Every time you shield yourself or a patient from radiation, you should thank Rolf Maximilian Sievert, a Swedish medical physicist whose major contribution was the study of the biological effects of ionizing radiation.

Born in Sweden to German parents on May 6, 1896, Sievert was also born into wealth, as his father was a leading exporter/importer of machines. When his father died, Rolf, at 17, inherited an enormous fortune, said to be enough so he could live a comfortable life on the interest alone.

Good thing, maybe, because rich Rolf was a poor student. He dropped out of school. Finally, between 1915 and 1917, Sievert started studying at Uppsala University, the Swedish institution leading the academic world in physics. By 1919, he crossed paths with a professor who helped him understand theoretical physics in the field of meteorology, and Sievert’s career was launched.

With the increasing use of X-rays during and after the First World War, hematologic diseases began to occur frequently among those handling X-rays, with a growing number of deaths. This prompted discussion about radiation protection. By the mid-1920s, radiation was considered hazardous, and serious discussions about trials for determining tolerable doses had begun.

Sievert started working to measure radiation. He used his own money to stock and staff his lab. In 1921, he theorized measurements on the spatial distribution of radiation from various radium compounds and mathematically calculated the intensity of radiation from radium compounds arranged simultaneously along a line, in the form of rings, and on a plane. This would become known as the Sievert Integration Theory.

This is when he began to emphasize radiation protection and the need to limit professionals’ exposure to radiation. He used a portable dosimeter when visiting hospitals, to measure tube voltage, tube current, and dose rate. By 1926, Sievert succeeded in standardizing the skin erythema dose and made a capacitor-type dosimeter, called a Sievert chamber. In 1928, he played the central role in the adoption of the roentgen as the international unit and in recommendations for protecting medical radiology practitioners from radiation. Soon, he was consulting on how to build more protective chambers, including pioneering the use of thick, iron-ore concrete walls as radiation shields.

Sievert drafted the world’s first radiation protection law in collaboration with top radiologists.  In 1925, Italy was the first to put it into practice, for those working in radiotherapy establishments and also for patients. Sweden also enforced regulations on radiation protection quite early, in 1941. France and Germany soon followed.

The Sievert-founded Radiation Physics Research Institute oversaw regulation of radiation protection. New radiation legal standards made it mandatory to submit reports on X-ray machines, radioactive isotopes such as radium, the health history of the person in charge, and any disorders in the radiation practitioner. The institute evaluated reports, performed inspection duties, and conducted important research in fields such as radiation physics, biophysics, and the implementation of laws.

Sievert continued to pioneer both thought and action in the radiology community, serving as a global leader throughout his career. In 1965, Sievert retired. He died in 1966, at age 70, from conditions that have nothing to do with radiation. In honor of his lifetime achievements, the unit for the dose of radiation affecting the human body (equivalent dose) was named the Sv (Sievert), in 1979.