REFLECT – Research flight of EURADOS and CRREAT: Intercomparison of various radiation dosimeters onboard aircraft

Aircraft crew are one of the groups of radiation workers which receive the highest annual exposure to ionizing radiation. Validation of computer codes used routinely for calculation of the exposure due to cosmic radiation and the observation of nonpredictable changes in the level of the exposure due to solar energetic particles, requires continuous measurements onboard aircraft. Appropriate calibration of suitable instruments is crucial, however, for the very complex atmospheric radiation field there is no single reference field covering all particles and energies involved. Further intercomparisons of measurements of different instruments under real flight conditions are therefore indispensable. In November 2017, the REFLECT (REsearch FLight of EURADOS and CRREAT) was carried out. With a payload comprising more than 20 different instruments, REFLECT represents the largest campaign of this type ever performed. The instruments flown included those already proven for routine dosimetry onboard aircraft such as the Liulin Si-diode spectrometer and tissue equivalent proportional counters, as well as newly developed detectors and instruments with the potential to be used for onboard aircraft measurements in the future. This flight enabled acquisition of dosimetric data under well-defined conditions onboard aircraft and comparison of new instruments with those routinely used. As expected, dosimeters routinely used for onboard aircraft dosimetry and for verification of calculated doses such as a tissue equivalent proportional counter or a silicon detector device like Liulin agreed reasonable with each other as well as with model calculations. Conventional neutron rem counters underestimated neutron ambient dose equivalent, while extended-range neutron rem counters provided results comparable to routinely used instruments. Although the responses of some instruments, not primarily intended for the use in a very complex mixed radiation field such as onboard aircraft, were as somehow expected to be different, the verification of their suitability was one of the objectives of the REFLECT. This campaign comprised a single short flight. For further testing of instruments, additional flights as well as comparison at appropriate reference fields are envisaged. The REFLECT provided valuable experience and feedback for validation of calculated aviation doses

On the role of LET-dependent parameters in the determination of the absorbed dose by in-phantom recombination chambers

The paper discusses the theoretical background in terms of the use of in-phantom recombination chambers in mixed radiation fields, with special attention paid to the question of how the experimentally determined, linear-energy-transfer-dependent (LET) parameters can be applied with regard to the more accurate determination of the chamber response and absorbed dose in mixed radiation fields. Methods of taking the recombination index of radiation quality (RIQ) measurements and theoretical consideration concerning the determination of the absorbed dose are described. Classical Bragg-Gray and Spencer-Attix cavity theories were analysed and their relationship to in-phantom recombination chambers was specifi ed. Methods concerning the estimation of correction factors with regard to RIQ measurements and their importance are highlighted

Calculated neutron energy dependence of the dose-response of large recombination chamber

A model of REM-2-type chamber was modeled with MCNPX code to study the dose-response to monoenergetic neutrons in wide energy range from thermal to 20 MeV for various compositions of gas in the chamber. The energy dependence of the total dose absorbed in the fi lling gas was compared with the energy dependence of ambient absorbed dose D*(10) and with experimental data. The results of the studies will be useful for designing new, improved generation of recombination chambers

Proposed Use of Monte Carlo Simulated Images to Evaluate the Accuracy of Measurements on X-Ray Computed Tomography

X-ray computed tomography (CT) is increasingly recognized as a promising measuring technique for dimensional metrology. Various methods are being developed to improve measurement accuracy. Tests of new methods for such applications include accuracy evaluation with the use of calibrated workpieces; however, the internal algorithms of image acquisition and data processing might influence the experimental error, and then also the comparison of methods at different CTs. The accuracy of the results of tomographic measurements is influenced by many factors, one of which is the setting of the threshold value. The article presents the results of an attempt to use Monte Carlo simulated images to estimate deviations to determine threshold values to improve measurement accuracy and additionally, to estimate the impact of data processing. The differences of the results obtained from the simulated images were up to 4 % larger than those from tomographic images. It was caused by degradation of the image contrast by scattered radiation

BADANIE OSŁONNOŚCI RADIACYJNEJ BETONÓW SPECJALNYCH

W artykule przedstawiono wyniki badań właściwości osłonnych betonów eksperymentalnych przed promieniowaniem gamma, z wykorzystaniem zamkniętego źródła promieniotwórczego 137Cs. Do analiz sporządzono i opisano specjalne stanowisko badawcze o określonej geometrii. Do badań wykorzystano odpowiednio przygotowane próbki betonów ciężkich o zróżnicowanym składzie. W ramach prac przebadano piętnaście rodzajów betonów różniących się przede wszystkim zawartością kruszyw oraz gęstością objętościową. Na podstawie uzyskanych danych pomiarowych, dla poszczególnych prób betonów, otrzymano wartości grubości kolejnych warstw połówkowych (HVL) i dziesięciochłonnych (TVL). Z przeprowadzonych analiz wynika, iż najlepsze parametry osłonne w polu promieniowania gamma dla izotopu 137Cs mają betony, z których kruszywem magnetytowym oraz barytowym. Betony te miały bardzo wysoką gęstość - powyżej 3300 kg/m3. Gorszymi parametrami charakteryzowały się natomiast mieszanki zawierające w składzie tylko kruszywa zwykłe (serpentynit lub amfibolit), a ich gęstość nie przekraczała 2450 kg/m3. Otrzymane wyniki badań, zgodnie z wcześniejszymi założeniami, wskazują, że wraz ze wzrostem gęstości materiału osłonowego warstwa HVL (odpowiednio TVL) zmniejsza się, co oznacza, że właściwości osłonowe materiału przed promieniowaniem gamma ulegają poprawi

Evaluation of qualitative and quantitative data of Y-90 imaging in SPECT/CT and PET/CT phantom studies.

IntroductionWe aimed to assess the feasibility of SPECT and PET Y-90 imaging, and to compare these modalities by visualizing hot and cold foci in phantoms for varying isotope concentrations.Materials and methodsThe data was acquired from the Jaszczak and NEMA phantoms. In the Jaszczak phantom Y-90 concentrations of 0.1 MBq/ml and 0.2 MBq/ml were used, while higher concentrations, up to 1.0 MBq/ml, were simulated by acquisition time extension with respect to the standard clinical protocol of 30 sec/projection for SPECT and 30 min/bed position for PET imaging. For NEMA phantom, the hot foci had concentrations of about 4 MB/ml and the background 0.1 or 0.0 MBq/ml. All of the acquired data was analysed both qualitatively and quantitatively. Qualitative assessment was conducted by six observers asked to identify the number of visible cold or hot foci. Inter-observer agreement was assessed. Quantitative analysis included calculations of contrast and contrast-to-noise ratio (CNR), and comparisons with the qualitative results.ResultsFor SPECT data up to two cold foci were discernible, while for PET four foci were visible. We have shown that CNR (with Rose criterion) is a good measure of foci visibility for both modalities. We also found good concordance of qualitative results for the Jaszczak phantom studies between the observers (corresponding Krippendorf's alpha coefficients of 0.76 to 0.84). In the NEMA phantom without background activity all foci were visible in SPECT/CT images. With isotope in the background, 5 of 6 spheres were discernible (CNR of 3.0 for the smallest foci). For PET studies all hot spheres were visible, regardless of the background activity.ConclusionsPET Y-90 imaging provided better results than Bremsstrahlung based SPECT imaging. This indicates that PET/CT might become the method of choice in Y-90 post radioembolization imaging for visualisation of both necrotic and hot lesions in the liver

Research on BNCT in Poland and in the world

Przy Reaktorze MARIA w Narodowym Centrum Badań Jądrowych (NCBJ) powstaje stanowisko do badań nad terapią borowo-neutronową (BNCT). Terapia polega na napromienianiu nowotworu wiązką neutronów o odpowiednich parametrach po uprzednim podaniu pacjentowi związku boru, który w wyniku określonych mechanizmów gromadzi się głównie w komórkach rakowych. W wyniku reakcji 10B(n,α)7Li emitowane są cząstki jonizujące powodujące zniszczenie tylko tych komórek, w których zgromadzony jest bor [1]. Badania kliniczne prowadzone na świecie potwierdzają skuteczność metody, otwierając nowe perspektywy dla jej zastosowania w terapii konwencjonalnej.The stand for research on Boron Neutron Capture Therapy (BNCT) at the MARIA Reactor at the National Centre for Nuclear Research is being created. The therapy consists of irradiation of the tumour with a neutron beam with specific parameters after prior administration of the boron compound to the patient, which accumulates mainly in cancer cells as a result of specific mechanisms. As a result of 10B(n,α)7Li reaction, ionising particles are emitted and destroy only those cells, in which boron is accumulated. Clinical trials conducted in the world show relatively high efficiency of BNCT, opening new perspectives for its use in conventional therapy