In radiotherapy ionizing radiation is used to cause irreparable damage to the DNA and inhibit cell cycling of the cancer cells. However, radiation does not just cause selective damage in cancerous cells but also injures healthy tissue. Many strategies have been developed for delivering dose in radiotherapy to maximize the effect of radiation on tumor cells and to spare the surrounding healthy tissues. Recently a novel brachytherapy treatment option for solid tumors is being offered by the company Alpha TAU Medical Ltd. through alpha emitters released from 224Ra-loaded brachytherapy seeds. This novel technique is called diffusing alpha-emitters radiotherapy (DaRT) and delivers a lethal dose of radiation to the tumor while sparing nearby radiation sensitive healthy tissues due to the short range of alpha particles in tissue. However, currently the diffusion of the alpha emitting daughters from the 224Ra decay in different tumors is not well known. The aim of Mèlodie’s project is to establish parameters for the DaRT diffusion-leakage model through animal studies.