S. Rollet

AVIDOS--a software package for European accredited aviation dosimetry.

AVIDOS is a computer code used for the dose assessment of aircraft crew exposed to cosmic radiation. The code employs a multiparameter model built upon simulations of cosmic radiation exposure done using the FLUKA Monte Carlo code. AVIDOS calculates both ambient dose equivalent H*(10) and effective dose E for flight routes over the whole world at typically used altitudes and for the full range of solar activity. The dose assessment procedure using AVIDOS is accredited by the Austrian office for accreditation according to European regulations and is valid in the whole Europe. AVIDOS took part in an international comparison of different codes assessing radiation exposure of aircraft crew where a fully satisfactory agreement between codes has been found. An online version of AVIDOS with user friendly interface is accessible to public under the internet address: http://avidos.healthphysics.at.

Microdosimetric assessment of the radiation quality of a therapeutic proton beam: comparison between numerical simulation and experimental measurements

Using protons for the treatment of ocular melanoma (especially of posterior pole tumours), the radiation quality of the beam must be precisely assessed to preserve the vision and to minimise the damage to healthy tissue. The radiation quality of a therapeutic proton beam at the Centre Antoine Lacassagne in Nice (France) was measured using microdosimetric techniques, i.e. a miniaturised version of a tissue-equivalent proportional counter. Measurements were performed in a 1-µm site at different depths in a Lucite phantom. Experimental data showed a significant increase in the beam quality at the distal edge of the spread-out Bragg peak (SOBP). In this paper, the numerical simulation of the experimental setup is done with the FLUKA Monte Carlo radiation transport code. The calculated microdosimetric spectra are compared with the measured ones at different depths in tissue for a monoenergetic proton beam (E=62 MeV) and for a modulated SOBP. Numerically and experimentally predicted relative biological effectiveness values are in good agreement. The calculated frequency-averaged and dose-averaged lineal energy mean values are consistent with measured data.

A Novel Microdosimeter Based Upon Artificial Single Crystal Diamond

This paper represents the first attempt to discuss the use of an artificial single-crystal diamond as a new microdosimeter. The Diamond MicroDosimeter (DMD) detecting region is a thin layer of highly controlled thickness ( <; 5 μm) and high purity intrinsic monocrystalline diamond grown over a backing boron doped monocrystalline diamond. This viable, small, compact and user-friendly device is able to obtain spectra of the energy deposition in sensitive volumes of the order of micrometer. The paper reports the first experimental tests performed to measure the dose distribution in terms of lineal energy and the simulation performed by the Monte Carlo code FLUKA to optimize the design of the new DMD. Advantages and shortcomings of the DMD are discussed.

Investigations on Photon Energy Response of RadFET Using Monte Carlo Simulations

We describe investigations of RadFET energy response simulated with Geant4 and FLUKA2005 Monte Carlo codes. An analysis of energy deposition is carried out for photon irradiation with energies between 35 keV and 2 MeV. The absorbed dose in the silicon dioxide layer (few hundred nanometers) is compared for both transport codes.

MATSIM: Development of a Voxel Model of the MATROSHKA Astronaut Dosimetric Phantom

The AIT Austrian Institute of Technology coordinates the project MATSIM (MATROSHKA Simulation) in collaboration with the Vienna University of Technology and the German Aerospace Center, to perform FLUKA Monte Carlo simulations of the MATROSHKA numerical phantom irradiated under reference radiation field conditions as well as for the radiation environment at the International Space Station (ISS). MATSIM is carried out as co-investigation of the ESA ELIPS projects SORD and RADIS (commonly known as MATROSHKA), an international collaboration of more than 18 research institutes and space agencies from all over the world, under the science and project lead of the German Aerospace Center. During MATSIM a computer tomography scan of the MATROSHKA phantom has been converted into a high resolution 3-dimensional voxel model. The energy imparted and absorbed dose distribution inside the model is determined for various radiation fields. The major goal of the MATSIM project is the validation of the numerical model under reference radiation conditions and further investigations under the radiation environment at ISS. In this report we compare depth dose distributions inside the phantom measured with thermoluminescence detectors (TLDs) and an ionization chamber with FLUKA Monte Carlo particle transport simulations due to 60Co photon exposure. Further reference irradiations with neutrons, protons and heavy ions are planned. The fully validated numerical model MATSIM will provide a perfect tool to assess the radiation exposure to humans during current and future space missions to ISS, Moon, Mars and beyond.

Microdosimetric GEANT4 and FLUKA Monte Carlo Simulations and Measurements of Heavy Ion Irradiation of Silicon and Tissue

We describe microdosimetric measurements and simulations with Geant4 and FLUKA Monte Carlo codes in silicon and tissue. Analyses of deposited energy in sensitive volumes of some micrometers were carried out after exposure to heavy ion radiation

On the applicability of [18F]FBPA to predict L-BPA concentration after amino acid preloading in HuH-7 liver tumor model and the implication for liver boron neutron capture therapy

INTRODUCTION In recent years extra-corporal application of boron neutron capture therapy (BNCT) was evaluated for liver primary tumors or liver metastases. A prerequisite for such a high-risk procedure is proof of preferential delivery and high uptake of a 10B-pharmaceutical in liver malignancies. In this work we evaluated in a preclinical tumor model if [18F]FBPA tissue distribution measured with PET is able to predict the tissue distribution of [10B]L-BPA. METHODS Tumor bearing mice (hepatocellular carcinoma cell line, HuH-7) were either subject of a [18F]FBPA-PET scan with subsequent measurement of radioactivity content in extracted organs using a gamma counter or injected with [10B]L-BPA with tissue samples analyzed by prompt gamma activation analysis (PGAA) or quantitative neutron capture radiography (QNCR). The impact of L-tyrosine, L-DOPA and L-BPA preloading on the tissue distribution of [18F]FBPA and [10B]L-BPA was evaluated and the pharmacokinetics of [18F]FBPA investigated by compartment modeling. RESULTS We found a significant correlation between [18F]FBPA and [10B]L-BPA uptake in tumors and various organs as well as high accumulation levels in pancreas and kidneys as reported in previous studies. Tumor-to-liver ratios of [18F]FBPA ranged from 1.2 to 1.5. Preloading did not increase the uptake of [18F]FBPA or [10B]L-BPA in any organ and compartment modeling showed no statistically significant differences in [18F]FBPA tumor kinetics. CONCLUSIONS [18F]FBPA-PET predicts [10B]L-BPA concentration after amino acid preloading in HuH-7 hepatocellular carcinoma models. Preloading had no effect on tumor uptake of [18F]FBPA. ADVANCES IN KNOWLEDGE Despite differences in chemical structure and administered dose [18F]FBPA and [10B]L-BPA demonstrate an equivalent biodistribution in a preclinical tumor model. IMPLICATIONS FOR PATIENT CARE: [18F]FBPA-PET is suitable for treatment planning and dose calculations in BNCT applications for liver malignancies. However, alternative tracers with more favorable tumor-to-liver ratios should be investigated.

Advanced Radiation DOSimetry phantom (ARDOS): a versatile breathing phantom for 4D radiation therapy and medical imaging

A novel breathing phantom was designed for being used in conventional and ion-beam radiotherapy as well as for medical imaging. Accurate dose delivery and patient safety are aimed to be verified for four-dimensional (4D) treatment techniques compensating for breathing-induced tumor motion. The phantom includes anthropomorphic components representing an average human thorax. It consists of real tissue equivalent materials to fulfill the requirements for dosimetric experiments and imaging purposes. The different parts of the torso (lungs, chest wall, and ribs) and the tumor can move independently. Simple regular movements, as well as more advanced patient-specific breathing cycles are feasible while a reproducible setup can be guaranteed. The phantom provides the flexibility to use different types of dosimetric devices and was designed in a way that it is robust, transportable and easy to handle. Tolerance levels and the reliability of the phantom setup were determined in combination with tests on motion accuracy and reproducibility by using infrared optical tracking technology. Different imaging was performed including positron emission tomography imaging, 4D computed tomography as well as real-time in-room imaging. The initial dosimetric benchmarking studies were performed in a photon beam where dose parameters are predictable and the dosimetric procedures well established.

Simulation and test of a new MicroDosimeter based upon Single Crystal Diamond

In recent years, many ionizing radiation detectors based upon artificial diamond have been proposed and applied in many fields and at various energy ranges. Single Crystal Diamond (SCD) have not been used, so far, in microdosimetry and this paper represents one of the first attempts to obtain spectra of the energy deposition in artificial-diamond sensitive volumes of the order of the micrometer. The new Diamond MicroDosimeter (DMD) is based upon a layered structure with a detecting region of less then 5 µm. This prototype is fabricated at Rome “Tor Vergata” University using a Chemical Vapour Deposition (CVD) technique depositing a thin layer of highly controlled thickness. The paper reports the comparison between simulations performed by the Monte Carlo code FLUKA and first experimental tests performed with alphas to measure the dose distribution in terms of lineal energy.

MATSIM: A voxel model for the astronaut dosimetric phantom MATROSHKA

The AIT Austrian Institute of Technology coordinated the project MATSIM (MATROSHKA Simulation) in collaboration with the Vienna University of Technology and the German Aerospace Center, to perform FLUKA Monte Carlo simulations of the MATROSHKA numerical phantom for the radiation environment at the International Space Station (ISS). MATSIM, a voxel model of the MATROSHKA phantom was developed during the project MATSIM Phase-A. In this paper we describe results of the project Phase-B of MATSIM, Monte Carlo simulation of the absorbed dose and the neutron fluence assessed inside the whole model phantom. The simulations are verified by reference measurements using thermoluminescence dosimeters, an ionisation chamber and a tissue equivalent proportional counter (TEPC). Further investigations are carried out for ISS cosmic radiation conditions. MATSIM provides a comprehensive risk assessment of radiation hazard to humans working in space onboard the ISS, for missions to the Moon, Mars and beyond, as well as for terrestrial mixed radiation fields comprising ionizing high-energy particle radiation.