Measurement of activity distribution in an Am-241 disc source using peeled-off Gafchromic EBT3 films

Abstract

Commercial alpha-emitting sources are fabricated mainly in a disc type. An alpha particle irradiator in Radiation Bioengineering Laboratory at Seoul National University was installed with an Am-241 disc source. Commercial Am-241 disc sources are fabricated by incorporating the radioactive element into a thin substrate layer. Those disc sources are utilized assuming that the radioactive element is uniformly distributed in the active layer of disc sources. In this study, we employed peeled-off Gafchromic EBT3 films to investigate the uniformity of areal radioactivity density over the disc source and to measure the effect of non-uniform activity distribution on dose distribution at the bottom of the cell culture dish positioned in a varying distance from the source. The measurements with the peeled-off EBT3 films informed that the areal activity density in the disc source differed by up to approximately 45% from the average. However, the inhomogeneous Am-241 distribution in a disc source did not affect the radial distribution of fluence rate at the inner bottom of cell dish when the dish is apart from the source sufficiently. The dose distribution measured with an EBT3 film nearly accorded with that obtained by Monte Carlo simulation assuming the uniform Am-241 activity distribution in the active layer of the disc source. Finally, the dose to a single-cell layer of 5 μm in a nominal thickness was obtained by Monte Carlo simulation assuming a uniform Am-241 activity distribution in the disc source at distances of 20 and 30 mm from the source. The cellular dose estimates were higher than the film dose estimates at all radial distances. The cellular dose decreased with an increasing radial distance from the center to a smaller extent than the EBT3 film dose did.

Development and evaluation of a standard for absorbed dose to water from alpha-particle-emitting radionuclides

“…The FWHM of the E&Z 210 Po source was measured to be 25.58 keV using alpha spectroscopy (ORTEC Alpha Aria). The radius of the source was measured using unlaminated radiochromic films (EBT3 Ashland, NJ) and was determined to be 1.60 ± 0.30 mm [24]. Following the alpha spectroscopy and unlaminated EBT3 measurements, the source substrate was mounted on the source subassembly for ionization current measurements.…”

Low energy alpha particles dose mapping with a combination of CR-39 detector and a high resolution flatbed scanner

“…The resultant photomicrographs were analyzed using ImagJ software and compared the performance of the two scanning methods. Since the available microscope in our laboratory has a camera with a 2 8 -pixel color depth, the image of the scanner has been reduced from 2 16 bit to 2 8 bit to facilitate the comparison with the optical microscope.…”

“…Polymer-based solid state nuclear track detectors, including the CR-39 detector and polycarbonate (Makrofol and Lexan) detectors, are being successfully applied in heavy ion measurements and neutron radiography [1][2][3][4][5]. On the other hand, self-developing radiochromic films such as Gafchrmoic EBT3 and HD-V2 are utilized effectively in energetic heavy ions dose mapping, which is a prerequisite for radiotherapy, in the range of 0.2 Gy to 10 Gy, where the radiochromic films are readout using a variety of film scanners [6][7][8].…”

On the randomness and correlation in the trajectories of alpha particle emitted from ${}^{241}$Am: Statistical inference based on information entropy

“…Refs. [8][9][10][11][12][13][14][15][16]) had shown that the distribution of alpha particle tracks was neither uniform nor random, whatever the precaution made to make such a fact obvious. The reason may be any process from the decay to the registration on the detector surface.…”