Megavoltage X-rays are produced by linear accelerators ("linacs") operating at voltages in excess of 1000 kV (1 MV) range, and therefore have an energy in the MeV range.

[1] They are used in medicine in external beam radiotherapy to treat neoplasms, cancer and tumors.

Beams with a voltage range of 4-25 MV are used to treat deeply buried cancers because radiation oncologists find that they penetrate well to deep sites within the body.

[7] These properties help to make megavoltage x-rays the most common beam energies typically used for radiotherapy in modern techniques such as IMRT.

[9] However prior to this other devices had been capable of producing megavoltage radiation, including the 1930s Van de Graaff generator and betatron.