experimental verification of alpha dose rate calculated using statistic method (original) (raw)
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Using targeted ligands to deliver alpha-emitting radionuclides directly to tumor cells has become a promising therapeutic strategy. To calculate the radiation dose to patients, activities of parent and daughter radionuclides must be measured. Scintillation detectors can be used to quantify these activities; however, activities found in pre-clinical and clinical studies can exceed their optimal performance range. Therefore, a method of correcting scintillation detector measurements at higher activities was developed using Monte Carlo modeling. Because there are currently no National Institute of Standards and Technology traceable Actinium-225 (225Ac) standards available, a well-type ionization chamber was used to measure 70.3 ± 7.0, 144.3 ± 14.4, 222.0 ± 22.2, 299.7 ± 30.0, 370.0 ± 37.0, and 447.7 ± 44.7 kBq samples of 225Ac obtained from Oak Ridge National Lab. Samples were then placed in a well-type NaI(Tl) scintillation detector and spectra were obtained. Alpha particle activity f...
Estimation Method for Alpha Particle Counting Efficiency for Scintillation Flasks
Radiation Protection Dosimetry, 1997
Fluence-to-absorbed dose conversion coefficients and their variations with angle of incidence have been computed for monoenergetic beams of electrons incident on rod and pillar ICRU-tissue phantoms used for calibration of ring and wrist or ankle dosemeters for measurement of personal dose equivalent to the skin. Beams are normal to the axes of the cylindrical phantoms. For normally incident electrons, conversion coefficients for both the rod and pillar phantoms are equal to those for the slab phantom. However, they differ markedly from each other and from those for the slab phantom at electron angles of incidence as great as 90°, as measured between the beam direction and an inward directed radius through a dose point at distance 0.007 cm beneath the surface of the phantom. * By mass, 76.2% oxygen, 11.1% carbon, 10.1% hydrogen, and 2.6% nitrogen (1) .
Medical Physics, 2016
In targeted radionuclide therapy, regional tumors are targeted with radionuclides delivering therapeutic radiation doses. Targeted alpha therapy (TAT) is of particular interest due to its ability to deliver alpha particles of high linear energy transfer within the confines of the tumor. However, there is a lack of data related to alpha particle distribution in TAT. These data are required to more accurately estimate the absorbed dose on a cellular level. As a result, there is a need for a dosimeter that can estimate, or better yet determine the absorbed dose deposited by alpha particles in cells. In this study, as an initial step, the authors present a transmission dosimetry design for alpha particles using A549 lung carcinoma cells, an external alpha particle emitting source (radium 223; Ra-223) and a Timepix pixelated semiconductor detector. Methods: The dose delivery to the A549 lung carcinoma cell line from a Ra-223 source, considered to be an attractive radionuclide for alpha therapy, was investigated in the current work. A549 cells were either unirradiated (control) or irradiated for 1 /2, 1, 2, or 3 h with alpha particles emitted from a Ra-223 source positioned below a monolayer of A549 cells. The Timepix detector was used to determine the number of transmitted alpha particles passing through the A549 cells and DNA double strand breaks (DSBs) in the form of γ-H2AX foci were examined by fluorescence microscopy. The number of transmitted alpha particles was correlated with the observed DNA DSBs and the delivered radiation dose was estimated. Additionally, the dose deposited was calculated using Monte Carlo code SRIM. Results: Approximately 20% of alpha particles were transmitted and detected by Timepix. The frequency and number of γ-H2AX foci increased significantly following alpha particle irradiation as compared to unirradiated controls. The equivalent dose delivered to A549 cells was estimated to be approximately 0.66, 1.32, 2.53, and 3.96 Gy after 1 /2, 1, 2, and 3 h irradiation, respectively, considering a relative biological effectiveness of alpha particles of 5.5. Conclusions: The study confirmed that the Timepix detector can be used for transmission alpha particle dosimetry. If cross-calibrated using biological dosimetry, this method will give a good indication of the biological effects of alpha particles without the need for repeated biological dosimetry which is costly, time consuming, and not readily available.
Radiobiological Research and Dosimetry Using a Flat Alpha Source
RAP 2019 Conference Proceedings
The irradiation system consisting of an α-source and disc holder has been developed in the Heavy Ion Laboratory, University of Warsaw. A simple exposure system for irradiation of biological samples consists of the Am-241 disc source, source holder and biological samples cultured in special Petri dishes. The irradiation system has been investigated to determine the alpha spectrum and dose distribution in irradiated single cell layer attached to the Mylar foil. Commercial Am-241 disc source of 50 mm in diameter, with a radioactive element embedded into a substrate layer was examined to established the uniformity of surface radioactivity over the disc source. The experimental device is equipped with cell dishes of 40 mm in diameter and a 6 µm thick Mylar foil bottom. Care was taken for homogenous irradiation of the cells. Dose calibration for the irradiation system was calculated taking into account source-to-target geometry.
Journal of Radioanalytical and Nuclear Chemistry, 2013
Studies and evaluations of the main parameters of a high resolution multi-chamber alpha spectrometer and its full calibration using standard sources of 241 Am, 233 U and 244 Cm are presented for the validation of the complex method of characterization of an alpha spectrometer dedicated for alpha radioactive concentration measurements of various environmental samples. The resolution and efficiency were determined at all possible source-detector distances for all eight solid state ORTEC ULTRA-AS detectors. In addition, the solid angles associated to different measurement geometries and the repeatability of the results were assessed. A detailed inter-comparison of the results was performed drawing important conclusions regarding the quality of the alpha detector response to the alpha radiation of the standard sources used in measurements.
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.
Assessment of natural and man-made alpha emitting radionuclides
International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements, 1988
Damage track detectors have unique capabilities for measuring low concentrations of natural and man-made alpha emitters in biological and environmental samples. Mith electronic devices such as surface-barrier detectors, zinc-sulphide screen counters and large arsa grid ionization chambers, the detection sensitivity ie limited by the duration of exposure or the stability of electronic counting systems. Damage track detectors can be used for eu£ficisntly long exposure periods so that the intrinsic background of the detector material can be ignored. In particular, the applications of damage track detectors, described in this paper, re£er to the assessment o£ low concentrations of Uranium, Plutonium and radon, using the registration of alpha-particle and fissionfragment tracks. The sensitivity and the simplicity of track counting can be greatly enhanced by using the spark counter.
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.