Are FNAB correction factors correct?
Explore the source record for details and available documents.
Acute Disease↗
SEARCH · PubMed Health
Results for “Correction factor”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Blood gas analyses on equine blood: required correction factors [see comment].
Correction factors have been determined to obtain the best estimates of PO2, PCO2 and pH in equine blood with standard blood gas and pH electrodes. There was a significant difference between the PO2 readings for tonometred blood of most horses and the equilibrating gas. Thus, if the PO2 electrode is calibrated with a gas, an electrode correction factor should be obtained by tonometring a blood sample from each horse. This factor was not dependent on packed cell volume. No such correction is required for the PCO2 electrode. If the animal's temperature differs from that of the analyser, the PO2, PCO2 and pH values must be corrected to the animal's body temperature. Temperature correction factors determined for equine blood were similar to those for human blood. Failure to make temperature corrections can result in errors for PO2 and PCO2 of 6 to 7 per cent per degree of temperature difference.
Animals↗
Factors influencing the correction factor used to eliminate the apparent NADH fluorescence changes caused by alterations in cerebrocortical blood content.
Explore the source record for details and available documents.
Animals↗
On the technique of extrapolation to obtain wall correction factors for ion chambers irradiated by photon beams.
Wall correction factors, which correct ion chamber response for photon attenuation and scatter, can differ by as much as 1.0% for spherical chambers depending on whether they are obtained experimentally by extrapolation measurements or by Monte Carlo simulation. This difference is not explained by experimental or calculational statistics which lie in the range 0.05%-0.2%. In this paper it is demonstrated that linear extrapolation of experimental data for spherical chambers is inappropriate, owing to the curvature of the chamber walls. A simple nonlinear theory is constructed that resolves the difference. The Monte Carlo calculations and the nonlinear theory are compared with extrapolation measurements for the NIST (formerly NBS) spherical chambers. It is concluded that wall correction factors should be obtained by Monte Carlo calculation for spherical chambers and that linear-extrapolation techniques should be regarded with suspicion for all chambers.
Monte Carlo Method↗
Displacement correction factor for fast-neutron dosimetry in a tissue-equivalent phantom.
The displacement correction factor to be used for analysis of fast-neutron dosimetric measurements using air-filled EG and G tissue-equivalent ion chambers in a tissue-equivalent phantom has been investigated using the MANTA neutron radiotherapy beam generated by 35-MeV deuterons on a thick Be target. The displacement correction factor inferred from these measurements is 0.970 for the EG and G IC-17 (1.0-cm3) ion chamber, and is 0.989 for the EG and G IC-18 (0.1-cm3 ion chamber. This multiplicative displacement correction factor has no significant dependence on depth in the phantom or on neutron beam size.
Fast Neutrons↗
Electronic platelet counts with the Coulter counter. Reassessment of a correction factor.
Platelet counts are determined on the Coulter electronic counter by counting the diluted platelet-rich plasma obtained by sedimentation or centrifugation of whole blood. In calculating the whole-blood platelet count, an empirical correction factor for platelet-free plasma trapped by sedimented erythrocytes has been recommended, and a widely-distributed circular slide rule calculator incorporates the correction factor. In this study, visual and electronic platelet counts were compared in 100 specimens with counts ranging from 10 to 1,100 X 10(3) per mul and hematocrits ranging from 17.5 to 48.5%. Platelet-rich plasma samples prepared by a centrifugation method (Plateletfuge) gave machine counts in close agreement with those of samples prepared by sedimentation. Whole-blood platelet counts determined with the circular calculator were consistently lower than visual counts, with an average difference of -17%. The electronic counts were recalculated after elimination of the correction factor, and agreement then improved to an average difference of only +1.6%. The correction factor for trapped platelet-free plasma leads to erroneously low values and should not be used.
Blood Cell Count↗
Variation in the lung inhomogeneity correction factor with beam energy. Clinical implications.
In order to determine the magnitude of the dosimetry error introduced by failing to correct for increased transmission through lung tissue in treating thoracic malignancies, measurements in a phantom were taken using different field sizes, inhomogeneity thicknesses and photon qualities. The results indicate that the error introduced by neglecting the inhomogeneity correction is greatest at lower photon energies, smaller field sizes and greater thickness of inhomogeneity. Correction factors to account for the lung inhomogeneity were obtained from phantom measurements and were compared with those calculated using the tissue-air ratio and Batho-Young algorithms; correlation coefficients describing the relationship between measured and calculated values exceeded 0.995. The calculated values tended to overestimate the correction factor and differed most from the measured correction factors at lower energies, smaller field sizes, and greater inhomogeneity thicknesses. The importance of these results in clinical radiation therapy is discussed.
Cobalt Radioisotopes↗
[Rectal temperature-time of death nomogram: dependence of corrective factors of body weight in significant thermal insulating conditions].
98 test coolings were made under various cooling conditions (moving air, two types of both clothing and covering) on dummies of real masses of 1, 3.3, 9.9, 24.5 and 33.4 kg resp. which cool under standard conditions (unclothed, uncovered, still air) like human bodies of 14, 33, 41, 83 and 104 kg resp. The results provide evidence on a nonlinear dependence of corrective factors of body weight upon the body weight. The dynamics of the dependence increases with the thickness of thermic isolation. Transferred to the use of the nomogram method on bodies, cooling conditions requiring corrective factors known by experience between 0.75 (moving air) and 1.3 (rather thin clothing/covering) can be used as in the past independent on the body weight. Only in higher corrective factors for thicker clothing/covering according to experience the dependence of corrective factors on the body weight must be taken into account in bodies of a very high or low body weight. Beside a simplified table a formula for computing is also given for that purpose.
Body Temperature Regulation↗
Energy dependence of correction factors for the Victoreen Model 666 Portable Radiographic Health Survey System.
The energy dependence for each of three models of Victoreen 666 ionization chambers is characterized through an examination of the correction factors determined over the diagnostic x-ray range (0.4-4.9 mm A1 HVL) for many samples of each model. The results of an analysis of variance performed for each chamber model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error of less than 0.6% in all cases. Energy-dependence curves for the three chamber models are given, and their use is described.
Calibration↗
Energy dependence of correction factors for two models of Keithley diagnostic ion chambers.
The energy dependence for each of two models of ionization chambers compatible with the Keithley model 35020 Digital Dosimeter, is determined by measurement of the exposure correction factors determined over the diagnostic x-ray range (0.4--4.9 mm AL HVL) for several for several samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error of less than 1% for both cases. Energy-dependence curves for the two chamber models are given, and their use is described.
Evaluation Studies as Topic↗
Energy dependence of correction factors for some low-energy direct-reading pocket dosimeters.
The energy dependence for each of five models of low-energy direct-reading pocket dosimeters was characterized through an examination of the exposure correction factors determined over the diagnostic x-ray range (0.4-4.1-mm Al HVL) for many samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, the relative standard error being less than 0.8% in all cases. Energy-dependence curves for the dosimeter models are given, and their use is described.
Radiography↗
Energy dependence of correction factors for some Victoreen Model 570 Condensor R-Meter medium-energy chambers.
The energy dependence of each of six models of medium-energy Victoreen 570 Condenser R-Meter chambers was determined by measurement of the exposure correction factors over the diagnostic x-ray beam-quality range (0.4-4.1 mm A1 HVL) for several samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error less than 0.8% in all cases. Energy-dependence curves for the six chamber models are given; their use is described.
Calibration↗
Total perturbation correction factor for PTW and NACP plane parallel chambers in electron beams.
The international protocols of electron dosimetry published by the Nordic Association of Clinical Physics and the Sociedad Española de Física Médica recommend the use of a total perturbation correction factor pu, pp which is constant for all plane parallel chambers. In this work we have compared the dose measured with the PTW-Markus and NACP plane parallel chambers in respect to a cylindrical one. The obtained results indicate that for the ionization chamber NACP the value of pu, pp = 1.000 +/- 0.005 is adequate while for the ionization chamber PTW the observed difference is explained by considering an individual total perturbation correction factor variable with the mean energy at depth z, Ez, as the fluence perturbation correction factor pf is usually given for cylindrical chambers.
Humans↗
Rectal temperature time of death nomogram: dependence of corrective factors on the body weight under stronger thermic insulation conditions.
Ninety-eight test coolings were made under various cooling conditions (moving air, two types of both clothing and covering) on dummies of real masses of 1, 3.3, 9.9, 24.5 and 33.4 kg, respectively, which cool under standard conditions (unclothed, uncovered, still air) like human bodies of 14, 33, 41, 83 and 104 kg, respectively. The results provide evidence of a non-linear dependence of corrective factors of body weight upon the body weight. The dynamics of the dependence increases with the thickness of thermic insulation. Transferred to the use of the nomogram method on bodies, cooling conditions requiring corrective factors between 0.75 (moving air) and 1.3 (rather thin clothing/covering), known from experience on bodies of an average weight, can be used as in the past, independent of the body weight. According to experience the dependence of corrective factors on the body weight must be taken into account in bodies of a very high or low body weight. For that purpose both a simplified table and a formula for computing is given.
Bedding and Linens↗
Monte Carlo study of thermal flux profiles and body correction factors for body protein measurements of obese subjects.
In previous calculations for Total Body Nitrogen measurements of children, the anterior/posterior thermal neutron flux profile with depth was found to be fairly flat after an initial rise. However, for obese adults significant variations are found in the flux profile with the central flux value being as low as 20% of the peak value. The significance of these flux variations is examined. Correction factors are calculated for the varying attenuation of the nitrogen and hydrogen photons by a range of obese bodies. The calculations included the effect of the thermal flux profile as well as that of an outer layer of low nitrogen content adipose tissue. The bodies are assumed to have a homogeneous hydrogen content. A study of four obese body models with varying sex and fat content shows that the correction factors do not vary much between males and females. This is surprising since the female models are assumed to have a surface fat layer twice as thick as for the male models. The correction factors are found to be only slightly sensitive to the thermal flux variations with depth.
Adipose Tissue↗
Correction of metatarsus primus varus with the Chevron metatarsal osteotomy. An analysis of corrective factors.
A trigonometric evaluation of the amount of correction of metatarsus primus varus obtainable via lateral displacement of the first metatarsal head in a Chevron osteotomy technique revealed that approximately 1 degree of correction may be obtained for each millimeter of lateral shift. This calculated correction was correlated with the actual correction obtained in ten feet. Narrowing of the metatarsal head associated with removal of the medial eminence was an additional corrective factor.
Adult↗
The use of correction factors in the determination of mutant frequencies in populations of human diploid skin fibroblasts.
The need and validity for using a number of correction factors in the determination of mutant frequencies in human diploid skin fibroblasts was investigated. Resistance to the purine analogue 8-azaguanine was used as selective system. It appears that, under the conditions used, there were no effect of the cell density on the cloning efficiency. Therefore observed mutant frequencies need to be corrected for cloning efficiency. The reliability of using Lesch-Nyhan cells as a prototype mutant in the estimation of the efficiency of mutant recovery was investigated and found to hold true. The relation between the efficiency of mutant recovery and cell density, which reflects the degree of inter-clone metabolic cooperation, was measured. The use of this relationship enhances the accuracy of the estimated mutant frequencies. With these correction factors the mutation rate was estimated to be 5.7 - 10(-6) per cell per generation. The influence of intra-clone metabolic cooperation was determined and found to be small if present.
Azaguanine↗
Absorbed dose dependence of the correction factors for ionization chamber cable irradiation effects.
A simple method was developed, for possible use by hospital physicists, to evaluate the irradiation effects on cables and connectors during large-radiation-field dosimetry with ionization chambers and to determine correction factors for the used system or geometry. This method was based on the absorbed dose dependence of the correction factor.
Humans↗