Study of Biological Effects by Pulsed Bremsstrahlung Radiation of Ultrahigh Dose Rate at the Angara-5-1 Facility
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Study of Biological Effects by Pulsed Bremsstrahlung Radiation of Ultrahigh Dose Rate at the Angara-5-1 Facility1 V. P. Smirnova, V. K. Bozhenkob, T. I. Gimadovac, E. V. Grabovskid, A. N. Gritsukd, A. V. Ivanovb, G. M. Oleinikd,*, E. V. Khmelevskiie, A. G. Tsov’yanovc, and A. M. Shishkinb a
Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia b Russian Scientific Center of Roentgenoradiology, Moscow, 117997 Russia c State Research Center Burnasyan Federal Medical Biophysical Center of Federal Medical Biological Agency, Moscow, 123098 Russia dTroitsk Institute for Innovation and Fusion Research, Moscow, 142190 Russia e Hertsen Moscow Oncology Research Center, Branch of FSBI NMRRC of the Ministry of Health of Russia, Moscow, 125284 Russia *e-mail: [email protected] Received October 18, 2018
Abstract—Radiological methods of treatment of malignant tumors are widespread in medical practice. In addition to the type of radiation and dose and fractionation of the radiation regime, the dose rate is one of the factors that affects the effectiveness of treatment. The therapeutic dose rate lies in the range of tens of mGy/s. At modern high-current accelerators of relativistic electron beams, a significant increase in the dose rate to hundreds of MGy/s is achievable, which is more than 108 times greater than the therapeutic dose rate. It is difficult to predict the nature of processes in tissues and its cells at such radiation intensities. To determine the effect of extreme dose rate on the radiosensitivity of tissues at the Angara-5-1 facility, experiments were conducted to determine the lethal dose (LD50/30) for laboratory mice. Our result on the study of the LD50/30 dose (~100 MGy/s) allows us to make a conclusion about a possible higher lethal dose than the power range of the doses used for medical purposes. DOI: 10.1134/S1063780X18120103
1. INTRODUCTION Radiological methods of treatment of malignant tumors are widespread in medical practice. Specialized medical accelerators or radioisotope sources are used for photon or electron irradiation. In addition to the type of radiation and dose and fractionation of the radiation regime, the dose rate is one of the factors that affects the effectiveness of treatment. In typical situations, the therapeutic dose rate is tens of mGy/s. If we assume that the average photon energy of a medical accelerator with a power of up to 1 kW is about 1 MeV, then, in a cell with a characteristic size of 10 μm averagely absorbed 10 photons per second. Thus, the acts of the primary interaction of photons with the cell are separated by a time interval of 1−10 ms. At the same time, due to the appearance of the degradation spectrum of secondary electrons, this time is reduced by several tens of times. On modern high-current accelerators of relativistic electron beams, as well as on pulsed laser installations, a significant increase in the dose rate to hundreds of MGy/s is achievable. 1 The article was translated by the authors.
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