Publications (27)38.5 Total impact
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Article: Detection of glass foreign bodies in soft tissues with low-frequency EPR spectroscopy
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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 04/2012; 20(4):579-582. · 0.75 Impact Factor -
Article: The Third International Intercomparison on EPR Tooth Dosimetry: part 2, final analysis.
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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. · 0.82 Impact Factor -
Article: Multi-frequency electron paramagnetic resonance study of irradiated human finger phalanxes.
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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. · 2.10 Impact Factor -
Article: The 3rd international intercomparison on EPR tooth dosimetry: Part 1, general analysis.
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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. · 1.17 Impact Factor -
Article: Non-invasive determination of the irradiation dose in fingers using low-frequency EPR.
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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. · 2.83 Impact Factor -
Article: Retrospective dosimetry after criticality accidents using low-frequency EPR: a study of whole human teeth irradiated in a mixed neutron and gamma-radiation field.
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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. · 2.68 Impact Factor -
Article: An in vitro L-band EPR study with whole human teeth in a surface coil resonator
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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. -
Article: Influence of Axial Coordination on the g-Factor Anisotropy of the Tetraimine Macrocyclic Cobalt(II) Complex [Co(C10H20N8)Cl(H2O)]Cl.cntdot.H2O
04/2002; -
Article: An in vitro L-band electron paramagnetic resonance study of highly irradiated whole teeth.
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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. · 0.82 Impact Factor -
Article: The second international intercomparison on EPR tooth dosimetry
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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. · 1.18 Impact Factor -
Article: Free radicals in licorice-flavored sweets can Be detected noninvasively using low frequency electron paramagnetic resonance after oral administration to mice.
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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. · 3.92 Impact Factor -
Article: ESR study of elephant tooth enamel from the Kärlich-Seeufer site in Germany.
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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. · 1.17 Impact Factor -
Article: The 2nd International Intercomparison on EPR tooth dosimetry
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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 01/2000; 32:549-557. · 1.18 Impact Factor -
Article: Small particles of fusinite and carbohydrate chars coated with aqueous soluble polymers: preparation and applications for in vivo EPR oximetry.
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ABSTRACT: The development of oxygen-sensitive paramagnetic materials is being pursued actively because of their potential applications in in vivo EPR oximetry. Among these materials, several charcoals and carbohydrate chars are of special interest because of their desirable EPR properties: high sensitivity of the EPR linewidth to the partial pressure of oxygen, simple EPR spectra, and high spin density. Their potential use in humans, however, is limited by the need to demonstrate that they will not lead to deleterious effects. A strategy was used to optimize the biocompatibility of the oxygen-sensitive materials by decreasing the size of the particles and coating them with suspending or surfactive agents such as arabic gum, poloxamer (Pluriol 6800), and polyvinylpyrrolidone. The coated particles of a carbohydrate char and fusinite were characterized in vitro for their size, stability, and pO2 sensitivity. The feasibility of performing pO2 measurement was examined in vivo by inducing ischemia in the gastrocnemius muscle of mice. The use of arabic gum for coating the fusinite particles preserved the pO2 sensitivity in vivo, whereas the other surfactive agents led to a loss of the pO2 sensitivity in vivo. Small particles of fusinite coated by arabic gum and intravenously administered to mice accumulated in the liver, whereas the uncoated fusinite was toxic when injected intravenously due to the large size and aggregation of the particles. Histological studies performed up to 6 months after the injection in muscles of mice did not indicate any toxicity from the materials used in the present study.Magnetic Resonance in Medicine 08/1998; 40(1):152-9. · 2.96 Impact Factor -
Article: Development of biocompatible implants of fusinite for in vivo EPR oximetry.
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ABSTRACT: The development of oxygen-sensitive paramagnetic materials is being actively pursued because of their potential applications for in vivo electron paramagnetic resonance (EPR) oximetry. Among these materials, fusinite is of particular interest because of the high sensitivity of the EPR linewidth to the partial pressure pO2. Although this material has led to a number of very useful results in experimental systems, its potential use in humans is limited by the need to prove that it will not cause deleterious effects. The strategy used in this study to optimize the biocompatibility of the oxygen-sensitive materials was to prepare small silicon implants containing the fusinite. The use of silicon permits the diffusion of oxygen inside the implant while the material does not have contact with the biological environment. Radiosterilization did not affect the pO2 sensitivity of the material. The feasibility of performing pO2 measurement was verified in vivo by periodically inducing ischemia in the gastrocnemius muscle of mice over a period of 6 weeks.MAGMA Magnetic Resonance Materials in Physics Biology and Medicine 04/1996; 4(1):71-5. · 1.88 Impact Factor -
Article: The effects of pasteurisation on albumin: an EPR binding assay for polymeric albumin.
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ABSTRACT: The ability of a nitroxyl fatty acid (NFA) to bind specifically to albumin is abolished when, in the absence of stabilizers, a 4% solution of this protein is heated above a critical temperature of 60 degrees C. This treatment leads to the formation of "albumin polymers" as classically evidenced by GPC. Since the bound fraction is evidenced in EPR spectroscopy by a large anisotropic component, the presence of this anisotropy can be used in the assessment of the quality of the pharmaceutical preparations of albumin, which are usually pasteurized in order to inactivate viruses. Moreover, in sharp contrast with the behavior of albumin dispersions, lyophilised albumin subjected to heat treatment at 70 degrees C for 24 h left the protein untouched regarding its NFA binding and GPC profile.Journal of Pharmaceutical and Biomedical Analysis 12/1995; 13(12):1449-52. · 2.97 Impact Factor -
Article: Spin labelled arabinogalactan as MRI contrast agent.
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ABSTRACT: In this study, we report the synthesis and the evaluation as MRI contrast agent of arabinogalactan/pyrrolidinoxyl radicals (PCA) covalent adduct (SLAG:Spin Labelled ArabinoGalactan). Arabinogalactan was used as targeting device, as it is recognized by the asialoglycoprotein receptor specific to the hepatocytes. The higher relaxivity R1 in water of SLAG, compared with small hydrophilic nitroxyl radicals, was explained by the molecular dynamics study using EPR spectroscopy that showed some immobilization of the radical into the polysaccharide. A binding study on isolated hepatocytes revealed that SLAG still recognizes the asialoglycoprotein receptor. MR imaging was performed using spin-echo T1 weighted images on mice to compare the contrast effect obtained with SLAG and PCA after IV injection (1 mmol/kg free radical). The percent signal enhancement observed in the liver 5 min after IV injection was 40 +/- 3% and 13 +/- 5% for SLAG and PCA, respectively. The signal was also dramatically increased in the renal cortex. This latter effect as well as the prolonged duration of the contrast (+/- 3 h), indicates at least a partial nonselective biodistribution; the high concentration needed to obtain a contrast effect could account for the saturation of the asialoglycoprotein receptor and hence for the apparent nonselective biodistribution.Magnetic Resonance Imaging 02/1994; 12(1):61-9. · 1.99 Impact Factor -
Article: Relaxivity and molecular dynamics of spin labeled polysaccharides
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ABSTRACT: Synthetic methods are described leading to polysubstituted spin labeled polysaccharides (dextran 70, 110, 200, and arabinogalactan), which are potential contrast agents in magnetic resonance imaging. The nitroxyl moieties bound to a polysaccharide yield relaxivity enhanced by a factor of 1.6 (at 0.47 T and 37C) compared to that of the small hydrophilic radicals. An EPR study at variable temperature and viscosity (by adding sucrose) reveals the presence of two mobile bound spin labels. The less mobile ones are characterized by an order parameterS0.6 and a macromolecular rotational correlation time of 1.6 ns at 20C for the substituted dextrans. Substitution rate effects are observed and might be related to conformational changes.MAGMA Magnetic Resonance Materials in Physics Biology and Medicine 01/1994; 2(1):61-68. · 1.88 Impact Factor -
Article: Evaluation of a nitroxyl fatty acid as liver contrast agent for magnetic resonance imaging.
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ABSTRACT: In this study, we report the synthesis and the evaluation as MRI contrast agent of a new compound (nitroxyl fatty acid, NFA), where a pyrrolidinoxyl radical (3-carboxy-proxyl, PCA) is linked to a fatty acid moiety. Fatty acids were selected as vector because they present a high affinity for the liver, their efficient cellular uptake being the result of a specific interaction with a transmembrane transporter (liver plasma membrane-fatty acid binding protein). The uptake of 3H-oleic acid is inhibited after the injection of 1 mmol/kg of NFA, suggesting that NFA recognizes the same transmembrane transporter as the natural fatty acids. The higher relaxivity R1 of NFA in albumin solutions, compared with PCA, was explained by the immobilization of the nitroxyl radical in the protein. MR imaging was performed using T1-weighted images on mice in order to compare the contrast effect obtained after the injection of 1 mmol/kg of radical. The % signal enhancement in the liver 5 min after intravenous injection was 49 +/- 4 and 14 +/- 5 for NFA and PCA, respectively. NFA allowed a better delimitation of some necrotic tumors (Novikoff hepatocarcinoma) due to its preferential uptake by the nontumorous tissue.Magnetic Resonance in Medicine 12/1993; 30(5):592-9. · 2.96 Impact Factor -
Article: Mutagenicity of nitroxyl compounds: structure-activity relationships.
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ABSTRACT: Three piperidinoxyl radicals were found to be directly mutagenic in Salmonella typhimurium TA 100, one pyrrolidinoxyl compound had weaker activity, and two other pyrrolidinoxyl derivatives did not produce an increase of the spontaneous revertants. The tester strain TA 100 was selected in preliminary tests for its higher sensitivity compared to TA 98 and TA 102. The mutagenic activity of the three active compounds was abolished by partial reduction with ascorbic acid, suggesting that the mutagenicity was linked to the free radical nature of these compounds, and reduced in the presence of a cofactor supplemented rat liver subcellular fraction. The mutagenicity of the tested compounds was correlated to the resistance of the nitroxyl spin labels to reduction: the more reactive radicals were found to possess higher mutagenic activity.Toxicology Letters 11/1992; 63(1):35-45. · 3.23 Impact Factor
Top co-authors
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Institutions
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1992–2012
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Université Catholique de Louvain
Louvain-la-Neuve, WAL, Belgium
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2005
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Ghent University
- Department of Solid-state Physics
Gent, VLG, Belgium
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