Estimation of Absorbed Dose During Process Interruption in Radiation Processing

The quality control system enables the standardization of product quality. Dosimetry has an important role in the quality control of radiation processing. The area of radiation processing which is governed most strictly by regulations is radiation sterilization. This process is used as the example to describe the new method for establishing the effect of process interruption on absorbed dose in the Co-60 irradiation plant at the Vinca Institute of Nuclear Sciences. Establishing the effect of process interruption is one of requirements in international regulations, but there are no recommendations for its implementation. A new method has been worked out by graphical extrapolation. The advantage of this method is the ability to carry it out during the sterilization process. The ethanol-chlorobenzene (ECB) dosimeter is used to select the suitable place where absorbed dose is expected to be the most influenced by source transit, i.e. the most close to the source. In the same time, it should be convenient and reproducible for placing dosimeters. Alanine dosimeters were irradiated on this place in time intervals: 2 min., 4 min., 6 min., 8 min., 10 min. Measurements of time starts when the button to lift source is pressed and stops by pressing the button for process interruption (to sink source down). The absorbed doses were measured by ESR spectrometer. The function of absorbed dose versus irradiation time is linear as expected. The extrapolation back to zero time gives the maximal absorbed dose that can be delivered to product during source transit. In our experiment this absorbed dose obtained by this method is 154 Gy.3rd International Conference on Radiation and Applications in Various Fields of Research (RAD), Jun 08-12, 2015, Budva, Montenegr

Calibration of Routine Dosimeters in Radiation Processing: Validation Procedure for In-Plant Calibration

The essential prerequisite of radiation dosimetry is to provide quality assurance and documentation that the irradiation procedure has been carried out according to the specification requirement of correct calibration of the chosen dosimetry system. At the Radiation Plant of the Vinca Institute of Nuclear Sciences we compared two recommended protocols of irradiation procedures in the calibration of dosimetry systems in radiation processing: (1) by irradiation of routine dosimeters (ethanol-chlorobenzene - ECB) at the calibration laboratory and (2), by in-plant calibration with alanine transfer - dosimeters. The critical point for in-plant calibration is irradiation geometry, so we carefully positioned the phantom carrying both dosimeters in order to minimize dose gradients across the sample. The analysis of results obtained showed that the difference among determined absorbed doses for the construction of calibration curves between these two methods, (alanine vs. ECB), is less than 1%. The difference in combined standard uncertainty for each calibration procedure is 0.1%. These results demonstrate that our in-plant calibration is as good as calibration by irradiation at the calibration laboratory and validates our placement of the irradiation phantom during irradiation

DOSIMETRY USING HS GafChromic FILMS The influence of readout light on sensitivity of dosimetry

The goal of this study is to compare the sensitometric curves for HS model of GafChromic film using different dose read-out systems. Two commercial densitometers using fluorescent light source were tested and compared with results obtained using spectrophotometry. It was found that sublinear response of densitometers is due to the polychromaticity of emitted light and that response curve can be predicted by analysing absorption spectra of the film.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Influence of the irradiation conditions on the effect of radiation on polyethylene

Two types of polyethylene, low density (LDPE) and high density (HDPE), as well as low density polyethylene containing an antioxidant were subjected to gamma-irradiation in the presence of air and in water. The irradiated polymers were studied using IR spectrophotometric analysis. The radiation induced oxidative degradation was followed through the formation of oxygen containing groups by the development of bands in the 1850-1650 cm(-1) region and double bonds formation by the development of bands in the 1050-850 cm(-1) region. The crosslinking efficiency was determined by measuring the gel content by extraction with xylene. The radiation induced changes in the molecular structure, evolution of oxygen containing species and formation, of vinyl double bonds as well as of the crosslinking efficiency are discussed in terms of the properties of the polymers in an electric field of low strength

Radiation-mediated induction of apoptotic cell death in rat hippocampus

Ionizing radiation is commonly used in the treatment of brain tumors but it can impair cognitive functions, such as learning and memory. Since cognitive dysfunctions are predominantly result of cell death by apoptosis in hippocampal cells, in this study we analyzed acute effects of cranial gamma-irradiation (10 Gy) on expression of proapoptotic molecules (p53, Bax) and antiapoptotic molecule Bcl-2, as well as caspase-3 activation and cytochrome c redistribution in the hippocampus of young rats. The selected regimen of irradiation resembles the established animal model for childhood prophylactic cranial radiotherapy. Our results demonstrated that p53 mRNA expression was unchanged after irradiation, while induction of p53 protein was rapid. In parallel, Bax mRNA and protein levels were also increased following irradiation, whereas Bcl-2 expression was not changed during the examined post-irradiation period. These changes were accompanied with early hallmarks of apoptosis, such as increased cytochrome c release and stimulated activation of caspase-3. Overall, this study demonstrates that cranial irradiation is associated with the augmented apoptotic pathway in the rat hippocampus, which could be related to the cognitive decline observed in patients after prophylactic cranial radiotherapy, but also opens perspective in finding radioprotectors that can mitigate radiation injury of normal brain tissue.Jonizujuće zračenje se često koristi u tretmanu tumora mozga ali ono može da ošteti kognitivne funkcije, kao što su učenje i pamćenje. Pošto je smanjenje kognitivnih funkcija većinom rezultat ćelijske smrti putem apoptoze u hipokampalnim ćelijama u ovoj studiji su analizirani efekti kranijalnog gama-zračenja (10 Gy) na ekspresiju proapoptotskih (p53, Bax) i antiapoptotskih molekula (Bcl-2), kao i na aktivaciju kaspaze-3 i redistribuciju citohroma c u hipokampusu mladih pacova. Odabrani režim zračenja odgovara uspostavljenom životinjskom modelu za dečiju profilaktičku kranijalnu radioterapiju. Naši rezultati pokazuju da je ekspresija p53 i RNK nepromenjena nakon zračenja, dok je indukcija p53 proteina veoma brza. Istovremeno Bax iRNK i protein su povećani nakon zračenja, dok je ekspresija Bcl-2 nepromenjena tokom ispitivanog perioda. Ove promene su praćene ranim znacima apoptoze, kao što su povećano oslobađanje citohroma c i aktivacija kaspaze-3. Generalno, ova studija pokazuje da je kranijalno zračenje povezano sa stimulisanim apoptotskim putem u hipokampusu pacova, što se može povezati sa kognitivnim oštećenjima uočenih kod pacijenata nakon profilaktičke kranijalne radioterapije, ali takođe otvara perspektive u pronalaženju radioprotektora koji smanjuju oštećenje normalnog nervnog tkiva nakon zračenja.nul

Radiation-mediated induction of apoptotic cell death in rat hippocampus

Ionizing radiation is commonly used in the treatment of brain tumors but it can impair cognitive functions, such as learning and memory. Since cognitive dysfunctions are predominantly result of cell death by apoptosis in hippocampal cells, in this study we analyzed acute effects of cranial gamma-irradiation (10 Gy) on expression of proapoptotic molecules (p53, Bax) and antiapoptotic molecule Bcl-2, as well as caspase-3 activation and cytochrome c redistribution in the hippocampus of young rats. The selected regimen of irradiation resembles the established animal model for childhood prophylactic cranial radiotherapy. Our results demonstrated that p53 mRNA expression was unchanged after irradiation, while induction of p53 protein was rapid. In parallel, Bax mRNA and protein levels were also increased following irradiation, whereas Bcl-2 expression was not changed during the examined post-irradiation period. These changes were accompanied with early hallmarks of apoptosis, such as increased cytochrome c release and stimulated activation of caspase-3. Overall, this study demonstrates that cranial irradiation is associated with the augmented apoptotic pathway in the rat hippocampus, which could be related to the cognitive decline observed in patients after prophylactic cranial radiotherapy, but also opens perspective in finding radioprotectors that can mitigate radiation injury of normal brain tissue.Jonizujuće zračenje se često koristi u tretmanu tumora mozga ali ono može da ošteti kognitivne funkcije, kao što su učenje i pamćenje. Pošto je smanjenje kognitivnih funkcija većinom rezultat ćelijske smrti putem apoptoze u hipokampalnim ćelijama u ovoj studiji su analizirani efekti kranijalnog gama-zračenja (10 Gy) na ekspresiju proapoptotskih (p53, Bax) i antiapoptotskih molekula (Bcl-2), kao i na aktivaciju kaspaze-3 i redistribuciju citohroma c u hipokampusu mladih pacova. Odabrani režim zračenja odgovara uspostavljenom životinjskom modelu za dečiju profilaktičku kranijalnu radioterapiju. Naši rezultati pokazuju da je ekspresija p53 i RNK nepromenjena nakon zračenja, dok je indukcija p53 proteina veoma brza. Istovremeno Bax iRNK i protein su povećani nakon zračenja, dok je ekspresija Bcl-2 nepromenjena tokom ispitivanog perioda. Ove promene su praćene ranim znacima apoptoze, kao što su povećano oslobađanje citohroma c i aktivacija kaspaze-3. Generalno, ova studija pokazuje da je kranijalno zračenje povezano sa stimulisanim apoptotskim putem u hipokampusu pacova, što se može povezati sa kognitivnim oštećenjima uočenih kod pacijenata nakon profilaktičke kranijalne radioterapije, ali takođe otvara perspektive u pronalaženju radioprotektora koji smanjuju oštećenje normalnog nervnog tkiva nakon zračenja.nul

Comparison of dichromate and ethanol-chlorobenzene dosimeters in high dose radiation processing

Dichromate and ethanol-chlorobenzene dosimeters were studied in conditions of annual temperature changes during process control at the Radiation Unit of the Vinca Institute. Measurements were performed in February (10-14 degrees C) and August (22-35 degrees C) for the dose range 10-50 kGy. The difference between measurements using these dosimeters is in agreement with the previous laboratory studies of temperature effect on the dose response of a dichromate dosimeter. The absorbed doses measured by these two dosimeters are in good agreement and the difference is within a limit of 3% for the studied dose range. The uncertainties of dose measurements using dichromate dosimeter arising from irradiation during annual temperature changes appear to be well within acceptable limits indicating that this dosimeter can be used as a routine dosimeter

Comparison of dichromate and ethanol-chlorobenzene dosimeters in high dose radiation processing

Dichromate and ethanol-chlorobenzene dosimeters were studied in conditions of annual temperature changes during process control at the Radiation Unit of the Vinca Institute. Measurements were performed in February (10-14 degrees C) and August (22-35 degrees C) for the dose range 10-50 kGy. The difference between measurements using these dosimeters is in agreement with the previous laboratory studies of temperature effect on the dose response of a dichromate dosimeter. The absorbed doses measured by these two dosimeters are in good agreement and the difference is within a limit of 3% for the studied dose range. The uncertainties of dose measurements using dichromate dosimeter arising from irradiation during annual temperature changes appear to be well within acceptable limits indicating that this dosimeter can be used as a routine dosimeter

New applications of radiochromatic films in radiation pysics

New methods for evaluating the energy spectrum of a source generating the radiation field, based on space-dependent flux distribution measured, data is proposed. The measured data are assumed to be obtained by using radiochromatic films. Mathematical modelling is defined as reversed transport problem. The semigroup method is proposed to reverse the transport problem.Conference on Applied Physics in Serbia, May 27-29, 2002, Belgrade, Yugoslavi