Procjena rizika za nastanak karcinoma zbog izloženosti malim dozama ionizirajućeg zračenja

Although ionising radiation has proven beneficial in the diagnosis and therapy of a number of diseases, one should keep in mind that irradiating healthy tissue may increase the risk of cancer. In order to justify an exposure to radiation, both the benefits and the risks must be evaluated and compared. The deleterious effects of medium and high doses are well known, but it is much less clear what effects arise from low doses (below 0.1 Gy), which is why such risk estimates are extremely important. This review presents the current state, important assumptions and steps being made in deriving cancer risk estimates for low dose exposures.Unatoč velikoj važnosti i koristi ionizirajućeg zračenja u dijagnosticiranju i liječenju mnogih bolesti, treba imati na umu da se ozračivanjem zdravog tkiva može povećati rizik od karcinoma. Stoga je vrlo važno znati kakve rizike možemo očekivati ovisno o primljenoj dozi zračenja. Za razliku od područja srednjih i velikih doza za koje su štetni učinci dobro poznati, područje malih doza (ispod 0,1 Gy) puno je nejasnoća, a procjena rizika vrlo je važna. U ovom radu prikazane su osnovne pretpostavke i koraci u procjeni rizika od karcinoma uzrokovanih zračenjem u području malih doza

Secondary Standard Dosimetry Laboratory at the Ruđer Bošković Institute

Sekundarni standardni dozimetrijski laboratorij (SSDL) Instituta “Ruđer Bošković”, Zagreb, formiran je tijekom nekoliko zadnjih godina. Uspostavu laboratorija svesrdno je pomogla Međunarodna agencija za atomsku energiju (IAEA) programom tehničke pomoći (projekt CRO/1/004, Establishing Calibration Services). Od državnih institucija SSDL su poduprli Državni zavod za normizaciju i mjeriteljstvo, Državni zavod za zaštitu od zračenja te Ministarstvo zdravstva i socijalne skrbi. SSDL raspolaže dvjema kalibracijskim i dvjema kontrolnim prostorijama uređenim u skladu sa zahtjevima IAEA-e za ovu vrstu laboratorija. U prvoj prostoriji, na suprotnim stranama 6-metarskog kalibracijskog stola, nalaze se zatvoreni izvori zračenja 60Co (Alcyon II, Cis BioInternational) za kalibraciju radioterapijskih ionizacijskih komora i kombinirani izvor 60Co/137Cs (Hopewell Design, Inc.) za potrebe zaštite od zračenja. U drugoj prostoriji smješten je kalibracijski rendgen (ISOVOLT 420, Seifert) s pripadajuæim 5-metarskim kalibracijskim stolom. Sve kalibracije rade se u skladu s protokolima IAEA-e.The Secondary Standard Dosimetry Laboratory at the Ruðer Boškoviæ Institute (SSDL), Zagreb, Croatia, was set up over the last few years with a strong support by the International Atomic Energy Agency (IAEA) through the Technical Cooperation Project CRO/1/004, Establishing Calibration Services. The SSDL occupies two calibration rooms, each 9.6 m long and 6 m wide and each with proper air conditioning. Their walls are concrete and 1 m thick, and the entrance doors are plated with lead to protect the control rooms and the surroundings against radiation. In the first calibration room in the basement, there are two sealed sources which share the same, 6 m long calibration bench. A 30 TBq 60Co source on one side of the bench is used for calibrating ionising chambers and other high-dose radiation equipment. The irradiation unit on the other side of the bench combines two sealed sources, that is, a 740 MBq 137Cs source and a 185 MBq 60Co source, and is used for radiation protection purposes. It has three attenuators with nominal attenuations of x10, x100, and x1000. The second calibration room, which is just above the first, accommodates an X-ray unit (ISOVOLT 420, 40 kV to 300 kV, 1 mA to 20 mA) with a 5 m long calibration bench, aperture wheel assembly designed to modify the X-ray beam diameter to meet various configuration requirements for calibration instruments, a set of filter assemblies to control beam definition according to ISO 4037-3, and a half-value layer kit

Koncentracija bjelančevina i bjelančevinskih frakcija u krvnoj plazmi pilića izleženih iz jaja ozračenih malom dozom gamazračenja.

This study was performed to investigate the effect of egg irradiation by low dose gamma rays on the concentration of total proteins and protein fractions in the blood plasma of chickens hatched from irradiated eggs. The eggs of heavy breed chickens were irradiated with a dose of 0.15 Gy gamma-rays (60Co) before incubation. Blood samples were taken from the right jugular vein on the 1st and 3rd days, or from the wing vein on day 7 after hatching. The total protein concentrations in the blood plasma was determined by the biuret method using Boehringer Mannheim GmbH optimized kits. The protein fractions (albumin, α1-globulin, α2- globulin, β- and γ- globulins) were estimated electrophoretically on cellulose acetate strips. The total protein concentration was significantly decreased in the blood plasma of chickens hatched from irradiated eggs on days 3 (P<0.05) and 7 (P<0.001). The albumin concentration in the blood plasma of chickens hatched from irradiated eggs was significantly decreased on the 7th day (P<0.001), and the concentration of α2-globulin was decreased on days 1 (P<0.05) and 7 (P<0.001). β- and γ-globulins concentration was significantly decreased on the 7th day of life (P<0.05). The obtained results indicate that a low dose of gamma radiation has an inhibitory effect upon the concentration of total proteins and protein fractions in the blood plasma of chickens hatched from irradiated eggs before incubation, during the first week of their life.U našem prethodnome radu pokazano je da se u krvnoj plazmi pilića, izleženih iz jaja ozračenih dozom od 0,15 Gy gama-zračenja prije inkubacije, povećava aktivnost aspartat-aminotransferaze i alanin-aminotransferaze tj. dvaju enzima koji imaju važnu ulogu u metabolizmu bjelančevina. Stoga je u ovom radu istražen učinak ozračivanja jaja dozom od 0,15 Gy gama-zračenja prije inkubacije na koncentraciju ukupnih bjelančevina i bjelančevinskih frakcija u krvnoj plazmi pilića izleženih iz ozračenih jaja. Jaja teške pasmine pilića ozračena su dozom od 0,15 Gy gama-zračenja iz radioaktivnog izvora kobalt-60 (60Co) prije inkubacije. Krv za analizu vađena je iz desne jugularne vene u dobi od prvog i trećeg dana, te iz krilne vene 7. dana. Koncentracija ukupnih bjelančevina određivana je u skupnom uzorku krvne plazme od 10 pilića uzetim slučajnim odabirom, biuretmetodom na spektrofotometru rabeći gotove komplete reagencija proizvođača Boehringer Mannheim GmbH. Bjelančevinske frakcije (albumini, α1-globulini, α2-globulini te β- i γ-globulini) određivane su elektroforezom na trakicama geliranog celuloznog acetata. Koncentracija ukupnih bjelančevina u krvnoj plazmi pilića izleženih iz ozračenih jaja bila je statistički značajno smanjena trećeg (P<0,05) i 7. dana života (P<0,001). Koncentracija albumina u krvnoj plazmi pilića izleženih iz ozračenih jaja bila je značajno smanjena 7. dana (P<0,001), a koncentracija α2-globulina bila je smanjena prvog (P<0,05) i 7. dana starosti (P<0,001). Koncentracija β- i γ-globulina u krvnoj plazmi pilića izleženih iz ozračenih jaja bila je značajno smanjena 7. dana života (P<0,05). Dobiveni rezultati pokazuju da male doze gama-zračenja imaju inhibicijski učinak na koncentraciju ukupnih bjelančevina i bjelančevinskih frakcija u krvnoj plazmi pilića, izleženih iz ozračenih jaja prije inkubacije, tijekom prvih sedam dana života

A descriptive and broadly applicable model of therapeutic and stray absorbed dose from 6 MV to 25 MV photon beams

Purpose was to develop a simple model of therapeutic and stray absorbed dose for a variety of treatment machines and techniques without relying on proprietary machine-specific parameters. Dosimetry measurements conducted in this study and from the literature were used to develop an analytical model of absorbed dose from a variety of treatment machines and techniques in the 6 MV to 25 MV interval. A modified one-dimensional gamma-index analysis was performed to evaluate dosimetric accuracy of the model on an independent dataset consisting of measured dose profiles from seven treatment units spanning four manufacturers. The average difference between the calculated and measured absorbed dose values was 9.9% for those datasets on which the model was trained. Additionally, These results indicate that the model can provide accurate calculations of both therapeutic and stray radiation dose from a wide variety of radiotherapy units and techniques. We have developed a simple analytical model of absorbed dose from external beam radiotherapy treatments in the 6 MV to 25 MV beam energy range. The model has been tested on measured data from multiple treatment machines and techniques and is broadly applicable to contemporary external beam radiation therapy

Out-of-Field Doses Produced by a Proton Scanning Beam Inside Pediatric Anthropomorphic Phantoms and Their Comparison With Different Photon Modalities

Since 2010, EURADOS Working Group 9 (Radiation Dosimetry in Radiotherapy) has been involved in the investigation of secondary and scattered radiation doses in X-ray and proton therapy, especially in the case of pediatric patients. The main goal of this paper is to analyze and compare out-of-field neutron and non-neutron organ doses inside 5- and 10-year-old pediatric anthropomorphic phantoms for the treatment of a 5-cm-diameter brain tumor. Proton irradiations were carried out at the Cyclotron Centre Bronowice in IFJ PAN Krakow Poland using a pencil beam scanning technique (PBS) at a gantry with a dedicated scanning nozzle (IBA Proton Therapy System, Proteus 235). Thermoluminescent and radiophotoluminescent dosimeters were used for non-neutron dose measurements while secondary neutrons were measured with track-etched detectors. Out-of-field doses measured using intensity-modulated proton therapy (IMPT) were compared with previous measurements performed within a WG9 for three different photon radiotherapy techniques: 1) intensity-modulated radiation therapy (IMRT), 2) three-dimensional conformal radiation therapy (3D CDRT) performed on a Varian Clinac 2300 linear accelerator (LINAC) in the Centre of Oncology, Krakow, Poland, and 3) Gamma Knife surgery performed on the Leksell Gamma Knife (GK) at the University Hospital Centre Zagreb, Croatia. Phantoms and detectors used in experiments as well as the target location were the same for both photon and proton modalities. The total organ dose equivalent expressed as the sum of neutron and non-neutron components in IMPT was found to be significantly lower (two to three orders of magnitude) in comparison with the different photon radiotherapy techniques for the same delivered tumor dose. For IMPT, neutron doses are lower than non-neutron doses close to the target but become larger than non-neutron doses further away from the target. Results of WG9 studies have provided out-of-field dose levels required for an extensive set of radiotherapy techniques, including proton therapy, and involving a complete description of organ doses of pediatric patients. Such studies are needed for validating mathematical models and Monte Carlo simulation tools for out-of-field dosimetry which is essential for dedicated epidemiological studies which evaluate the risk of second cancers and other late effects for pediatric patients treated with radiotherapy