Varian Medical Systems is an American radiation oncology treatments and software maker based in Palo Alto, California.

[12][13] In August 2020, Siemens Healthineers announced plans to acquire Varian Medical Systems in an all-stock deal valued at $16.4 billion.

[27] Varian manufactures a range of megavoltage LINACs with varying levels of features and complexity, for example different numbers of multileaf collimators or the ability to perform radiosurgery.

[citation needed] Varian manufactures the ProBeam Proton Therapy System, with current and planned installations at several sites globally.

On September 16, 2019, during the 2019 American Society for Radiation Oncology (ASTRO) annual meeting, being held Sept. 15–18 in Chicago, Varian announced Ethos therapy, an artificial intelligence (AI)-driven system designed to increase the capability, flexibility and efficiency of radiotherapy.

[citation needed] In 1999, Varian Medical Systems, Inc. sued a former employee for defamation after they posted numerous messages criticizing the company on the Internet.

[35] The lawsuit led to the ruling of Varian v. Delfino by the California Supreme Court on the question whether a trial could proceed while denial of the defendant's anti-SLAPP motion was under appeal.