- Built by Lawrence in 1929
- Accelerates positive particles rather than the electrons
- Uses positively charged particles such as proton, neutron, alphas, deuterons, short- lived radioisotopes
- Particles are accelerated in a circular chamber called dees
- The particles are accelerated by electric fields between the dees until the particle acquires the desired energy
- Powerful magnetic filed are employed to confine the particle to a circular path
- Protons are not commonly used for radiation therapy
- In some centers, deuterons produced by cyclotron are brought out and allowed to strike targets of beryllium leading to the production of neutrons, such neutrons can be used for radiation therapy
- Neutron beam is not universally available for therapy but have been tried clinically by various group in the US
- Short- lived isotopes are used in radiopharmaceuticals research
