Radiotherapy. Masked female patient undergoing neutron therapy for cancer. Laser cross-hairs (red) are being aimed onto the site of the patient's tumour. Once targeted, a beam of high energy neutrons will be fired at the tumour. The neutron beam is formed by bombarding a beryllium target with protons which are deflected by a linear accelerator or linac. The neutron beam will stop the tumour's growth and hopefully destroy it. The patient is wearing a mask to hold the head still whilst the treatment takes place. The treatment is taking place at Fermilab (Fermi National accelerator laboratory) near Chicago, USA.