Tomotherapy or Helical TomoTherapy describes a type of radiation therapy in which the radiation is delivered slice-by-slice (hence the use of the Greek prefix tomo-, which means "slice"). This method of delivery radiation differs from other forms of external beam radiation therapy in which the entire tumor volume is irradiated at one time.
![](https://i.ytimg.com/vi/3uojNqglptY/mqdefault.jpg)