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Scientific news from division 6

News 2019

Abb.: Nahaufnahme des Detektorsystems auf einer DJI Matrice 600 Pro Drohne.

Within the scope of the EMPIR project 16ENV04 entitled "Preparedness", PTB is developing a spectrometer–based dosimetry system which can be operated while attached to an unmanned aerial vehicle (UAV). The monitoring system aims at minimizing the exposure of the relief units to ionizing radiation in the case of a nuclear or radiological incident, as the UAV is not only able to cover a large area...

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Fig. 1: UHDpulse logo

“UHDpulse – Metrology for advanced radiotherapy using particle beams with ultra‑high pulse dose rates” is an EMPIR project launched in September 2019. It aims at developing and improving dosimetry standards for FLASH radiotherapy, VHEE radiotherapy and laser‑driven medical accelerators. In the case of these novel radiation modalities, the pulse dose rates are significantly higher than in the case...

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MR image-guided radiation therapy, i.e. irradiation with high-energy photon radiation and simultaneous imaging by means of MR tomography, could turn into one of the standard methods in radiation therapy in the years to come. To ensure precise dosimetry in the presence of strong magnetic fields, suitable primary and secondary standards are required for measuring the absorbed dose to water in MR...

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Radiation of tumoral tissue with high‑energy photons is a widely used treatment method. Around one in ten cancer patients undergoes treatment of this kind. Several hospitals now have MR‑linacs – innovative special‑purpose devices that allow radiation to be directed to the afflicted tissue with even greater precision. PTB has investigated methods designed to ensure the traceable measurement of the...

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The primary measurement of the absorbed dose to water for X‑ray therapy radiation qualities using calorimeters is extremely time‑consuming. Alternatively, ionization chambers can be calibrated in the “air kerma” measurand, and then conversion factors can be used to calculate the calibration factor for the absorbed dose to water. In a joint research project with McGill University in Montreal...

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Reference dosimetry performed with calibrated ionization chambers in carbon beams currently still shows a significantly higher measurement uncertainty than that in high–energy photon fields. This is mainly attributable to a high uncertainty of the correction factor for the radiation quality kQ, which must be theoretically determined because there are no experimental data available.

In a previous...

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Mathematical model observers are used to determine the image quality of computed tomography (CT) scanners. In a joint research project of two of the Physikalisch-Technische Bundesanstalt’s (PTB’s) divisions – Ionizing Radiation and Medical Physics and Metrological Information Technology – a novel model observer was developed. This is based on a regression procedure in which especially correlations...

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The influence of ambient humidity on the structure of DNA was simulated by means of molecular–dynamics simulations. These simulations were performed both for single DNA strands and for DNA bundles to find out whether bundles have a stabilizing effect.

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Propane is an important filling gas in tissue-equivalent radiation detectors. After measuring the doubly differential ionization cross sections, the differential elastic electron scattering cross sections of propane were, to a large extent, completely determined both experimentally and theoretically. In this context, two well-known theoretical approaches were evaluated on the basis of experimental...

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The harmful effects of space radiation on an astronaut’s health represent a major limiting factor for long-duration human space missions beyond low Earth orbit. National space agencies have recognized the risks related to exposure to space radiation and are developing complex model-based risk mitigation strategies. The space radiation risk models are based on the interplay of basic physical and...

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The Dosepix is a hybrid pixel detector that is specifically designed to meet the needs of mobile radiation dosimetry measurements. The tightly coupled combination of sensor material and specific integrated circuit electronics (ASIC) also makes this detector an example of a so-called smart sensor.

To process the large amount of data from several of these detectors, an electronic evaluation unit...

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Within the scope of Preparedness, an EMPIR project, the usability of dose-rate data made available by non-governmental open-access networks has been analyzed. On the websites of such networks, measurement data recorded by individuals by means of simple electronic systems or mobile telephones (the latter devices have simple additional modules in some cases) is sometimes published in real time.

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The optical detection of alpha particles is realized by measuring the ionization-induced UV light emission (radioluminescence) of air molecules. This new technique makes it possible to detect a radiological hazard from a safe distance that is much greater than the range of the alpha particles.  During a scientific visit to Tampere University in Finland, it was successfully demonstrated that...

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As a result of joint research and development between PTB and EURADOS WG 3, supported by the results of MetroERM, an EMRP project, and Preparedness, an EMPIR project, PTB has proposed the use of a CeBr3 detector system as a secondary standard for determining the area dose rate. It was successfully demonstrated that the use of well‑characterized spectrometers is the best state of the art.

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The energy of PTB's research electron accelerator is freely adjustable in the range of 0.5 - 50 MeV. To be able to measure the specific desired energy and beam power in real time during the preparation and optimization of an electron beam, a Multi-Leaf Faraday Cup (MLFC) with 128 absorber plates and the corresponding readout electronics has been developed. The range of the electron beam in the...

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Abb.: MMC-Modul mit Aufhängung zur Vibrationsentkopplung

After metallic magnetic calorimeters (MMCs) have successfully been established at PTB, these low–temperature particle detectors are now being used to measure fundamental decay data of electron capture decays. These results allow the uncertainties of other activity determination techniques to be reduced and also serve as a basis for new theoretical descriptions of the energy spectra.

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At the EURADOS Annual Meeting at the beginning of 2019, Dr. Oliver Hupe, Head of Working Group 6.31, "Photon     Dosimetry", was elected to the EURADOS Council by a large majority. He will take on the duties of the Treasurer in the Council. This means that PTB is now also represented on EURADOS’s Executive Board (made up of the Chair, Vice-Chair, Secretary and Treasurer).

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Council Directive 2013/59/Euratom of 5 December 2013 on the protection against the dangers arising from exposure to ionizing radiation deals with the subject of “radon” in detail.

This subject was taken up by EURADOS in its 12th Winter School. A scientific committee consisting of Arturo Vargas (UPC, Spain), Annette Röttger (PTB, Germany), James Marsh (PHE, United Kingdom) and Pawel Olko...

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Over the past few years, digital volume tomography (DVT) has increasingly gained in importance in various fields, such as interventional radiology and post‑operative diagnostics. Unfortunately, it is difficult to compare the radiation exposure of DVT with that of computer tomography (CT) as their parameters – the dose area product (DAP) for DVT and the dose length product (DLP) for CT – are based...

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After 10 years, the first successful absolute comparison of gaseous radon-222 activity standards has been achieved together with participants from 8 countries. Under the auspices of the LNHB (France), the radon-222 gas activities provided by the LNHB were determined absolutely and the results were compared. PTB participated in this comparison with two methods: a primary method, based on alpha...

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IEC 61526 "Radiation protection instrumentation – Measurement of personal dose equivalents Hp(10) and Hp(0.07) for X, gamma, neutron and beta radiations – Direct-reading personal dose equivalent meters" is being revised and adapted to the current state of the art in science and technology. Among other things, this standard represents the basis for the PTB requirements on personal dose equivalent...

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In the last twenty years, PTB has used the high-energy neutron beam at the iThemba LABS near Cape Town for its own work and for projects with external partners. In these experiments, the infrastructure needed for the neutron metrology was set up and put into operation for each measurement campaign, which meant a considerable amount of human and logistical effort.

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New assessment methods are being tested in order to reduce uncertainties in spectrometry, to shorten measuring times, to achieve prescribed uncertainties and to use more adequate detectors. These new procedures, such as artificial intelligence (AI), deep learning (DL), convolutional neural networks (CNNs) and Markov Chain Monte Carlo (MCMC), use Bayesian statistics to adapt calibration...

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Die Charakterisierung des Referenzstrahlungsfeldes und die Arbeiten zur Qualitätssicherung in der Bestrahlungseinrichtung mit thermischen Neutronen der PTB sind abgeschlossen. Die PTB stellt damit ein stark thermalisiertes Neutronenreferenzstrahlungsfeld für die Charakterisierung und Kalibrierung von Neutronenmessgeräten und Strahlenschutzdosimetern zur Verfügung. Die Bestrahlungseinrichtung...

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Determining the activity concentration of a thorium–227 solution very accurately by means of liquid scintilliation counters has been achieved for the first time at PTB. Traceable activity measurements of this radionuclide, which is being tested for radioimmunotherapy in nuclear medicine, are thus possible from now on. Besides this, the half-life of thorium–227 was determined by means of two...

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