RADIATION & RISK
Bulletin of the National Radiation and Epidemiological Registry
since 1992
About the Journal : 2017 : vol. 26, No. 1 : Local absorbed doses of irradiation of medical personnel at brachytherapy of prostate cancer using I-125 microsources of Russian production

Local absorbed doses of irradiation of medical personnel at brachytherapy of prostate cancer using I-125 microsources of Russian production

«Radiation and Risk», 2017, vol. 26, No. 1, pp.44-59

DOI: 10.21870/0131-3878-2017-26-1-44-59

Authors

Stepanenko V.F. – Head of Lab., D. Sc., Biol., Prof. A. Tsyb MRRC, Obninsk, Russia. Contacts: 4 Korolyov str., Obninsk, Kaluga region, Russia, 249036. Tel.: (484) 399-70-02; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. .
Biryukov V.A. – Senior Researcher, C. Sc., Med. A. Tsyb MRRC, Obninsk, Russia.
Karyakin O.B. – Head of Dep., MD, Prof. A. Tsyb MRRC, Obninsk, Russia.
Kaprin A.D. – General Director, Academician of RAS, MD, Prof. A. Tsyb MRRC, Obninsk, Russia.
Galkin V.N. – Director, MD, Prof. A. Tsyb MRRC, Obninsk, Russia.
Ivanov S.A. – Deputy Director, MD. A. Tsyb MRRC, Obninsk, Russia.
Mardinskiy Yu.S. – Head of Dep., Corresponding Member of RAS, MD, Prof. A. Tsyb MRRC, Obninsk, Russia.
Kolyzhenkov T.V. – Senior Researcher, C. Sc., Biol. A. Tsyb MRRC, Obninsk, Russia.
Petukhov A.D. – Research Assistant. A. Tsyb MRRC, Obninsk, Russia.
Bogacheva V.V. – Engineer; Akhmedova U.A. – Engineer. A. Tsyb MRRC, Obninsk, Russia.
Yaskova E.K. – Lead. Researcher, C. Sc., Biol.A. Tsyb MRRC, Obninsk, Russia.
Lepilina O.G. – Med. Phys-icist; Sanin D.B. – Med. Physicist, C. Sc., Biol. A. Tsyb MRRC, Obninsk, Russia.
Skvortsov V.G. – Head of Lab., C. Sc., Biol. A. Tsyb MRRC, Obninsk, Russia.
Ivannikov A.I. – Lead. Researcher, C. Sc., Phys.-Math. A. Tsyb MRRC, Obninsk, Russia.
Khailov A.M. – Senior Researcher, C. Sc., Biol. A. Tsyb MRRC, Obninsk, Russia.
Anokhin Yu.N. – Senior Researcher, C. Sc., Med. A. Tsyb MRRC, Obninsk, Russia.

Abstract

Brachytherapy with microsources of 125I is effective and minimally invasive method of radiation therapy of prostate cancer. At present moment the "State National Center of Russian Federation – Physical-Energetic Institute named after A.I. Leipunskiy" (Obninsk) is producing 125I microsources for treatment of prostate cancer. The Medical Radiological Research Center named after A.F. Tsyb (MRRC, Obninsk) is responsible for clinical trials of these radioactive sources. In connection with these circumstances it is necessary to obtain information about local radiation doses of personnel – irradiation the skin of the fingers and eyes of radiation oncologist and medical physicist, performing necessary procedures at the stages of preparation and conduction of the operation with 125I microsources of Russian production. Results of such dosimetry are very important for wide dissemination and implementation of 125I microsources of Russian production in the radiological clinics. Due to low energy of photon irradiation, as well as due to features of the preparatory procedures and the operation itself, fingers and eyes of medical staff may be the most irradiated locations of the body during the brachytherapy of prostate cancer with 125I sources. The radionuclide 125I decays by electron capture mode with a half-life of 60.2 d, emits characteristic photon radiation (average energy of 28.33 keV, the layer of half attenuation in soft tissue is about 2 cm), electrons of internal conversion and Auger-electrons (these electrons are completely absorbed in the material of the sealed capsule of source). When measuring the absorbed doses from low-energy radiation quanta, the main problem is the validity of measurement results, because the dosimeters must be sensitive enough in the range of low energies and the energy dependence of their response must be known. For dosimetry of irradiation from 125I microsources during brachytherapy the miniature crystals of aluminum oxide (α-Al2O3:C) were used as thermoluminescent (TL) dosimeters of low energy quantum radiation. The intensity of thermo stimulated luminescence emitted by crystals of aluminum oxide is proportional to radiation dose. The “Harshaw 3500” TL reader was used for measurements of thermo stimulated luminescence. The dosimeters were placed in light-tight envelops. The three dosimeters were placed in the conditions of electronic equilibrium in each opaque envelop. The area of each set of dosimeters is equal to 2.7 cm2, the thickness of the covering layers of dosimeters is equal to 40 mg/cm2 (for the skin of hands) and 300 mg/cm2 for eyes (in accordance with the terms of the Russian Radiation Safety Standards RSS-99/2009). Dosimeters were placed on the all fingers of both hands of medical personnel, as well as near eyes of radiation oncologist. At average energy of 125I quantum irradiation (28.33 keV) the aluminum oxide dosimeters provides increased values of doses – value of factor of overestimation of dose in relation to the dose from irradiation by high energy gammas is equal to 2.84±0.04. Therefore the measured values of absorbed doses have been reduced by the value of this factor. It was shown that under standard conditions of brachytherapy of prostate cancer, the local absorbed doses of radiation oncologist are equal to 0.18±0.019 mGy (in the skin of index finger of the left hand – the highest dose) and 0.053±0.0057 mGy (in the skin of little finger of the right hand – the smallest dose). The absorbed doses in right and left eyes, are equal to 0.11±0.012 mGy and 0.035±0.0039 mGy, respectively. Local absorbed doses of medical physicist are equal to 0.16±0.034 mGy (in the skin of index finger of the left hand – the highest dose) and 0.013±0.0012 mGy (in the skin of ring finger of the right hand – the lowest dose). The background dose was taken into account when analyzing the results of measurements of the local exposure of personnel by 125I microsources. The differences between the right and left sides of personnel’s body can be explained by peculiarities of location of radioactive sources in relation to the bodies of medical staff: the radioactive sources were supported by the fingers of the left hand his and the right hand were in motion with the tool. The radioactive sources were located on the right side in relation to the head of radiation oncologist. It was concluded that even the maximum value of the measured local absorbed doses do not present a radiation hazard during radio-therapy by 125I microsources of Russian production, as far as according to Russian Radiation Safety Standards (RSS-99/2009) annual dose limits for population is 50 mSv/year for hands, feet and skin and 15 mSv/year for eyes. For staff (groups B and A), these limits are even higher: to 2.5 and 10 times, respectively. Measuring of local radiation doses of medical personnel at brachytherapy by imported 125I microsources (production of Eckert@Ziegler BEBIG GmbH, Berlin, Germany) showed that local radiation doses of radiation oncologist at brachytherapy by 125I microsources of Russian production do not differ within the experimental errors from local doses when imported microsources were used in the same conditions. The magnitudes of the normalized absorbed doses (per unit of total activity of sources and per unit of time of the work of radiation oncologist with 125I microsources of Russian production) were obtained for various localizations – the skin of the fingers and the eyes. These data can be used for estimates of expected local absorbed doses to medical personnel at brachytherapy with 125I microsources of Russian production with different activity and for various durations of work.

Key words
Brachytherapy, interstitial radiotherapy, 125I, prostate cancer, 125I microsources, local absorbed doses of irradiation, radiation safety of personnel, dosimentry of low-energy quantum radiation, thermoluminescent dosimetry, TL-dosimeters.

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