For dose measurement in clinical practice, ionization chambers are used which are calibrated to indicate the absorbed dose to water in a 60Co radiation field. If such a dosemeter is used in a high-energy photon or electron field of a clinical linac, the change in the response of the dosemeter has to be taken into account by applying a radiation quality correction factor kQ. For seven types of...

In radiotherapy, one differentiates between external radiotherapy and internal radiotherapy - the latter being called brachytherapy. In brachytherapy (Greek "brachys" = short, close), the tumour is irradiated directly by implanting small radioactive sources (so-called "seeds") into the patient. The seeds are placed inside or close to the tumour. The advantage of this form of therapy is that...

In radiotherapy, one increasingly relies on irradiation with small fields and with fields that can be adapted to the tumour profile such as, e.g., in intensity-modulated radiotherapy (IMRT). This poses particular challenges to dosimetry, since methods have to be developed to be able to measure the dose distribution of these fields with high spatial resolution. Due to their simple handling and the...

The number of CT examinations has more than doubled in Germany since 1996. In 2010, 61 % of the collective effective dose of the population could be attributed to X-ray examinations for CT imaging. This statistic shows how important CT dosimetry has become.

Fragmentation cross sections of tetrahydrofuran measured for electrons.

The nine-strong international working group dealing with the elaboration of an ICRU Report on radon measurements held its last common work meeting in Dublin.

Implementation of the ISO 11929 standard for mixed exposures to Rn-222/Rn-220: The determination of the exposure to Rn-222 and Rn-220 with adapted passive detector systems, each with the corresponding background is a special case that has not been dealt with to date.

Track structure simulations of alpha particles (100 keV - 20 MeV) in nitrogen and propane have been successfully extended by detailed interaction cross sections for charge exchange processes.

The stopping power of liquid water for carbon ions with energies in the region of the maximum stopping power can be determined by means of the so-called "Inverted Doppler Shift Attenuation Method".

For calibrations and irradiations of neutron dosemeters, PTB mainly uses 252Cf neutron sources. Due to the Cf-252 half-life of 2.645 years, the 10-year-old existing source could no longer attain the necessary dose rates. A new Cf-252 source was thus purchased, thoroughly characterized and mounted in the irradiation facility.

The diamagnetic tensor of the water molecule was calculated from the electron density distribution.

Besides the nucleon-nucleon scattering, the scattering of a neutron on a deuteron – i.e. on a nucleus of the heavy hydrogen atom ²H consisting of a neutron and a proton – is one of the fundamental processes in quantum-mechanical few-body systems.

The XENON Dark Matter Project is an experiment which takes place in the Gran Sasso underground laboratory and is geared to searching for WIMPs (Weakly Interacting Massive Particles), a variant of Dark Matter. Determining precisely the emission rate of a neutron source used in this experiment could clarify discrepancies.

Ionization cross-sections of trimethylphosphate for electrons measured.

The frequency distributions of the ionization cluster sizes for carbon ion radiation of different energies have been measured in 1.2 mbar N₂ and in 1.2 mbar C₃H₈.

The partial orientation of water molecules in a 1.5 T strong magnetic field has no influence on the mean values of the scattering ionization cross sections for electrons in the energy region from 50 eV to 1 keV.

Currents from ionization chambers lie in the range from less than a femtoampere up to a few nanoamperes and the most reliable way of determining them is to measure the charge. Such an instrument capable of measuring the charge with several measuring ranges and an input bias current of less than 0.3 fA is not commercially available and has therefore now been developed. For quality assurance...

Radon trägt nach neuesten Erkenntnissen gleichauf mit der Medizin am stärksten zur Strahlenbelastung der Bevölkerung bei. Im Hinblick auf die geplante EU-weite Absenkung der Referenzwerte, ausgelöst durch die Neubewertung des Radons seitens der International Commission on Radiological Protection (ICRP), ist in der PTB eine neuartige Anlage zur Kalibrierung von Radon-Messgeräten entwickelt worden,...

Neutron resonance radiography is a technique to measure the distribution of certain light elements (C, N, O, H) in large-volume samples. WINBUGS, a program using Bayesian Monte Carlo methods, was used for the reconstruction of the element distribution from experimental and simulated data sets and has been successfully tested with the aid of radiographic experiments and simulations.

In medicine, the use of medical linacs is constantly increasing to treat tumours by means of radiotherapy. Due to the high photon energy they generate, an intense scattering radiation field occurs also outside of the primary beam. This scattering radiation field, which leads to an additional, undesired exposure rate, was determined by means of special ionization chambers and personal dosemeters at...

Within the scope of the European Metrology Research Programme (EMRP), PTB is coordinating the research project "BioQuaRT: Biologically weighted Quantities in Radiotherapy". Together with partners from 6 countries and with funds amounting to 3.5 million euros over a period of 3 years, the project is aimed at advancing the development of a metrological basis for the consistent quantification...

PTB has extended its services with regard to Rn-222

The neutron monitor AGREM, developed at PTB, has been tested in different pulsed radiation fields and compared with other neutron monitors. Whereas commercial monitors exhibited a saturation behaviour with increasing dose in the pulse, the indication of PTB's monitor increased, in all cases, in a linear manner with the dose.

At the request of the Ministry of the Environment, Energy and Climate Protection of Lower Saxony, measurements were carried out in the centre of the town of Gorleben. Data from measurement hut No. 5, which is located approx. 2 km from the transport cask storage facility, have shown that exclusively neutrons from cosmic radiation contribute to the ambient dose equivalent.