External beam radiotherapy machine used for cancer treatment. External beam radiotherapy is a localised treatment where beams of radiation target a tumour. This is a linear accelerator machine that emits beams of high-energy X-rays or electrons. The machine is able to take into account movement such as breathing to maintain precision whilst targeting the tumour. The radiation kills or slows the growth of the cancerous cells by damaging their DNA (deoxyribonucleic acid).