances corresponding to the natural meteoric water ratio, self-compensating changes in k values for both deuterium and oxygen will result in minimal error to the DLW energy expenditure calculations, provided that the dose ratio of isotopes also mimics the meteoric water line. However, in situations where relative shifts in abundance of each isotope across the measurement period are not in parallel relative to the natural meteoric water line, then the potential for larger DLW errors exists. Optimally, subjects should equilibrate with the new water source. Failing this, correction for shifting baseline can be accomplished by measuring isotopic abundance changes in a control group of subjects not given the DLW dose, but performing similar tasks and consuming the same diet as the group given DLW. Alternatively, theoretically based correction values can be calculated given knowledge of the abundances of the final drinking water and the interval time that subjects consumed the new fluid.
Body Water↗
Application of the keyhole technique to T1rho relaxation mapping.
PURPOSE: To demonstrate the feasibility of using the keyhole technique to minimize error in a least squares regression estimation of T(1rho) from magnetic resonance (MR) image data. MATERIALS AND METHODS: The keyhole method of partial k-space acquisition was simulated using data from a virtual phantom and MR images of ex vivo bovine and in vivo human cartilage. T(1rho) maps were reconstructed from partial k-space (keyhole) image data using linear regression, and error was measured with relation to T(1rho) maps created from the full k-space images. An error model was created based on statistical theory and fitted to the error measurements. RESULTS: T(1rho) maps created from keyhole images of a human knee produced levels of error on the order of 1% while reducing standard image acquisition time approximately by half. The resultant errors were strongly correlated with expectations derived from statistical theory. CONCLUSION: The error model can be used to analytically optimize the keyhole method in order to minimize the overall error in the estimation of the relaxation parameter of interest. The keyhole method can be generalized to significantly expedite all forms of relaxation mapping.
Animals↗
Optimized pulse parameters for reducing quantitation errors due to saturation factor changes in magnetic resonance spectroscopy.
We present an analysis of the effects of chemical exchange and changes in T(1) on metabolite quantitation for heart, skeletal muscle, and brain using the one-pulse experiment for a sample which is subject to temporal variation. We use an optimization algorithm to calculate interpulse delay times, TRs, and flip angles, theta, resulting in maximal root-mean-squared signal-to-noise per unit time (S/N) for all exchanging species under 5 and 10% constraints on quantitation errors. The optimization yields TR and theta pairs giving signal-to-noise per unit time close or superior to typical literature values. Additional simulations were performed to demonstrate explicitly the dependence of the quantitation errors on pulse parameters and variations in the properties of the sample, such as may occur after an intervention. We find that (i) correction for partial saturation in accordance with the usual analysis neglecting variations in metabolite concentrations and rate constants may readily result in quantitation errors of 15% or more; the exact degree of error depends upon the details of the system under consideration; (ii) if T(1)'s vary as well, significantly larger quantitation errors may occur; and (iii) optimal values of pulse parameters may minimize errors in quantitation with minimal S/N loss.
Adenosine Triphosphate↗
The genetic code at the balance point of error and demand.
The origin and organizing principles of the genetic code remain central problems in molecular evolution. The low probability of the natural codon-to-amino acid mapping arising by chance has spurred the hypothesis that its structure is optimized for robustness to mutations and translational errors. For the construction of effective molecular machines, the repertoire of encoded amino acids must also be diverse enough in physicochemical features. Here, we examine whether the standard genetic code can be understood as a near-optimal solution balancing these two objectives: minimizing error load and aligning codon assignments with the naturally occurring amino acid composition. Using simulated annealing, we explore this trade-off across a broad range of parameters. We find that the standard genetic code resides near an optimum in the fitness landscape of possible genetic codes. The degeneracy of the code plays a dual role, minimizing mistranslation errors while matching codon multiplicity to amino acid usage frequencies. As a result, uniform codon usage alone is sufficient to recover the empirical amino acid composition, without any additional bias. It is a highly effective solution that balances fidelity against resource availability constraints. A comparative analysis of natural variants also reveals a functional decoupling: error robustness acts as a rigid global constraint determined by code topology, whereas compositional alignment serves as a more flexible variable that adapts to lineage-specific demands. These results support a multi-objective optimization framework in which the genetic code reflects a balance between translational fidelity and proteomic demand.
Genetic Code↗
Infrared patient positioning for stereotactic radiosurgery of extracranial tumors.
We report on a novel, non-invasive patient positioning system for radiosurgery of extracranial tumors. The system consisted of infrared cameras and reflective markers attached to the skin. Because localization accuracy is critical in radiosurgery, we performed a theoretical analysis of the accuracy of the system. A computer simulation program modeled errors in marker position, and was used to predict errors in targeting and study methods for minimizing errors. The use of redundant markers improved the overall accuracy of targeting. Experimental data was collected using a rigid torso phantom and correlated with theoretical results. The accuracy of the infrared system was compared with existing systems.
Computer Simulation↗
Error rates in clinical radiotherapy.
PURPOSE: Error rates in clinical oncology are undergoing increasing scrutiny. The purpose of this study was to understand error frequency, error patterns, underlying causal links, consequences, and possible prevention strategies in clinical radiotherapy. PATIENTS AND METHODS: Treatment information, self-reported error documentation, and retrospective analyses of electronic treatment verification transcripts for 1,925 consecutive patients treated with a total of 93,332 individual radiotherapy fields were reviewed and analyzed. RESULTS: A total of 59 separate errors that affected 168 individual treatment fields were detected, which yielded a crude radiation delivery error rate of 0.18%. All 59 errors were judged to be level I (negligible chance of adverse medical outcome) with the most common error category being a minor treatment field block misplacement. A comprehensive quality assurance program and an electronic record-and-verify linear accelerator interlock system seem to have prevented the occurrence of many additional errors. However, nine of the 59 errors were directly related to the use of this system and generally involved the transposition of similar numbers within series of treatment coordinate data-sets. Overall, radiotherapy error rates favorably compare with reported error rates for pharmaceutical administration in large tertiary care hospitals. CONCLUSION: When modern automated error-minimization methods are used along with nonpunitive error reporting systems, clinical radiotherapy seems to be highly safe. Formal error analysis studies may allow the rational design of prevention strategies that are attuned to the frequency, seriousness, and antecedent causes of many classes of potential radiotherapy errors.
Humans↗
Signal detection via residence times statistics: noise-mediated minimization of the measurement error.
We study the problem of detecting a small dc signal by quantifying its effect on the mean difference DeltaT in residence times in the stable steady states of a bistable dynamical measurement device, in the presence of a noise floor and a known time-sinusoidal bias signal. Errors in the measurement process occur due to a finite observation time that is present in most practical scenarios. The error is found to have a nonmonotonic dependence on the noise intensity; at a critical noise intensity, the error is minimized. This phenomenon, reminiscent of the well-known stochastic resonance effect, can also be obtained by adjusting the device tuning parameters for a given noise floor. The effect appears to be most pronounced for subthreshold bias signals in the strongly nonlinear response regime.
Journal Article↗
Interruptions improve choice performance in gray jays: prolonged information processing versus minimization of costly errors.
Under the assumption that selection favors minimization of costly errors, erroneous choice may be common when its fitness cost is low. According to an adaptive-choice model, this cost depends on the rate at which an animal encounters the choice: the higher this rate, the smaller the cost of choosing a less valuable option. Errors should thus be more common when interruptions to foraging are shorter. A previous experiment supported this prediction: gray jays, Perisoreus canadensis, were more error prone when subjected to shorter delays to access to food rewards. This pattern, though, is also predicted by an attentional-constraints model. Because the subjects were able to inspect the rewards during delays, their improved performance when subjected to longer delays could have been a byproduct of the experimentally prolonged opportunity for information processing. To evaluate this possibility, a follow-up experiment manipulated both delay to access and whether rewards could be inspected during delays. Depriving jays of the opportunity to inspect rewards (using opaque lids) induced only a small, nonsignificant increase in error rate. This effect was independent of length of delay and so the jays' improved performance when subjected to longer delays was not simply a byproduct of prolonged information processing. More definitively, even when the jays were prevented from inspecting rewards during delays, their performance improved when subjected to longer delays. The findings are thus consistent with the adaptive-choice model.
Animals↗
Picogram detection of stable dye-DNA intercalation complexes with two-color laser-excited confocal fluorescence gel scanner.
The stable complexes between highly fluorescent, polyfunctional intercalators and dsDNA can be used to detect dsDNA in agarose gels at picogram levels and for multicolor detection of multiplexed dsDNA fragments. Development of additional DNA-binding fluorophores with appropriate spectroscopic properties will expand the range of applications. In principle, the DNA-dye intercalation complexes represent a more sensitive alternative to an established approach to fluorescent labeling and detection of restriction fragments by ligation to single-stranded short oligonucleotides labeled with different fluorochromes, followed by separation on denaturing polyacrylamide gels. The latter technique gives near single-base resolution up to 400 bases and the ability to quantitate fragment size up to 2000 bases, and has been successfully applied to cosmid mapping. Detection of DNA fragments as intercalation complexes requires that the separations be performed on agarose gels under nondenaturing conditions. Such conditions have been used for extensive mapping of yeast cosmids with postelectrophoresis staining with ethidium bromide. For the patterns on agarose gels, the magnitude of the "error window," which specifies how similar two fragments must be before the corresponding fragments in different digests are paired, was reported to be strongly size dependent. The error window was expanded by a factor of 1.3 for fragments from 400 to 600 bp, 1.2 for fragments from 600 to 800 bp, and 1.1 for fragments from 800 to 1000 bp. Moreover, it was necessary to introduce corrections for systematic differences between size estimates taken from two different gels. For the multiplexing procedure described here, the size estimates for fragments from 600 bp to over 23 kbp were in close agreement with actual sizes as determined from DNA sequence (Table I), and certainly within the error windows given above. The multiplexing procedure should also minimize errors introduced by gel-to-gel variations in mobility, because the standard and unknowns are always run in the same lanes. Kohara et al. established a physical map of almost the entire Escherichia coli chromosome by analysis of a large genomic library. In this case, partial restriction digests were used to generate patterns of fragments and the mapping was performed by agarose gel electrophoresis. The disadvantage of this approach is that fewer fragments are generated. However, this is compensated for by the fact that partial digests reveal the order of the fragments produced and thus greatly increase the amount of information relevant to the question of overlap between different DNA fragments.(ABSTRACT TRUNCATED AT 400 WORDS)
Benzothiazoles↗
Sensory adaptation as Kalman filtering: theory and illustration with contrast adaptation.
Sensory adaptation allows biological systems to adjust to variations in the environment. A recent theoretical work postulated that the goal of adaptation is to minimize errors in the performance of particular tasks. The proposed minimization was Bayesian and required prior knowledge of the environment and of the limitations of the mechanisms processing the information. One problem with that formulation is that the environment changes in time and the theory did not specify how to know what the current state of the environment is. Here, we extend that theory to estimate optimally the environmental state from the temporal stream of responses. We show that such optimal estimation is a generalized form of Kalman filtering. An application of this new Kalman-filtering framework is worked out for retinal contrast adaptation. It is shown that this application can account for surprising features of the data. For example, it accounts for the differences in responses to increases and decreases of mean contrasts in the environment. In addition, it accounts for the two-phase decay of contrast gain when the mean contrast in the environment rises suddenly. The success of this and related theories suggest that sensory adaptation is a form of constrained biological optimization.
Adaptation, Physiological↗
Quality and liability issues with the Papanicolaou smear: lessons from the science of error prevention.
The pathologists and cytologists who study Papanicolaou smears perform a highly successful cancer screening test in a low-prevalence population. This leads to a mathematically inevitable false-negative error rate even in the most competent professional hands. The US judicial system supports a public expectation of perfect performance by civil and, recently, criminal punishment of error. Lessons are sought from a considerable industrial experience with accident prevention for possible insights into process improvement that might mitigate the risk of false-negative errors. The elements that, by system analysis, contribute to accidents are reviewed, and the conditions that enhance the accident potential are outlined. The cognitive functions and aberrations that are involved in the operator component of error analysis are described. As a result of pathologists' activities in the systematic measurement of laboratory performance for the last half century, the College of American Pathologists' accreditation program and its derivative Clinical Laboratory Improvement Act requirements have already laid out the avenues of error minimalization. There are no lessons from the science of error prevention that can affect the public expectation of zero error in a screening test and the consequent punishment of cytology professionals. A thesis is offered that the problem is society's if its goal is eradication of cervical cancer mortality. A call is made for leadership by a prestigious, nonpathologist, national organization to make the public understand that the current cytology liability issue is primarily a threat to women and the public health. To initiate public dialogue, a mechanism is suggested to protect simultaneously a patient's right of access to the judicial system and the general availability of the Papanicolaou smear to reduce cervical cancer mortality and morbidity.
Diagnostic Errors↗
Primary error detection and minimization (PEDMIN) strategies in social cognition: a reinterpretation of confirmation bias phenomena.
A broad empirical literature demonstrates what has been termed a confirmation bias or positive test strategy heuristic in reasoning (Klayman & Ha, 1987), a potentially maladaptive pattern of data preferences that coexists with more normative preferences for highly diagnostic information (Skov & Sherman, 1986). A model is developed to account for these variations in test strategies, beginning with the premise that cognitive processes are adapted to reducing particularly costly errors rather than to detecting "truth" (Cosmides & Tooby, 1992). By specifying the information required to minimize various errors of primary concern, the model clarifies the adaptiveness of certain confirmatory preferences, identifies conditions under which such preferences should diminish, and outlines how error minimization goals might produce data preferences coincidentally consistent with normative prescriptions.
Attention↗