R. Debuyst

Catholic University of Louvain, Walloon Region, Belgium

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Publications (57)61.16 Total impact

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    ABSTRACT: L'ion manganeux présente des variations du taux d'adsorption en fonction du pH de la solution et en fonction du temps de contact entre le Mn(II) et l'adsorbant (Al2O3).Ces phénomènes sont contrôlés par voie chimique grâce à l'utilisation de traces de manganèse radioactif (54Mn) ainsi que par résonance paramagnétique électronique (R.P.E.).
    Bulletin des Sociétés Chimiques Belges. 09/2010; 82(1‐2):75 - 86.
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    ABSTRACT: The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.
    Radiation Protection Dosimetry 02/2006; 120(1-4):176-83. · 0.91 Impact Factor
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    ABSTRACT: Electron paramagnetic resonance (EPR) is often used in dosimetry using biological samples such as teeth and bones. It is generally assumed that the radicals, formed after irradiation, are similar in both tissues as the mineral part of bone and tooth is carbonated hydroxyapatite. However, there is a lack of experimental evidence to support this assumption. The aim of the present study was to contribute to that field by studying powder and block samples of human finger phalanxes that were irradiated and analyzed by multi-frequency EPR. The results obtained from bones are different from the ones obtained in enamel by several respects: the ordering of the apatite crystallites is much smaller in bone, complicating the assignment of the observed CO2- radicals to a specific location, and one type of CO3(3-) radical was only found in enamel. Moreover, a major difference was found in the non-CO2- and non-CO3(3-) signals. The elucidation of the nature of these native signals (in bone and tooth enamel) still represents a big challenge.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 11/2005; 61(13-14):3131-8. · 1.98 Impact Factor
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    ABSTRACT: The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.
    Applied Radiation and Isotopes 03/2005; 62(2):163-71. · 1.18 Impact Factor
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    M. Zdravkova, B. Gallez, R. Debuyst
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    ABSTRACT: L-band () EPR has the potential to measure the absorbed radiation dose in human teeth inside the mouth (in vivo analyses). One crucial point in the development of the method is to know if dosimetry evaluation carried out in vivo after accidental exposures can be reliably based on calibration curves built in vitro. The aim of the present work is to specifically address this point. First, we compared L-band in vitro and in vivo analyses in irradiated rat teeth and estimated the possible loss in in vivo experiments due to rat movements and mouth proximity. Second, the lower pair of rat incisors were analysed by L-band EPR before and after irradiation , first on the living rat, then on the same dead rat, finally after extraction of the teeth. X-band powder spectra were also taken after crushing of the two teeth. Irradiations of dead rats and extracted teeth were also carried out. Comparing L-band spectra obtained with living rats and removed heads does not show any significant difference due to possible small rat movements or breathing. Relative standard deviations of the amplitudes of the dosimetric signal are quite high (27–54%). Nevertheless, it seems to be a tendency to have higher signals in irradiated extracted teeth than in irradiated animals.
    Radiation Measurements 02/2005; · 0.86 Impact Factor
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    ABSTRACT: The purpose of this study was to provide insight into the processes that occur after the irradiation of solid-state drugs. Electron paramagnetic resonance (EPR) experiments were performed at two different frequencies, X-band (about 9.5 GHz) and Q-band (about 34 GHz), to identify the radicals present in irradiated captopril. The results confirmed that an irradiated drug can trap several main radicals. Moreover, the radical composition varied as a function of the treatment. In addition, non-volatile final products were studied by liquid chromatography coupled to UV and to mass spectrometry (LC-MS). The variation of the radical composition did not influence the profile of the final products; this appears to indicate that, in the case of captopril, the trapped radicals observed by EPR are not the main precursors of the final products. Finally, high-performance liquid chromatography data appear to indicate that radiosterilization of captopril is feasible.
    Radiation Research 01/2005; 162(6):616-22. · 2.70 Impact Factor
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    ABSTRACT: Several reports in the literature have described the effects of radiation in workers who exposed their fingers to intense radioactive sources. The radiation injuries occurring after local exposure to a high dose (20 to 100 Gy) could lead to the need for amputation. Follow-up of victims needs to be more rational with a precise knowledge of the irradiated area that risks tissue degradation and necrosis. It has been described previously that X-band electron paramagnetic resonance (EPR) spectroscopy could be used to assess the dose in irradiated amputated fingers. Here, we propose the use of low-frequency EPR spectroscopy to evaluate non-invasively the absorbed dose. Low-frequency microwaves are indeed less absorbed by water and penetrate more deeply into living material (approximately 10 mm in tissues using 1 GHz spectrometers). This work presents preliminary results obtained with baboon and human fingers compared with human dry phalanxes placed inside a surface-coil resonator. The EPR signal increased linearly with the dose. The ratio of the slopes of the dry bone to whole finger linear regression lines was around 5. The detection limit achievable with the present spectrometer and resonator is around 60 Gy, which is well within the range of accidentally exposed fingers. It is likely that the detection limit could be improved in the future, thanks to further technical spectrometer and resonator developments as well as to appropriate spectrum deconvolution into native and dosimetric signals.
    Physics in Medicine and Biology 08/2004; 49(13):2891-8. · 2.70 Impact Factor
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    ABSTRACT: In the context of accidental or intentional radiation exposures (nuclear terrorism), it is essential to separate rapidly those individuals with substantial exposures from those with exposures that do not constitute an immediate threat to health. Low-frequency electron paramagnetic resonance (EPR) spectroscopy provides the potential advantage of making accurate and sensitive measurements of absorbed radiation dose in teeth without removing the teeth from the potential victims. Up to now, most studies focused on the dose-response curves obtained for gamma radiation. In radiation accidents, however, the contribution of neutrons to the total radiation dose should not be neglected. To determine how neutrons contribute to the apparent dose estimated by EPR dosimetry, extracted whole human teeth were irradiated at the SILENE reactor in a mixed neutron and gamma-radiation field simulating criticality accidents. The teeth were irradiated in free air as well as in a paraffin head phantom. Lead screens were also used to eliminate to a large extent the contribution of the gamma radiation to the dose received by the teeth. The EPR signals, obtained with a low-frequency (1.2 GHz) spectrometer, were compared to dosimetry measurements at the same location. The contribution of neutrons to the EPR dosimetric signal was negligible in the range of 0 to 10 Gy and was rather small (neutron/gamma-ray sensitivity in the range 0-0.2) at higher doses. This indicates that the method essentially provides information on the dose received from the gamma-ray component of the radiation.
    Radiation Research 09/2003; 160(2):168-73. · 2.70 Impact Factor
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    ABSTRACT: This article describes a simple preliminary test to determine whether a drug is sufficiently radioresistant to withstand radiosterilization. The test is based on the electron spin resonance (ESR) detection of radicals produced after irradiation of a solid-state drug, assuming that these radicals are the precursors of the final products detected after dissolution of the drug. A calibration curve has therefore been established by measuring ESR spectra of l-alanine irradiated at different doses. The response factor to quantify the radicals is the normalized double integration (DI) of the whole first-derivative ESR spectrum. The curve gives the relationship between the normalized DI and the number of radicals. Eight beta blockers have been chosen and their radical yield determined. This is the first time that several different drugs of the same pharmacological group have been studied and compared. The results obtained are similar for seven of the eight beta blockers; the mean G value (excepted for nadolol) is 3 x 10(-9) mol/J. This means that beta blockers are radioresistant. The two most radiosensitive drugs (nadolol and esmolol hydrochloride) were also studied by high-performance liquid chromatography (HPLC). No significant loss of the active compound was detected, which confirms this radioresistant property. Moreover, no change in color or smell was observed. Using ESR and HPLC, beta blockers were identified as potential candidates for radiosterilization.
    Radiation Research 08/2003; 160(1):103-9. · 2.70 Impact Factor
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    ABSTRACT: L-band EPR measurements were done in vitro on extracted human teeth with the objective to evaluate the feasibility of retrospective in vivo EPR dosimetry. In a recent study, the relative contributions of individual tooth components (enamel, crown dentin and root) to the total response of a whole tooth inside an L-band surface coil resonator was investigated. In the present work, the gamma-dose response curves were evaluated for diierent EPR signal evaluation methods, using 35 whole teeth with absorbed doses in the range 1–100 Gy. The paper reports on the ÿrst attempt to deconvolute the single composite L-band EPR line in components due to CO − 2 and native radicals. The L-band EPR spectrum of teeth could be approximated by combining powder-simulated spectra of orthorhombic and quasi-axial signals of the CO − 2 radical and an isotropic signal of the native radicals. Among the applied EPR signal evaluation methods, the evaluation by spectrum deconvolution revealed the lowest detection limit for absorbed dose. A detection limit of about 0:5 Gy was estimated for the currently available L-band equipment.
    Radiation Measurements 01/2003; 37:347-353. · 0.86 Impact Factor
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    ABSTRACT: This paper reports the first attempt to use L-band spectroscopy for estimating the sensitivity of whole teeth to fast neutrons and gamma-rays. Three teeth were successively irradiated first with fast neutrons with a wide energy spectrum (mean energy around 30 MeV) up to approximately 160 Gy and then with gamma-rays up to approximately 14 Gy. After each irradiation, L-band (approximately 1 GHz) EPR spectra of each whole tooth surrounded by the surface-coil resonator were recorded, yielding a single composite line principally due to CO2- and native radicals. The sensitivities are estimated by the slopes of the linear dose response curves of the dosimetric CO2- radicals. The ratios of the gamma/neutron sensitivities were found to be in the range 8-9 (+/- 2) for the three teeth.
    Radiation Measurements 01/2003; 35(6):603-8. · 0.86 Impact Factor
  • Inorganic Chemistry - INORG CHEM. 04/2002; 33(14).
  • The Journal of Physical Chemistry. 04/2002; 94(1).
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    ABSTRACT: Regarding in vivo L-band dosimetry with human teeth, a number of preliminary experiments were carried out that were linked to the resonators response and the relative contribution of enamel to the EPR signal intensity of irradiated whole teeth. The sensitivity of the extended loop resonator varies in the antenna plane, but this variation tends to vanish when the sample is moved away from this plane. When the loop antenna is placed just above the highly irradiated molar, around 88% of the dosimetric signal is due to the crown enamel. The sensitivity inside a birdcage cavity is approximately equal over the volume of a molar; only 30% of the molar's total dosimetric signal results from enamel. Some decrease in the intensity of the dosimetric signal from enamel is observed after irradiation. At room temperature, the signal is reduced by about 20% within 90 days and approaches a plateau with a time constant of about 35 days.
    Radiation Protection Dosimetry 02/2002; 101(1-4):497-502. · 0.91 Impact Factor
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    ABSTRACT: Recently, we have participated in ‘The 2nd International Intercomparison on EPR Tooth Dosimetry’ wherein 18 laboratories had to evaluate low-radiation doses (100–1000 mGy) in intact teeth (Wieser et al., Radiat. Meas., 32 (2000a) 549). The results of this international intercomparison seem to indicate a promising picture of EPR tooth dosimetry. In this paper, the two Belgian EPR participants present a more detailed and critical study of their contribution to this intercomparison. The methods used were maximum likelihood common factor analysis (MLCFA) and spectrum subtraction. Special attention is paid to potential problems with sample preparation, intrinsic dose evaluation, linearity of the dose response, and determination of dose uncertainties.
    Radiation Measurements. 01/2001;
  • B. Gallez, R. Debuyst
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    ABSTRACT: The detection of glass particles in glass-induced injuries is often difficult. Most commercial glasses contain iron (Fe3+) centers which present a characteristic electron paramagnetic resonance (EPR) spectrum nearg = 4.3. The detection of small glass particles in vivo can be achieved with low-frequency EPR spectroscopy (1.2 GHz) operating at low field. The method was sucessfully applied in anesthetized live animals where small pieces of glass were implanted under the skin in their backs. This could be a new clinically relevant application of EPR spectroscopy.
    Applied Magnetic Resonance 01/2001; 20(4):579-582. · 0.83 Impact Factor
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    ABSTRACT: Eighteen international EPR laboratories participated in the second intercomparison programme. Each participant had to prepare enamel samples and evaluate the absorbed dose from molars that were irradiated in vitro in the range 0–1000 mGy. The objective of the programme was to bring together all methods which are currently applied by different laboratories for EPR dose reconstruction and to demonstrate the present state of dosimetry. An overview of the essential features of the different methods is presented. The current accuracy of EPR tooth enamel dosimetry under defined conditions of irradiation is evaluated.
    Radiation Measurements 12/2000; 32(5-6):549-557. · 0.86 Impact Factor
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    R Debuyst, M Frechen, S Idrissi
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    ABSTRACT: A natural monohydrocalcite sample from Australia was submitted to γ-irradiations and analysed by TL and ESR. Spurious TL signals are observed, probably due to the presence of water and organic impurities. TL and ESR dose response curves are presented and discussed. The organic impurities seem responsible for a delay of around 200 Gy in the increase of the TL peaks and the appearance of the ESR carbonate derived radicals (supralinear behaviour). Dating was not possible and no direct correlation exists between the three TL peaks and the ESR signals due to CO−3, CO−2 and SO−2 radicals.
    Radiation Measurements 12/2000; · 0.86 Impact Factor
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    B Gallez, C Baudelet, R Debuyst
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    ABSTRACT: The observation of the fate of free radicals coming from food after oral administration could be important in evaluating their reactivity in vivo. The aim of this study was to demonstrate that it is feasible to detect directly in vivo free radicals coming from food with the use of low frequency electron paramagnetic resonance (EPR) spectroscopy. Because polyphenols are easily oxidized into stable radicals, we assumed that these radicals could be detected in food. We chose licorice, which contains several types of polyphenols. The presence of free radicals was demonstrated in licorice-flavored sweets. Using low frequency EPR spectroscopy, we detected these free radicals directly and noninvasively after oral administration to mice. These radicals were rather stable in the guts of the mice. This study is the first report demonstrating noninvasively the presence of free radicals in vivo coming from food.
    Journal of Nutrition 08/2000; 130(7):1831-3. · 4.20 Impact Factor
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    ABSTRACT: Enamel from 6 different positions in a well preserved elephant tooth from the Kärlich-Seeufer site in Germany has been irradiated up to 32 kGy. The X-band (v = 9.5 GHz) ESR spectra of two subsamples have been decomposed into three real components with Maximum Likelihood Common Factor Analysis (MLCFA). One of these components due to orthorhombic CO2- radicals is predominant. Dose response curves for the contributions of these MLCFA components and for different heights in the ESR spectra have been obtained and fitted with different models. Depending on the model, the equivalent dose for the preferably used height at g = 1.9973, due to CO2-, ranges from 70 to 130 Gy. Due to a very low uranium and thorium content in both enamel and dentine (< or = approximately 10 ppb) and to an important external y-attenuation, the ages fluctuate between 300 and 575 ka.
    Applied Radiation and Isotopes 06/2000; 52(5):1327-36. · 1.18 Impact Factor

Publication Stats

357 Citations
61.16 Total Impact Points

Institutions

  • 1976–2006
    • Catholic University of Louvain
      • • Institute of Experimental and Clinical Research (IREC)
      • • School of Pharmacy - FARM
      Walloon Region, Belgium
  • 2005
    • Ghent University
      • Department of Solid-state Physics
      Gent, VLG, Belgium