Pioneers of radiotherapy

Looking back on a shared history

In 2021, Siemens Healthineers and Varian combined to form a single company. But, the shared history that has united these teams with impressive legacies extends back much further. In the mid-20th century, both were engaged in research into the best possible radiotherapy technology for cancer treatment. This work pointed to the linear accelerator as the technology that would pave the way for further development. In 1969, Varian and Siemens embarked on a collaboration that would develop into a strategic partnership and ultimately led to a combination of the two companies under the umbrella of Siemens Healthineers in April 2021.

Queen Elizabeth vor Betatron

Queen Elizabeth, the Queen Mother, examines the Siemens Betatron at the International Congress of Radiology in London in 1950

The development of medical imaging has played a pivotal role in the history of Siemens Healthineers. In January 1896, just a few days after the announcement of Wilhelm Conrad Röntgen’s discovery of X-rays, Siemens Medical Technology Division began developing special X-ray units for diagnosing diseases. It became increasingly clear over the following years that high-energy X-rays could prevent cell division in tumor tissue and could therefore be used to treat cancer. Siemens began conducting initial experiments with a view to harnessing the power of X-rays for radiotherapy. Over subsequent decades, numerous approaches were devised in the search for the optimum technology.

In the early days of radiotherapy in the 1910s, Siemens developed the “Reform Apparatus.” This device pioneered the use of numerous techniques that are still applied in radiotherapy today, such as the targeted irradiation of tumors from multiple directions. From 1942 onward, the Siemens physicist Konrad Gund built an exceptionally complex system, known as a betatron, in Erlangen. This device used an electromagnet to accelerate electrons almost to light speed around a circular path and then abruptly brought them to a halt. The high-energy X-rays emitted by the braking particles were directed at tumors inside the body. After World War II, betatrons became the preferred method of radiotherapy.

In the 1950s, as an alternative to complex betatrons, Siemens developed systems that used the radioactive element cobalt as a source of radiation. Here, the radioactive decay produced gamma rays, which were more effective for cancer treatment than the electron beams of the betatron. Meanwhile, in California, Varian was working on implementing a concept that proved to be the ideal technology for radiotherapy: the generation of precise and energy-rich beams by linear accelerators (linacs).

Russell and Sigurd Varian with Klystron

Russell (below) and Sigurd Varian next to their first major invention, the klystron tube

Stanford University, June 5, 1937: Russell Varian had an idea that would shape the future development of countless technologies. At that time, he was working with his brother Sigurd and the Stanford physicist William W. Hansen on a way of improving navigation in the aviation sector. They wanted to make airplanes “visible” in the dark and in bad weather. This would require a generator that could emit radio waves with very short wavelengths for use in positioning. Russell’s idea was based on “bunching” the electron stream in order to produce microwaves—in an approach that was fundamentally different from other known methods at the time. The Varians and Hansen named the device “klystron,” a word derived from the Ancient Greek verb klyzo, which refers to the movement of waves on a beach. In spring 1939, Stanford President Ray Lyman Wilbur publicly announced the invention of “a powerful new radio tube.”

One of the first Stanford scientists to work with the new high-power tube was an electrical engineering student by the name of Edward Ginzton. Working as part of a research group, Ginzton tested the capabilities of the klystron in radio networks, radar systems, and various other technologies. “Almost everything we tried worked immediately and quite well,” he recalled several years later. From that point onward, the klystron would change the course of development for several technologies, including and extending far beyond microwave and communication systems. Following their successful collaboration, the Varians and the Stanford University scientists also decided to found their own company. Those on board with this new endeavor included Sigurd, Russell and his wife, Dorothy, Edward Ginzton, and William W. Hansen.

Nine directors signed the articles of incorporation on April 20, 1948. Around two months later, with a starting capital of USD 22,000 and just a handful of tools, Varian Associates began its work. The articles of incorporation set out the company’s aim as being “to conduct general research in the fields of physical science of every kind of nature” and specifically mentioned technologies relating to heat, sound, light, optics, X-rays, charged particles, ionizing radiations, electricity, vacuum technology, magnetism, chemistry, and many other fields. Some 40 years later, Varian was one of the world’s largest technological pioneers and ranked third in the list of companies in Silicon Valley to have filed the most patent applications.

Varian innovations played a pivotal role in the history of many technologies. For example: the introduction of the klystron tube had a decisive impact on the development of television and satellite technology. In 1949, Varian launched the world’s first instrument that could analyze the properties and interactions of matter using magnetic resonance—this represented a significant contribution to the field of analytical chemistry and provided a technological basis for modern magnetic resonance imaging (MRI). In 1991, the chemist Richard Ernst received the Nobel Prize for his work on magnetic resonance spectroscopy, which he began while working at Varian in 1963. One of Varian’s best-known inventions is the magnetometer, which allowed precise measurements of the Earth’s magnetic field for the first time in the mid-1950s. In 1988, the company received an Emmy Award for the development of an energy-efficient TV transmitter tube. Today, Varian is best known for its leadership in medical technology. Beginning in its early days as a company, Varian embarked on a course that would see it become the leading supplier of radiotherapy systems.

Varian revolutioniert 1960 mit dem Linearbeschleuniger Clinac 6 die Strahlentherapie

In 1960, Varian revolutionized radiotherapy with the Clinac 6 linear accelerator

In the early 1950s, Varian and Stanford University worked together on a huge system for studying atoms in the field of particle physics. Measuring almost 70 meters in length, the linear accelerator represented a historic development in the world of science and technology. A few years later, the Stanford Professor Robert Hofstadter received the Nobel Prize in Physics for his research using this device—and the linac also inspired Stanford professor and radiologist Henry Kaplan to make a suggestion that led to the invention of modern radiotherapy. Kaplan invited Edward Ginzton to lunch and suggested developing a medical linear accelerator specifically for use in cancer treatment. Ginzton succeeded in convincing the other directors at Varian despite the considerable costs involved in the project. Some five years later, in January 1956, the “Stanford Cancer Gun” was used for the first time at the university’s medical center in San Francisco.

The next challenge facing Varian was that of converting this bulky and immovable prototype into a compact system that could be installed quickly and easily in hospitals. After four years of work to develop the device into a clinical system, Varian delivered the first “Clinac 6” model to UCLA Medical Center in Los Angeles and to Henry Kaplan at Stanford’s Palo Alto campus in 1960. In many respects, this initial model was already far superior to the cobalt devices that were commonplace at the time. The treatment beam generated by a klystron could reach tumors deep inside the body thanks to an acceleration potential of 6 million volts—and, for the first time in the history of radiotherapy, the gantry could be rotated through 360 degrees around the patient. From that point onward, Varian began investing significantly in the further development of Clinac systems. The development of the first medical linac was particularly important to Edward Ginzton, whose father had died of cancer a few years earlier. 


Early in the new millennium, Varian presented Dynamic Targeting™ image-guided radiation therapy (IGRT). To accomplish IGRT, the linear accelerator was combined with an on-board imager

At that time, however, cobalt devices were still far more cost-effective to run than linear accelerators. In subsequent years, the two technologies existed alongside one another—and these circumstances gave rise to the initial collaboration between Varian and Siemens. In 1969, Varian and Siemens signed their first agreement to work together in the field of cancer treatment. Over the years, the two companies expanded their collaboration to include other disciplines. In 1988, Varian and Siemens founded their first joint company, Spectroscopy Imaging Systems Corporation (SISCO), in order to work together on the development, production, and sale of magnetic resonance imaging spectrometers for use in industry, medicine, and various natural sciences.

By that point, Varian had significantly expanded its lead in the field of radiotherapy. Thanks to innovations such as the first commercially available multileaf collimator and the development of intensity-modulated radiotherapy (IMRT), Varian rose to become the world’s leading manufacturer of cancer radiotherapy treatment systems. Over the years, the radiotherapy division developed from a relatively small side project to become a key pillar of the company.

In 2012, the Siemens medical technology division discontinued the development of its own linear accelerators. In April that year, Varian and Siemens announced a new worldwide strategic partnership in the areas of radiotherapy and radiosurgery. From then on, Varian supplied radiation oncology clinics with Siemens imaging systems such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scanners—and, for its part, Siemens offered its customers Varian’s range of radiotherapy and radiosurgery systems. Together, the two companies supplied systems that covered the entire clinical workflow from initial diagnosis to follow-up. They decided that, in the future, they would work together on new imaging and treatment solutions that drew on the strengths of both companies. Over the next few years, this partnership grew stronger and stronger. By 2013, Varian and Siemens were able to announce that the first jointly developed software, which seamlessly brought together specific systems from the two companies, had been installed at the therapy center of Ohio State University.

On August 2, 2020, Siemens Healthineers and Varian Medical Systems announced they had reached an agreement whereby Siemens Healthineers would acquire all of Varian’s shares for a total price of around USD 16.4 billion. By April 2021, the companies were in a position to announce the successful completion of the combination. “Through the transformative combination of Varian and Siemens Healthineers, our united company will address the growing need for personalized, data-driven diagnosis and precision cancer care that enables us to fight back against globally increasing cancer rates,” explained Chris Toth, the new head of the Varian Business Area within Siemens Healthineers. “By bringing together our unique and highly complementary portfolios and capabilities, we will support oncology clinicians and patients in achieving better outcomes and move even closer to achieving our vision of a world without fear of cancer.”


One manifestation of the strengths that come with the combination of Siemens Healthineers and Varian is HyperSight™, an innovative imaging solution and feature for radiation therapy systems like Halcyon.

The innovations that Varian has developed over the last 75 years have helped shape the history of radiotherapy, and now, as a Siemens Healthineers company, these innovations are transforming cancer care. Since the combination of the two companies, Varian and Siemens Healthineers have jointly reached over 400 million patients around the globe each year. This combination has further extended our reach, as we address the entire cancer care pathway – from screening to survivorship – and expanded our shared vision for the future and what we can achieve for patients. Together, we are getting closer than ever to a world without fear of cancer.