In 1905, Kornike established that cell division is inhibited under the influence of ionizing radiation. Bergonié and Tribondeau then discovered an unequal sensitivity of different cells to radiation. On the basis of these experiments, in 1906, they formulated the rule of Bergonié and Tribondeau: the sensitivity of cells to radiation is directly proportional to mitotic activity and inversely proportional to the degree of their differentiation.
In the 20s of the XX century, the standard radiation loads required to obtain high-quality images were determined, and thus, the use of special lead screens has become mandatory for research. The requirements were becoming more and more stringent: since its appearance in 1931, the permissible radiation exposure during the study has decreased by more than ten times. X-ray diagnostics has firmly entered the practice of doctors, becoming a universal method for diagnosing various pathologies of the human body.
In the 20-30s of the XX century, the formation of dosimetry of ionizing radiation began. This made it possible to further quantitatively normalize the effect of ionizing radiation on the body during diagnostic procedures and radiation treatment of tumor and non-tumor diseases. Finally, after World War II, the widespread use of artificial radionuclides and medical accelerators has led to the gradual displacement of X-rays and radium as a means of radiation therapy for cancer patients.