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At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

[The craniometric individuality of the human skull].

Experimental findings indicate that if the basic position of the skull is assessed visually (as is usually done in expert photocombination), various video images of the same skull never fully conform to each other, the deviations reaching 1.5 and more degrees. As a result of this, the accuracy of determining the reference points on the video image varies from 1.-1.5 to 4.0-4.5 mm (en face) and 1.5-2.0 to 6.0-6.5 mm (profile). The task of identification of two images of the skull is reliably solved in 87.7% cases, and in 12.3% cases the results may be false-positive or false-negative. The individuality of the skull, that is, the impossibility of its replacement during computer-aided photocombination is realized in the absence of aspect distortions and minimal errors of measurements. Hence, a new technology of studies is to be introduced: coordination-monitored stable complex of video camera and computer with metric monitoring of all parameters liable to change.

Cephalometry↗
PubMed1996

Comparative study of bedside and laboratory measurements of hemoglobin.

OBJECTIVE: The purpose of this study was to examine the effects of variations in technique on measurements of hemoglobin level done at the bedside and to compare these results with laboratory measurements of hemoglobin. DESIGN: In accordance with hospital policy, procedure, and protocol, various techniques were used to obtain samples of capillary and venous blood and of blood from arterial and central venous catheters. Levels of hemoglobin were measured at the bedside and in the laboratory, and the results were compared. SETTING: The Johns Hopkins Hospital adult postanesthesia care unit. SAMPLE: A total of 187 blood samples were obtained from 62 adults who had undergone general surgery. Group I comprised 20 subjects with capillary and venous blood samples. Group II comprised 21 subjects with arterial blood samples. Group III comprised 21 subjects with central venous blood samples. RESULTS: The results showed that the amount of blood to be discarded before obtaining samples of arterial and central venous blood need not be any larger than double the dead space of the catheter, and that shaking the blood sample for 10 seconds was sufficient to mix the sample before measurement of hemoglobin levels. Results of bedside and laboratory measurements of hemoglobin level were comparable. CONCLUSION: Bedside measurement of hemoglobin increases efficiency in patient care, decreases risk of blood-transmitted infection for staff, and decreases cost to the patient. However, the persons who perform the assay must be responsible in adhering to the standard of practice to minimize errors in the measurements.

Adult↗
PubMedDate not supplied

[The conclusions from an analysis of 9 approaches to determining the value of KT/Vur].

Causes underlying different results in estimation of KT/V (ur) according to 9 mathematical models are analyzed. These models are the following: 1) classic approach F.A. Gotch, 2) estimation according to E.G. Lowrei, KT/V = KT/0.6* (body mass), 3) according to R.M. Hakim, KT/V = ln(CoC), 4) according to K.K. Jindal, KT/V = 0.04*(1 - C/Co)*100% - 1.3; 5), 5) according to P. Calzavara, KT/V = (Co - C)*2/(Co + C), 6) according to J.T. Daugirdas, KT/V = ln[C/Co - 0.03 - UF/(dry mass), 7) according to C. Basile, KT/V = 0.023(1- C/Co*100%- 0.284, 8) according to P. Malchesky, 9) according to L. Garred et. al. Basing on the results of examination of a random sample of 120 patients on chronic dialysis it is inferred that the results obtained according to the approaches 1, 3 and 5 are more dependent on emergence of water sectors during the procedure leading to underestimation of KT/V value. In approaches 2, 8 and 9 the dialysis "dose" is estimated with minimal error. It is believed insufficient to estimate dialysis adequacy by KT/V only. It is proposed to make allowances also for the value of the ratio of true to apparent volume of urea distribution. The estimation should be made according to the formula: V/V = ln(Co/C)*0.6* (body mass)/KT.

Humans↗
PubMedDate not supplied

[Calculation of potential accuracy in measuring the angular coordinates of targets by the echolocator of bats using the equal-signal zone method].

Potential accuracy in measuring the course to a target is calculated. This accuracy is physically achievable it the hypothesis that an accurate measurement of angular coordinates of the target of bat's echolocator is realized by the method similar to that of equally signaling zone in radiolocation is true. Possible application of such a method is based on the "pulsation" of direction diagram in the course of radiation of the probing impulse. In this case crossing of partial diagrams of radiation corresponding to high- and low-frequancy regions of the impulse form the equally signaling zine. If the target is in this direction the amplitudes of autocorrelation functions formed by corresponding regions of reflected and probing impulses will be equal. The minimal error of the method is limited by the optimum duration of each of the compared correlation functions, which forms the basis for derivation of the formula evaluating this error. Numerical calculation of the accuracy of measurements of the angle achievable for the echolocator of Myotis blythi is performed by this formula proceeding from average experimental values of the echolocator characteristics. The model under consideration is shown to agree with a number of experimental data.

Animals↗
PubMed1995

The role of protocols and professional judgement in emergency medical dispatching.

The task of evaluating incoming calls to Emergency Medical Services (EMS) systems in order to determine the most appropriate response is performed in many different ways in current EMS systems. At one end of the spectrum, the process is entirely dependent on the judgement of professionals, while at the other end protocols specify the exact questions to be asked and corresponding decisions. This case study describes the experience of the Montreal EMS system, Urgences santé, where professional telephone evaluation performed by nurses since 1981 was replaced by a protocolized system in 1992. During the professional era, there were many attempts to formalize the nurses' decision-making process. These first revealed that professional judgement tended to override decision-support tools that did not allow a flexible processing of the information spontaneously provided by callers. Second, the choice of a single protocol for each call was unnatural for professionals who could spontaneously integrate multiple aspects of a problem in parallel. Third, when protocols were used by professionals, it was a posteriori in order to document their decisions rather than actually support them. Fourth, the use of Artificial Intelligence (AI) methods in order to formalize professional judgement revealed its great complexity, which was confirmed by cognitive analyses of the nurses' decision-making processes. In particular, decisions of not sending EMS resources seemed to be the most difficult. These unsuccessful attempts at formalizing professional judgement led to an evaluation of its performance in terms of results, i.e. to which extent actual decisions minimized errors (both false positives and false negatives) and decision times. A random sample of 1006 calls was collected and the ideal decision was determined by concensus of experts for each call based on the patient's clinical condition. This theoretical decision was considered as a goal standard to which actual decisions were compared. Data analysis revealed that sensitivity of telephone triage (i.e. decision to send EMS resources or not) was almost perfect and specificity was 0.55. The necessary compromise between sensitivity and specificity varied with the types of decisions. Decision times were related to the urgency of the situations, more urgent calls being processed more rapidly. These results were interpreted as representing sophisticated optimization processes in professional judgement. The professional system was replaced by a non-professional protocolized system in 1992. This new system has not yet been formally evaluated in terms of results, but many sources of evidence suggest that it was accompanied by a deterioration of performance. Many contextual factors influence the organization of telephone assessment in EMS systems. This case study suggests that professional judgement may be most useful in contexts where the demand for EMS services often exceeds the availability of resources. On the other hand, protocolized systems may be more appropriate in the absence of such constraints, and where the litigation context prohibits the occurrence of any false negative.

Artificial Intelligence↗
PubMedDate not supplied

[Design of reference panels of serum for testing the quality of HIV antibody tests in practical laboratories].

The authors define the scientific basis for development of panels of reference sera intended for effective control of the quality of enzyme immunoassay of HIV antibody screening. Special attention was paid to developing the technology of preparing standards highly stable serum samples with a preset concentration of anti-HIV antibodies. The resultant panel of reference sera was tried in screening for anti-HIV antibodies by enzyme immunoassay at seven diagnostic laboratories. Mathematical analysis of the results permits the detection of the minimal errors in studies with the use of serum panel of practical laboratories.

Blood↗
PubMedDate not supplied

Radiology information systems: evaluation and selection issues.

This article describes attributes of effective computer systems for radiology department management, such as the ability to minimize errors and data entry time while maximizing flexibility, data access and productivity. It also discusses implementation issues managers should be aware of in evaluating computer systems, including hardware platforms, input screens, output options and interfaces with other computer systems.

Computers↗
PubMed1976

[Method of superimposing the angiographically located supratentorial lesion on the scalp prior to craniotomy].

One of the important points in operation of the intracranial supratentorial lesion is appropriate site and size of bony window made by craniotomy and this matter is also important first step in procedure of craniotomy. On the other hand, the site and size of bony window made in craniotomy for supratentorial lesion has relationship with perfectibility of operation. The detail intracranial situation and extent of supratentorial lesion is decided from the datas of various examinations and the findings in cerebral angiogram give a most important and valuable information to the neurosurgeon at present. The neurosurgeons used to decide the area of craniotomy from the findings of cerebral angiogram but there are some difficulty in transfer of findings related with situation of supratentorial lesion in angiogram to the patient's scalp, because the film of cerebral angiography is a projected picture of spheric head by X-ray to the plane. The author devised the planning method of site and size of bony window in craniotomy by transfer the location and extent of supratentorial lesion in cerebral angiogram to the patient's scalp and the author have been recognized for the past five years that this method is simple one and has clinical accuracy. The principle of the author's method are as follows. The film of cerebral angiography in lateral projection and the patient's scalp are divided into nine parts by same manner and the relation of the site and extent of lesion in cerebral angiogram with divided parts transfer to the division of the patient's scalp under special care to make minimize errors due to use the cerebral angiogram which is picture made by projection in a plane from spheric intracranial supratentorial space. Five points and seven lines are used to divide the film of cerebral angiography and the patient's scalp. Five divide points are most upper part of margin of external acoustic meatus, most posterior edge of auricle, upper, lower and lateral edge of orbit. The following divide lines are drawn by use of these five divide points. Two horizontal lines are eye-ear horizontal line and superior eye horizontal line. Three vertical line are external acoustic meatus vertical line, auricular vertical line and temporal orbital margine vertical line. Two oblique lines are anterior and posterior oblique lines. The film of lateral cerebral angiography and patient's scalp are divided into nine parts by these seven divide lines. In the areas above the superior eye horizontal line, following procedure for correction of error due to transfer the point of X-ray film to the patient's scalp is needed because of strong curved brain surface. One end of celluloid or steel scale place closely with the scalp below the superior eye horizontal line and the other end of scale make freely from curved scalp surface. The point of lesion on the divide line of X-ray film marks at correspond point on the scale...

Brain Neoplasms↗
PubMed2002

A comparison of techniques to optimize measurement of voltage changes in electrical impedance tomography by minimizing phase shift errors.

In electrical impedance tomography, errors due to stray capacitance may be reduced by optimization of the reference phase of the demodulator. Two possible methods, maximization of the demodulator output and minimization of reciprocity error have been assessed, applied to each electrode combination individually, or to all combinations as a whole. Using an EIT system with a single impedance measuring circuit and multiplexer to address the 16 electrodes, the methods were tested on resistor-capacitor networks, saline-filled tanks and humans during variation of the saline concentration of a constant fluid volume in the stomach. Optimization of each channel individually gave less error, particularly on humans, and maximization of the output of the demodulator was more robust. This method is, therefore, recommended to optimize systems and reduce systematic errors with similar EIT systems.

Artifacts↗
PubMed2005

Do universal codon-usage patterns minimize the effects of mutation and translation error?

BACKGROUND: Do species use codons that reduce the impact of errors in translation or replication? The genetic code is arranged in a way that minimizes errors, defined as the sum of the differences in amino-acid properties caused by single-base changes from each codon to each other codon. However, the extent to which organisms optimize the genetic messages written in this code has been far less studied. We tested whether codon and amino-acid usages from 457 bacteria, 264 eukaryotes, and 33 archaea minimize errors compared to random usages, and whether changes in genome G+C content influence these error values. RESULTS: We tested the hypotheses that organisms choose their codon usage to minimize errors, and that the large observed variation in G+C content in coding sequences, but the low variation in G+U or G+A content, is due to differences in the effects of variation along these axes on the error value. Surprisingly, the biological distribution of error values has far lower variance than randomized error values, but error values of actual codon and amino-acid usages are actually greater than would be expected by chance. CONCLUSION: These unexpected findings suggest that selection against translation error has not produced codon or amino-acid usages that minimize the effects of errors, and that even messages with very different nucleotide compositions somehow maintain a relatively constant error value. They raise the question: why do all known organisms use highly error-minimizing genetic codes, but fail to minimize the errors in the mRNA messages they encode?

Animals↗
PubMed2005

Quality assessment of the mammographic screening programme in the Azienda Sanitaria locale Provincia Milano 1 -- analysis of interval cancers and discussion of possible causes of diagnostic error.

PURPOSE: To evaluate the sensitivity of the mammographic screening programme and the causes of diagnostic fault in cases surfacing as interval cancers. MATERIALS AND METHODS: Interval cancers (CI) were identified by linkage of the screening database for the years 2000-2002 to the database of hospital discharge records (HDR) for breast cancer during 2000-2002. Linkage between screening attenders during 2000-2001 and HDR (biennial follow-up for year 2000, one year follow-up for year 2001) was used to calculate the proportional rate of observed/expected IC. The observed/ expected rate was compared with international standards and literature data. Screening mammograms followed by IC, randomly admixtured with negative controls, underwent blind review by an independent radiologist, using the recommended classification criteria to evaluate causes of error (occult, minimal signs, screening error). RESULTS: The analysis of HDR during 2000-2002 allowed us to identify 31 out of 89 expected IC. Proportional observed/expected IC rate in the first or second year of screening interval was 26 or 67%, respectively. Screening mammograms for radiological review were available in 38 of 61 total IC: 20 cases (52.6%) were classified as occult, whereas minimal signs or screening errors were 2 (5.2%) or 16 (42.1%), respectively. Diagnostic suspicion had been reported at screening in 7 of 16 cases classified as screening error, but were not diagnosed at the subsequent diagnostic assessment. CONCLUSIONS: Proportional IC rate was higher than reported in the literature or currently recommended (<30% in the 1st, <50% in the 2nd year). The analysis of error causes shows an excess of screening errors with respect to current recommendations (<20% of IC should be classified as screening error at review), but also an excess of IC suspected at screening but misdiagnosed at assessment (7/38=18.4 %). Overall the analysis revealed a reduced sensitivity of the screening programme, as often observed in service screening as compared to excellence centres, and suggests proper action to improve diagnostic accuracy. Analysis and critical review of IC is an early indicator of screening efficacy which is not currently used in Italian screening programmes. Using HDR for this purpose may have limited drawbacks, but gives the advantage of earlier identification of IC as compared to cancer registries and is the most reliable source of information in areas lacking a cancer registry. The present study methodology might be currently applied in screening programmes.

Aged↗
PubMed1999

Neural network pattern recognition analysis of graft flow characteristics improves intra-operative anastomotic error detection in minimally invasive CABG.

OBJECTIVE: The intra-operative assessment of the quality of anastomosis in minimally invasive coronary artery bypass surgery (CABG) is critical. Recent investigations demonstrated that flow probes used intra-operatively to assess anastomotic errors may give the surgeon a false sense of confidence as only severely stenotic anastomoses (>90%) could be reliably detected. We developed a neural network system using graft flow data and assessed its potential to improve anastomotic error detection. METHODS: Mammary to LAD grafts (n = 46) were constructed in mongrel dogs off-pump. Continuous beat-to-beat graft flow was recorded using transit-time flow probes. Various degrees of anastomotic stenoses (0-100%) were created by an additional suture. The degree of anastomotic stenosis was confirmed by postoperative angiography. A learning vector quantization neural network was created using heart rate, mean aortic pressure, mean systolic, maximum systolic, minimum systolic, mean diastolic, maximum diastolic, minimum diastolic, and mean graft flows. In addition, a spectral analysis of the flow waveforms was performed and the magnitude and phase of the first five harmonics were used to further develop the neural network. RESULTS: The neural network pattern recognition system was 94% accurate in detecting any stenosis >50%. To validate the model, a testing set was used with 20% of the data values, and the accuracy remained at 100% above chance alone. CONCLUSION: Pattern recognition of transit-time flow probe tracings using neural network systems can detect anastomotic errors significantly better than the surgeon's visual assessment, thereby improving the clinical outcome of minimally invasive CABG.

Anastomosis, Surgical↗
PubMed2005

Patient-controlled analgesia safety issues.

Patient controlled analgesia (PCA) offers meaningful advantages over traditional analgesia. However, PCA medical errors with PCA can be dangerous and even fatal. Errors associated with patient controlled analgesia (PCA) therapy are described as are ways to minimize such errors. This report is based on data from the United States Pharmacopeia (USP) and Institute for Safe Medication practices (ISMP) Medication Errors Reporting Program. PCA by proxy, appropriate patients selection for PCA, patient monitoring, patient education, medication mix ups and practice related errors are discussed. Staff training is addressed. Methods to minimize errors associated with pump purchasing, PCA prrescribing, initiation, and monitoring are described. Recommendations for pharmaceutical manufacturers elated to PCA therapy are provided.

Analgesia, Patient-Controlled↗
PubMedDate not supplied

Quality control of mammography screening in the Veneto Region. Evaluation of four programs at a local health unit level--analysis of the frequency and diagnostic pattern of interval cancers.

AIMS AND BACKGROUND: Service mammography screening has been reported to have suboptimal performance compared to controlled trials. The aim of this study was to evaluate the sensitivity of the mammography screening program in four Local Health Units (ASL) and the possible causes of diagnostic error in cases further surfacing as interval cancers. MATERIAL AND METHODS: Interval cancers were identified by cross checking of screened women databases with hospital discharge records reporting breast cancer. Proportional interval cancer incidence (observed interval cancers/expected invasive cancers) was determined by matching the database of women screened during 1999-2002 to the hospital discharge records databases during 1999-2003. The ratio of observed interval cancer rate to underlying incidence was compared to international standards and with literature data. Screening mammograms reported as negative and followed by interval cancers were randomly mixed with true-negative controls, and the resulting set underwent blind review by an external radiologist who applied the conventional criteria recommended for the classification of the type of diagnostic error (occult, minimal signs, screening error). RESULTS: Matching of screening archives with the hospital discharge records databases allowed for the identification of 154 invasive interval cancers compared to 480 expected. The proportional observed/expected interval cancer incidence in the first and second year of the interval was 21% and 46%, respectively (ASL 1 = 14% or 38%, ASL 2 = 19% or 48%, ASL 3 = 30% or 53%, ASL 4 = 25% or 49%). Radiological review included 38 further interval cancer cases, identified after the time limits defined for proportional interval cancer incidence assessment, and could not include 18 interval cancers, not retrieved from ASL 4 archives: overall, 174 interval cancers were reviewed, of which 135 were classified as occult (77.3%) (ASL 1 = 83.3%, ASL 2 = 71.1%, ASL 3 = 78.6%, ASL 4 = 75%), 12 (6.9%) as minimal signs (ASL 1 = 6.6%, ASL 2 = 11.5%, ASL 3 = 2.4%, ASL 4 = 5%), and 27 (15.5%) as screening error (ASL 1 = 8.3%, ASL 2 = 17.3%, ASL 3 = 19.0%, ASL 4 = 25%). CONCLUSIONS: Observed proportional interval cancer incidence was lower than commonly reported for service screening programs and currently recommended (< 30% in the first, < 50% in the second year of the interval). The analysis of interval cancer causes showed a screening error rate below the maximum acceptable standard (< 20% of interval cancers should be classified as screening error) in three of four programs and in average figures. Substantial differences observed among single programs (one did not comply to recommended standards) suggest that space is available for the improvement of overall performance by optimizing program organization and by further training of radiologists. Overall, the analysis showed a good sensitivity of the screening program in the Veneto Region, although the performance was inferior to that of excellence centers, and further action to improve it is possible. Assessment and review of interval cancers is an early indicator of screening efficacy which has not yet been fully adopted in Italian screening programs. Although using hospital discharge records to identify interval cancers may be affected by limited errors, such a procedure is particularly convenient, as data from hospital discharge records are available much in advance compared to cancer registries and are the most reliable source of information for areas uncovered by a cancer registry. Hospital discharge records-based procedures for interval cancers assessment should be employed routinely in screening programs.

Breast Neoplasms↗
PubMed1983

Ophthalmic prisms. Measurement errors and how to minimize them.

Variable results of strabismus surgery may be due in part to errors in prism measurement. The amount of deviation neutralized by an ophthalmic prism is variable depending on how the prism is held. For example, a 40 delta glass prism with the posterior face held in the frontal plane gives only 32 delta of effect. Glass prisms are calibrated for use in the Prentice position. Plastic prisms are calibrated for use in the frontal plane position. Surprisingly large errors in prism measurement are produced when adding a small prism to a large prism. For example, adding a 5 delta glass prism to a 40 delta glass prism gives not 45 delta of effect, but 59 delta. This error can be minimized but not eliminated by holding one prism in front of each eye. The error can also be calculated so that the appropriate correction can be made.

Calibration↗
PubMed2003

An algorithm for three-way data analysis that alternatively minimizes coupled vector (COV) resolution error and PARAFAC error.

A novel algorithm, alternatively minimizing coupled vector (COV) resolution error and PARAFAC error algorithm, is proposed in this paper. This algorithm can overcome the problem of slow convergence and is insensitive to the estimation of component number, such problems are unavoidable while using the traditional parallel factors analysis (PARAFAC) algorithm. In other words, this algorithm is capable of improving the computing speed and providing accurate resolutions provided that the number of factors used in the computation is no less than that of the actual underlying ones. The characteristic performances were demonstrated with a novel fluorescence data array.

Journal Article↗
PubMed1985

Strategies and tactics in NMR imaging relaxation time measurements. I. Minimizing relaxation time errors due to image noise--the ideal case.

The effect of NMR image noise on errors in calculated values of relaxation times is quantitatively assessed by use of relaxation time noise figures, which are derived on the basis of statistical principles as functions of pulse delay, repetition, and recovery intervals for several types of pulse sequences. Two strategies for determining relaxation times are considered: two point (ratio of intensities for two experiments) and multipoint (least-squares fit of intensities to pulse-sequence functions for n experiments). For given total measurement times, values of pulse interval times are found which give minimum relaxation time noise figures. A comparison of ratio methods shows that the best is a combination saturation-recovery, inversion-recovery (SR/IR) technique. For short measurement times (less than about 10T1) this optimized SR/IR ratio determination is also superior to the best multipoint method, a series of inversion-recovery experiments with equally incremented inversion-recovery times. An examination of the effect of signal averaging on the relaxation time noise shows that up to a measurement time characteristic of the particular method used (e.g., for times up to about 5T1 for the SR/IR ratio determination, 100T1 for the multipoint inversion-recovery method), increased measurement time is more effectively allotted to longer pulse intervals than to signal averaging. Numerical examples are tabulated which can help one to set optimum values for pulse intervals, given a rough estimate of the relaxation time to be determined.

Magnetic Resonance Spectroscopy↗