Beta Radiation Sources Research Articles

Doses from radon progeny as a source of external beta and gamma radiation

Great deal of work has been devoted to determine doses from alpha particles emitted by (222)Rn and its progeny. In contrast, contribution of beta particles and following gamma radiation to total dose has mostly been neglected so far. The present work describes a study of the detriment of (222)Rn progeny for humans due to external exposure. Doses and dose conversion factors (DCFs) were determined for beta and gamma radiation in main organs and remainder tissue of the Oak Ridge National Laboratory phantom, taking into account (222)Rn progeny (214)Pb and (214)Bi distributed in the middle of a standard or typical room with dimensions 4 m × 5 m × 2.8 m. The DCF was found to be 7.37 μSv/WLM. Skin and muscle tissue from remainder tissue receives largest dose. Beta and gamma radiation doses from external exposure were compared with alpha, beta, and gamma doses from internal exposure where the source of radioactivity was the lungs. Total doses received in all main organs and remainder tissues were obtained by summing up the doses from external and internal exposure and the corresponding DCF was found to be 20.67 μSv/WLM.

Depth-dose curves of the beta reference fields 147Pm, 85Kr and 90Sr/90Y produced by the beta secondary standard BSS2

The most common reference fields in beta dosimetry are the ISO 6980 series 1 radiation fields produced by the beta secondary standard BSS2 and its predecessor BSS. These reference fields require sealed beta radiation sources ((147)Pm, (85)Kr or (90)Sr/(90)Y) in combination with a source-specific beam-flattening filter, and are defined only at a given distance from the source. Every radiation sources shipped with the BSS2 is sold with a calibration certificate of the Physikalisch-Technische Bundesanstalt. The calibration workflow also comprises regular depth-dose measurements. This work publishes complete depth-dose curves of the series 1 sources (147)Pm, (85)Kr and (90)Sr/(90)Y in ICRU tissue up to a depth of 11 mm,when all electrons are stopped. For this purpose, the individual depth-dose curves of all BSS2 sources calibrated so far have been determined, i.e. the complete datasets of all BSS2 beta sources have been re-evaluated. It includes 191 depth-dose curves of 116 different sources comprising more than 2200 data points in total. Appropriate analytical representations of the nuclide-specific depth-dose curves are provided for the first time.

TRITIUM: RELATIVE BIOLOGICAL EFFECTIVENESS AND CANCER RISK

Background and Aims: The relationship between exposure to tritium, a source of beta radiation, and risk of cancer has received little attention in the epidemiological literature. For radiation protection purposes, and for radiation risk assessments, tritium dose and gamma radiation doses are often combined. This is done under the assumption that the biological effectiveness of the absorbed dose of tritium relative to the absorbed dose of gamma radiation, or RBE, is 1. In this paper, we utilize Bayesian methods in order to evaluate the excess relative rate (ERR) of leukemia and leukemia excluding CLL per unit of absorbed dose of tritium as well as its RBE compared to absorbed dose of gamma radiation. Methods: In order to conduct this analysis, we utilize an incidence density sampling procedure to select cases and controls from the Savannah River Site occupational cohort of workers employed from 1951-1999. Markov chain Monte Carlo methods are used for the analysis in order to incorporate informative priors. Results: The ERR/10mGy and associated 90% highest posterior density (HPD) of leukemia and leukemia excluding CLL are 0.272 (0.024, 0.660) and 0.304 (0.044, 0.753), while the RBEs are 8.36 and 5.36, respectively. Conclusions: This is the first empirical estimate of tritium’s relationship to cancer risk based on epidemiological data.

The PSIodine Code: A computer program to model experimental data on iodine and other species in irradiated CsI solutions sparged with argon, air, or nitrous oxide

Experimental study programmes were carried out at Paul Scherrer Institute (PSI), Switzerland on iodine behaviour under conditions relevant to postulated severe-accidents in NPP containments. To interpret the results obtained from bench-scale, gas-sparged and irradiated iodide solutions, a mechanistic computer code (PSIodine) was developed using the FACSIMILE Software to provide data for comparison. The code models reactions for the iodine oxidation states −1 to +5 in solution under strong (N 2O-saturated) and weak oxidising (argon- and air-saturated) conditions. An empirical model was developed to transport I 2 and other species from solution to the gas space by gas bubbles (sparging). By using measured I 2 mass transfer rates for specific reaction vessels, the need to apply assumptions, e.g., uniform and estimated bubble sizes and concentration, diffusion coefficients, was circumvented. By using the same I 2 transfer rate for irradiation of CsI solutions with and without additional ions, data for % I 2 yields for initial chemical conditions can be compared. Reaction rate changes due to solution evaporation are also modelled. The predicted and experimental data (I 2 fractional releases, pH changes and H 2O 2 formation) correlate well for initial CsI concentrations from 4.0 × 10 −5 to 1.0 × 10 −3 mol dm −3 and for pH 4.6–7.1 in weak oxidising systems (argon- and air-sparged solutions). Data correlations for strong oxidising conditions (N 2O-saturated CsI solutions) are also satisfactory. Irradiated containment atmospheres can generate oxides of nitrogen, which form nitrate and nitrite ions in the sump. Nitrate concentrations up to 5.0 × 10 −3 mol dm −3 in irradiated and argon or air-sparged CsI solutions can lower fractional I 2 release ( Cripps et al., 2011). The model confirms the observed trend of fractional I 2 releases for the pH range 4.6–7.1. Silver aerosols from control rods are postulated in PWR severe accidents to form AgI. The decomposition of aqueous colloidal suspensions of AgI was investigated using 188Re as an in situ beta-radiation source ( Güntay et al., 2005). Under strong oxidising conditions, large I 2 fractions were released. The described model predicts data which support the interpretation of the direct oxidation of AgI particle surfaces.

Silver addition in CaSO4:Eu, TL and TSEE properties

Abstract CaSO 4 :Eu with Ag incorporation was studied in order to evaluate the improvement in its response to dosimetry. Thermoluminescence and thermally stimulated exoelectronic of CaSO 4 :Eu,Ag showed responses to absorbed doses from a beta radiation source that were significantly enhanced when silver was incorporated as a co-dopant in the form of nanoparticles (NP).

COMPARISON OF TWO DIFFERENT TYPES OF LIF:MG,CU,P THERMOLUMINESCENT DOSIMETERS FOR DETECTION OF BETA RAYS (BETA-TLDS) FROM 90SR/90Y, 85KR AND 147PM SOURCES

Targeted radionuclide therapies in nuclear medicine departments increasingly depend on using unsealed beta radiation sources in the labeling of peptides and antibodies. Monitoring doses received by the fingers and hands during these procedures is best accomplished with TLD dosimeters that can be located at the fingertips. The present study examines the response of two TLD dosimeters (MCP-Ns and GR200A) to 90Sr/90Y, 85Kr, and 147Pm. The dosimeters were supplied by two different services, and all irradiations were performed at the PTB Institute in Germany. Each dosimetry service evaluated the dosimeters without knowledge that they had been purposefully irradiated. The accuracy and precision of the dosimeters were evaluated as a function of delivered dose, energy of beta particles and angular incidence. The results are compared to performance measures recommended by the IEC. Both dosimeter types displayed significant energy dependence. Angular dependence was moderate. Accuracy and precision as a function of dose (linearity) differed between the two systems, with the MCP-Ns being noticeably better than the GR200A. The superior precision makes the MCP-Ns much more useful for extremity dose measurements. The differences between these two dosimeter systems reinforce the need to evaluate a dosimeter carefully before using it in the daily work routine.

Effects of radiation on established forensic evidence containment methods

The Federal Bureau of Investigation (FBI) Laboratory is currently exploring needs and protocols for the storage of evidentiary items contaminated with radioactive material. While a large body of knowledge on the behavior of storage polymers in radiation fields exists, this knowledge has not been applied to the field of forensics and maintaining evidentiary integrity. The focus of this research was to evaluate the behavior of several traditional evidentiary containment polymers when exposed to significant alpha, beta, gamma, neutron and mixed radiation sources. Doses were designed to simulate exposures possible during storage of materials. Several products were found to be poorly suited for use in this specific application based on standardized mechanical testing results. Remaining products were determined to warrant further investigation for the storage of radiologically-contaminated evidence.

Doses in human organs due to alpha, beta and gamma radiations emitted by thoron progeny in the lung

This work consists of two parts. In the first part, the doses in the human lung per unit exposure to thoron progeny, the dose conversion factor (DCF), was calculated. Dependence of the DCF on various environmental and subject-related parameters was investigated. The model used in these calculations was based on ICRP 66 recommendations. In the second part, the human lungs were considered as the source of beta and gamma radiation which target the other organs of the human body. The DCF to other organs was obtained as 20 µSv WLM(-1), which is larger than the DCF for radon progeny, which was 13 µSv WLM(-1). This is a consequence of the longer half-life of the relevant thoron progeny than that of the radon progeny. It is interesting to note that after the lungs, where the radiation source is actually located, muscle tissue receives the largest dose.

Radiation protection in inhomogeneous beta-gamma fields and modelling of hand phantoms with MCNPX

The usage of beta-radiation sources in various nuclear medicine therapies is increasing. Consequently, enhanced radiation protection measures are required, as medical staff more frequently handle high-activity sources required for therapy. Inhomogeneous radiation fields make it difficult to determine absorbed dose reliably. Routine monitoring with dosimeters does not guarantee any accurate determination of the local skin dose (LSD). In general, correction factors are used to correct for the measured dose and the maximum absorbed dose received. However, strong underestimations of the maximum exposure are possible depending on the individual handling the process and the reliability of dose measurements. Simulations can be used as a tool for a better understanding of the maximum possible exposure depending on the individual-related handling. While measurements reveal the overall dose during the entire irradiation time of the dosimeter, simulations help to analyse sequences of action. Hence, simulations allow for tracking the points of highest absorbed dose received during the handling process. In this respect, simulations were performed using the MCNPX software. In order to investigate the LSD, two hand phantoms were used, a model based on geometrical elements and a voxel hand. A typical situation of radiosynoviorthesis, i.e. handling a syringe filled with (90)Y, was simulated. The results of the simulations show that the annual dose limit may be exceeded within minutes at the position of maximum absorbed dose received and that finger-ring dosimeters measure significantly different doses depending on their wearing position. It is of essential importance to wear the dosimeter properly and to use suitable correction factors with respect to the individual. Simulations are a suitable tool for ensuring reliable dose determination and may help to derive recommendations regarding radiation protection measures.

Beta radiation exposure of medical staff and implications for extremity dose monitoring

Sealed and unsealed beta radiation sources come into use to a greater extent in radiation therapy, e.g. for treating inflammatory joint diseases by radiosynoviorthesis (RSO), by injecting 90Y, 186Re or 169Er-solutions. Sealed 90Sr/90Y and 32P-sources or 188Re-liquid-filled balloon catheter are applied in vascular brachytherapy. Recently, 90Y-labelled antibodies are being successfully used in radioimmunotherapy (RIT) of malign lymphoma. Such practices require handling of high activities at small distances to the skin. Thus, the medical staff may be exposed to high beta doses. Investigations of the extremity exposure were performed at several workplaces, in particular during RSO treatments. The local skin dose (LSD), Hp(0,07), was measured with thin-layer TLD (LiF:Mg,P,Cu) fixed to the fingers (TLD-tapes). The findings indicate that the exposure of the staff can exceed the annual dose limit of 500 mSv when working at low protection standard. Routine monitoring of the extremity exposures with ring dosemeters appropriate to beta radiation and provided by the approved German dosimetry services was found to be needed. But even monitoring with these official 'beta-dosemeters' does mostly not give suitable results to demonstrate compliance with the dose limit. A study was conducted at RSO-workplaces in order reveal a correlation between doses measured with ring dosemeters and the maximum LSD obtained from the TLD-tapes. The results are discussed and conclusions for routine monitoring are drawn.

Dependência energética e angular de materiais termoluminescentes para monitoração beta

As dependências energética e angular de diferentes materiais termoluminescentes foram estudadas com o objetivo de verificar que tipo de detector seria o mais adequado para a monitoração de trabalhadores envolvidos com a radiação beta. Três tipos de pastilhas de CaSO4:Dy + teflon foram estudados. A dependência energética foi verificada usando-se fontes padrões de radiação beta (147Pm, 204Tl e 90Sr+90Y). A dependência angular foi verificada irradiando-se as amostras com feixes de radiação beta, variando-se o ângulo de incidência entre 0° e 90°. Os dosímetros de CaSO4:Dy + teflon + 10% C mostram-se os mais adequados para uso na monitoração de trabalhadores expostos à radiação beta, em relação às características estudadas.

RECONSTRUCTION OF EXTERNAL DOSE FROM BETA RADIATION SOURCES OF NUCLEAR WEAPON ORIGIN

In response to requests from the Department of Veterans Affairs, a methodology was developed to assess the external dose accrued by personnel in the vicinity of beta radiation sources of nuclear weapon origin. This methodology has been applied in support of the Nuclear Test Personnel Review (NTPR) Program implemented by the Department of Defense. As required by the Code of Federal Regulations (Title 32, Part 218 and Title 38, Part 3.311), the NTPR Program must evaluate radiological hazards from nuclear testing activities that include alpha particle, beta particle, neutron, and photon emissions from radionuclides. Prior to the development of this methodology, only photon and neutron radiations were explicitly quantified for external dose assessments in this program. Alpha radiation of external origin presents no risk for biological effects due to external dose potential to skin tissue because of the particle's very limited range. However, beta particles are sufficiently penetrating to have such potential. Methods are provided to quantify ionizing radiation doses to the skin and lens of the eye from beta radiation sources of nuclear weapon origin located external to the body. This formulation allows the estimation of beta dose from a film badge (gamma) dose or from an equivalent reconstructed gamma dose.

On the Radiolytic Decomposition of Colloidal Silver Iodide in Aqueous Suspension

The decomposition of aqueous colloidal suspensions of AgI induced by ionizing radiation was investigated under various conditions using 188Re as an in situ beta-radiation source. The suspensions were stabilized by an initial excess of either I- or Ag+ ions. Although the results were somewhat scattered, the following trends were observed. With an initial excess of I- and under strong oxidizing conditions (N2O sparging) at pH 2, ˜65% AgI was decomposed into nonvolatile and volatile iodine (ratio 2:1) for doses of ˜20 kGy, and up to ˜80% was decomposed (mostly nonvolatile iodine) at pH 5. Chloride ions greatly enhanced the volatile and lowered the nonvolatile fractions. Little decomposition (<10%) was obtained with air sparging at both pH 2 and pH 5. Chloride ions increased the maximum decompositions to ˜60% (˜47% volatile) and ˜20% (mainly nonvolatile iodine), respectively. With an initial excess of Ag+ with N2O sparging and at pH 2 and pH 5, very little volatile iodine was produced. The maximum decomposition was ˜20% after ˜20 kGy. Chloride ion addition at pH 2 had greatly enhanced the volatile iodine yield. The relevance of these results to the possible release of iodine to the environment following a nuclear reactor accident is discussed.

A 3D computer graphics approach to brachytherapy planning.

Intravascular brachytherapy (IVB) can significantly reduce the risk of restenosis after interventional treatment of stenotic arteries, if planned and applied correctly. In order to facilitate computer-based IVB planning, a three-dimensional reconstruction of the stenotic artery based on intravascular ultrasound (IVUS) sequences is desirable. For this purpose, the frames of the IVUS sequence are properly aligned in space, possible gaps inbetween the IVUS frames are filled by interpolation with radial basis functions known from scattered data interpolation. The alignment procedure uses additional information which is obtained from biplane X-ray angiography performed simultaneously during the capturing of the IVUS sequence. After IVUS images and biplane angiography data are acquired from the patient, the vessel-wall borders and the IVUS catheter are detected by an active contour algorithm. Next, the twist (relative orientation) between adjacent IVUS frames is determined by a sequential triangulation method. The absolute orientation of each frame is established by a stochastic analysis based on anatomical landmarks. Finally, the reconstructed 3D vessel model is visualized by methods of combined volume and polygon rendering. The reconstruction is then used for the computation of the radiation-distribution within the tissue, emitted from a beta-radiation source. All these steps are performed during the percutaneous intervention.

Recombination index of radiation quality of low-LET radiation

Recombination index of radiation quality (RIQ) was measured for X-rays ranging from 40 to 230 kVp, for accelerator beams of photons with energy of 7 and 9 MeV and for several gamma and beta radiation sources. The obtained values ranged from 0.8 for high-energy photons to 1.3–1.9 for X-rays. The peak value was observed for 241Am source and for 100 kVp X-rays with mean energy of about 55 keV. Values of RIQ reflect mean local ionisation density of investigated radiation and can be correlated with its relative biological effectiveness.

Centered versus noncentered source for intracoronary artery radiation therapy: A model based on the scripps trial

Background The Scripps Trial was a randomized study of intracoronary artery radiation therapy with iridium 192 used to treat restenotic vessels. We used the intravascular ultrasound data from the Scripps Trial to investigate whether a lumen-centered gamma or beta radiation source would reduce radiation dose heterogeneity compared with the noncentered source position used. Methods Analysis included 28 patients with stent placement in 20 native vessels and 8 saphenous vein grafts enrolled in this trial. Radiation dosimetry for gamma radiation was calculated to deliver 800 cGy to the far field target, provided the maximum dose to the near field target did not exceed 3000 cGy. Prescribed dosimetry for beta radiation by use of yttrium 90 was 1600 cGy at 2 mm distance from the source. Results The calculated average minimum source to target distance by use of a lumen-centered source increased by 0.18 mm from 1.70 ± 0.25 to 1.88 ± 0.36 mm, whereas the maximum distance decreased by 0.17 mm from 3.64 ± 0.60 to 3.47 ± 0.43 mm (P <.05). On the basis of these distances, the maximum radiation dose, as well as radiation dose heterogeneity (ratio of maximum to minimum), would have been reduced in 22 of 28 patients by use of a lumen-centered gamma or beta source (P <.005). The reduction in dose heterogeneity was substantially greater with a beta source compared with a gamma source (48% vs 16% reduction). Conclusions Centering of the intracoronary artery radiation therapy delivery catheter within the vessel lumen can significantly reduce radiation dose heterogeneity when compared with a noncentered source position. This dose reduction is substantially greater for a beta compared with a gamma source. (Am Heart J 2002;143:342-8.)

Optimization of a 90Sr/ 90Y radiation source train stepping for intravascular brachytherapy

Purpose: Intravascular brachytherapy (IVB), using Beta radiation sources, has been shown to reduce the risk of subsequent restenosis in patients suffering from in-stent restenosis. The Beta-Cath™ device (Novoste Corporation, GA) that is currently used for such treatment has a 3 cm long 90Sr/90Y radiation source train (RST). While this device can deliver a relatively uniform radiation dose to a target coronary vessel of ≤ 2.5 cm in length, treatment of longer vessel lengths is challenging since abutting or overlapping fields must be used, and the RST must be stepped to achieve target coverage. However, such stepping of the RST may produce hot/cold spots in the target. We have developed and herein present a deterministic optimization algorithm that modulates the RST dwell time and dwell position to minimize dose heterogeneity in the target vessel. The dose distributions resulting from uniform stepping and the optimized dwell patterns are compared.

Encapsulation of isotope on novel beta-emitting poly(ethylene terephthalate) surfaces.

Recent data indicate that intravascular betaa-irradiation from centrally located sources at the time of balloon angioplasty or stenting reduces proliferation of smooth muscle cells, neointima formation, and restenosis. In an effort to simplify radiation delivery, a novel beta-radiation source was developed based on the adsorption of 32P (phosphoric acid) by pH-sensitive chitosan hydrogel on a poly(ethylene terephthalate) balloon surface. To prevent the 32P-isotope desorption in the patient's blood, the adsorbed phosphoric acid was precipitated as CaHPO4 on the surface by a saturated Ca(OH)2/5% CaCl2 solution. Various polyurethanes were applied to seal the radioactive surface by the dip-coating method. The isotope off-rate results were determined. Optimal results were obtained by serially coating with two polyurethane solutions. This approach holds promise for simplifying and improving the safety, and minimizing the cost of intravascular brachytherapy.

Progress in clinical trials for coronary arterial restenosis using beta radiation sources

Vascular brachytherapy has yet taken the leap into progression from emerging technology to standard of care dependent on the outcome of clinical trials. Data collected from early pilot trials and on-going clinical trials indicate that such a progression is achievable. Three-year follow-up data from patients treated with intracoronary radiation for the prevention of restenosis are now available. Data from larger trials are being assessed using angiographic and intravascular ultrasound analysis. The beta radiation studies are demonstrating different levels of efficacy, raising new issues regarding dosimetry and potential complications. Past trials have examined the use of vascular brachytherapy for recurrence prevention of restenosis in patients with in-stent restenosis. New data related to the use of liquid-filled balloon systems and radioactive stent are also being collected. This article updates the current status of clinical trials in vascular brachytherapy utilizing beta emitters, highlighting preliminary results and assessing their implications for the development of this field.

A simple procedure for the fabrication of high activity beta-radiation sources of147Pm for use in beta-ray thickness gauges

A simple procedure is described for the fabrication of mCi level strong sources of147Pm radioisotope on a noble metal substrate like Palladium as a source for β−-ray thickness gauge. The procedure is based on the principle of internal electro-deposition of147Pm from aqueous solutions containing147Pm3+ ions, using metallic magnesium for the purpose. Investigations conducted towards ascertaining the adherence of the147Pm radioactivity onto the palladium substrate. Leaching studies conducted on these source indicated that the radioactive film is satisfactorily adherent to the palladium substrate, suggesting that the method can be used for fabricating satisfactorily safe high β−-activity sources of147Pm contained in small active dimensions. Results of leaching studies keeping the sources fully immersed in boiling water for 15 minutes are also presented.