Brachytherapy (contact radiation therapy) - is a type of radiotherapy when a radiation source (Ra-226, Ir-192, I-125, Cs-137, Co-60) is injected into the affected organ. The advantage of the method lies in the possibility of bringing the maximum doses of radiation therapy directly to the tumor focus and to the area of interest while minimizing the impact on critical organs and adjacent tissues. It is widely used in the treatment of tumors of the cervix, uterine body, prostate (prostate), vagina, esophagus, rectum, tongue, etc.

Currently, only six radionuclides are actively used in Brachytherapy. These include Co-60, Cs-137, Ir-192, I-125, Pd-103, Sr-90. Radionuclides Au-198, Ru-106 and Cf-252 are relatively rarely used. The use of Ra-226 and Rn-222 has been practically discontinued for reasons of radiation safety, but the long history of their use has an impact on modern concepts of brachytherapy.