Determination of relative biological effectiveness of 3.2 MeV proton beam from folded tandem ion accelerator

789-792In the present study, DNA damage induced by proton beam from Folded Tandem Ion Accelerator (FOTIA) and gamma radiation from a 60Co source on human tumor adeno carcinoma (HT 29) cells has been studied. Dosimetry for proton radiation has been carried out using surface barrier semiconductor detectors and flux was adjusted to be 1.6<span style="font-family:Symbol;mso-ascii-font-family: " times="" new="" roman";mso-hansi-font-family:"times="" roman";mso-char-type:symbol;="" mso-symbol-font-family:symbol"="" lang="EN-GB">106 with fluence variation to deliver different doses. Proton beam of intermediate LET (12.5 keV µm-1), which has a penetration of 150 µm in tissue, was used for the study. Radiation damage induced on cells was evaluated by comet assay and the comet parameter used was Olive Tail Moment (OTM). The average RBE was calculated from the proton and gamma dose required for the iso-effective OTM<span style="mso-ansi-language:EN-IN; mso-bidi-font-weight:bold">.