In vivo radiobiological assessment of the CNAO clinical carbon beams

To assess CNAO carbon beam in order to ensure safe and accurate patient therapy. We performed radiobiological study in vivo concerning the uniformity of biological doses in PTV and to calculate the values of the RBE at different depths in the SOBP. Uniformity of the biological dose; (physical Dose) x (biological RBE) in SOBP / PTV of the CNAO carbon ion beams were determined using jejunal crypt regeneration in mice as biological system at three different depths along with a 6 cm SOBP at proximal, middle and distal positions. Groups of each three C3H/He female mice at 11-12 weeks old were kept in a Lucite jig under anesthesia and irradiated at each depth position. The jig was positioned perpendicularly to the beam axis in order to irradiate mice in abdomen-dorsum direction. This study was approved by the Ethical Committee of the University of Pavia. We irradiated 71 mice with the CNAO carbon ion therapeutic beams. The dose-effect curves for jejunal crypt after the irradiation at the three positions along the SOBP were found to be at the expected position and separated among each other, with the distal one more effective than the proximal and center. The RBE values calculated from the isoeffect doses to reduce crypt survival per circumference to 30 and 10, well corresponded to those obtained from other carbon ion facilities#. According to the criteria already used for the comparisons of the carbon ion beams by NIRS and GSI, we can conclude that the clinical carbon ion beam by CNAO has similar biological characteristics by NIRS and GSI.Heavy Ion in Therapy and Space Radiation Symposium 2013 (HITSRS2013