The X-ray spectrometry is subject to a diversity of problems that distort the measured beam. To observe them, spectra from N20, N25, N30, N60, N80, and N100 radiation qualities were obtained and evaluated their non-correction impact in the values of mean energy when compared with the requirements on ISO 4037-1 standard. The error percentages calculated were 2%, 2%, 2%, 11%, 9%, and 6%, respectively, related to partial energy deposition, efficiency loss, and charge trapping. These results suggest the need for correction of measured spectra, mainly for voltages higher than 30 kV.
Purpose
The Fricke dosimeter has been shown to be a viable option as an absorbed dose standard. This work aims to provide the dose distribution in an irradiator container during blood irradiation using Fricke dosimetry.
Methods
Measurements were performed using a Gammacell Elan 3000 blood irradiator at Hemocenter in Rio de Janeiro, Brazil. A specific phantom was constructed and patented by the authors to perform these measurements. Fricke solution was prepared according to international protocols, and polyethylene bags filled with Fricke solution (n = 19) were spatially distributed within the phantom. Control bags were also submitted to the same process, except the irradiation. The irradiation time was calculated to give 25.7 Gy to the central portion of the phantom, the same dose used for blood bags.
Results
Encouraging results were obtained with an overall uncertainty of 2.1% (k = 1). The obtained results were compared with the doses calculated by the physicist from Hemocenter based on parameters provided by the manufacturer. The mean dose delivered to the Fricke bag in the center of the phantom (cavity 2) was 28.7 ± 0.5 Gy, which is 12% higher than the planned dose of 25.7 Gy.
Conclusions
The obtained results showed that the setup (Fricke and phantom) is able to perform dosimetry for blood irradiators. The delivered dose was higher than expected. This highlights the importance in controlling all the parameters during irradiation to ensure the correct dose for all irradiated bags.
A global need exists for new and more effective contrast agents for computed tomography and traditional X-ray modalities. Among the few options available nowadays, limitations imposed by industrial production, performance, and efficacy restrict the use and reduce the potential of both imaging techniques. The use of nanomaterials as new contrast agents for X-ray and computed tomography is an innovative and viable way to increase the options and enhance performance. In this study, we evaluated eight nanomaterials: hydroxyapatite doped with zinc (Zn-HA 10%); hydroxyapatite doped with strontium (Sr-HA 10%); hydroxyapatite without thermal treatment (HA 282 STT); thermally treated hydroxyapatite (HA 212 500 °C and HA 01.256 CTT 1000 °C); hydroxyapatite microspheres (HA microspheres); gold nanoparticles (AuNP); and graphene oxide doped with copper (Cu-GO). The results showed that for both imaging modalities; HA microspheres were the best option, followed by hydroxyapatite thermally treated at 1000 °C. The nanomaterials with the worst results were hydroxyapatite doped with zinc (Zn-HA 10%), and hydroxyapatite doped with strontium (Sr-HA 10%). Our data demonstrated the potential of using nanomaterials, especially HA microspheres, and hydroxyapatite with thermal treatment (HA 01.256 CTT 1000 °C) as contrast agents for X-ray and computed tomography.
Digital breast tomosynthesis (DBT) is a screening and diagnostic modality that acquires images of a breast at multiple angles during a short scan. The Selenia Dimensions (Hologic, Bedford, Mass) DBT system can perform both full-field digital mammography and DBT. The system acquires 25 projections over a 15° angular range (from −7.5° to +7.5°). X-ray spectroscopy is generally linked with a high-resolution semiconductor detector through a correction to its energy response function. The energy spectrum describes the radiation field, in which several quality parameters can be extracted, such as the effective energy, half-value layer and exposure. X-ray spectroscopy is usually performed with solid-state semiconductor detectors. Radiation dose is a concern in mammography, as the current protocols recommend that medical physicians evaluate mean glandular dose (MGD) as a part of service quality control. Studies are needed for radiation dose optimization from tomosynthesis patients. The COMET metrological X-ray tube, considered as with a constant potential and cooled, has proved to be a crucial tool in order to obtain the high energy resolution for low-energy radiographs in mammography. The Monte Carlo method, through Monte Carlo N-Particle eXtended (MCNPX), was proven to be an essential tool for image formation and posterior analysis of the deposited dose from breast simulators and radiographic contrast evaluation, for several anode/filter combinations. The purpose of this work was to assess the MGD and spectra in slabs of polymethyl methacrylate (PMMA) and breast equivalent thicknesses using four experiments with a Hologic Selenia Dimensions mammography X-ray tube with multimeter, a spectrometer (only for spectra, in this case), a metrological X-ray tube with a multimeter, and the MCNPX code. References indicate that the real conditions for a mammography X-ray tube that conducts tomosynthesis include tube voltages of 26, 29, 30 and 33 kVp. Taking into account several thicknesses of PMMA, both the MGD and spectral results were in accordance with the references. Most of the spectra were in accordance with the references, showing that the resources used in the experiments can evaluate the energy level received by a patient. The MGD values were lower than those in the references from 30 to 50 mm PMMA, and the data can be used for improvements in the detectors used in the Laboratory of Metrology in the State of Rio de Janeiro University, Brazil. Additionally, in the future, optimization of image quality can be performed for both semiconductors and mammography X-ray equipment.
The objective of the present work was to study the feasibility of the use of an ionization chamber dedicated to mammography in the characterization of radioprotection qualities referring to the series of narrow spectrum beams provided by ISO 4037-1. The results were satisfactory, and we conclude that it is feasible to use the ionization chamber dedicated to mammography to characterize the radiation protection qualities ISO-N15 to ISO-N120.
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