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46019681991199319941997199920002004200920142014Gamma Knife was bone in Karolinska SwedenThe first Gamma Knife Unit was started at Tokyo University in Japan.The first Linac Radiosurgery system in Japan was started in Nagasaki Univ Hosp.The second Linac Radiosurgery was started in Juntendo Univ Hosp.Cyber knife treatment started in Japan.Mitubishi Electric co. released the C-armed Radiosurgery system.IMRT started in JapanLinac Radiosurgery covered by insurance in Japan. (63000)Linac radiosurgery with micro-multileaf collimator by Elekta synergy started at the JSDF Hosp.Gamma Knife I-con released. (Automatic Mask Syetem)Lancet oncology 2014: Stereotactic radiosurgery for patients with multiple brain metastases (JLGK0901 : Stereotactic radiosurgery without whole brain radiotherapy as the initial treatment for patients with five to ten brain metastases is non- inferior to that for patients with two to four brain metastases in terms of overall survival.Linac Radiosurgery for multiple brain metastasis started by Elekta Versa HD2020In 2009, the Self-Defense Forces Central Hospital, Japan, routinely performed SRS with a micro multi-leaf and a mask system. Prior to that, SRS was performed by fixing the patient’s head with an invasive metal pin. A non-invasive method of fixa-tion was desirable to reduce the anxiety of the patients. In 2014, the Gamma Knife technology developed a mask system. The same year, a multi-center collaborative study reported positive outcomes of the Gamma Knife treatment for multiple brain metastases1). Following this, the Gamma Knife treatment was actively performed in cases of multiple brain metastases to preserve the cognitive function. The history of SRS in Japan began with Figure 1　Winston-Lutz test of the first linear accelerator installed in Juntendo UniversityTable 1　Short history of brain Stereotactic Radiosurgery in Japanthe Gamma Knife technology. A few years later, this was replaced by the LINAC system owing to the rapid technological development of both the software and hardware, which continues to the present date.The first case of SRS in Juntendo UniversityThe first LINAC system was equipped at the Juntendo University in 1993. Figure 1 shows the Winston-Lutz test2） that performs quality control of couch and gantry less than 2 mm. Figure 2 illus-trates the star-shot technique. Using a 2 mm colli-mator, a pencil beam is emitted from the LINAC system to the low-sensitivity X-ray film. This