DISTANCE SOURCE-SURFACE — the distance from a radioactive source of the gamma and therapeutic device or from a target, on a cut is generated ionizing radiation, to a surface of the irradiated object. In radiation therapy (see) the distance a source — a surface (DSS) — one of the main characteristics of conditions of tele-irradiation with the help rentgeno-and gamma and therapeutic devices, particle accelerators and generators. RIP is also one of the key parameters at problem solving connected with planning of radiation of patients and calculation of conditions of radiation on the specific device (see. Dosimetry of ionizing radiation ). In relation to radiation of the person or an animal often use the terms equivalent to RIP — «distance a source — skin» (DSS) or «skin focal length» (KFR). The second term is used only in relation to x-ray emission (see).