Dose calculation in a mouse lung tumor and in secondary organs during radiotherapy treatment: A Monte Carlo study

Abstract

Radiotherapy in cancer treatment always affects surrounding tissues and even deposits doses in distant tissues not traversed by the radiation beams. In the present work, we report energy transfer and absorbed dose in a target tumor and in other distant organs in a digital mouse by Monte Carlo simulations. We simulated a selection of X-rays beams with seven energies, 50, 100, 150, 200, 250, 350 and 450 keV each oriented in seven irregularly incremented angles, and we computed the dose and the energy deposit as a function of photon interaction types. The results show that the absorbed dose increased with increasing energy even in the secondary organs not receiving the radiation beam, and that the lowest dose was obtained with 100 keV beam. The spinal cord, of comparable size to the tumor and excluding the spinal bones, which was not directly irradiated by the beams, received a dose representing in average 1% of that of the tumor, while the spinal bone received doses of 6.6 and 0.12 times those in the tumor at 50 and 450 keV, respectively. Such Monte Carlo simulations could be necessary to select the appropriate beam energy and beam angles to efficiently treat the tumor and to moderately reduce the impact of the radiations in the other organs.