Collimator angle optimization software CAOS was developed in Python and integrated with the Eclipse 13.6 platform to support stereotactic radiosurgery treatment planning. Twenty-five cases of multiple brain metastasis (10 with two lesions, 10 with three, and 5 with four) were planned using stereotactic radiosurgery in Eclipse 13.6, followed by optimization with CAOS. Eclipse uses a conventional method, while CAOS software first determines the isocenter co-ordinate and then optimizes the collimator angles. The CAOS-optimized plans exhibited significantly improved dosimetric outcomes in stereotactic radiosurgery planning. They reduced gradient index and gradient measure values for the tumor, decreased the mean normal brain volume receiving 12 Gy, and lowered the maximum dose to organs-at-risk, compared to Eclipse plans.
The inherent safety feature of a pebble-bed reactor can be observed from its kinetic parameters. Proper modeling for calculating the reactor kinetic is also a concern for safe operation during normal and transient conditions. This study is intended to investigate the kinetic parameters characteristics of a pebble bed reactor using HTR-Proteus. A series of calculations were conducted using MCNP6 code and ENDF/B-VII library. The calculation results show that the negative value on core temperature reactivity is affected dominantly by the Doppler broadening effect. Prompt neutron lifetime l and mean generation time ? are slightly changed due to an increase in fuel temperature, moderator, and reflector that changed the neutron moderation and absorption over this part of the reactor. For (Th, U)O2, UO2, and PuO2 cores, the effective delayed neutron fraction ?eff values are more influenced by 233U, 235U, and 239Pu, respectively. In terms of stability during reactivity insertion, the UO 2 core is more stable and easier to control because its ?eff value is the largest compared to (Th,U)O2 and PuO 2 cores. It can be concluded that temperature must be controlled because it does not only affect the reactivity but also kinetic parameters as part of developing inherent safety features on the pebble-bed reactor.
Alexandros Clouvas, Anna Makridou, Michalis Chatzimarkou
The capabilities of electret ion chambers to measure non-target absorbed dose during radio- therapy treatment was investigated for the first time. During radiotherapy, non-target doses can be classified as one of three approximate dose levels: high doses, intermediate doses and low doses. Low doses (<5 % of the prescription dose) are not generally considered during treatment planning, due to the fact that is difficult to measure, characterize, or model them in the planning system. In this work were performed measurements with electret ion chambers of absorbed dose outside the treated volume (<5 % of the prescription dose), during external photon radiation therapy in an Elekta Infinity Linear Accelerator of Theagenio Cancer Hospital of Thessaloniki, Greece. The absorbed dose values for distances 8-100 cm from the borders of the irradiated volume varied from 0.3 to 17 mGy which corresponds to 0.01 % up to % of the prescription dose (2660 mGy). Near the irradiation volume the absorbed dose values were greater than the upper detection limit of the electret ion chambers (threshold 40 mGy). The results are compared with the calculated ones by the Monaco treatment planning system ? TPS (Elekta Monaco at November 5, 2003) in three positions distanced at 8 cm and about 30 cm from the border of the irradiation zone. In the position at 8 cm from the irradiation zone, where Monaco TPS calculates (within uncertainty of about 15 %) the absorbed dose, measured and calculated doses are the same within experimental uncertainties. On the contrary for the other two positions, where leakage radiation becomes the dominant source of out-of-field dose the absorbed dose values calculated by the TPS are seriously underestimated ( by a factor of 4) due to the fact that TPS does not take into account the leakage radiation. However, adding to the TPS values an estimated dose due to leakage radiation, the difference between measured and calculated doses are about 30 %.
Analysis of the steady-state and reactivity insertion accident is very important for the safety of reactor operations. In this study, steady-state and reactivity insertion accident analysis when the low enriched uranium foil target is irradiated in the reactor core has been carried out. The analysis is carried out by the best estimate method by using a coupled neutronic, kinetic, and thermal-hydraulic code, MTR-DYN. The MTR-DYN code is based on the 3-D multigroup neutron diffusion method. The cell calculations for the target are carried out by the WIMSD/5 and MTR-DYN code. After reactivity insertion, the coolant, fuel, and clad temperature are observed. The calculation results for the initial power of 1 W showed that the maximum temperature of the coolant, clad, and fuel are 49.76?C, 65.01?C, and 65.26?C, respectively. Meanwhile, when the reactivity insertion at the initial power of 1 MW, the maximum temperature of the coolant, clad, and fuel are 72.23?C, 140.79?C, and 141.97?C, respectively. Based on those calculation results during irradiation low enriched uranium foil target, the temperature in the steady-state and reactivity insertion accident does not exceed the allowable safety limit.
Marija Suric-Mihic, Robert Bernat, Jerko Sisko
et al.
Individual hand monitoring for workers who manipulate unsealed radioactive sources in nuclear medicine is a necessity and the results can serve as the base for optimization processes. We performed an analysis of individual hand doses for medical staff preparing and applying radiopharmaceuticals (99mTc, 123I, 201Tl, 131I, or 125I) in three Croatian clinical hospitals, for a period of one year since extremity monitoring became legally mandatory in Croatia. The majority of annual hand doses for workers were below or slightly above 150 mSv per year with only a few workers exceeding the annual dose limit of 500 mSv. The analysis confirmed that the radiation protection expert's role in an individual monitoring programme and personal dosimetry is crucial in order to achieve the optimal radiation protection of workers.
Marija Majer, Zeljka Knezevic, Jelena Popic
et al.
The use of computed tomography is increasing rapidly and doses are not negligible especially when medical procedures require more than one scan. The purpose of the present study was to measure doses in an anthropomorphic Rando phantom during a standard and low dose computed tomography protocol of the thorax and to estimate risks of radiation induced cancer for adult patients that undergo multiple computed tomography scans of the thorax. Thermoluminescent and radiophotoluminescent dosimeters were used for dose measurements. Radiation risks of cancer incidence, in the form of lifetime attributable risk, were estimated using the BEIR VII model. For five exposures with the standard protocol mean organ doses were 94 mGy (breast), 85 mGy (stomach), 85 mGy (thyroid), 78 mGy (lung), 52 mGy (liver), and 16 mGy (colon). Associated lifetime attributable risk were found to be up to 0.401 % (401 breast cancers per 100 000 exposed patients) and 0.116 % (116 lung cancers per 100 000 exposed patients) for female and male, respectively. A low dose protocol reduces doses (and risks) by the average factor of 5 and therefore the use of a low dose protocol is recommended whenever it is medicaly justified.
Editorial Board of the Nuclear Technology & Radiation Protection journal regrets to inform the audience of the journal that in the header of the article INFLUENCE OF ELECTROMAGNETIC AND NUCLEAR RADIATION IN MEDICINE FOR THERAPY AND DIAGNOSIS THROUGH PROCESSES, FACTS AND STATISTICAL ANALYSIS by Monika M. ZIVKOVIC, Milesa Z. SRECKOVIC, Tomislav M. STOJIC, and Bojana M. BOKIC published in the Vol. 32 (2017), 1, pp. 91-98, was made a mistake concerning the first author's name. It shold be as follows: M.M. Zivkovic, et al.: Influence of Electromagnetic and Nuclear Radiation ... Editorial Board offers an apology for this mistake to Dr. Monika M. Zivkovic and the readers of the Nuclear Technology & Radiation Protection journal. <br><br><font color="red"><b> Link to the corrected article <u><a href="http://dx.doi.org/10.2298/NTRP1701091Z">10.2298/NTRP1701091Z</a></b></u>
Published in the Nuclear Technology & Radiation Protection journal, 32 (2017), 2, pp. 155-165, during the technical preparation of the article, errors in equations (1) and (3) and in the accompanying texts were made. <br><br><font color="red"><b> Link to the corrected article <u><a href="http://dx.doi.org/10.2298/NTRP1702155V">10.2298/NTRP1702155V</a></b></u>
Yury Teterin, Konstantin Maslakov, Mikhail Ryzhkov
et al.
Quantitative analysis was done of the valence electrons X-ray photoelectron spectra structure in the binding energy (BE) range of 0 eV to ~35 eV for crystalline dicaesium tetrachloro-dioxouranium (VI) (Cs2UO2Cl4). This compound contains the uranyl group UO2. The BE and structure of the core electronic shells (~35 eV-1250 eV), as well as the relativistic discrete variation calculation results for the UO2Cl4(D4h) cluster reflecting U close environment in Cs2UO2Cl4 were taken into account. The experimental data show that many-body effects due to the presence of cesium and chlorine contribute to the outer valence (0-~15 eV BE) spectral structure much less than to the inner valence (~15 eV-~35 eV BE) one. The filled U5f electronic states were theoretically calculated and experimentally confirmed to be present in the valence band of Cs2UO2Cl4. It corroborates the suggestion on the direct participation of the U5f electrons in the chemical bond. Electrons of the U6p atomic orbitals participate in formation of both the inner (IVMO) and the outer (OVMO) valence molecular orbitals (bands). The filled U6p and the O2s, Cl3s electronic shells were found to make the largest contributions to the IVMO formation. The molecular orbitals composition and the sequence order in the binding energy range 0 eV-~35 eV in the UO2Cl4 cluster were established. The experimental and theoretical data allowed a quantitative molecular orbitals scheme for the UO2Cl4 cluster in the BE range 0-~35 eV, which is fundamental for both understanding the chemical bond nature in Cs2UO2Cl4 and the interpretation of other X-ray spectra of Cs2UO2Cl4. The contributions to the chemical binding for the UO2Cl4 cluster were evaluated to be: the OVMO contribution - 76%, and the IVMO contribution - 24 %.
The radiation shielding properties of three different stainless steels have been investigated. For this purpose, linear attenuation coefficients at photon energy levels of 662 keV and 1250 keV have been measured. The obtained results showed that ferritic stainless steel was more capable in stopping the high energy photons than its non-magnetic counterpart.
In the present study, the effect of gantry orientation on the photoneutron and capture gamma dose calculations for maze entrance door was evaluated. A typical radiation therapy room made of ordinary concrete was simulated using MCNPX Monte Carlo code. Gantry rotation was simulated at eight different angles around the isocenter. Both neutron and capture gamma dose vary considerably with gantry angle. The ratios of the maximum to the minimum values for neutron and capture gamma dose equivalents were 1.9 and 1.4, respectively. On the other hand, comparison of the Monte Carlo calculated mean value over all orientations with Monte Carlo calculated neutron and gamma dose showed that the Wu-McGinley method differed by 5% and 2%, respectively. However, for more conservative shielding calculations, factors of 1.6 and 1.3 should be applied to the calculated neutron and capture gamma doses at downward irradiation. Finally, it can be concluded that the gantry angle influences neutron and capture gamma dose at the maze entrance door and it should be taken into account in shielding considerations.
Rade Sekulic, Nikola Slavkovic, Milesa Sreckovic
et al.
The fiber optics technology is constantly being developed, and is becoming an essential component of contemporary communications, medicine and industry. Fibers, their connections and system components play a major role in optical signal transmission, telecommunications, power transmission, and sensing processes using fiber technology. The two main light propagation characteristics of an optical fiber are attenuation and dispersion. The possibility of controling these parameters is of utmost importance for obtaining the requested transmission quality. This paper reports on an investigation to determine the influence of gamma radiation of 60Co on the variation of optical fiber propagation parameters, such as polarization mode dispersion. In addition, it also considers chosen topics in the field of fiber optics technology.
Gene therapy offers a novel approach to treating human joint diseases such as rheumatoid arthritis. In the present study, we have used the retrovirus, MFG-IRAP, to transfer the human IL-1 receptor antagonist protein (IRAP) gene to rabbits' knees and have assessed its impact on inflammatory and chondrodestructive aspects of the acute phase of antigen-induced arthritis in these joints. Surprisingly, intra-articular expression of IRAP was three- to fivefold higher in arthritic knees than in nonarthritic knees, accumulating to levels of over 20 ng/knee in the highest expressing joints. This level of expression produced a marked chondroprotective effect but a milder anti-inflammatory one. Both the increased cartilage matrix catabolism and the inhibition of matrix synthesis that occur in antigen-induced arthritis were abrogated in the presence of the IRAP gene; the latter effect was particularly strong. Of the indices of inflammation that were examined, only leukocyte influx into the joint space was inhibited, and this effect declined with time. Concentrations of rabbit IL-1 were reduced by the IRAP gene, suggesting inhibition of an autocrine induction loop. These data demonstrate that the course of arthritic disease in the rabbit knee can be altered by genetic manipulation, thus encouraging the further development of gene treatments for human joint diseases.