ON SOME METHODOLOGICAL ISSUES OF STUDYING CYTOGENETIC EFFECTS IN CANCER PATIENTS TREATED WITH NEUTRON THERAPY USING U-120 CYCLOTRON
Abstract and keywords
Abstract (English):
Purpose: To study dosimetric characteristics of neutron radiation field, to determine their role in the formation of the total cytogenetic effect in the patient’s body and to assess the cytogenetic dosimetry capabilities in improving the quality of NT. Material and methods: A therapeutic beam with the average neutron energy of ~6.3 MeV was obtained from the V-120 cyclotron. The radiation field of the beam was investigated with the help of two ionization chambers with different sensitivity to neutrons. Chamber with high and low sensitivities were made of polyethylene and graphite, respectively. To exclude the uncertainty associated with the change in beam intensity in time, a dosimeter monitor operating in the integral mode was used. Results: The dependence of the monitor factor on the irradiated area was measured. The distributions of the absorbed dose of neutrons and γ-radiation over the depth of the tissue-equivalent medium were found. The contribution of γ-radiation to the neutron dose was increased from ~10 % at the entry to the medium to ~30 % at a depth of 16 cm. Dose distributions of scattered neutron and γ-radiation in the plane of the end face of the forming device were obtained. The contribution of these radiations to the dose received by the patient’s body was estimated. This contribution was shown to be comparable with that from the therapeutic beam. The analysis of the influence of NT on the estimation of the frequency of chromosome aberrations in the blood of patients was carried out. Conclusion: The frequency of chromosome aberrations in the blood of patients was determined by the whole-body dose, including dose due to scattered radiation. When using equal focal doses, the cytogenetic effect was found to be dependent on the area of the irradiated field and the depth of the tumor in the patient’s body. The differences in the RBE of neutrons and γ-radiation as well as the instability of the therapeutic neutron beam intensity create uncertainties that do not allow for the necessary control over the doses using the cytogenetic dosimetry. Therefore, cytogenetic dosimetry should be combined with an effective instrument dosimetry method. The use of biodosimetry based on the assessment of the frequency of chromosome aberrations is promising for controlling the average whole-body dose, on which the overall radiation response of the body depends.

Keywords:
neutron therapy, cytogenetic effect, cyclotron U-120
Text

Исследование цитогенетических эффектов, возникающих в организме человека при воздействии на него ионизирующих излучений, представляет несомненный интерес. Исследователей интересует характер цитогенетических нарушений, генерируемых редкоионизирующим и плотно ионизирующим излучением, например, нейтронами. Одно из направлений в подобных исследованиях предполагает разработку метода оценки дозы, полученной индивидуумом, по выявленному у него цитогенетическому эффекту. Внимание к этой задаче обусловлено ее высокой научной и практической значимостью. Развитие ядерной энергетики, применение ускорителей и радиоактивных изотопов сопряжено с реальным риском возникновения радиационных аварий того или иного масштаба. При радиационной аварии радиационному воздействию могут быть подвергнуты лица, не имеющие при себе приборов дозиметрического контроля, а лица, имеющие такие приборы, могут быть облучены в дозах, превышающих верхний предел измерения прибора. Поэтому цитогенетическую дозиметрию можно рассматривать как важное условие готовности к радиационным аварийным ситуациям и реагированию на них.

References

1. Sources and effects of ionizing radiation. United Nations Scientific Committee on the Effects of Atomic Radiation. New York. 1978. 1. 382 p.

2. Jia Cao, Yong Liu, Huaming Sun, et al. Chromosomal aberrations, DNA strand breaks and gene mutations in nasopharyngeal cancer patients undergoing radiation therapy. Mutation Research, 2002;(5046):85-90.

3. Khvostunov IK, Kursova LV, Shepel NN, et al. Evaluation of the expediency of using biological dosimetry based on the analysis of chromosome aberrations in blood lymphocytes in lung cancer patients in the therapeutic fractionation of gamma irradiation. Radiation Biology. Radioecology. 2012;52(5):467-479. (In Russ.).

4. Melnikov AA, Vasilyev SA, Smolnikova EV, et al. Changes in chromosome aberrations and micronuclei in lymphocytes of cancer patients undergoing neutron therapy. Siberian Journal of Oncology. 2012;(4):52-56. (In Russ.).

5. Koryakina EV, Potetnya VI. Cytogenetic effects of low doses of neutrons in mammalian cells. Almanac of Clinical Medicine. 2015;(41):72-78. (In Russ.).

6. Cytogenetic dosimetry: applications in preparedness for and response to radiation emergencies. International Atomic Energy Agency. - Vienna, 2011. IAEA-EPR, 229 p.

7. Musabaeva LI, Zhogina ZhA, Slonimskaya EM, Lisin VA. Current methods of radiation therapy for breast cancer. Tomsk. 2003. 200 p. (In Russ.).

8. Zolotukhin VG, Keirim-Markus IB, Kochetkov OA, et al. Neutron tissue doses in human body. Guide. - Moscow. Atomizdat. 1972. 320 p. (In Russ.).

9. Bregadze YuI. The technique of measuring absorbed dose rate of neutron radiation by the ionization method. Moscow. 1989. 20 p. (In Russ.).

10. Lisin VA, Gorbatenko AI. Heterogeneous ionization chambers for dosimetry of mixed fields of fast neutrons and gamma radiation. Instruments and Experimental Techniques. 1989;(6):71-73. (In Russ.).

11. Lisin VA. Thimble ionization chamber // Author’s certificate 1494805 as of March 15, 1989. (In Russ.).

12. Guter RS, Ovchinsky BV. Theory of errors // Elements of numerical analysis and mathematical processing of the results of the experiment. Moscow. 1970. P. 343-367 (In Russ.).

13. Ryabukhin YuS, Chekhonadsky VN, Sushchikhina MA. Conception of isoeffective doses in radiation therapy. Medical Radiology. 1987;32(4):3-6. (In Russ.).

14. Lisin V.A. The TDF model for external beam radiation therapy of malignant neoplasms by fast neutrons. Medical Radiology. 1988;33(9):9-12. (In Russ.).

Login or Create
* Forgot password?