Stereotactic Radiosurgery/Radiotherapy: A Historical Review

"Stereotactic" is an exact radiotherapy treatment modality which implements invasive and non-invasive facilities for improving precise dose delivery. Stereotactic refers to three-dimensional localization of a specific point in space by a unique set of coordinates that relate to a fixed external reference frame. An accurate delivery of radiation is attainable using these techniques with high precision (1-2 mm) which leads to dose reduction in critical organs and adjacent normal tissues while delivering the highest dose to tumoral tissue. Stereotactic irradiation consists of two techniques of delivery: Stereotactic RadioSurgery (SRS) which is an accurate single fractionated delivery of radiation to intracranial lesions and is attained by converging series of radiation beams on a target from various angles. Stereotactic Radiotherapy  (SRT) which is a fractionated irradiation of intra and extra cranial lesions. This review article intends to highlight the radiobiological and physical aspects of these techniques and also introduces three commercially available stereotactic machines systematically and functionally.