EUROPEAN RADIATION RESEARCH 2012

Low dose/dose rate gamma irradiation facility for in vitro biological systems

17 Oct 2012, 16:11

1m

Poster Hall (Vietri sul Mare)

poster preferred Non-Targeted Effects of Radiation Poster Session 2

Speaker

Dr Giuseppe Esposito (Istituto Superiore di Sanità and INFN Gr. Coll. Sanità, Roma, Italy)

Description

The response of in vitro biological systems to low dose and low dose rate irradiations is a topic that is important both for the determination of still unclear basic mechanisms and for its implications in radiation protection and therapy (late response of healthy tissue). The study of low dose/dose rate effects requires experiments performed under strictly controlled conditions where the dose and the dose-rate are evaluated with great accuracy and kept as uniform as possible on the sample. The realization of a dedicated irradiator appears to be the most convenient approach, since its design can be optimized for low dose-rate exposures of cultured cells under physiological conditions, protracted for several weeks. Here we present a gamma irradiation facility for the exposure of cultured mammalian cells to dose rates ranging from few μGy/h to some tens of mGy/h. The irradiator has been designed at the Istituto Superiore di Sanità (ISS), and, as of June 2012, it is in the phase of construction. Once fully operational, the facility will make use, alternatively and depending on the dose rate required, of three Cs-137 sources with different activities: 37 MBq, 740 MBq and 18.5 GBq. Each source will be housed in an appropriate holder placed at the center of an irradiation chamber. These three chambers are made of lead hollow cylinders with internal and external radius of about 14 mm and 84 mm respectively, and about 130 mm high. The top is closed by a suitable electrically removable lead cap. For a cell irradiation experiment, one of the irradiation chambers will be put into a shielded CO2 cell culture incubator. Also the design of the incubator shielding has been carried out at the ISS. The facility will be particularly suitable for non targeted effects studies. The most relevant characteristics of this especially designed irradiator are: 1) a dose rate uniformity on the sample at least of 95% and 2) a percentage of 662 keV (energy of the photon released in the Cs-137 decay) photons impinging on the sample greater than 80%. The dose will be evaluated with Geant4 simulations and measured with dosimeters such as TLD, OSL, alanine and/or ionization chamber. A monitoring system of the critical parameters (temperature, CO2, humidity) will also be installed. The realization of the facility has been made possible by a special EU funding, through a dedicated task, “LIBIS”, of the EURATOM Network of Excellence “DoReMi” (7th FP).