The name comes from the use of a strip-shaped beam, so that only one “slice” (Greek prefix “tomo-”) of the target is exposed at any one time by the radiation.

Conventional linacs do not work on a slice-by-slice basis but typically have a large area beam which can also be resized and modulated.

[17][18][19] In general, radiation therapy (or radiotherapy) has developed with a strong reliance on homogeneity of dose throughout the tumor.

Tomotherapy embodies the sequential delivery of radiation to different parts of the tumor which raises two important issues.

[21] Non-helical static beam techniques such as IMRT and TomoDirect are well suited to whole breast radiation therapy.

[22][23][24] This risk is accentuated in younger patients with early-stage breast cancer, where cure rates are high and life expectancy is substantial.

[25][26][27] The tomotherapy technique was developed in the early 1990s at the University of Wisconsin–Madison by Professor Thomas Rockwell Mackie and Paul Reckwerdt.

With this combination, the unit was one of the first devices capable of providing modern image-guided radiation therapy (IGRT).