The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Klemens Zink - One of the best experts on this subject based on the ideXlab platform.
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optimization of the stopping power ratio to hounsfield value Calibration Curve in proton and heavy ion therapy
Zeitschrift Fur Medizinische Physik, 2015Co-Authors: Matthias Witt, Uli Weber, Daniel Kellner, Rita Engenhartcabillic, Klemens ZinkAbstract:Abstract For CT-based dose calculation in ion therapy a link between the attenuation coefficients of photons and the stopping-power of particles has to be provided. There are two commonly known approaches to establish such a Calibration Curve, the stoichiometric Calibration and direct measurements with tissue substitutes or animal samples. Both methods were investigated and compared. As input for the stoichiometric Calibration the data from ICRP-report 23 were compared to newly available data from ICRP-report 110. By employing the newer data no relevant difference could be observed. The differences between the two acquisition methods (direct measurement and stoichiometric Calibration) were systematically analyzed and quantified. The most relevant change was caused by the exchange of carbon and oxygen content in the substitutes in comparison to the data of the ICRP-reports and results in a general overshoot of the Bragg peak. The consequence of the differences between the Calibration Curves was investigated with treatment planning studies and iso-range surfaces. Range differences up to 6 mm in treatment plans of the head were observed. Additionally two improvements are suggested which increase the accuracy of the Calibration Curve.
Aqil Jamal - One of the best experts on this subject based on the ideXlab platform.
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Optimized Calibration Curve for size exclusion chromatography applied to poly(vinyl chloride)
Polymer, 1994Co-Authors: Muhammad Atiqullah, Ikram Hussain, Aqil JamalAbstract:Abstract The problem of using a polystyrene-standard-based Calibration Curve for other polymers has been overcome by developing an algorithm based on the concept of parameter estimation and optimization. The algorithm modifies the regression coefficients of the polystyrene-standard-based Calibration Curve by interactively using the chromatographic output and the absolute number-average molecular weight of the experimental polymer. Analytical expressions have been derived for calculating the directional derivatives, which ensure rapid convergence of the objective function. The algorithm, applied to commercial poly(vinyl chloride), offered a number-average molecular weight of 32037 whereas that measured by membrane osmometry is 32 000. The polymer characterization parameters calculated from the optimized Calibration Curve closely matched those obtained from the universal Calibration Curve and Q -factor values. The algorithm needs no narrow standard of the experimental polymer, and holds for homopolymers, copolymers and polymer blends. It can be easily incorporated into commercial size exclusion chromatography data-reduction software packages.
Matthias Witt - One of the best experts on this subject based on the ideXlab platform.
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optimization of the stopping power ratio to hounsfield value Calibration Curve in proton and heavy ion therapy
Zeitschrift Fur Medizinische Physik, 2015Co-Authors: Matthias Witt, Uli Weber, Daniel Kellner, Rita Engenhartcabillic, Klemens ZinkAbstract:Abstract For CT-based dose calculation in ion therapy a link between the attenuation coefficients of photons and the stopping-power of particles has to be provided. There are two commonly known approaches to establish such a Calibration Curve, the stoichiometric Calibration and direct measurements with tissue substitutes or animal samples. Both methods were investigated and compared. As input for the stoichiometric Calibration the data from ICRP-report 23 were compared to newly available data from ICRP-report 110. By employing the newer data no relevant difference could be observed. The differences between the two acquisition methods (direct measurement and stoichiometric Calibration) were systematically analyzed and quantified. The most relevant change was caused by the exchange of carbon and oxygen content in the substitutes in comparison to the data of the ICRP-reports and results in a general overshoot of the Bragg peak. The consequence of the differences between the Calibration Curves was investigated with treatment planning studies and iso-range surfaces. Range differences up to 6 mm in treatment plans of the head were observed. Additionally two improvements are suggested which increase the accuracy of the Calibration Curve.
Harold Richardson - One of the best experts on this subject based on the ideXlab platform.
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In-house Calibration of the International Sensitivity Index or Calibration Curve for Determination of the International Normalized Ratio
Archives of Pathology & Laboratory Medicine, 2004Co-Authors: William F. Brien, Linda Crawford, Anne Raby, Harold RichardsonAbstract:Abstract Context.—The international normalized ratio (INR) has been used since 1983 to standardize prothrombin time results for patients on oral anticoagulants. However, significant interlaboratory variations have been noted. Attempts have been made to address these differences with the use of instrument-specific International Sensitivity Index (ISI) values and in-house Calibration of ISI values. Objective.—To assess the performance of laboratories using a Calibration Curve for INR testing. Design.—Attempts to improve performance of the INR include the use of instrument-specific ISI values, model-specific ISI values, in-house Calibration of ISI values, and more recently, the preparation of a Calibration Curve. Several studies have shown an improvement in performance using these procedures. In this study of licensed laboratories performing routine coagulation testing in the Province of Ontario, Canada, the determination of the INR by a Calibration Curve was compared with the laboratories' usual method of assessment. These methods were subsequently analyzed by comparing the results to instrument-specific ISI, model-specific ISI, and in-house calibrators. International normalized ratios derived by both methods were analyzed for accuracy and precision. The stability of a Calibration Curve was also investigated. Results.—Performance of INR testing has improved with use of a Calibration Curve or in-house calibrators. Conclusion.—The results confirm that either in-house calibrators or the Calibration Curve improve performance of INR testing. The Calibration Curve may be easier to use and appears stable up to 4 months.
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in house Calibration of the international sensitivity index or Calibration Curve for determination of the international normalized ratio
Archives of Pathology & Laboratory Medicine, 2004Co-Authors: William Brien, Linda Crawford, Anne Raby, Harold RichardsonAbstract:Abstract Context.—The international normalized ratio (INR) has been used since 1983 to standardize prothrombin time results for patients on oral anticoagulants. However, significant interlaboratory variations have been noted. Attempts have been made to address these differences with the use of instrument-specific International Sensitivity Index (ISI) values and in-house Calibration of ISI values. Objective.—To assess the performance of laboratories using a Calibration Curve for INR testing. Design.—Attempts to improve performance of the INR include the use of instrument-specific ISI values, model-specific ISI values, in-house Calibration of ISI values, and more recently, the preparation of a Calibration Curve. Several studies have shown an improvement in performance using these procedures. In this study of licensed laboratories performing routine coagulation testing in the Province of Ontario, Canada, the determination of the INR by a Calibration Curve was compared with the laboratories' usual method of a...
A. Vancu - One of the best experts on this subject based on the ideXlab platform.
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Calibration Curve for SnO2-based gas sensors
Sensors and Actuators B: Chemical, 1994Co-Authors: N. Bărsan, R. Ionescu, A. VancuAbstract:Abstract Even in the absence of interfering gases, the lack of stability in the response of SnO 2 -based gas sensors does not allow their use as measuring devices. The cause is the dependence of the conductance of the sensor, in the absence of the reducing gas, on ambient atmosphere conditions and on ageing. As a result, at the same value of the concentration of the reducing gas, the conductance of the sensor measured at different moments has different values. In this paper, based on previous calculations, a formula for conductance is derived: the parameters which depend on the ambient atmosphere conditions and on ageing, on one hand, and the sensor constants, on the other hand, are separated. Based on this formula a Calibration Curve, valuable at gas concentrations higher than 20 ppm, is proposed: the ratio between the conductance of the sensor in the presence of the reducing gas and the conductance in the presence of a known gas concentration versus the concentration of the reducing gas. The results obtained for C 2 H 5 OH and CO showed that during a week, using the proposed Calibration Curve, the errors in the measurements of the gas concentration were less than 7%.
