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Biomedical subjects

P Berkvens

Publications and source records attributed to P Berkvens.

12 recordsLinked to original sources
PubMed2006

Superheated drop neutron detectors used at the ESRF.

The ESRF operates a 6 GeV electron storage ring to produce X-rays. The experimental hall is classified as a free access area in terms of radiation protection. Interlocked radiation monitors guarantee the corresponding dose constraint. Measurements have shown that the radiation field outside the storage ring is dominated by neutrons. Apfel REMbrandt superheated drop detectors have been chosen. In total, 64 monitors are installed around the storage ring, interlocked to the accelerator personnel safety system. Since the radiation fields are highly pulsed, the response of the REMbrandt monitors to pulsed radiation was measured and compared with theoretical predictions. Dose recordings from the bubble detectors are shown, illustrating the good correlation between beam losses and dose rates, as well as showing the correspondence between neutron and photon dose values. Finally, around the beamline hutches, REMbrandt neutron monitors have been used to evaluate the ratio between neutron and photon dose rates.

Dose-Response Relationship, Radiation↗
PubMed2005

Induced radioactivity in the ESRF storage ring.

The new French radiation protection legislation requires the definition of the zoning of accelerator facilities with respect to radioactive waste. This activation inside the ESRF 6 GeV storage ring is essentially due to photonuclear reactions. This paper describes the first results of Monte Carlo calculations that were started to prepare this zoning. The electron beam losses inside the storage ring, required to calculate saturation activities, are described. Results for the activation of the air inside the ring tunnel and of the cooling water are presented. The activation of accelerator components is illustrated with the results of the activation of the stainless steel vessels in a standard cell and in a cell with higher losses due to the presence of a vertical scraper. The amount of activation is compared with clearance levels given in the European directive 96/29/Euratom.

Computer Simulation↗
PubMed2000

First human transvenous coronary angiography at the European Synchrotron Radiation Facility.

The first operation of the European Synchrotron Radiation Facility (ESRF) medical beamline is reported in this paper. The goal of the angiography project is to develop a reduced risk imaging technique, which can be used to follow up patients after coronary intervention. After the intravenous injection of a contrast agent (iodine) two images are produced with monochromatic beams, bracketing the iodine K-edge. The logarithmic subtraction of the two measurements results in an iodine enhanced image, which can be precisely quantified. A research protocol has been designed to evaluate the performances of this method in comparison with the conventional technique. Patients included in the protocol have previously undergone angioplasty. If a re-stenosis is suspected, the patient is imaged both at the ESRF and at the hospital with the conventional technique, within the next few days. This paper reports the results obtained with the first patients. To date, eight patients have been imaged and excellent image quality was obtained.

Angioplasty, Balloon, Coronary↗
PubMed2000

Research at the European Synchrotron Radiation Facility medical beamline.

The application of synchrotron radiation in medical research has become a mature field of research at synchrotron facilities worldwide. In the relatively short time that synchrotrons have been available to the scientific community, their characteristic beams of UV and X-ray radiation have been applied to virtually all areas of medical science which use ionizing radiation. The ability to tune intense monochromatic beams over wide energy ranges differentiates these sources from standard clinical and research tools. At the European Synchrotron Radiation Facility (Grenoble, France), a major research facility is operational on an advanced wiggler radiation beamport, ID17. The beamport is designed to carry out a broad range of research ranging from cell radiation biology to in vivo human studies. Medical imaging programs at ID17 include transvenous coronary angiography, computed tomography, mammography and bronchography. In addition, a major research program on microbeam radiation therapy is progressing. This paper will present a very brief overview of the beamline and the imaging and therapy programs.

Animals↗
PubMed2000

In vivo K-edge imaging with synchrotron radiation.

We present in this paper two imaging techniques using contrast agents assessed with in vivo experiments. Both methods are based on the same physical principle, and were implemented at the European Synchrotron Radiation Facility medical beamline. The first one is intravenous coronary angiography using synchrotron radiation X-rays. This imaging technique has been planned for human studies in the near future. We describe the first experiments that were carried out with pigs at the ESRF. The second imaging mode is computed tomography using synchrotron radiation on rats bearing brain tumors. Owing to synchrotron radiation physical properties, these new imaging methods provide additional information compared to conventional techniques. After infusion of the contrast agent, it is possible to derive from the images the concentration of the contrast agent in the tumor area for the computed tomography and in any visible vessel for the angiography method.

Animals↗
PubMed1988

Three-dimensional treatment of steady-state 222Rn diffusion in building materials: introducing a practical modified one-dimensional approach.

A three dimensional solution of the steady state diffusion equation, with boundary conditions applicable to closed can 222Rn exhalation measurements is described. A modified one-dimensional formalism is introduced which allows the interpretation of the results from exhalation measurements in terms of one-dimensional 222Rn exhalation from walls.

Construction Materials↗
PubMed1988

Limb conservation in primary bone tumours by resection, extracorporeal irradiation and re-implantation.

En-bloc resection, extracorporeal irradiation and re-implantation of the irradiated bone have been used to treat 15 patients suffering from primary malignant tumours of bone or cartilage and two with benign lesions. This treatment is an alternative to replacement by prosthesis or allograft bridging techniques. After a mean follow-up of over five years results are encouraging, despite some complications and the relatively long period before weight-bearing is allowed.

Adolescent↗