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Biomedical subjects

S Pommé

Publications and source records attributed to S Pommé.

13 recordsLinked to original sources
PubMed2006

The solid angle subtended by a circular detector for a linear source.

An exact solution is presented for the solid angle subtended by a circular detector for a linear source. It is based on Conway's equation for a non-coaxial point source, involving an integral of Bessel functions [Conway, J.T., 2006. Generalizations of Ruby's formula for the geometric efficiency of a parallel-disk source and detector system. Nucl. Instrum. Methods A 562, 146-153]. Some numerical examples are calculated and compared with the results obtained with a recently published closed formula (Galiano, E., Pagnutti, C., 2006. An analytical solution for the solid angle subtended by a circular detector for a symmetrically positioned linear source. Appl. Radiat. Isot. 64, 603-607), which is incorrect but can be improved by applying a correction factor.

Journal Article↗
PubMed2006

An intuitive visualisation of intercomparison results applied to the KCDB.

A simple and intuitive graphical method is presented for producing a summary overview of experimental results of a common measurand, e.g. in the frame of an intercomparison. The PomPlots display (relative) deviations of individual results from the consensus value on the horizontal axis and (relative) uncertainties on the vertical axis. The z-scores, z=1, 2 and 3, are represented by diagonal lines, creating the aspect of a pyramidal structure. The most accurate and precise measurement results should be situated close to the top of the pyramid. The plots are used to visualise data from the BIPM key comparison database on primary radioactivity measurements.

Algorithms↗
PubMed2006

Half-life measurement of 55Fe.

The half-life of 55Fe was determined experimentally and compared with literature values. A solid 55Fe source was prepared by electrodeposition and repeatedly measured in an X-ray detector at a constant, low solid angle. In total, more than six hundred measurements were performed over a period of ten months, corresponding to one third of the half-life. The experimental method and the corresponding uncertainty budget are presented. The result of 1005.2+/-1.4 days is slightly higher than the current recommended values.

Algorithms↗
PubMed2001

k0-NAA, a valuable tool for reference-material producers.

The main concern of producers of certified reference materials (CRM) is the preparation of high-quality products with demonstrated homogeneity and stability, combined with a well established set of certified characteristics. CRM producers must, furthermore, comply with other constraints imposed by the ISO Guide 34: production processes, production control, and certification analyses should be performed by expert laboratories, using validated protocols documented in their respective quality assurance manuals; laboratory mean values and the corresponding "expanded" uncertainties, must be used for the determination of the certified values, as recommended by the ISO Guide to the Expression of Uncertainties in Measurements (GUM); and when possible, traceability of the certified value to the SI units, using appropriately validated and/or primary methods, must be ensured. k0-NAA, i.e. neutron activation analysis with k0 standardization, is one of the analytical techniques implemented at the Reference Material Unit of IRMM; it meets the first two requirements.

Journal Article↗
PubMed2001

Intercomparison of efficiency transfer software for gamma-ray spectrometry.

The EUROMET project 428 examines efficiency transfer results for Ge gamma-ray spectrometers when the efficiency is known for a reference point source geometry. For this, different methods are used, such as Monte Carlo simulation or semi-empirical computation. The exercise compares the application of these methods to the same selected experimental cases to determine the usage limitations versus the requested accuracy. For carefully examining these results and trying to derive information for improving the computation codes, this study was limited to a few simple cases. The first part concerns the simplest case of geometry transfer, i.e., using point sources for 3 source-to-detector distances: 2, 5 and 20 cm; the second part deals with transfer from point source geometry to cylindrical geometry with three different matrices. The general conclusion is that the deviations between the computed results and the measured efficiencies are mostly within 10%. The quality of the results is rather inhomogeneous and shows that these codes cannot be used directly for metrological purposes. However, most of them are operational for routine measurements when efficiency uncertainties of 5-10% can be sufficient.

Journal Article↗
PubMed1999

Is loss-free counting under statistical control?

A new formula for the statistical uncertainty of "loss-free counting" (LFC) is presented. Its validity is demonstrated by comparing with experimental data obtained with a HPGe gamma-ray spectrometer. Also, computer simulation data of nuclear counting with different types of count loss (pileup rejection, extending and nonextending dead time) are in agreement with the predicted counting uncertainty. The proposed formula for LFC uncertainty is applicable to spectrometers with a classical semi-Gaussian pulse-shaping amplifier as well as with a gated-integrator amplifier. Hence, achieving statistical control seems to be a feasible goal.

Computer Simulation↗
PubMed1999

In-vivo measurement of low energy photon emitters: room-temperature semiconductor diodes vs. large scintillators and germanium crystals.

The in-vivo monitoring of low energy x- and gamma-ray emitters gained importance with the increasing use of these radionuclides in nuclear medicine and nuclear energy production. The main problems encountered are the lack of accuracy in the measurement and the high detection limits obtained with the classical techniques [proportional counters, thin NaI(TI) or phoswich scintillators]. The best technique available today is the array of planar germanium detectors. The purpose of this paper is to analyze specific problems in the assessment of low energy photon emitters in the body and to describe applications of room-temperature diodes (silicon and CdZnTe) using a new technique involving a portable jacket. In certain cases, the device can be used outside a shielded room, making possible an immediate long counting, reducing the psychological stress, and optimizing the medical treatment and the intervention. By considering the attenuation effect, this work shows that an optimized volume of the diodes reduces the detection limits of the counting. The developed methodology offers new possibilities in the assessment of radioactive deposition in the body and in the long term follow-up of the metabolism of radionuclides in small quantities.

Germanium↗
PubMed1997

Survey of the 137Cs contamination in Belgium by in-situ gamma spectrometry, a decade after the Chernobyl accident.

The residual radiocesium concentration, nearly 10 y after the Chernobyl accident, is measured at different sites on the Belgian territory by means of in-situ gamma-spectrometry. A possible link between the rainfall at the beginning of May 1986 and the actual cesium concentration is investigated. The radiological impact of this contamination, even in the most affected regions in the Ardennes, is very small (<6 microSv y(-1)).

Belgium↗
PubMedDate not supplied

Concept for an off-line gain stabilisation method.

Conceptual ideas are presented for an off-line gain stabilisation method for spectrometry, in particular for alpha-particle spectrometry at low count rate. The method involves list mode storage of individual energy and time stamp data pairs. The 'Stieltjes integral' of measured spectra with respect to a reference spectrum is proposed as an indicator for gain instability. 'Exponentially moving averages' of the latter show the gain shift as a function of time. With this information, the data are relocated stochastically on a point-by-point basis.

Algorithms↗
PubMedDate not supplied

Study of alpha-particle emission probabilities and energies in the decay of 240Pu.

In the frame of EUROMET Project No 325 "Analysis of Plutonium Alpha-Particle Spectra", the isotopic composition of a 238, 239, 240Pu mixture was measured by mass spectrometry and by high-resolution alpha-particle spectrometry. The latter revealed a discrepancy with published data of the alpha-particle emission probabilities (Palpha) and the energies (Ealpha) of the two major peaks of 240Pu. New values have been derived: Palpha1 = 0.7256 (6), Palpha2 = 0.2735 (7) and Ealpha1 = 5168.54 (14)keV, Ealpha2 = 5124.10 (15)keV, relative to reference peaks of 238Pu and 239Pu.

Alpha Particles↗
PubMedDate not supplied

Experimental verification of the half-life of 65Zn.

The half-life of 65Zn was determined experimentally and compared with literature values. Two ampoules of a 65Zn solution were measured at regular intervals in two ionisation chambers over a period corresponding to nearly two half-lives. The result of 243.8+/-0.3 days is in agreement with the value of 244.0+/-0.2 days obtained by De Roost et al. (Z. Phys. 250 (1975) 395) at the same institute (previously called CBNM) in 1972. Moreover, this half-life is supported by most of the other measurements reported in the literature.

Belgium↗
PubMedDate not supplied

Standardisation of low-activity actinide solutions by alpha-particle counting at a defined solid angle.

In the frame of an IAEA co-ordinated research project 232U, 236Pu and 229Th tracers were standardised by alpha-particle counting at a defined solid angle. The aim of this project was to assign property values that are traceable to the International System of Units (SI). This article depicts the standardisation of the tracers, elaborating on problems related to low activity and interference from daughter nuclides. The activity concentrations of 232U, 236Pu and 229Th were found to be, respectively (734+/-4), (142.0+/-0.9) and (528.2+/-2.6) Bq g(-1), at reference date (1 January 2003).

Journal Article↗