Lars Leksell (1907–1986) was a Swedish physician and Professor of Neurosurgery at the Karolinska Institute in Stockholm, Sweden. He was the inventor of radiosurgery. Life and career Lars Leksell was born in Fässberg Parish, Sweden on November 24, 1907. He completed medical studies at the Karolinska Institute and began his neurosurgical training in 1935 under Herbert Olivecrona. Development of electronystagmography and his thesis on muscular control and gamma motor neurons were his early scientific achievements. In 1949, he developed his arc centered stereotactic frame based on A polar coordinate system. In 1951, using the Uppsala University cyclotron, Leksell and the physicist and radiobiologist Borje Larsson, developed the concept of radiosurgery. Leksell and Larsson first employed proton beams coming from several directions into a small area into the brain, in experiments in animals and in the first treatments of human patients. Thus, he achieved a new non-invasive method of destroying discrete anatomical regions within the brain while minimizing the effect on the surrounding tissues. He became a professor of surgery at University of Lund in 1958. From 1960 until his retirement, in 1974, he was Professor & Chairman of neurosurgery at the Karolinska Institute in Stockholm, succeeding Herbert Olivecrona, who was the department's founder in 1920. During this time Leksell pursued his work on stereotactic radiosurgery and refinement of stereotactic methods. The first prototype of the gamma knife was installed in Sophiahemmet in 1968. Over the rest of his career, Leksell treated 762 patients with it. Throughout this time he would propose improving radiosurgery with modern imaging modalities including CT, MRI and angiography, as is currently used. Today, Leksell's technique is used as an effective treatment for many conditions such as arteriovenous malformations, pituitary tumors, acoustic neuromas, craniopharyngiomas, meningioma, metastatic and skull base tumors, and primary brain tumors. The device is manufactured by Elekta Instruments, Inc., a Swedish company which manufactures stereotactic surgery and radiosurgery equipment, based on the inventions of Leksell. It was founded by him in 1972. He died peacefully at age of 78 in 1986 while taking a brisk walk in Swiss alps. First years and the "stereotactic frame" Leksell started his neurosurgical training with Herbert Olivecrona in 1935 at the Serafimer Hospital, one of the oldest hospitals in Sweden founded in 1752. The Olivecrona neurosurgical service enjoyed a solid international reputation and attracted a large number of trainees from all over the world. For a short period