Biomedical subjects

M C Cantone

Publications and source records attributed to M C Cantone.

At least 19 recordsLinked to original sources

PubMed2006

Determination of dose rates from natural radionuclides in dental materials.

Different types of materials used for dental prosthetics restoration, including feldspathic ceramics, glass ceramics, zirconia-based ceramics, alumina-based ceramics, and resin-based materials, were investigated with regard to content of natural radionuclides by means of thermoluminescence beta dosimetry and gamma spectrometry. The gross beta dose rate from feldspathic and glass ceramics was about ten times higher than the background measurement, whereas resin-based materials generated negligible beta dose rate, similarly to natural tooth samples. The specific activity of uranium and thorium was significantly below the levels found in the period when addition of uranium to dental porcelain materials was still permitted. The high-beta dose levels observed in feldspathic porcelains and glass ceramics are thus mainly ascribable to (40)K, naturally present in these specimens. Although the measured values are below the recommended limits, results indicate that patients with prostheses are subject to higher dose levels than other members of the population. Alumina- and zirconia-based ceramics might be a promising alternative, as they have generally lower beta dose rates than the conventional porcelain materials. However, the dosimetry results, which imply the presence of inhomogeneously distributed clusters of radionuclides in the sample matrix, and the still unsuitable structural properties call for further optimization of these materials.

Ceramics↗

PubMed2006

The use of alpha-Al2O3:C in Risø OSL single grains attachment system for assessing the spatial dose rate distribution due to incorporation of 90Sr in human teeth.

The possibility of using a single grain OSL attachment system developed by the Risø National Laboratory (Roskilde, Denmark) for assessing the spatial distribution of radionuclides incorporated in human tissues was investigated. Detectors containing arrays of single grains of alpha-Al2O3)C powder (Landauer Inc., USA) were prepared using aluminium discs (diameter 9.7 mm), which can accommodate 100 single grains in 0.3 mm holes positioned in a 10 x 10 grid. The luminescence and dosimetric properties of each grain were investigated by exposing the detectors to uniform photon radiation fields. After the characterisation of the detectors, the systems were tested to assess the spatial dose rate distribution because of 90Sr incorporated in a tooth sample extracted from an inhabitant of the Techa River region.

Aluminum Oxide↗

PubMed2004

Influence of the chemical form on the plasma clearance of ruthenium in humans.

The radioisotopes of ruthenium (103Ru and 106Ru) are abundant fission products and represent a radiological risk for the population in case of nuclear accidents. Few biokinetic studies have been performed on humans up to now and consequently the current model recommended by ICRP for ruthenium is derived mainly by extrapolation from animal data. The stable isotope 101Ru and proton activation analysis have been used to study the biokinetics of Ru in blood plasma samples taken during 8 studies in three healthy volunteers. The results obtained demonstrated that complexed Ru (in the form of citrate Ru(IV) complexes) is cleared from blood plasma very rapidly (characteristic half time of 17+/-2 min), while inorganic Ru remains longer in the systemic circulation, and is transferred to other organs and/or excreted with a biological half time of 23+/-2h. Good reproducibility of the clearance curves indicated no evidence of inter- or intra-individual variability when the same Ru solution was injected in repeated experiments to different subjects.

Adult↗

PubMed2003

Regional dependence of urinary uranium baseline levels in non-exposed subjects with particular reference to volunteers from Northern Italy.

Knowledge of the level of natural uranium (U) in the human body is fundamental in order to estimate the potentially hazardous incorporation in accidentally exposed subjects. A constant monitoring of exposed workers needs reliable reference baseline values, which can be determined by measuring the U concentration in urine. ICPMS has proven to be a fast, reliable and highly sensitive technique for this purpose. Non-uniformity in the distribution of U levels in various regions and differences in dietary habits account for the significant regional variations of U concentration in urine in non-exposed subjects. In this paper, the determination of daily uranium urinary excretion levels in a group of 12 non-exposed subjects from Northern Italy is presented and compared to data present in the published literature and to values obtained in a larger group of German volunteers. The urinary U output values observed in the Italian subset are generally higher than the corresponding levels measured in other groups. This could be the result of a higher intake of U from liquids, as assessed by the determination of U concentration in drinking waters.

Adolescent↗

PubMed2003

A re-evaluation of the biokinetics of zirconium in humans.

There is much interest in understanding the biokinetics of zirconium in humans due to the potential radiological risk represented by the radionuclide 95Zr and by its daughter 95Nb. Despite the significance of zirconium, few data are available on the actual biokinetics of zirconium in humans. Accordingly the biokinetic model currently recommended by ICRP for this element is based mainly on data from animal experiments. In this study, the use of the stable isotopes 90Zr and 96Zr as tracers has enabled the conduct of 6 biokinetic investigations in 3 healthy volunteers. These studies have provided new valuable information about intestinal absorption and kinetics in blood plasma of zirconium and have been used for the set-up of a more realistic compartmental model with possible applications for dosimetric purposes.

Adult↗

PubMed2003

Stable tracer investigations in humans for assessing the biokinetics of ruthenium and zirconium radionuclides.

The interest in the biokinetics of ruthenium and zirconium in humans is justified by the potential radiological risk represented by their radionuclides. Only a few data related to the biokinetics of ruthenium and zirconium in humans are available and, accordingly, the biokinetic models currently recommended by the ICRP for these elements are mainly based on data from animal experiments. The use of stable isotopes as tracers, coupled with a proper analytical technique (nuclear activation analysis with protons) for their determination in biological samples, represents an ethically acceptable methodology for biokinetic investigations, being free from any radiation risk for the volunteer subjects. In this work, the results obtained in eight biokinetic investigations for ruthenium, conducted on a total of three healthy volunteers, and six for zirconium, performed on a total of three subjects, are presented and compared to the predictions of the ICRP models.

Administration, Oral↗

PubMed2003

Sensitivity analysis techniques applied to a revised model of molybdenum biokinetics.

A revised model of molybdenum biokinetics in humans was recently developed on the basis of experimental data gathered in specific investigations conducted with stable tracers. The model can be used for radiation protection purposes, and it is also a suitable working tool for designing new investigations aimed at further improvements to the model. For the latter goal, a sensitivity analysis was performed in order to determine the most significant model parameters in relation to output measurements performed in studies of molybdenum metabolism. A typical sensitivity analysis approach was adopted, considering the effects in variation of model parameters on the time courses of model outputs such as urinary excretion and blood clearance. A recent new sensitivity technique was considered too, based on the calculation of the so-called generalised sensitivity functions. This combines the sensitivities of the model output with respect to model parameters (as in the typical sensitivity analysis method), with the sensitivities of parameter estimates with respect to changes in model outputs. The results obtained in this analysis suggests that data collected in the first 7 h are critical for the definition of the process of blood clearance and related parameters, whereas reliable information at later times is required for a proper characterisation of urinary excretion.

Body Burden↗

PubMed2002

Assessment of intestinal absorption of trace metals in humans by means of stable isotopes.

This study is aimed to demonstrate the feasibility of stable isotopes for the assessment of reliable data on fractional intestinal absorption of trace metals in healthy humans. Among the various methods available, the double isotope technique, i.e. one isotope given orally together with the test substance to be investigated and another isotope injected intravenously to correct for retention and endogenous excretion of the particular trace metal, provides quantitative figures of intestinal absorption at reasonable expenses with regard to costs for materials and number of samples to be evaluated. The trace metals exemplarily included in this study, i.e. iron, cobalt and molybdenum show diverging relations between absorbed fractions and amounts administered which are indicative for different regulatory mechanisms of their body content. Food ligands influence the fractional absorption significantly so that the uptake from a composite meal cannot be derived from results on uptake from particular foodstuffs. Therefore, validated data on the behaviour of intestinal absorption will significantly contribute to a better understanding of human trace metal metabolism.

Female↗

PubMed2001

Kinetics of systemic ruthenium in human blood using a stable tracer.

The biokinetics of ruthenium after oral and intravenous administration has been investigated in two human subjects using the stable isotope 101Ru as a tracer. Tracer concentrations in blood plasma have been determined using activation analysis with protons. The results presented here prove that the stable tracer technique is a valuable tool for obtaining relevant information about the biokinetics of ruthenium in humans. From these pilot studies, it may be argued that the clearance of systemic ruthenium from plasma is significantly slower than the predictions of the biokinetic model currently recommended by the International Commission on Radiological Protection (ICRP). The experimental data for the orally administered tracer, which reflect the gastrointestinal absorption process, differ from the curve derived from the ICRP model, suggesting that the uptake into the systemic circulation may be lower than predicted. On the basis of these preliminary data, investigations on a larger number of subjects with improvements in the experimental design are scheduled.

Administration, Oral↗

PubMed2000

Determination of biokinetic parameters for ingestion of radionuclides of zirconium in animals using stable tracers.

Exposure to the radioactive isotope 95Zr, as in nuclear accidents, and to stable zirconium, due to its use in industry, has increased the interest in the biokinetics of this element. Information has been derived mainly from tests performed on animals by means of radioactive tracers. Due to the fact that extrapolation from animals to humans is always open to question, there is an increasing need of a methodology which allows data to be obtained directly from humans. The use of stable tracers, being ethically justifiable, is a powerful tool for providing this information. As two tracers of the same element must be utilized in order to evaluate gut absorption, an analytical technique which is capable of distinguishing and measuring simultaneously different isotopes of zirconium in biological samples is required. Preliminary tests on laboratory animals were performed in order to assess the feasibility of the double tracer technique combined with proton activation analysis.

Animals↗

PubMed2000

Internal biokinetic behaviour of molybdenum in humans studied with stable isotopes as tracers.

Although molybdenum is considered to be an essential trace metal for humans, the knowledge about its metabolism is rather limited. The present study was aimed at the assessment of biokinetics following intravenous injection of trace amounts of 95Mo or 96Mo into five healthy volunteers. In a total of 11 investigations, the plasma clearance up to eight hours and the urinary excretion for at least three days after the injection were evaluated. The tracer concentrations were determined by proton nuclear activation analysis in blood plasma and by thermal ionization mass spectrometry in urine samples respectively. In all subjects, the plasma clearance is much faster than expected from the literature. The data obtained for the plasma clearance of the tracer can reasonably be fitted by a two exponential equation. The half times of the fast component range between 4 and 70 minutes and for the slow component between 3 and 30 hours. The urinary excretion of the injected tracer seems also to be faster than expected and the fractions lost are higher for larger doses administered. For the smallest dose given, 34% of the injected tracer were excreted within one day whereas for the four times larger dose about 60% were lost. These findings on urinary excretion are in agreement with recently published results.

Adult↗

PubMed2000

Internal dose for ingestion of molybdenum radionuclides based on a revised biokinetic model.

Recent investigations with human volunteers showed that the model recommended by ICRP for the description of the biokinetics of molybdenum radionuclides is not able to describe some characteristic features, like the clearance from the transfer compartment and the urinary excretion profile. Therefore, a revision of the model was presented in a previous paper. In the current work, dose coefficients for ingestion of radionuclides of molybdenum from members of the public have been calculated according to the ICRP guidelines, but using the revised biokinetic model. The results obtained for the effective dose do not differ remarkably from the ICRP estimates. However, considerable deviations are observed for the equivalent dose to some individual organs; for example, the dose coefficient for colon after ingestion of 99Mo in solid form is about 7 times higher than the ICRP value, whereas for other organs the new estimates are about one tenth of the ICRP ones. This fact could be of importance with respect to deterministic effects to particularly radiosensitive organs.

Adult↗

PubMed1998

Use of charged particle activation as an analytical technique in the biological field.

Some applications of Charged Particle Activation Analysis (CPAA) in the biological field are presented. This technique has been used frequently for the analysis of the light elements which are inaccessible to neutron activation analysis (NAA), but it is especially effective in the detection of medium-heavy trace elements and there is increasing interest in its employment in biological and medical fields. CPAA enables the identification and simultaneous quantification of different isotopes of the same element. Recent applications show that it can be used as a reference method in stable isotope determination for biokinetic studies of selected elements in complex organic matrices such as blood plasma.

Activation Analysis↗

PubMed1998

A revised model of molybdenum biokinetics in humans for application in radiation protection.

The biokinetic models used to describe the fate of radionuclides incorporated by humans often lack the support of reliable experimental evidence. Recent investigations conducted in human volunteers using stable isotopes as tracers have shown that some important features of the biokinetics of ingested molybdenum are not taken into account by the model currently adopted by the International Commission on Radiological Protection. Compartmental analysis has been used to develop an improved model which better describes the available data. Major modifications with respect to the International Commission on Radiological Protection model concern the description of the urinary excretion and the values of the transfer parameters describing intestinal absorption and distribution to organs. Separate sets of parameter values for liquid and solid materials are also given.

Humans↗

PubMed1997

A methodology for biokinetic studies using stable isotopes: results of repeated molybdenum investigations on a healthy volunteer.

A method for biokinetic studies in humans using stable isotopes is presented. The technique is based on double tracer administration and on proton activation as the analytical method. As an application, the results of investigations on molybdenum metabolism in humans are reported. The contents of 95Mo and 96Mo in biological samples were determined by inducing (p,n) reactions and by analysing the gamma-rays emitted by the radioactive products. The minimum detectable quantity was 2 ng/mL plasma for both Mo isotopes. Four investigations on molybdenum metabolism were performed on a healthy volunteer subject in the course of 3 yr. Two absorption studies with different amounts of tracers in aqueous solution were performed by giving 96Mo orally and 95Mo intravenously. Two investigations were performed with single oral administration of 96Mo in aqueous solution and of a 96Mo solution mixed with an infant formula respectively. The stability with time of the biokinetic parameters was tested. The fractional absorption values measured in this volunteer were 0.84, 0.98 and 0.95 for three studies with Mo in HCl and 0.51 for a single study with Mo administered in an infant formula, these data are discussed.

Humans↗

PubMed1995

Influence of the administered mass of tellurium on plasma clearance in rabbits.

The combination of analytical techniques such as PNA and SIMS with a compartmental approach enables the study of the metabolism and biokinetics in humans of several elements by using stable isotopes as tracers. The techniques developed for Te require the administration of greater masses than those used for similar studies performed with radioactive tracers, therefore a test was carried out in rabbits in order to assess the possible influence of the administered amounts on the determination of the biokinetic parameters. The behaviour of the tracers was found to be similar for Te administration of up to 70 micrograms/kg of body weight. An inter-individual variability in the size of the transfer compartment was observed and has to be taken into account.

Animals↗

PubMed1995

Proton activation analysis of stable isotopes for a molybdenum biokinetics study in humans.

Molybdenum is a trace element essential to life. Nevertheless, little information is available on its metabolism in humans. A methodology based on stable isotope administration that combines compartmental analysis, simultaneous use of two tracers, and proton nuclear activation (PNA) is presented. A four-compartment metabolic model was adopted. The compartments are stomach, small intestine, transfer compartment, and unquantified tissue pool. The employment of two different stable isotopes of the element under investigation as tracers was made possible by PNA. Optimization of the technique for molybdenum determination in plasma led to the choice of 95Mo and 96Mo as tracers. Their concentrations in plasma can be determined measuring the disintegration gamma lines of the corresponding technetium radioisotopes produced via (p,n) reaction. In the adopted experimental conditions, a minimum detectable concentration of 2 ng isotope/ml plasma was attained. A kinetics study was performed on two healthy volunteers. To both subjects one tracer was orally administered, and the other intravenously injected. Venous blood samples were withdrawn at different postinjection times and the concentrations for both isotopes determined. The model parameters describing molybdenum kinetics were obtained for the two individuals. Total absorbed fraction was found to be 0.84 +/- 0.03 and 0.86 +/- 0.07, respectively.

Activation Analysis↗

PubMed1994

Dose-response curve slope improvement and result reproducibility of ferrous-sulphate-doped gels analysed by NMR imaging.

Ferrous sulphate gel analysed by relaxation time measurements with NMR imaging is considered a useful dosimeter for 3D determinations of absorbed dose. A protocol for the gel preparation with agarose SeaPlaque that leads to a dosimeter with very high dose sensitivity is described. The dose-response curve slope is about 0.2 s(-1) Gy(-1) and the G factor turns out to be approximately 185 ions per 100 eV of absorbed energy. A method for making the measurements and analysing the results that brings about good result reproducibility is suggested. A thorough experimental study of the dependence of the dosimeter response on the elapsed time from preparation to irradiation and from irradiation to NMR measurement has revealed good reproducibility. The above characteristic of the gel system is very interesting, because it shows the possibility of utilizing the dosimeter for absolute dose determinations with satisfactory reliability.

Dose-Response Relationship, Radiation↗