Background
One of the most important problems in radiotherapy (RT) with χ and γ-rays is hypoxic cells, in the centre of solids tumors. Due to insufficient blood perfusion, these cells are more resistant to RT. The purpose of this study is to assess the effect of heating cells on chromosomal damages induced by an extremely low dose of neutron or γ irradiation, in human lymphocytes.

Method 
Human blood samples were exposed to hyperthermia (HT), 6 cGy neutron (or γ-rays), HT+neutron/γ, and neutron/γ+HT. HT was applied at 41.5°C for 30 and 60min as well as 43°C for 15 and 30min. The time interval between the two treatments was 1hr. After cell culture, harvesting, fixation, and staining, the chromosomal damages were scored in metaphase stage and statistical analyses were performed.

Results
In comparison to the control groups, HT alone at 41.5°C (neither for 30 nor 60min) did not induce significantly higher chromosomal damages (p=0.8); however, the number of damages was significantly higher at 43°C for 30min (p