Calibration Figures Research Articles

Multi-way figures of merit in the presence of heteroscedastic and correlated instrumental noise: Unfolded partial least-squares with residual multi-linearization

In the presence of correlated and/or heteroscedastic noise, i.e., for measurement noise which is not independent and identically distributed (iid), new expressions are required to estimate multi-way calibration figures of merit. They are derived in the present report, with focus towards a useful multi-way approach based on unfolded partial least-squares with residual multi-linearization. The expressions allow one to estimate figures of merit under a generalized noise propagation scenario, and to gain insight into the various uncertainty sources contributing to the overall prediction error and limit of detection. Through the study of both simulated and experimental data, it is shown that significant differences exist between the values estimated assuming an iid noise structure and when the underlying structure deviates from this classical paradigm.

Validation of an ion chromatographic method for the quantification of anions in water

In this work, the validation of the method for the determination of chloride, nitrate and sulphate in potable drinking water and non-treated water was performed. The instrumental setup used was an automated ion chromatograph equipped with chemical suppression system for anion analysis. The significance of this paper falls on the statistical study of the analytical method, where all the uncertainty contributions involved in the process have been considered. Parameters such as repeatability, reproducibility, precision, accuracy, uncertainty, limits of detection and quantification, range of measurement and calibration figures of merit, were determined in this paper.

Results of an international comparison of 57Co

As part of a Cooperative Research Project (CRP) aimed at improving the state of radioactivity measurement in nuclear medicine, the International Atomic Energy Agency (IAEA) organized a comparison of (57)Co solutions among the participants of the project. The comparison solutions were prepared from a single master stock solution and distributed to the participating laboratories, who measured the activity concentration of the solution using either the laboratory's radionuclide activity calibrator or primary standardization methods. A total of 9 sets of results were received, with 5 laboratories reporting results of primary measurements, one reporting results of secondary measurements calibrated against primary standards, and three laboratories reporting values based on measurements in commercial re-entrant ionization chambers using manufacturer-recommended calibration figures. Most of the laboratories reporting primary standardizations also provided results from secondary standardizations. The Comparison Reference Value was calculated from the mean of the five primary standardizations and was found to be 35.54 MBq g(-1), with a standard deviation of the mean of 0.17 MBq g(-1). Degrees of equivalence were calculated for each reporting laboratory and demonstrated that equivalence to within about 4% could be achieved, even in the case of those laboratories that used instruments calibrated by third parties.

IFIN-HH ionization chamber calibration and its validation; electrometric system improvement

The paper presents the results obtained in the calibration of the CENTRONIC IG12/20A ionization chamber for 18 gamma ray emitters, and its improvement with a Keithley 6517A electrometer. The calibration figures were determined either directly in pA MBq(-1) units, or calculated from old units, by using the system capacity value. The calibration figures, determined with RML's standards, are compared with those deduced from the KCRV or the mean of the comparisons, and the values determined at PTB-Germany.

Calculation of calibration figures and the volume correction factors for 90Y, 125I, 131I and 177Lu radionuclides based on Monte-Carlo ionization chamber simulation method

Many metrology laboratories are dealing with activity measurements of different radionuclides with special interest in nuclear medicine as well as in radiopharmaceutical industry. In improving the accuracy of radionuclide activity measurements, a key role plays the calculation of calibration figures and the volume correction factors for the radionuclide under study. It is well known that the chamber calibration factors depend on the measurement geometry including the volume of the source and the type of the measurement vessel. In this work, the activity standards in the form of radioactive solutions are delivered in sealed Jena glass 5 ml FIOLAX ®-klar ampoule. Calculation of the calibration figures (or efficiencies) for 90Y, 125I, 131I and 177Lu radionuclides on 5 ml ampoule are presented in this paper. Additionally, their appropriate volume correction factors are determined. These calibration figures for the ISOCAL IV pressurized well re-entrant ionization chamber (IC) are pointed out based on the Monte-Carlo (MC) simulation method of such chamber using the PENELOPE-2005 MC computer simulation code. The chamber is filled with nitrogen gas pressurized to approximately 1 MPa. In determining the volume correction factors, the variation of calibration factors versus the mass of radioactive solution filling the 5 ml ampoule glass is investigated. From the point of view that impurity of 177 m Lu isomer is always accompanying the 177Lu radionuclide, for making possible the correction due to presence of this impurity, the calibration factor and the volume correction factors for 177 m Lu are reported as well.

Absolute counting of 188Re radiopharmaceuticals

The Institute of Nuclear Energy Research (INER) has provided 188Re radiopharmaceuticals for hospitals in Taiwan. To enhance the accuracy of commercial radionuclide calibrators used by radiopharmacies and hospitals, and to ensure that patients receive proper doses of these radiopharmaceuticals, it is very important to standardize this nuclide. The 4 πβ- γ coincidence counting method was used to standardize the mass activities of 188Re in this study. At the same time, three well type ionization chambers, Centronic IG11-N20, Centronic IG11-A20, and ISOCAL-IV, were calibrated by the standardized solutions of the nuclide. In this research, the calibration figures of ISOCAL-IV for the nuclide were consistent with the results of National Physical Laboratory (NPL, UK). The outcome implied that the results of coincidence counting did mutually agree. On the other hand, the radionuclide calibrator in the radiopharmacy was producing measurement errors of about 20% when using the manufacturers recommended calibration setting: an accurate correction factor has now been determined in this study.

Calibration of pre-cut iridium-192 wires for low dose rate interstitial brachytherapy using a Farmer-type ionization chamber.

A technique, originally developed for calibrating small low activity caesium sources, which uses a Farmer-type ionization chamber, has been further developed for use with iridium wires. Correction factors have been generated to account for the finite source and detector sizes, and attenuation in the source carriers. The air kerma calibration factor for heavily filtered 280 kV X-rays was used for reference back to the National Standard. The results of this calibration method have been compared with the calibration figures given by the manufacturers over a 5 year period for the emissions from 50 batches of wires of varying strengths. Agreement to within +/- 3.2% was achieved in all cases, establishing that the method is satisfactory for acceptance testing purposes. The mean agreement was good to within 0.2%, but the possibility of a systematic error of between 1% and 3% existing both in this method and in the method used by the manufacturer is discussed.

NPL secondary standard radionuclide calibrator: new calibration figures for 106Ru, 153Sm and 188re

The NPL secondary standard radionuclide calibrator was introduced in 1985 in order to provide a highly stable, sensitive and accurate facility for the assay of radionuclides. One of its principal advantages is the direct traceability of its calibration figures to national standards of radioactivity. Since its introduction, several additional calibration figures have been measured for radionuclides which had not been previously standardised at NPL. Details of these new calibration figures are presented together with their appropriate volume correction factors.

Portability of the calibration of SIR of BIPM to other ionization chambers for radioactivity measurements

Portability of the calibration of the ionisation chambers of the International Reference System, SIR, of the BIPM to other ionisation chambers used for activity measurements and without having direct access to SIR is described. A linear relationship between calibration figures of different ionisation chambers at IRMM, NPL and NAC and 1/ A e of SIR was established. In favourable cases uncertainties of the slope of less than 1% were obtained.

Calibration of the NPL secondary standard radionuclide calibrator for 32P, 89Sr and 90Y

Pure beta particle emitting radionuclides have many therapeutic applications in nuclear medicine. The response of the NPL secondary standard radionuclide calibrator to 32P, 89Sr and 90Y has been measured using accurately calibrated solutions. For this purpose, high efficiency solid sources were prepared gravimetrically from dilute solutions of each radionuclide and assayed in a 4π proportional counter; the source activities were determined using known detection efficiency factors. Measurements were made of the current response (pA/MBq) of the NPL secondary standard radionuclide calibrator using the original concentrated solutions. Calibration figures have been derived for 2 and 5 ml British Standard glass ampoules and Amersham International plc P6 vials. Volume correction factors have also been determined. Gamma-ray emitting contaminants can have a disproportionate effect on the calibrator response and particular attention has been paid to this.

Calibration of the NPL secondary standard radionuclide calibrator for 192Ir brachytherapy sources

Safe and effective treatment with brachytherapy sources requires an accurate knowledge of the local tissue absorbed dose rate derived from the source reference air kerma rate. It is desirable that these air kerma rate measurements be traceable to national standards. The NPL has embarked on a programme that will enable the user to assay brachytherapy sources to a convenient manner prior to treatment. Calibration figures have been derived for the NPL secondary standard radionuclide calibrator for 192Ir brachytherapy sources manufactured by Amersham International plc. The calibration figures enable the user to accurately estimate the reference air kerma rate and activity of such sources by measuring the ionization chamber response. Calibration figures for other brachytherapy sources are also being derived.

The 4 πβ − γ coincidence method for parent-daughter decay in non-equilibrium: The measurement of the disintegration rates of 47Ca- 47Sc, 45Ca

A 4 π β − γ coincidence technique, employing the “computer discrimination” method of data collection with a pressurized gas flow proportional counter in the β-channel, is used to determine the individual activities in a mixture of 47Ca- 47Sc and 45Ca, where the parent-daughter decay 47Ca- 47Sc is not in equilibrium. Calibration figures for an NPL ionization chamber are derived for both 47Ca and 47Sc. The general case of a mixture of β −- γ or β −-emitting radionuclides is discussed and the difficulties which can result from the use of conventional methods of efficiency variation are outlined, and the advantage of using the computer discrimination method is pointed out, particularly when the shortest half-life is of the order of a day.

Arterial blood gas tensions and pH.

1 The definition of PO2 and its relationship to the oxygen saturation (SO2) by the oxygen dissociation curve (ODC) is described with details of the ligands of the ODC and the effects of haemoglobinopathies on P50 (the position of the ODC) and the slope of the ODC (Hill's 'n'). 2 The definition of PCO2 and description of CO2 transport by blood leads to consideration of the basis of acid base balance. 3 Acid base balance is expressed in terms of arterial blood (H+) (or pH) PCO2 relationship using a non-logarithmic diagram. 4 The measurement of arterial blood gas tensions is described with comments on arterial puncture and available modern automated blood gas electrodes and their calibration. 5 Non-invasive indirect measurements of blood gas tensions, by ear oximetry are described, with calibration figures on the Hewlett-Packard 47021A ear oximeter. End-tidal PO2 and PCO2 measurements by mass spectrometer or infra-red CO2 analyser, and of transcutaneous PO2 measurements by a heated polarographic electrode are described. 6 These measurements are necessary to study the effects of pharmacological agents on the chemical control of breathing, on pulmonary gas exchange, and on acid base balance in humans. The measurements are in everyday use in clinical practice, both to aid diagnosis of respiratory diseases, assess their severity, and to quantiate the effects of therapeutic agents.

A beta—gamma ionization chamber for substandards of radioactivity—I: Uses and calibration

This paper gives information on the construction, characteristics and calibration of the type 1383A chamber for the guidance of users. This instrument is a combination of a re-entrant cylinder (well-type) gamma-ray chamber with an approximately “2π” beta-ray chamber which in conjunction with a d.c. amplifier or electrometer, is suitable for the measurement of samples of γ-emitting and β-emitting isotopes. The γ-ray and β-ray ionization currents and the background are of the order of 10 −11, 10 −10 and 10 −14 A/mc, respectively. The calibration figures for standard Na 24, P 32, K 42, Fe 59, Co 60, Br 82, Y 90, Au 198 and Ra 226 sources and the correction factors applicable to measurements of solutions in 2 ml and 5 ml ampoules, and 10 ml bottles are given.