The determination of binary mixtures in metallic coatings

Some common metallic coatings on steel are in fact binary mixtures (Gignoux and Gouel, 1991). These are Zn/Al, Zn/Ni and Zn/Fe.The measurement of the first two coatings using x-ray fluorescence easily yields value for both the coating weight and the composition.However, Zn/Fe (galvanneal) poses special problems because Fe K_α fluorescence arises from the Fe contained in the coating and from the steel substrate.A solution involving a special x-ray beam geometry and correct selection of beam energy is presented.     

电感耦合等离子体质谱法测定低硼硅玻璃安瓿中锑的浸出量

目的建立电感耦合等离子体质谱法测定低硼硅玻璃安瓿中锑浸出量的方法。方法用4％的乙酸溶液浸出安瓿中的锑,用电感耦合等离子体质谱法（ICP—MS）测定,研究ICP—MS测定锑的光谱干扰,建立干扰方程来消除光谱干扰。结果锑在0～17．82μg／L的范围线性关系良好（r=0．99993）,加样回收率98．3％,RSD=2．6％（n=6）,检出限为0．027μg／L。结论所建立的检测方法专属性强、简便、灵敏度高,可用于玻璃安瓿中锑浸出量的测定,有效控制低硼硅玻璃安瓿中锑的残留量。     

Evaluation of elemental composition of sediments from the Adriatic Sea by using EDXRF technique

723 sediment samples collected along the eastern Adriatic coast have been analyzed using Energy Dispersive X-Ray Fluorescence. Factor Analysis and GIS have been used for the evaluation of the resulting data base containing information on K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, and Pb concentration levels in order to find spatial relationships in distribution of measured elements. This study can be used to identify background values and to evaluate sediment quality standards.     

Direct activity determination of 54Mn and 65Zn by a non-extrapolation liquid scintillation method.

The measurement of 54Mn and 65Zn by liquid scintillation coincidence counting results in low detection efficiencies. The activity obtained from the extrapolation of efficiency data can therefore become problematic if curvature is present. The simple decay scheme exhibited by these radionuclides, with the emission of an energetic gamma ray, allows the absolute activity to be determined from 4pie-gamma data by direct calculation without the need for efficiency extrapolation. The method, which relies on determining the probability of the gamma-ray interacting with the scintillator solution, is described and validated by measurements made on 60Co.     

Direct determination of the attenuation coefficient for radionuclide volume measurements

Correcting for the attenuation of photons between the cardiac chambers and chest surface is crucial for accurate nongeometric ventricular volume determinations from equilibrium radionuclide angiograms. Previous techniques have assumed that the attenuation coefficient of water for 99mTc (0.15/cm) should be used for this correction. In this study, this assumption was tested directly by measuring attenuation of the activity of a radioactive source within the right and left cardiac chambers. The balloon of a flow-directed catheter, filled with 99mTc, was used as a source and its depth within the body was measured with biplane fluoroscopy. In ten patients, a total of 36 measurements of attenuation were made. With linear regression analysis, the overall calculated attenuation coefficient, mu, was 0.12/cm (standard error of slope = 0.01, R = 0.93). Although the mean value of mu varied from 0.08 to 0.13 for four different intracardiac locations these differences were not significant. These direct measurements indicate that the attenuation of photons in the heart is not equivalent to that of water and suggest that an attenuation coefficient of 0.12/cm should be used in analyzing ventricular activity.     

A rapid improved method for gamma-spectrometric determination of 202Tl impurities in [201Tl]-labelled radiopharmaceuticals.

Despite the cyclotron production method and the efficiency of the radiochemical procedures adopted, the long-lived radio-isotopic impurity 202Tl is always present in [201Tl]-labelled radio-pharmaceuticals, together with other short-lived impurities like, 200Tl. Rapid determination of the 202Tl impurity, can be achieved using HPGe gamma spectrometry and a detector shielded by a 5 mm thick envelope of lead. In this way, dead-time correction errors, Compton and X-ray background, are very efficiently avoided and suppressed. The same method could be applied routinely in nuclear medicine, to determine the radioisotopic purity of 201Tl by means of an ionisation chamber dose calibrator.     

Radioisotopic impurities in bismuth chemicals

Radioisotopic impurities of ²⁰⁷Bi and occasionally ²⁰⁸Bi were found among a wide variety of bismuth chemicals. The specific activity of ²⁰⁷Bi ranging from 1.5 to 12 mBq Bi-g⁻¹ was determined by low-level γ-spectrometry. It is conjectured that the contamination was due to fallouts concentrated in the smelting and refining processes.     

Heating effects of metallic implants by MRI examinations

Magnetic radiofrequency fields applied in magnetic resonance imaging examinations induce electrical currents in metallic implants. These eddy currents may heat up the implants and thus may be capable of causing localized tissue heating. The rf power deposition and the joule heating of the implant can be calculated by solving Maxwell's equations for the specific problem. First, extreme in vitro worst-case experiments were performed with a large and very thin aluminum sheet, which was placed in a 1.5-T MRI device in a position parallel to the magnetic rf field. In agreement with the theoretical results the temperature rise of a thermally insulated sheet amounted to only 0.08 degrees C after a 15-min MRI examination at 64 MHz. No temperature rise in the aluminum sheet could be measured for a sheet immersed in a saline solution. Second, in vitro experiments with a hip joint prosthesis and an osteosynthetic plate were performed to confirm the theoretical results, which predict nearly no temperature rise in the metallic implants. No temperature rise in the implants could be measured.     

Reduction of CT artifacts caused by metallic implants

A technique to reduce metallic implant artifacts on computed tomography scans is presented. The implant boundaries are determined semiautomatically; the missing projection data are replaced by linear interpolation. The complete procedure requires 1-2 minutes per scan. Images with greatly improved quality were obtained in the presence of surgical clips and pelvic implants; success is limited in highly structured regions, such as the facial skull.     

Rapid determination of Sr impurities in freshly “generator eluted” Y for radiopharmaceutical preparation

⁹⁰Y is one of the most useful radionuclides for radioimmunotherapeutic applications and has a half-life (t_1/2=64.14 h) suitable for most therapeutic applications, beta particles of high energy and decays to a stable daughter. It is significant that ⁹⁰Y is available conveniently and inexpensively from a radionuclide “generator” by decay of its parent, ⁹⁰Sr. Nevertheless, current and planned clinical applications with [⁹⁰Y] labelled compounds employ activity levels that cannot be readily obtained from an in-house generator, but from commercial sources. We have evaluated Eichrom's Sr-resin, either as an “in-house” generator or as a fast QC method for analysis of ⁹⁰Y solutions.In particular, for the development as a generator, we investigated the percentage of the radio-Sr in the first 8 M HNO₃ eluate: in this fraction the concentration of ⁹⁰Sr must be smaller than 10⁻⁵% (recommendations of the International Commission on Radiological Protection). For evaluation as a rapid QC method, we analyzed the concentration of ⁹⁰Y in all the fractions containing “only” radio-Sr: ⁹⁰Y should not be present in these eluates. After the collection of β⁻ and γ spectra and analysis of them, we concluded that commercial Sr-resin minicolumn cannot give us the results expected; we developed an in-house system loaded with 4 mL of Sr-resin which gave better results as a generator and a rapid QC method.     

Detection of radionuclide impurities

The knowledge of radionuclide impurities is of great importance both for activity measurements as well as in the preparation of Radioactive Standard Reference Materials. It is relevant also in the field of Life Sciences. Equipment, measurement and evaluation methods, uncertainties and detection limits are discussed. OMH experiences on impurity tests of radionuclides frequently used in the Hungarian medical practice are outlined.     

EDXRF analysis for elements of adjacent atomic number but grossly different concentrations

A method to overcome difficulties inherent in quantitative analysis by energy-dispersive x-ray fluorescence of samples that contain widely different concentrations of two or more elements having similar atomic numbers (Z) was investigated. Results obtained by computer simulations and simple experiments show that significant increases in the intensities of the x-rays emitted by the lower-Z element relative to those from the higher-Z element can be achieved through the proper design of a primary-source secondary-fluorescer exciter system and a detector window filter.     

Non-destructive and Quantitative Investigation of Jingdezhen Blue and White Porcelains Using EDXRF

The fabrication of the calibration source is a critical part for the non-destructive and quantitative investigation of blue and white porcelains using EDXRF. In order to minimize the effects on the results due to the matrix difference between the samples and the calibration source, broken porcelain pieces of the Ming and Qing dynasties with matrix conditions similar to those of the measured samples are used directly as calibration sources. The 13 trace elements, viz. Ti, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pb, Rb, Sr, Y, and Zr, have been quantitatively measured for 20 imperial blue and white porcelains of the Qing dynasty and for 11 contemporary Jingdezhen porcelains. The data are then analyzed by the principal component analysis method. The clustering of the data and the identification of the porcelains are then investigated.     

Estimation of radiation dose produced by impurities in nuclear medicine studies using Tl-201 chloride

Radionuclide impurities can significantly increase the absorbed dose in Nuclear Medicine examinations. The aim of this study is to evaluate the dose of Tl-200 and Tl-202 in patients injected with Tl-201 for myocardial scintigraphy. All relevant nuclear and biological data are reported; Thallium distribution in the body is then discussed with particular regard to the gastro-intestinal tract. Since MIRD Committee has not published "S" values for Tl-200 and Tl-202, these have been calculated by a computer code and are reported. The absorbed dose for these Thallium isotopes is presented. For example, kidney doses in Gy/GBq are 0.29 (Tl-200), 0.27 (Tl-201) and 0.97 (Tl-202). The total dose increase for a 2% presence of Tl-202 is about 11%.