Experimental and computational investigation on low-dose radiation absorption in some living tissues

The influence of low radiation doses on some types of living tissues was studied. Samples of animal tissues such as liver, brain, and bone placed on glass dishes were exposed to gamma radiation on a 137 Cs laboratory source with 3.14 MBq activity. To determine the irradiation times required to reach the absorbed doses we used in our experiment, the 137 Cs gamma radiation source, including the lead protection, was modeled using BEAMnrc Monte Carlo code. A phase space data file containing complete information (charge, energy, position, direction, history) on every particle leaving the simulated geometry was used as input in DOSRZnrc Monte Carlo code to calculate the Monte Cardose in cylindrical phantoms made of organic substitutes for the living tissues under investigation. We analyzed the depth doses and dose profiles obtained in these phantoms and estimated not only the irradiation times but also the sizes of the samples. Finally, the spectrophotometric assay of the average DNA and RNA content was carried out by standard biochemical methods. The experimental results revealed similar behaviors in the tissues with higher water content (liver and brain): a slight (logarithmic) increase in nucleic acid content was emphasized. The response of bone tissue (with the lowest water content) was also an increase that was fitted by an exponential function. The interpretation of these experimental data could be related to the stimulator effect of low radiation doses (up to 11 mGy) on nucleic acid biosynthesis. The living cell adaptive reaction seemed to be higher in tissues with lower water content (bone), which could be associated with the reduced influence of water radicals (following radiolysis). (authors)