PubMed Health⌕ Search

Biomedical subjects

F Spurný

Publications and source records attributed to F Spurný.

12 recordsLinked to original sources
PubMed2006

Microdosimetry distributions for 40-200 MeV protons.

Theoretical calculations have been performed to obtain microdosimetrical characteristics for protons in energy range from 40 to 200 MeV. This energy range is a representative of proton energies in tissue during radiation therapy and it also represents a large portion of the proton fluency in the South Atlantic Anomaly. Distributions of deposited energy calculated using Monte Carlo track structure code TRIOL and own-made programs were compared with experimental data obtained using spherical tissue-equivalent proportional counter. A good agreement between calculated and experimentally obtained microdosimetry spectra has been found.

Algorithms↗
PubMed2005

Biological weighted effective dose in 205 MeV clinical proton beam.

The contribution of high linear energy transfer (L) charged particles to dosimetric and microdosimetric characteristics in a clinical proton beam was experimentally studied using an ionization chamber and track etched detectors. The particles mentioned are produced by proton nuclear interactions; at the Bragg peak region slowed down protons also contribute in the L region above several keV microm(-1). Due to these particles the biological weighted effective dose (BWED) of the beam changes with depth. The spectra of particles with L above 7 keV microm(-1) were established by means of track etched detectors, which permitted us to determine their contribution to dosimetric and microdosimetric characteristics of clinical proton beams. The studies were realized in the clinical proton beam of the JINR Dubna Phasotron, with a primary energy of 205 MeV. The relative contribution to the absorbed dose of the particles with L above 7 keV microm(-1) increases from several per cent at the beam entrance to several tens of per cent at the Bragg peak region. The relative biological weighted efficiency (RBWE) for radiotherapy has been calculated using a biological weighting function. It increases with depth from 1.02 at the beam entrance to about 1.25 at the Bragg peak region.

Animals↗
PubMed2005

Aircrew dosimetry by means of experimental measurements and calculations: results obtained during the year 2003.

The results of measurements performed during the year 2003 onboard aircraft, mostly during regular commercial flights of the Czech Airlines (CSA) are presented. The studies were performed during more than 30 individual flights, several dosemeters and equipments were used for both neutron and non-neutron components of the onboard radiation field. CSA colleagues submitted us for all flights with navigation data necessary for the calculation of onboard aircraft crew exposure with transport codes EPCARD and CARI. Direct readings of experimental equipments were corrected on the base of the calibration in CERN high-energy radiation fields. A reasonable agreement of measured and calculated data was observed. During one of the flights, a very deep Forbush decrease occurred. The experimental results confronted with calculation permitted to obtain new view on the influence of such events on aircraft crew exposure.

Aerospace Medicine↗
PubMed2005

Some recent measurements onboard spacecraft with passive detector.

Several passive detectors were used to estimate dosimetry and microdosimetry characteristics of radiation field onboard spacecraft, namely: thermoluminescent detectors (TLDs), mainly to appreciate the contribution of radiation with low-linear energy transfer (LET); Si diode, to try to establish the contribution of fast neutrons; an LET spectrometer based on the chemically etched polyallyldiglycolcarbonate etched track detectors (PADC-TEDs). Detectors have been exposed onboard MIR and International Space Station (ISS) since 1997, they were also used during the MESSAGE 2 biological experiment, October 2003. The results are presented, analysed and discussed. Particular attention is devoted to the possibility of estimating neutron contribution based on data obtained with PADC-TED spectrometer of LET.

Astronauts↗
PubMed2004

Aircrew exposure monitoring: results of 2001 to 2003 studies.

Aircrew exposure represents one of the recent subjects of occupational individual dosimetry. Since 1991 many new results have been found; there is however a need to gather further data on this exposure and its variation with geomagnetic position, solar activity and flight route parameters. Since 2001, many individual and six long-term monitoring programmes have been conducted onboard aircraft of Czech Airlines (CSA). In these programmes, a Si-diode spectrometer was fixed in an aircraft. Together with it, passive dosemeters thermoluminescent detector, track-etch based neutron dosemeter linear energy transfer and spectrometer) were exposed. More than 700 regular commercial flights were monitored in this manner. CSA supplied us also with full navigation data, which allowed us to calculate the exposure levels using EPCARD 3.2 and CARI6 codes. Direct experimental readings obtained with the detectors mentioned above were interpreted on the basis of calibrations in on-Earth reference fields and compared with calculated data. A satisfactory correlation between all sets of data was observed.

Aircraft↗
PubMed2004

Passive spectrometry of linear energy transfer: development and use.

A linear energy transfer (LET) spectrometer based on the evaluation of particle track parameters in a chemically etched polyallyldiglycolcarbonate (PADC) track detector has been developed at our laboratory. It permits us to determine LET spectra between 10 and 700 keV microm(-1) in tissues. The LET spectra obtained permit us to calculate total dose and dose equivalent corresponding to particles with etchable tracks also. We have recently been able to verify the calibration curves used by using C, Mg, Ne, Si and Fe ion beams with different energies. The calibration curves obtained are presented and compared with those originally used, and a good correlation is found. The LET spectrometer with new calibration was used to analyse the radiation quality of the radiotherapy proton beam at the Joint Institute for Nuclear Research (JINR). The radiation quality was studied along the proton's range, particular attention being devoted to the region of the Bragg peak. It was found that the biologically weighted effective dose (BWE) reaches a value of about 1.25 at the Bragg peak region. At the beam entrance this value increases to about 1.02 due to secondary particles created through primary proton nuclear reactions in tissues.

Algorithms↗
PubMed2004

Track-etched detectors for the dosimetry of the radiation of cosmic origin.

Cosmic rays contribute to the exposure on the Earth's surface as well as in its surroundings. At the surface and/or at aviation altitudes, there are mostly secondary particles created through the cosmic rays interaction in the atmosphere, which contribute to this type of exposure. Onboard a spacecraft, the exposure comes mostly from primary cosmic rays. Track-etched detectors (TED) are able to characterise both these types of exposure. The contribution of neutrons, of cosmic origin, on the Earth's surface was studied at altitudes from few hundreds to 3000 m using TED in a moderator sphere. The results obtained are compared with other data on this type of natural radiation background. The results of studies performed onboard aircraft and/or spacecraft are presented afterwards. We used TED-based neutron dosemeter, as well as a spectrometer of linear energy transfer based on a chemically etched TED. The results of studies performed onboard aircraft, as well as spacecraft, are presented and discussed, including an attempt to estimate a neutron component onboard the spacecraft. It was found that they correlate with the results of other independent investigations.

Aircraft↗
PubMed2002

On-board aircrew dosimetry using a semiconductor spectrometer.

Radiation fields on board aircraft contain particles with energies up to a few hundred MeV. Many instruments have been tested to characterise these fields. This paper presents the results of studies on the use of an Si diode spectrometer to characterise these fields. The spectrometer has been in use since spring 2000 on more than 130 return flights to monitor and characterise the on-board field. During a Czech Airlines flight from Prague to New York it was possible to register the effects of an intense solar flare, (ground level event, GLE 60), which occurred on 15 April 2001. It was found that the number of deposition events registered was increased by about 70% and the dose in Si by a factor of 2.0 when compared with the presence of galactic cosmic rays alone. Directly measured data are interpreted with respect to on-earth reference field calibration (photons, CERN high-energy particles): it was found that this approach leads to encouraging results and should be followed up.

Aerospace Medicine↗
PubMed2002

Microdosimetric characteristics of the clinical proton beams at JINR, Dubna.

High-energy proton radiotherapy beams give rise to secondary heavy charged particles with elevated linear energy transfer (LET), which contribute to the dose in a patient. This contribution to the characteristics of radiotherapy proton beams was experimentally studied by means of a LET spectrometer based on a track detector. The spectrometer permits LET spectra to be established in the region above 10 keV.micron-1 in tissue. Sets of track detectors were exposed in the various depths of a phantom irradiated with protons of two energies, 150 and 205 MeV. It was observed that the contribution of particles with the values of LET mentioned increases with the depth, representing from about 2 (at the surface) up to few tens% close to Bragg peak region of the total dose. There, some of primary protons contribute also above 10 keV.micron-1. Using the 'biological weighted function' proposed, the clinical RBE was calculated, it could approach 1.3. This effect has to be taken into account during the clinical beam production and the radiotherapy.

Linear Energy Transfer↗
PubMed1996

The contribution of secondary heavy particles to the absorbed dose from high-energy photon beams.

High-energy photon radiotherapy sources produce non-negligible numbers of secondary heavy particles (neutrons, protons and alphas) which contribute to the dose in a patient. They also present a radiation protection problem. The contribution of such particles to the absorbed dose in a tissue-like medium and to the equivalent dose is considered in this study experimentally. Track etch detectors were chosen as a basic type of measuring instrument: cellulose nitrate Kodak LR115 and polyallyldiglycol carbonate CR39 were used as detectors. Several methods of directly read datum (track density, track parameter, LET spectrum etc) interpretation have been analysed. It has been ascertained that the contribution of secondary heavy particles represents approximately 0.002 of the photon dose and 0.02 of the equivalent dose, both at 50 MeV as maximum photon energy. The contribution of a 20 MV bremsstrahlung beam is roughly one-fifth of that at 50 MV.

Alpha Particles↗