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At least 1,531 records · Page 85Linked to original sources
PubMed2001

Monocrystalline iron oxide nanoparticles: possible solution to the problem of surgically induced intracranial contrast enhancement in intraoperative MR imaging.

BACKGROUND AND PURPOSE: Intraoperative MR imaging is increasingly being used to control the extent of surgical resection; however, surgical manipulation itself causes intracranial contrast enhancement, which is a source of error. Our purpose was to investigate the potential of monocrystalline iron oxide nanoparticles (MIONs) to solve this problem in an animal model. METHODS: In male Wistar rats, surgical lesions of the brain were produced. The animals underwent MR examination immediately afterward. In the first group, a paramagnetic contrast agent was administered, whereas the second group of animals received MIONs 1 day before surgery. In a third group of animals, malignant glioma cells were stereotactically implanted in the caudoputamen. Two weeks later, MIONs were IV injected and the tumor was (partially) resected. Immediately after resection, MR examination was performed to determine the extent of residual tumor. RESULTS: Surgically induced intracranial contrast enhancement was seen in all animals in which a paramagnetic contrast agent was used. Conversely, when MIONs had been injected, no signal changes that could be confused with residual tumor were detected. In the animals that had undergone (partial) resection of experimental gliomas, MR assessment of residual tumor was possible without any interfering surgically induced phenomena. CONCLUSION: Because MIONs are stored in malignant brain tumor cells longer than they circulate in the blood, their use offers a promising strategy to avoid surgically induced intracranial contrast enhancement, which is known to be a potential source of error in intraoperative MR imaging.

Animals↗
PubMed1985

[Errors in blood transfusion. Causes and prevention].

Authors, analyzed the possible sources of errors resulting in the administration of incompatible blood and of the specific professional responsibilities connected to that error, point out the precautions to minimize it and the therapy which is to be followed in the cases of serious haemolytic transfusion reactions.

Anemia, Hemolytic↗
PubMed1995

Approach to genotyping errors caused by nontemplated nucleotide addition by Taq DNA polymerase.

Thermostable DNA polymerases can catalyze nontemplated addition of a nucleotide to the 3' end of amplification products. This presents a potential source of error in genotyping studies employing Taq DNA polymerase to amplify microsatellite loci. Although the activity is marker specific, experimental variation is often seen in the degree of modification. Consequently, for a given microsatellite marker, an allele may be inconsistently identified as either the unmodified or modified amplification product. Full automation of high-throughput genotyping has been hampered by the need for manual editing of data because of this source of allele misidentification. In this study we estimate a 1% to 3% error rate attributable to nontemplated nucleotide addition in the ABI PRISM genotyping system. We present a PCR-based strategy to minimize this source of error.

Alleles↗
PubMed2002

Iron-oxide-enhanced magnetic resonance imaging of atherosclerotic plaques: postmortem analysis of accuracy, inter-observer agreement, and pitfalls.

INTRODUCTION: Contrast-enhanced magnetic resonance (MR) imaging using ultra small superparamagnetic iron oxide (USPIO) particles is a new noninvasive modality for imaging inflammatory atherosclerotic plaques. We determined the accuracy, interobserver agreement, and potential sources of error of this technique by means of postmortem MR imaging of aortic preparations. MATERIAL AND METHODS: Anesthetized atherosclerotic Watanabe heritable hyperlipidemic (WHHL) rabbits were studied after administration of different dosages of intravenous USPIO (DDM 43/34, IDF Berlin, Germany) and different postcontrast time intervals. A (n = 5) received 0 micromol Fe/kg. B (n = 5) received 50 micromol Fe/kg, 8-hour postcontrast interval. C (n = 5) received 50 micromol, 24 hours. D received 200 micromol, 48 hours. The aortas were removed and 3-mm segments prepared for postmortem examination by MR imaging using a T2-weighted gradient-echo sequence (TR/TE/FA; 41 milliseconds/11 milliseconds/15 degrees ), radiography (mammography), and histology (iron staining). USPIO accumulation was defined as the presence of 20 iron-positive cells per microscopic view (x100 magnification). Two independent readers analyzed the MR images and rated their confidence level for a positive MRI finding, defined as a focal signal loss, on a 5-point scale. The results were evaluated by receiver-operator characteristic (ROC) analysis. RESULTS: Of a total of 621 vessel segments technically acceptable for evaluation, 534 were histologically negative and 87 positive. Accuracy, expressed as the area under the ROC curve, was 0.85 for reader 1 and 0.88 for reader 2. Interobserver agreement was 0.67. False-positive findings were established by at least one reader for 121 of the 621 segments, false-negative findings for only 15 segments. Calcifications and mural thrombi were identified as potential sources of error of the method. CONCLUSION: Postmortem USPIO-enhanced MR imaging of atherosclerotic plaques showed a high accuracy and good interobserver agreement in the animal model used here. Further optimization of the method should aim at reducing the rather high percentage of false-positive results.

Animals↗
PubMed1995

On the reduction of error in alpha track detector measurements of indoor 222Rn.

Small plastic chambers containing alpha track detectors are often used for measuring indoor concentrations of 222Rn. This paper reports an experimental assessment of sources of error in measurements made with alpha track detector-containing chambers. The results demonstrate the feasibility of a nondestructive test for the identification of alpha track detector-containing chambers that are packaged in a way that does not effectively prevent ambient 222Rn from inducing tracks prior to field exposure. Results also indicate that there is statistically significant variation among manufacturing lots and among chemical processing batches. Error from these sources can be avoided or compensated if appropriate control measures are implemented as part of a quality assurance program during any survey using alpha track detector-containing chambers.

Air Pollutants, Radioactive↗
PubMed2006

Environmental and individual predictors of error in field estimates of blood alcohol concentration: a multilevel analysis.

OBJECTIVE: Using self-report survey data and measures of breath alcohol concentration (BrAC), this study examined the validity of an estimate of blood alcohol concentration (eBAC). Differences between eBAC and BrAC were modeled to identify sources of error related to survey-derived eBAC. Further, using hierarchical multilevel analyses, environmental event characteristics were examined as sources of eBAC error. METHOD: College students were interviewed and provided breath samples at randomly selected parties on Friday and Saturday nights. Interviews included items assessing the total number of drinks consumed, duration of drinking event, gender, and weight, which allowed for the calculation of eBAC. RESULTS: Overall, eBACs were inaccurate. Total number of drinks consumed was associated with underestimates of eBAC, whereas time drinking was associated with overestimates of eBAC. Environmental variables, including party size, rowdy behavior, having food present, and observing many intoxicated partygoers, were also associated with eBAC errors. CONCLUSIONS: Current self-report survey methodology to calculate eBAC may be insufficient to estimate BAC with any accuracy. Environmental factors associated with the last drinking event for which BAC is being estimated should be considered when calculating eBAC.

Adolescent↗
PubMed1985

Low-voltage ELF electric field measurements in ionic media.

Low-voltage electric fields were measured in conductive tissue culture media using three techniques: voltage slope, current density-conductivity, and dipole methods. All three methods tested yielded comparable results. However, all three techniques have associated errors. These errors fall into three major categories: those associated with the measurement equipment, those associated with electrodes, and errors in cross-sectional area measurements. Each source of error is discussed so that all can be taken into account during construction and/or testing of exposure equipment.

Culture Media↗
PubMed1987

Surgical staging of gastric carcinoma: sources and consequences of error.

Macroscopic 'TNM' staging was performed during 78 consecutive operations for gastric carcinoma and compared with subsequent pathological staging. Surgical assessment was correct for tumour (T) in 60 per cent when depth of invasion was assessed, for nodes (N) in 61 per cent, for liver metastases (M) in 92 per cent but for all aspects in only 21 per cent. Curability (conservatively defined as T1-3, N0-1, M0) was correct in 8 of 18 patients thus assessed at surgery and incurability was pathologically correct in 58 of 60 patients. Despite inaccurate surgical staging, no patient was denied a resection although 10 patients had unduly radical procedures for their stage and 2 had inappropriately conservative procedures for their stage (but without evidence of residual disease). Staging errors did not jeopardize conventional surgical management substantially and use of intra-operative microscopic sampling of nodes would have improved surgical treatment only minimally.

Humans↗
PubMed1993

Sizes and sources of field placement error in routine irradiation for prostate cancer.

Discrepancies between prescribed and treated field edges have been measured from 76 film pairs taken on 29 patients being treated for prostate cancer. The distribution of field edge discrepancies is described by a standard deviation of 4.5 mm and has an average absolute value of 3.5 mm. The observed discrepancies are shown to be attributable to field position errors and hence, in principle, are easily rectifiable.

Carcinoma↗
PubMed2006

Sample to sample carryover: a source of analytical laboratory error and its relevance to integrated clinical chemistry/immunoassay systems.

BACKGROUND: Integrated systems that combine clinical chemistry and immunoassay analyzers are used routinely. Sample to sample carryover is an inherent risk and can cause erroneously high patient test results for immunoassays. IVD manufacturers and laboratories must be aware of this phenomenon and guard against it. METHODS: We used a sample carryover protocol that directs the clinical chemistry module to process samples with very high immunoassay analyte concentrations followed by samples with very low concentrations for the same analyte. Low concentration samples were then tested by the immunoassay module to determine if the clinical chemistry module caused primary sample tube to primary sample tube carryover of the immunoassay analyte. RESULTS: Sample carryover was assessed on the Abbott ci8200 for HBsAg, AFP, beta-hCG, and PSA. Observed HBsAg carryover met the design specification of <0.1 ppm. Carryover for the other analytes was <0.1 ppm or below the assay limit of detection. CONCLUSIONS: IVD manufacturers must design integrated systems to minimize primary specimen tube carryover and avoid analytical laboratory error that can impact patient safety. Carryover testing is difficult for clinical laboratories to perform in order to verify system performance. Laboratories must consider the potential for specimen carryover and its impact on results whether moving primary sample tubes between separate analyzers or using an integrated system.

Clinical Chemistry Tests↗
PubMed1995

Drug administration errors: a study into the factors underlying the occurrence and reporting of drug errors in a district general hospital.

Drug administration is one of the highest risk areas of nursing practice and a matter of considerable concern for both managers and practitioners. The aim of this study, carried out in a district general hospital, was to identify any common themes that underlie the occurrence and reporting of drug administration errors. Data were collected from a variety of sources: drug error reports, questionnaires to nurses and nurse managers, and interviews with nurses who had been involved in drug errors. Several areas of particular concern emerged, including: the nurses' confusion regarding the definition of drug errors and the appropriate actions to take when they occurred; their fear of disciplinary action; their loss of clinical confidence; the variation in managerial response; and a possible lack of nurses' mathematical skills. The results from the study demonstrated that it was likely that many drug errors were not reported, for a variety of reasons. It is recommended that all of these issues are addressed as a matter of urgency, for the sake of both patients and nurse practitioners.

Documentation↗
PubMedDate not supplied

Constraint conflict: the source of an unusual error pattern.

Certain phonological error patterns have been judged to be "unusual" or "idiosyncratic", posing a number of theoretical and clinical problems. This paper reconsiders an especially challenging case of an unusual error pattern documented by Leonard and Brown (1984). T (age 3;8) replaced all word-final consonants (except for labial stops) with [s] but more importantly inserted [s] after word-final vowels. Our purpose is to show that optimality theory offers a fresh perspective on this error pattern and its course of development by providing an account of the facts that is entirely consistent with general principles relevant to the description of fully developed languages and acquisition.

Articulation Disorders↗
PubMed2000

Accuracy considerations when using early (four- or six-hour) radioactive iodine uptake to predict twenty-four-hour values for radioactive iodine dosage in the treatment of Graves' disease.

Although literature has offered methods to predict 24-hour radioactive iodine uptake values from early (4- to 6-hour) measurements, the resultant dosage errors have not been examined. Potential errors include underdosage, overdosage, and a failure to recognize rapid turnover patients (early-to-late uptake ratios > or = 1) who are at high risk for treatment failure and full-body radiation exposure. We developed and tested a novel method for minimizing error involved in using a single early uptake measurement to derive late uptake. From a retrospective analysis of 203 Graves' disease patients, receiver operating characteristic (ROC) curve analysis enabled us to identify patients likely to experience rapid turnover and therefore should receive 24-hour studies. Twenty-four-hour uptake measurements are necessary with 77% or more 4-hour uptake values and 80% or more 6-hour values. After eliminating these patients, we developed linear regression equations to predict the 24-hour uptake from 4-hour (n = 61) and 6-hour (n = 22) rule groups, testing their efficacy on separate 4-hour (n = 61) and 6-hour (n = 21) patient groups. We also used our test population to measure error in four early-to-late uptake conversion formulas presented in the literature. Error involved in these predictions ranged from a 10.6% overestimate for 4-hour calculations to a 5.9% underestimate for 6-hour calculations. When applied to two dosage formulas incorporating gland size, absorbed dose, and 24-hour uptake, average dosage error was 7%. In comparison to the other sources of error radioactive iodine (131I) dosimetry, potential error in predicting 24-hour uptake from 4- or 6-hour uptake values is low.

Graves Disease↗