We have made Monte Carlo calculations of the scintillation spectrometer response for the photon field from a cloud of contaminated air after selected scenarios of a nuclear power plant accident. Calculations (using MCNP5 code-X-5 Monte Carlo Team, 2005) were performed for 36 main energy lines of the expected radionuclides. The evaluated spectra enable us to simulate real composite spectra and their evolution in time, and to assess the applicability of a specific spectrometry system for a semi-qualitative and semi-quantitative analysis of the composition of the cloud.
- MeSH
- Equipment Failure Analysis MeSH
- Equipment Design MeSH
- Air Pollutants, Radioactive analysis MeSH
- Radioactive Fallout analysis MeSH
- Radioisotopes analysis MeSH
- Reproducibility of Results MeSH
- Scintillation Counting instrumentation MeSH
- Sensitivity and Specificity MeSH
- Publication type
- Journal Article MeSH
- Evaluation Study MeSH
- Research Support, Non-U.S. Gov't MeSH
A Timepix detector covered with polyethylene convertors of different thicknesses is presented as a fast neutron real-time dosemeter. The application of different weighting factors in connection with the position of a signal in a Timepix detector enables one to obtain an energy-dependent signal equal to neutron dose equivalents. A simulation of a Timepix detector covered with polyethylene convertors using monoenergetic neutrons is presented. The experimental set-up of a dosemeter was also produced. The first results of detector response using different fast neutron sources are presented.
- MeSH
- Algorithms MeSH
- Americium MeSH
- Beryllium MeSH
- Radiation Dosage MeSH
- Equipment Design MeSH
- Californium MeSH
- Neutrons MeSH
- Computer Simulation MeSH
- Polyethylene MeSH
- Probability MeSH
- Protons MeSH
- Radiation Protection methods MeSH
- Scattering, Radiation MeSH
- Radiometry instrumentation methods MeSH
- Fast Neutrons * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
There are various different detectors, which can be used for radiotherapy measurements, and more are about to be adopted. Hybrid pixel detectors (HPD) have been originally developed for the high energy physics. However, over the last few years they also expanded in the medical physics. Novel 2D detector Pantherpix is a HPD designed specifically for the radiotherapy. In this article, its properties are characterised and an assessment of its use in radiotherapy photon beams is provided. Properties such as response stability, response linearity, angular dependence and energy dependence were studied. In order to prove sufficient clinical quality for relative dosimetry, further measurements were undertaken (i.e. dose profiles and collimator scatter factors). Acquired results were compared with ion chamber and gafchromic film results. Namely the applicability of PhPix for cobalt beam therapy, which is still widely used (and will be used in near future) in economically less developed countries, is considered.
- MeSH
- Radiotherapy Dosage MeSH
- Radiometry * MeSH
- Publication type
- Journal Article MeSH
A precise model of a 40% relative efficiency p-type HPGe detector was created for photon detection efficiency calculation using the MCNP code. All detector parameters were determined by different experiments. No experimental calibration points were used for the modification of detector parameters. The model was validated by comparing calculated and experimental full energy peak efficiencies in the 40-2754 keV energy range, for point-source geometry with the source-to-detector distance of 25 cm.
- MeSH
- Algorithms MeSH
- Equipment Failure Analysis MeSH
- Models, Chemical MeSH
- Radiation Dosage MeSH
- Computer-Aided Design MeSH
- Equipment Design MeSH
- Monte Carlo Method MeSH
- Models, Molecular MeSH
- Computer Simulation MeSH
- Radiometry methods instrumentation MeSH
- Radioisotopes analysis MeSH
- Reproducibility of Results MeSH
- Sensitivity and Specificity MeSH
- Spectrometry, Gamma methods instrumentation MeSH
- Models, Statistical MeSH
- Dose-Response Relationship, Radiation MeSH
- Gamma Rays MeSH
- Publication type
- Evaluation Study MeSH
Saccharides and their derivatives are typical polar analytes without a suitable UV-chromophore that are nowadays analyzed by HPLC (high-performance liquid chromatography) under HILIC (hydrophilic interaction liquid chromatography) mode. Usually an evaporative light scattering detector (ELSD) is utilized which, however, gives a nonlinear response. A procedure to overcome the problem of mutarotating (time-varying) analytes recorded with such a nonlinear response detector is described. The procedure was applied for determination of glucosamine in two commercially available pharmaceutical formulations containing the common inorganic ions that the detector gives a response to. Under optimized conditions, both the anomers of glucosamine were separated and could be determined separately. Owing to the short retention time of the analyte (a run time <4 min) and relatively slow kinetics of the anomeric conversion (equilibration time 2.5 h), mutarotation could be monitored and corresponding rate constants calculated.
... 3.3.5 Heat and moisture exchanger filter (HMEF) 47 -- 3.3.6 Colourimetric end-tidal C02 (EtC02) detector ... ... 49 -- 3.3.7.3 Pulse oximeter: fingertip 51 ü WHO Priority medical devices list for the COVID-19 response ... ... procurement 154 -- References 161 -- Resources 161 -- WHO Priority medical devices list for the COVID-19 response ...
ix, 162 stran
- MeSH
- Betacoronavirus MeSH
- COVID-19 MeSH
- Disease Outbreaks MeSH
- Delivery of Health Care MeSH
- Therapeutics MeSH
- Equipment and Supplies MeSH
- Conspectus
- Veřejné zdraví a hygiena
- NML Fields
- veřejné zdravotnictví
- infekční lékařství
- NML Publication type
- publikace WHO
BACKGROUND: FLASH radiotherapy necessitates the development of advanced Quality Assurance methods and detectors for accurate monitoring of the radiation field. This study introduces enhanced time-resolution detection systems and methods used to measure the delivered number of pulses, investigate temporal structure of individual pulses and dose-per-pulse (DPP) based on secondary radiation particles produced in the experimental room. METHODS: A 20 MeV electron beam generated from a linear accelerator (LINAC) was delivered to a water phantom. Ultra-high dose-per-pulse electron beams were used with a dose-per-pulse ranging from ̴ 1 Gy to over 7 Gy. The pulse lengths ranged from 1.18 μs to 2.88 μs at a pulse rate frequency of 5 Hz. A semiconductor pixel detector Timepix3 was used to track single secondary particles. Measurements were performed in the air, while the detector was positioned out-of-field at a lateral distance of 200 cm parallel with the LINAC exit window. The dose deposited was measured along with the pulse length and the nanostructure of the pulse. RESULTS: The time of arrival (ToA) of single particles was measured with a resolution of 1.56 ns, while the deposited energy was measured with a resolution of several keV based on the Time over Threshold (ToT) value. The pulse count measured by the Timepix3 detector corresponded with the delivered values, which were measured using an in-flange integrating current transformer (ICT). A linear response (R2 = 0.999) was established between the delivered beam current and the measured dose at the detector position (orders of nGy). The difference between the average measured and delivered pulse length was ∼0.003(30) μs. CONCLUSION: This simple non-invasive method exhibits no limitations on the delivered DPP within the range used during this investigation.
Stray radiation produced by ultra-high dose-rates (UHDR) proton pencil beams is characterized using ASIC-chip semiconductor pixel detectors. A proton pencil beam with an energy of 220 MeV was utilized to deliver dose rates (DR) ranging from conventional radiotherapy DRs up to 270 Gy/s. A MiniPIX Timepix3 detector equipped with a silicon sensor and integrated readout electronics was used. The chip-sensor assembly and chipboard on water-equivalent backing were detached and immersed in the water-phantom. The deposited energy, particle flux, DR, and the linear energy transfer (LET(Si)) spectra were measured in the silicon sensor at different positions both laterally, at different depths, and behind the Bragg peak. At low-intensity beams, the detector is operated in the event-by-event data-driven mode for high-resolution spectral tracking of individual particles. This technique provides precise energy loss response and LET(Si) spectra with radiation field composition resolving power. At higher beam intensities a rescaling of LET(Si) can be performed as the distribution of the LET(Si) spectra exhibits the same characteristics regardless of the delivered DR. The integrated deposited energy and the absorbed dose can be thus measured in a wide range. A linear response of measured absorbed dose was obtained by gradually increasing the delivered DR to reach UHDR beams. Particle tracking of scattered radiation in data-driven mode could be performed at DRs up to 0.27 Gy/s. In integrated mode, the saturation limits were not reached at the measured out-of-field locations up to the delivered DR of over 270 Gy/s. A good agreement was found between measured and simulated absorbed doses.
- MeSH
- Silicon MeSH
- Linear Energy Transfer MeSH
- Proton Therapy * methods MeSH
- Protons MeSH
- Radiometry * methods MeSH
- Water MeSH
- Publication type
- Journal Article MeSH
