experimental verification of alpha dose rate calculated using statistic method (original) (raw)
Beta Measurements for Dose Estimation
The difficulties in performing beta dose rate measurements and consequently estimating the deep and shallow dose equivalents are discussed. Simple instruments may respond well to photon calibration sources, but are inaccurate in practical situations where energetic electrons and low energy photons are present. Approaches to making field estimates are described, as well as two new types of instruments that have been developed at the Idaho National Engineering Laboratory.
Proceedings of 10th Latin American Symposium on Nuclear Physics and Applications — PoS(X LASNPA), 2014
Nuclear medicine clinical practices for neoplasic disease diagnose and treatment are based on the incorporation of α, β and γ radiotracers and radiopharmaceuticals, which might be associated with potential damage. Thus, being necessary accurate dosimetry strategies. In vivo absorbed dose appears as an ideal solution. However, its implementation in clinics does not attain enough reliability. In this sense, different approaches were proposed for internal dosimetry calculations. This work presents a novel analytical-numerical approach for internal dosimetry purposes. Dedicated Monte Carlo simulations were performed by subroutines adapted from the FLUKA code. In-water EDK were evaluated at different photon energies and some typical γ-emitters radiopharmaceuticals; whereas DPK were obtained for both α-and β-emitters. Additionally, EDK and DPK were calculated for several biological tissues.
Alpha counting using scintillation techniques: Observations on TSAC calibration and gas cell use
Radiation Measurements, 1997
Akstract-Two aspects of alpha counting using the scintillation technique in the field of luminescence and ESR dating are addressed. The first part of the article concerns the evaluation of the proportion of radon that emanates out of the studied samples. A modified version of the gas-cell developed in the Research Laboratory for Archaeology and the History of Art, Oxford, was used for this purpose. Basically the new cell shows a reduced volume above the ZnS screen. This geometry is intended to hinder thermal convection, which is suspected to be responsible for the irregular shifts in counting efficiency that are observed with the Oxford cell. It is demonstrated that the modified cell can be calibrated without sources of known emanation, unlike the Oxford cell. The second part of the article deals with the calibration of the Thick Source Alpha Counting technique (TSAC). This is usually achieved by adjusting the threshold of the electronic discriminator, according to certain rules, by means of standard samples. In the present study, calibration was achieved by comparing the observed count rate to the predicted count rate using a set of archaeological and geological samples of well known uranium and thorium contents. The results are discussed.
2000
The development of a spallation neutron source with a mercury target may lead to the production of rare radionuclides. The dose coefficients for many of these radionuclides have not yet been published. A collaboration of universities and national labs has taken on the task of calculating dose coefficients for the rare radionuclides using the software package: DCAL. The working group developed a procedure for calculating dose coefficients and a quality assurance (QA) program to verify the calculations completed. The first portion of this QA program was to verify that each participating group could independently reproduce the dose coefficients for a known set of radionuclides. The second effort was to divide the group of radionuclides among the independent participants in a manner that assured that each radionuclide would be redundantly and independently calculated. The final aspect of this program was to resolve any discrepancies arising among the participants as a group of the whole. The output of the various software programs for six QA radionuclides, 144 Nd, 201 Au, 50 V, 61 Co, 41 Ar, and 38 S were compared among all members of the working group. Initially, a few differences in outputs were identified. This exercise identified weaknesses in the procedure, which have since been revised. After the revisions, dose coefficients were calculated and compared to published dose coefficients with good agreement. The present efforts involve generating dose coefficients for the rare radionuclides anticipated to be produced from the spallation neutron source should a mercury target be employed.
The British Journal of Radiology, 2015
To develop an alpha dosimetry technique for activity calibration of alpha-emitting radiopharmaceuticals using the Gafchromic® EBT3 (Gaf-EBT3) radiochromic film (International Speciality product, Wayne, NJ). Methods: The Gaf-EBT3 has a tissue equivalent radiosensitive layer (approximately 28 mm) sandwiched between two 100-mm thick polyester sheaths, thereby making it insensitive to alpha particles. We have split a Gaf-EBT3 sheet using a surgical scalpel to remove one of the polyester protective layers and covered the radiosensitive layer with thin Mylar® foil (Goodfellow Cambridge Limited, Huntingdon, UK) (2.5 mm). Small pieces of modified film were exposed at contact with a 560-Bq thin 241 Am source for 5, 10, 24 and 94 h. The optical density of the films was evaluated using an optical densitometer. The alpha energy spectra of the 241 Am source were recorded using a Si(Li) surface barrier detector. Results: Time-integrated specific alpha surface activity (kBq cm 22 h) was represented as a function of optical density. Conclusion: By removing one of the 100 mm thick polyester protective layers, the authors have modified the Gaf-EBT3 film to a sensitive alpha dosemeter. The calibration function relevant to a 241 Am reference source was evaluated from the optical densities of the dosemeter foils. Furthermore, calibration functions for important alpha emitters such as 223 Ra, 225 Ac or 210 Bi were parameterized from the 241 Am reference data. Advances in knowledge: The authors have developed and tested the principle of a clinical alpha dosemeter using Gaf-EBT3 radiochromic films originally developed for photon dosimetry. This novel, user-friendly technique could be implemented in quality assurance and calibration procedures of important alpha-emitting radiopharmaceuticals prior to their clinical applications.
Comparative Study of a Multiple-element Dosimeter by Means of an Empirical Formula
In Algeria, the individual monitoring of workers occupationally exposed to external radiation (estimated at 10.000 workers) is carried out mainly by photographic dosimetry. This dosimetry, based on the use of traditional empirical formulas, for the measurement of individual dose equivalent, introduced unacceptable uncertainties in accordance with the new international recommendations (ICRP, ICRU, IAEA). However, many works undertaken recently, particularly the implementation of numerical methods suitable for the measurement of individual dose equivalent, allowed us to reach real progress in the field of photographic dosimetry. A sophistical algorithm enabling the evaluation of doses, for mixed radiation fields (X, γ), from the measurement of apparent doses under the various filter elements, is explained in the present paper.. In this study, a dosimeter standard PS1 which consists of an Eastman Kodak Type 2 film sandwiched within a film holder, was used. The energy response beneath each filter was determined over a photon energy range of 20 keV – 1.3 MeV, selected from series of reference radiations recommended by the International Standards Organisation (ISO) reference 4037-1. Two procedures allowing the evaluation of the individual dose equivalent have been tested, one developed by the Nuclear Research Center of Algiers (CRNA) based on an empirical formula, the second based on the Simplex algorithm method, stemmed from a software of linear programming developed by Frontline Systems Inc. The results obtained showed that the Simplex method, applied to the film dosimeter, gives better accuracy on the nature and the quantity of exposure in an unknown mixed radiation field.
PLOS ONE
Over the last decade, the γ-H2AX focus assay, which exploits the phosphorylation of the H2AX histone following DNA double-strand-breaks, has made considerable progress towards acceptance as a reliable biomarker for exposure to ionizing radiation. While the existing literature has convincingly demonstrated a dose-response effect, and also presented approaches to dose estimation based on appropriately defined calibration curves, a more widespread practical use is still hampered by a certain lack of discussion and agreement on the specific dose-response modelling and uncertainty quantification strategies, as well as by the unavailability of implementations. This manuscript intends to fill these gaps, by stating explicitly the statistical models and techniques required for calibration curve estimation and subsequent dose estimation. Accompanying this article, a web applet has been produced which implements the discussed methods.
Evaluation of the gamma dose distribution comparison method
Medical Physics, 2003
The ␥ tool was developed to quantitatively compare dose distributions, either measured or calculated. Before computing ␥, the dose and distance scales of the two distributions, referred to as evaluated and reference, are renormalized by dose and distance criteria, respectively. The renormalization allows the dose distribution comparison to be conducted simultaneously along dose and distance axes. The ␥ quantity, calculated independently for each reference point, is the minimum distance in the renormalized multidimensional space between the evaluated distribution and the reference point. The ␥ quantity degenerates to the dose-difference and distance-to-agreement tests in shallow and very steep dose gradient regions, respectively. Since being introduced, the ␥ quantity has been used by investigators to evaluate dose calculation algorithms, and compare dosimetry measurements. This manuscript examines the ␥ distribution behavior in two dimensions and evaluates the ␥ distribution in the presence of data noise. Noise in the evaluated distribution causes the ␥ distribution to be underestimated relative to the no-noise condition. Noise in the reference distribution adds noise in the ␥ distribution in proportion to the normalized dose noise. In typical clinical use, the fraction of points that exceed 3% and 3 mm can be extensive, so we typically use 5% and 2-3 mm in clinical evaluations. For clinical cases, the calculation time is typically 5 minutes for a 1ϫ1 mm 2 interpolated resolution on an 800 MHz Pentium 4 for a 14.1ϫ15.2 cm 2 radiographic film.
Internal microdosimetry of alpha-emitting radionuclides
Radiation and Environmental Biophysics
At the tissue level, energy deposition in cells is determined by the microdistribution of alpha-emitting radionuclides in relation to sensitive target cells. Furthermore, the highly localized energy deposition of alpha particle tracks and the limited range of alpha particles in tissue produce a highly inhomogeneous energy deposition in traversed cell nuclei. Thus, energy deposition in cell nuclei in a given tissue is characterized by the probability of alpha particle hits and, in the case of a hit, by the energy deposited there. In classical microdosimetry, the randomness of energy deposition in cellular sites is described by a stochastic quantity, the specific energy, which approximates the macroscopic dose for a sufficiently large number of energy deposition events. Typical examples of the alpha-emitting radionuclides in internal microdosimetry are radon progeny and plutonium in the lungs, plutonium and americium in bones, and radium in targeted radionuclide therapy. Several micro...
Introduction of a Reliable Software for the Calculation of the Gamma Index
Iranian Journal of Medical Physics, 2020
Introduction: The gamma index is a known parameter for radiotherapy dose verification. Many free and commercial programs have been written for the calculation of this index. However, the verification of the results has been overlooked in many of the programs. The present study tested the validity of three gamma index calculator programs. Material and Methods: The gamma indices for three measured and calculated dose distribution pairs presented in Low et al., Medical Physics, (1998) were calculated using three programs to compare with the results of the published paper. They included an executable program working in Gnuplot software environment (i.e., Gamma_index.exe), simple implementation of the formulas by MATrix LABoratory (MATLAB) software (i.e., Simple m-file), and CalcGamma MATLAB-based program distributed at GitHub website (i.e., Geurts). The resulted gamma distributions were compared with the three figures of the study by Low et al. Results: According to the results, it was ...