'BioQuaRT' project: design of a novel in situ protocol for the simultaneous visualisation of chromosomal aberrations and micronuclei after irradiation at microbeam facilities.

The aim of the 'BioQuaRT' (Biologically weighted Quantities in RadioTherapy) project is to develop measurement techniques for characterising charged particle track structure on different length scales, and to correlate at the cellular level the track structure properties with the biological effects of radiation. This multi-scale approach will allow characterisation of the radiation qualities used in radiotherapy and the related biological effects. Charged-particle microbeam facilities were chosen as the platforms for all radiobiology experiments in the 'BioQuaRT' project, because they allow targeting single cells (or compartments of a cell) with a predefined number of ionising particles and correlating the cell-by-cell induced damage with type and energy of the radiation and with the number of ions per cell. Within this project, a novel in situ protocol was developed for the analysis of the misrepaired and/or unrepaired chromosome damage induced by charged-particle irradiations at the Physikalisch-Technische Bundesanstalt (PTB) ion microbeam facility. Among the cytogenetic biomarkers to detect and estimate radiation-induced DNA damage in radiobiology, chromosomal aberrations and micronuclei were chosen. The characteristics of the PTB irradiation system required the design of a special in situ assay: specific irradiation dishes with a base made from a biofoil 25-µm thick and only 3000-4000 cells seeded and irradiated per dish. This method was developed on Chinese hamster ovary (CHO) cells, one of the most commonly used cell lines in radiobiology in vitro experiments. The present protocol allows the simultaneous scoring of chromosome aberrations and micronuclei on the same irradiated dish. Thanks to its versatility, this method could also be extended to other radiobiological applications besides the single-ion microbeam irradiations.

Dosimetry of secondary cosmic radiation up to an altitude of 30 km.

Dosimetric measurements in the field of secondary cosmic radiation were extensively made during the last years. Since the majority of these measurements were performed on-board passenger aircraft at altitudes between 10 and 12 km, measurements at higher altitudes are desirable for the verification of the legal dose assessment procedures for aircrew. A simple solution is to use a high-altitude balloon that reaches altitudes as high as 30 km. In this work, it is shown that the dose rate profile up to 30 km can be measured with acceptable uncertainties using a Si-detector.

Online imaging of initial DNA damages at the PTB microbeam.

In an inter-disciplinary collaboration of Physikalisch-Technische Bundesanstalt (PTB), German Collection of Microorganisms and Cell Cultures (DSMZ) and Heinrich-Heine University, live-cell imaging has been established at the charged-particle microbeam facility of PTB. Candidate genes participating in DNA strand-break repair pathways such as PARP-1, MRE11, MSH2, MDC1 and p53BP1 have been modified to generate fluorescent fusion proteins. Using multi-cistronic expression vectors, stable genomic integration was achieved in HT-1080 fibroblasts. The aim of this study is to characterise and use these highly reliable cell lines for studying initial steps of DNA damage responses and kinetics of repair after microbeam irradiation with high- and low-linear energy transfer (LET) particles in living cells at physiological conditions.

Field calibration of dosemeters used for routine measurements at flight altitudes.

Intercomparisons of dosemeters used in radiation protection are performed routinely in reference radiation fields under well-defined conditions. In the case of the radiation protection of aircrew members, such reference fields either do not exist or they can be partially simulated by accelerator-based fields. Another method is to perform simultaneous measurements on board an aircraft under constant flight conditions, i.e. at defined latitude, longitude and altitude. The intercomparison presented in this work is the second one of its kind. As reference instruments, two types of tissue-equivalent proportional counters (TEPC) were used in comparison with different silicon detector systems. The excellent agreement of the FDOScalc code, which is based on measurements made by PTB during different phases of solar cycle 23 with the TEPC measurements and the results of the preceding project "Coordinated Access to Aircraft for Transnational Environmental Research" (CAATER) even allows the in-field calibration of the Si dosemeters.

Photon contribution to ambient dose equivalent H(10) in the wide-spectrum neutron reference fields of the IRSN.

The photon contribution to ambient dose equivalent in several wide-spectrum reference neutrons fields of the Institute for Radiological Protection and Nuclear Safety were measured using a Geiger-Müller counter. For the investigated fields, the ratio of photon to neutron ambient dose equivalent ranged between 0.03 and 0.20. The results show that the Geiger-Müller tube is a versatile instrument for dosimetry in mixed photon-neutron fields if sufficient information for the calculation of corrections is available.

The PTB microbeam: a versatile instrument for radiobiological research.

The PTB microbeam is routinely used for the irradiation of living cells using protons (1-20 MeV) and alpha particles (1-28 MeV). The beam diameter is approximately 2 microm (fwhm), achieved by focussing, resulting in an excellent energy resolution and practically no scattered particles. Recently, an electrostatic beam scanner was added to the facility which allows targeting of each cell within 1 ms. This and other improvements led to an increase in the experimental speed of the system to a maximum of 50,000 cells per hour including all experimental steps. To improve the versatility of the facility further, a module for automatic quantification of immunocytochemical staining was implemented. This allows the analysis of protein activation, taking into account the positional information of the irradiation run.

A mobile TEPC-based system to measure the contributions to H*(10) at flight altitudes.

A very promising method to measure the ambient dose equivalent H*(10) at flight altitudes is to use Tissue Equivalent Proportional Counters (TEPC). The measured quantity is the lineal energy, y, which can be converted into equivalent dose as a good estimate of H*(10). According to the lineal energy transfer (LET) spectra one may even extract information about the composition of the radiation field. A new system was developed by adding a surrounding coincidence detector (CACS: Coincidence/Anti-Coincidence Shield) that allows one to identify the primary particle, which deposits energy in the TEPC, as neutral or charged. The entire system was calibrated in the neutron and high-energy photon reference fields at PTB. One of the results of these measurements is, the use of low- and high-LET calibration factors when performing measurements in mixed radiation fields. The TEPC/CACS system is now operated on-board aircrafts as a fixed or mobile dosimetry system.

Pulmonary injury in burned patients.

Inhalation injury has emerged as the number one cause of fatality in the burn patient. Fiberoptic bronchoscopy and 133Xe scanning complement traditional clinical signs of inhalation injury and have led to discovery of a higher incidence of these injuries among patients with burns. Patients with inhalation injury typically demonstrate three stages: acute pulmonary insufficiency, pulmonary edema, and bronchopneumonia, all of which carry at least 50 per cent mortality rates. The major early pathophysiologic changes in the lungs of burned patients are related to upper-airway obstruction and lower-airway permeability edema. Treatment consists of intubation for signs of respiratory distress, pulmonary toilet, humidification of inspired air, and antibiotics for documented infection.