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Collective dose, man-mSv 25000 20000 15000 10000 5000 0 The average individual dose, mSv . O. Klepalov et al. / Medical Physics in the Baltic States 7 (2009) 83 - 85 6,0 5,0 4,0 3,0 2,0 1,0 0,0 RC 3,79 INPP average dose - 0,96 mSv TC 0,07 SAM C 018 EC 0,11 CH C 85 CR C 1 MTKS 4,85 DSS 0,80 Fig. 3. Average individual doses in INPP in 2008. 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 8180 8660 6530 7260 8520 4800 7540 1012 1949 1458 1282 9880 1008 1146 1148 1033 8520 5097 7330 6655 4472 1912 2177 2219 2216 1136 1102 8140 1312 2180 7720 1094 1313 2263 1725 1623 1390 1509 1850 1506 1279 1071 6277 8808 8535 6824 2470 3408 2589 3287 4. Conclusions The installation of two described dosimetry systems allowed to improve the quality of measures that have to be considered implementing ALARA program. Performance measures which were undertaken within ALARA program in Ignalina NPP allowed to achieve 3287.2 man-mSv collective dose to the INPP + CO staff in 2008. This represents 74% of planned annual dose: Collective dose to the INPP staff was 2216.2 BSS 0,72 Fig. 4. Annual collective doses to workers of the Ignalina NPP. DC 0,0 man-mSv, instead of planned 3327 man-mSv in 2008 Planned. Collective dose to the staff from contractor organization was 1071.0 man-mSv as compared to the planned 1100 man-mSv. 4. References 1. K. Almenas, A. Kaliatka, E.Ušpuras. Ignalina RBMK-1500. A Source Book. 1998.
MEDICAL PHYSICS IN THE BALTIC STATES 7 (2009) Proceedings of International Conference “Medical Physics 2009” 8 - 10 October 2009, Kaunas, Lithuania APPLICATION OF NEUTRONS IN RADIOTHERAPY Gediminas ADLYS Kaunas University of Technology Abstract: An overview of neutron application for medical purposes from technological and physical point of view is presented in this article. It discusses the features of fast neutron therapy, neutron capture therapy and production of radionuclides by means of neutron activation and analyzes the requirements for neutron beams which are produced using different sources (nuclear reactors, accelerator driven systems neutron spallation sources). Keywords: neutron therapy, neutron sources, reactors, spallation sources 1. Introduction Advance of science and technology continually find its place in medicine practice. Soon after X- rays discovery it was used for diagnostics and therapy and it continues until now. Improvements in radiotherapy results were noted with each technological advance. The field of radiation therapy began to grow after discovery of the radioactive elements polonium and radium. Radium was used until the cobalt and caesium teletherapy machines came into use. Nowadays, these units are being replaced by linear accelerators, working without radioactive sources, which makes them safer in the radiological point of view. With invention of computed tomography threedimensional planning became a possibility. It allows more accurate determination of the dose distribution using images of the patient’s anatomy. Construction of superconducting magnets and progress in cryogenic technique was applied developing nuclear magnetic resonance equipment for new imaging modalities. Advance in nuclear and particle physics technologies was basis for the positron emission tomography. The development of high power compact accelerators such as radiofrequency quadrupole linacs or cyclotrons creates the possibility to use neutron related techniques in medicine at reasonable cost. In proton accelerators accelerated protons could be used for proton therapy or for the bombardment of the proper target, which releases neutrons of sufficient energy to treat tumors at the modest tissue depths. Additionally, research nuclear reactors are used as neutron sources for producing radionuclides for medicine and for direct neutron therapy as a part of radiation therapy. Recently attention of radiotherapists is paid to the new developing branch of nuclear physics and technology – nuclear spallation neutron sources. 86 2. The place of neutrons in radiotherapy Radiation therapy is the medical use of ionizing radiation primarily in the treatment of malignant tumor. The biological response of a cancer cells to ionizing radiation is described by its radiosensitivity. The types of cancer are classified as “radioresistant”; if tumors do not respond well to low LET radiation [1]. Highly sensitive cancer cells are rapidly killed by modest doses of radiation while radioresistant cancer cells require much higher doses for radical cure than may be safe in hospital practice. The majority of epithelial cancers are only moderately radiosensitive, which require 60-70 Gy dose of radiation to achieve a radical cure. Radiation therapy of cancer is based upon the basic effect of ionizing radiation to destroy the ability of cells to divide and grow by damaging their DNA strands. The damage is caused by a photon, electron, proton, neutron or ion beam. It is done directly or indirectly ionizing the atoms of the DNA chain. For photon, electron and proton beam the damage is caused as a result of atomic interactions. It entails primarily the ionization of water, forming free radicals, notably hydroxyl radicals, which then damage the DNA. With neutron radiation the damage is caused by nuclear interactions. Cells have mechanisms for repairing DNA damage. If radiation is delivered in small sessions, normal tissue will have time to repair itself. Tumor cells typically lack effective repair mechanisms compared to most healthy cells and are generally less efficient in repair between fractions. It is one of reasons why the total dose is spread out over time or fractionated. Accumulating damage to the cancer cells causes them to die or reproduce more slowly. Photon, electron and proton radiation are called low linear-energy-transfer (LET) radiation. Neutrons are high LET radiation. If radioresistant tumor cell is damaged by low LET radiation it has a good possibility
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2009 PROCEEDINGS OF THE 7 th INTERN
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Executive editor: D.Adlienė CONFER
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11.15-11.30 Daiva Leščiute, Valda
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MEDICAL PHYSICS IN THE BALTIC STATE
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