Beta-ray Sources Research Articles

Evaluation of radiation dose caused by bremsstrahlung photons generated by high-energy beta rays using the PHITS and GEANT4 simulation codes

ABSTRACT High-energy beta-ray sources generate bremsstrahlung photons in the building materials, generated by the radioactive nuclides inside the nuclear reactor buildings emitted by the Fukushima Daiichi nuclear reactor accident. Therefore, evaluating the bremsstrahlung dose subjected to the workers in the building is crucial for radiation protection. The precision for assessing the bremsstrahlung dose was investigated by comparing the Particle and Heavy Ion Transport code System (PHITS) and the GEometry ANd Tracking (GEANT4) simulation code results. Behind various shielding plates (lead, copper, aluminum, glass, and polyethylene with multiple thicknesses), the water cylinder was set to obtain the absorbed dose and the deposited energy spectrum by the bremsstrahlung photons. In comparing the deposited energy spectrum, the spectral shapes have consistent trends. Below several tens of keV, a peak is observed in the PHITS spectrum for lead. While comparing the absorbed dose, most of the results from both codes correlate within an ~10% difference for 2.280 MeV beta-ray sources and an ~20% difference for 0.5459 MeV beta-ray sources, except for ~30% for 20 mm thick lead. Although some differences occurred, the evaluation results of both codes correlated well with the above precision.

Comparison between beta radiation dose distribution due to LDR and HDR ocular brachytherapy applicators using GATE Monte Carlo platform

Eye applicators with 90Sr/90Y and 106Ru/106Rh beta-ray sources are generally used in brachytherapy for the treatment of eye diseases as uveal melanoma. Whenever, radiation is used in treatment, dosimetry is essential. However, knowledge of the exact dose distribution is a critical decision-making to the outcome of the treatment. The Monte Carlo technique provides a powerful tool for calculation of the dose and dose distributions which helps to predict and determine the doses from different shapes of various types of eye applicators more accurately. The aim of this work consisted in using the Monte Carlo GATE platform to calculate the 3D dose distribution on a mathematical model of the human eye according to international recommendations. Mathematical models were developed for four ophthalmic applicators, two HDR 90Sr applicators SIA.20 and SIA.6, and two LDR 106Ru applicators, a concave CCB model and a flat CCB model. In present work, considering a heterogeneous eye phantom and the chosen tumor, obtained results with the use of GATE for mean doses distributions in a phantom and according to international recommendations show a discrepancy with respect to those specified by the manufacturers. The QC of dosimetric parameters shows that contrarily to the other applicators, the SIA.20 applicator is consistent with recommendations. The GATE platform show that the SIA.20 applicator present better results, namely the dose delivered to critical structures were lower compared to those obtained for the other applicators, and the SIA.6 applicator, simulated with MCNPX generates higher lens doses than those generated by GATE.

Development of A phantom for ophthalmic beta source applicator quality control using TL dosimetry

Abstract Concave eye applicators with 90 Sr/ 90 Y and 106 Ru/ 106 Rh beta ray sources are usually used in brachytherapy for the treatment of superficial intraocular tumors as uveal melanoma with thickness up to 5 mm. The calculation of the dose delivered to the eye is carried out based on the data present in the beta source calibration certificate. Therefore, it would be interesting to have a system that could evaluate that dose. In this work, an eye phantom to be used with 106 Ru/ 106 Rh betatherapy applicators was developed in solid water. This phantom can hold nine micro-cube thermoluminescent (TL) dosimeters, TLD-100. The characteristics of the TL response of the dosimeters, namely reproducibility and individual sensitivity, were determined for a 60 Co source. Using Monte Carlo code MCNPX, the dose to a water eye was determined at different depths. Exposing the eye phantom with TL dosimeters to the 106 Ru/ 106 Rh applicator, it is possible to assess calibration factors using the dose values obtained by Monte Carlo simulation to each depth. Using mean calibration factors, dose values obtained by TL dosimetry were compared to the data present in the applicators certificate. Mean differences for both applicators were lower than ±10%, maximum value 17% and minimum value 0.08%. Considering that the certificate values present an uncertainty of ±20%, the calibration procedure and the developed phantom are validated and can be applied.

Assessment of ocular beta radiation dose distribution due to 106Ru/106Rh brachytherapy applicators using MCNPX Monte Carlo code

Purpose: Melanoma at the choroid region is the most common primary cancer that affects the eye in adult patients. Concave ophthalmic applicators with 106 Ru/ 106 Rh beta sources are the more used for treatment of these eye lesions, mainly lesions with small and medium dimensions. The available treatment planning system for 106 Ru applicators is based on dose distributions on a homogeneous water sphere eye model, resulting in a lack of data in the literature of dose distributions in the eye radiosensitive structures, information that may be crucial to improve the treatment planning process, aiming the maintenance of visual acuity. Methods : The Monte Carlo code MCNPX was used to calculate the dose distribution in a complete mathematical model of the human eye containing a choroid melanoma; considering the eye actual dimensions and its various component structures, due to an ophthalmic brachytherapy treatment, using 106 Ru/ 106 Rh beta-ray sources. Two possibilities were analyzed; a simple water eye and a heterogeneous eye considering all its structures. Two concave applicators, CCA and CCB manufactured by BEBIG and a complete mathematical model of the human eye were modeled using the MCNPX code. Results and Conclusion : For both eye models, namely water model and heterogeneous model, mean dose values simulated for the same eye regions are, in general, very similar, excepting for regions very distant from the applicator, where mean dose values are very low, uncertainties are higher and relative differences may reach 20.4%. For the tumor base and the eye structures closest to the applicator, such as sclera, choroid and retina, the maximum difference observed was 4%, presenting the heterogeneous model higher mean dose values. For the other eye regions, the higher doses were obtained when the homogeneous water eye model is taken into consideration. Mean dose distributions determined for the homogeneous water eye model are similar to those obtained for the heterogeneous eye model, indicating that the homogeneous water eye model is a reasonable one. The determined isodose curves give a good visualization of dose distributions inside the eye structures, pointing out their most exposed volume. Cite this article as: Barbosa NA, da Rosa LAR, de Menezes AF, Reis JP, Facure A, Braz D. Assessment of ocular beta radiation dose distribution due to 106Ru/106Rh brachytherapy applicators using MCNPX Monte Carlo code. Int J Cancer Ther Oncol 2014; 2 (3):02038. DOI : 10.14319/ijcto.0203.8

Brachytherapy treatment simulation of strontium-90 and ruthenium-106 plaques on small size posterior uveal melanoma using MCNPX code

Abstracts Concave eye applicators with 90Sr/90Y and 106Ru/106Rh beta-ray sources are usually used in brachytherapy for the treatment of superficial intraocular tumors as uveal melanoma with thickness up to 5 mm. The aim of this work consisted in using the Monte Carlo code MCNPX to calculate the 3D dose distribution on a mathematical model of the human eye, considering 90Sr/90Y and 160Ru/160Rh beta-ray eye applicators, in order to treat a posterior uveal melanoma with a thickness 3.8 mm from the choroid surface. Mathematical models were developed for the two ophthalmic applicators, CGD produced by BEBIG Company and SIA.6 produced by the Amersham Company, with activities 1 mCi and 4.23 mCi respectively. They have a concave form. These applicators' mathematical models were attached to the eye model and the dose distributions were calculated using the MCNPX ⁎F8 tally. The average doses rates were determined in all regions of the eye model. The *F8 tally results showed that the deposited energy due to the applicator with the radionuclide 106Ru/106Rh is higher in all eye regions, including tumor. However the average dose rate in the tumor region is higher for the applicator with 90Sr/90Y, due to its high activity. Due to the dosimetric characteristics of these applicators, the PDD value for 3 mm water is 73% for the 106Ru/106Rh applicator and 60% for 90Sr/90Y applicator. For a better choice of the applicator type and radionuclide it is important to know the thickness of the tumor and its location.

Monte Carlo calculation of dose to water of a 106Ru COB-type ophthalmic plaque

The concave eye applicators with 106Ru/106Rh or 90Sr/90Y beta-ray sources are worldwide used in brachytherapy for treating intraocular tumors. It raises the need to know the exact dose delivered by beta radiation to tumors but measurement of the dose to water (or tissue) is very difficult due to short range of electrons. The Monte Carlo technique provides a powerful tool for calculation of the dose and dose distributions which helps to predict and determine the doses from different shapes of various types of eye applicators more accurately. The Monte Carlo code MCNPX has been used to calculate dose distributions from a COB-type 106Ru/106Rh ophthalmic applicator manufactured by Eckert & Ziegler BEBIG GmbH. This type of a concave eye applicator has a cut-out whose purpose is to protect the eye nerve which makes the dose distribution more complicated. Several calculations have been performed including depth dose along the applicator central axis and various dose distributions. The depth dose along the applicator central axis and the dose distribution on a spherical surface 1 mm above the plaque inner surface have been compared with measurement data provided by the manufacturer. For distances from 0.5 to 4 mm above the surface, the agreement was within 2.5 % and from 5 mm the difference increased from 6 % up to 25 % at 10 mm whereas the uncertainty on manufacturer data is 20 % (2s). It is assumed that the difference is caused by nonuniformly distributed radioactivity over the applicator radioactive layer.

4. Beta-Ray Sources and Spectra

4. Beta-Ray Sources and Spectra

4. Beta-Ray Sources and Spectra

4. Beta-Ray Sources and Spectra

Preparation of Beta-ray Calibration Sources for Estimating Tissue Doses from Skin Contamination

Preparation of Beta-ray Calibration Sources for Estimating Tissue Doses from Skin Contamination

Preparation of Beta-ray Calibration Sources for Estimating Tissue Doses from Skin Contamination.

Abstract A new type of β-ray calibration source was designed for estimating tissue doses from skin contamination. Thin polyethylene ion-exchange membranes were applied for the source preparation. The method of determining tissue absorbed dose rates with an extrapolation chamber was discussed for the calibration sources prepared with 147Pm, 204TI and 90Sr-90Y. The influence of backscattered β-rays by source mount materials was estimated as a function of membrane source thickness. The membrane sources are quite suitable for the present purpose, because they have large uniform radioactive areas and can be easily handled without radioactive contamination.

Dosimetry of ruthenium‐106 eye applicators

In view of the importance of clinical applications of ruthenium-106 beta-ray sources for the treatment of choroidal melanoma, experimental, and theoretical approaches are presented for the dosimetry of such sources. The absolute dose and percentage depth dose of ruthenium applicators have been measured with an extrapolation ionization chamber. For a special flat applicator the absolute dose could be measured with an accuracy of +/- 5%, which is determined by the collection efficiency of the extrapolation chamber. The percentage depth dose of concave applicators, employed in the clinical situation, could only be measured at a distance larger than 5 mm due to their geometry and the outer dimensions of the extrapolation chamber. A computer simulation was therefore developed for the absorption and scattering of electrons, taking into account the geometry and materials of the applicator, to predict the percentage depth dose at distances smaller than 5 mm. The calculated and experimentally determined depth doses are in good agreement. With the aid of the computer simulation a depth dose determination for concave applicators can be made for clinically relevant distances less than 10 mm from the source surface with an absolute accuracy of +/- 10%.

Beta Energy Dependence of LiF:Mg,Cu,P Thermoluminescent Films on Thickness of Sensitive Layer

The beta energy dependencies of LiF:Mg,Cu,P films has been investigated. LiF:Mg,Cu,P powders of six grain sizes were used for the preparation of the TL films. The film thicknesses are between 1.68 mg.cm-2 and 17.48 mg.cm-2 for the different grain sizes of LiF powder. Experimental results show that the responses for different beta ray sources (90Sr/90Y, 204Tl and 147Pm) were strongly dependent upon the sensitive thickness of the TL films. For the 2.28 mg.cm-2 thickness the TL sensitivity of the film to 147Pm was almost the same as that to 90Sr/90. A flat energy dependence of TL response is possible in a beta energy interval from 0.23 to 2.27 MeV. Experimental details are described.

Beta Energy Dependence of LiF:Mg,Cu,P Thermoluminescent Films on Thickness of Sensitive Layer

The beta energy dependencies of LiF:Mg,Cu,P films has been investigated. LiF:Mg,Cu,P powders of six grain sizes were used for the preparation of the TL films. The film thicknesses are between 1.68 mg.cm-2 and 17.48 mg.cm-2 for the different grain sizes of LiF powder. Experimental results show that the responses for different beta ray sources (90Sr/90Y, 204Tl and 147Pm) were strongly dependent upon the sensitive thickness of the TL films. For the 2.28 mg.cm-2 thickness the TL sensitivity of the film to 147Pm was almost the same as that to 90Sr/90. A flat energy dependence of TL response is possible in a beta energy interval from 0.23 to 2.27 MeV. Experimental details are described.

A new method for characterizing beta‐ray ophthalmic applicator sources

A technique is described which enables one to obtain detailed dose characteristics of 90Sr beta-ray ophthalmic applicators. A radiochromic radiation detector which is a solid-state solution of hexahydroxyethyl pararosaniline cyanide in a nylon polymer (i.e., thin foil), has been used to determine the surface dose rate and dose distribution of these sources. The detectors are rugged, easily handled, have an equivalent response (optical density per unit absorbed dose) to photons and electrons, and produce high-resolution images. They have been found useful for this application due to the high surface dose rates [0.10-1.0 Gy (H2O)/s] and their low sensitivity (approximately 10(4) Gy for an optical density of 1.0). The foils have been evaluated on a He-Ne scanning laser densitometer with a resolution of 0.3 mum. Comparison with NIST (formerly NBS) extrapolation ionization chamber measurements indicates surface dose-rate agreement within 6%. Spectral dosimetric characteristics are presented and discussed.

Methods and means of checking thermoluminescent and radiophotoluminescent dosimeters

The authors discuss methods of checking thermoluminescent and radiophotoluminescent dosimeters which are used often in monitoring radiation safety in various areas including nuclear power stations. When the dosimeters are checked in the fields of standard beta-ray sources, it is recommended that the standard absorbed-dose or equivalent-dose measures for beta radiation should be sources of /sup 90/Sr + /sup 90/Y, /sup 204/Tl, and /sup 147/Pm. Various safety guidelines are discussed.

Surface imaging with backscattered beta-rays using extended area beta-ray sources

A method for radiographic inspection with backscattered beta-rays using extended area beta-ray sources is briefly described. Various possible applications of the method are indicated.

Neutralization of Static Electricity Charged on Running Vinyl Chloride Sheet by the Use of Soft β-Ray Sources

The feasibility of 147Pm and 3H beta-ray sources as static eliminator was experimentally investigated. A sheet of vinyl chloride of 0.1 mm in thickness was used as an example of electrified materials. Its surface charge densities before and after beta-ray neutralization were measured as the function of electrostatic charge changing the speed of the sheet and the distance between the beta-ray source and the sheet. With a 147Pm beta-ray source of 200mCi in effective activity, almost complete neutralization was found for the sheet with the charge density less than 6 X 10(-6) C/m2 running at the speed of 0.18 m/s. In the case of the running speed of 0.5 m/s frequently used in industry, the electrostatic charge below 3 X 10(6) C/m2, where corona discharger is not so effective, was also perfectly eliminated. It was found that the optimal distance between the beta-ray source and the sheet was 10 cm in the case of 147Pm. The use of 3H beta-ray source of 1 Ci was not satisfactory. These results demonstrate that 147 Pm beta-ray source operates most efficiently as static eliminator when the charge density of material and/or its moving speed is not high.

A method for the calculation of beta-ray dose.

Equations to calculate the dose rate to points internal and external to spherical homogeneous beta ray sources are given. These equations are derived from a general formulation based on polynomial representation of Berger's tabulated scaled absorbed doses. The dose distribution around a homogeneous spherical beta ray source of radius 75 microm emitting electrons of 32.4 and 23.8 keV is calculated and compared with similar calculations by Gavron and Feige.

Calculation of electron slowing down spectra--II. Classical cross sections.

Classical Coulomb cross sections, which make approximate allowance for binding of the atomic electrons, have been used for calculating electron slowing down spectra. The main results of binding is to increase the flux at low energy which improves agreement with experiment. Calculations were made for four specific cases of beta ray sources in aluminum, copper and gold for which experimental results are available. In a simplified, empirical version of the theory it was found that the calculations were in reasonable agreement with experiment down to about 300 eV for all three metals. However, attempts to improve the results by more detailed consideration of the electronic structure of the metals showed that the particular classical model on which these cross sections are based is not adequate.

Thermoluminescent Internal Beta-Ray Dosimetry

The possibility of using thermoluminescence for in vivo and in vitro direct dose measurements in tiny body cavities (for example, bone marrow) suggested investigation of the response to beta radiation of LiF and CaF2 powder and single crystals of different thicknesses (down to microns). Several beta-ray sources were made in the form of gelatin or polyester resin molds. The emitters consisted of ${}^{3}{\rm H},{}^{63}{\rm Ni},{}^{35}{\rm S},{}^{45}{\rm Ca},{}^{204}{\rm Tl}$ , and ${}^{90}{\rm Sr}({}^{90}{\rm Y})$ , and the absorbed dose rate was computed from the known concentration in each case. As expected, the thermoluminescent output per unit weight and per unit absorbed dose was essentially the same for ${}^{204}{\rm Tl}$ and ${}^{60}{\rm Sr}$ as for60 Co but dropped for the lower-energy beta-ray emitters. Among the factors considered which might account for the drop in light output were (1) the relation of the beta-ray ...