Radiation Detection Instruments Research Articles

Establishment of beam qualities for medical applications (mammography and CT) in the gamma and X calibration laboratory of CNESTEN according to EN 61267 standards

The present study aimed to validate the different radiodiagnostic beam qualities (RQT, WAH and WAV) by the measurements of the X-ray beams HVL of a HOPEWELL generator, X80-225 kV from a high voltage range of 10 at 200 kV, at CNESTEN Gamma and X Calibration Laboratory. The experiments were carried out using the PTW TN 32005 ionization chamber, established at 100 cm from the center of the X-ray tube and connected to a SUPERMAX electrometer. The HVL values were measured by applying the attenuation law to the flow of Kair air kerma, including their uncertainties. The obtained HVL values were compared with standard values of diagnostic levels. It was observed that the HVL of the present X-ray machine in most qualities are smaller than the standard ones. An approved method (described in the STANDARD EN 61267 and IAEA TECHNICAL REPORTS SERIES n° 457) was applied to determine the amount of additional filtration required to meet the standard values, and by checking their compliance with the maximum absolute deviation. The results indicate the adequacy of the LEGX laboratory for the calibration of the radiation detection instruments used in computed tomography and mammography with an expanded uncertainty in the best measurement capability of ±4 % (k = 2).

Chemical, Biological, Radiological, and Nuclear Preparedness of Public Hospitals in Riyadh.

Chemical, biological, radiological, and nuclear (CBRN) incidents are those that involve chemical or biological warfare agents or toxic radiological or nuclear materials. These agents can cause disasters intentionally or accidentally. Hospitals play a crucial role in handling CBRN disasters. This study aimed to assess the CBRN preparedness of government hospitals in Riyadh. A descriptive cross-sectional study was conducted across government hospitals in Riyadh. All government hospitals with more than 100 inpatient beds and an emergency department met the inclusion criteria. Hospital preparedness was assessed using an adaptation of the CBRNE (chemical, biological, radiological, nuclear, or explosive event) Plan Checklist. This adaptation was chosen due to the inclusion of explosive events in hospital disaster readiness, and its structural composition of key clinical guidelines necessary for a comprehensive disaster and readiness plan. Results were described in frequencies across several domains such as foundational considerations and planning which are used to assess plan preparedness using readiness tools, training, and awareness among staff members in accordance to a pre-established emergency plan, placed procedures and their implementation, and modules for preparing for a biological incident, a chemical incident, and a radiological or nuclear incident. Of the 11 eligible hospitals, 10 participated in the study. Furthermore, CBRN considerations were included in the disaster plans of 7 hospitals. Drills had been conducted in collaboration with local agencies in only 2 hospitals. The staff had been trained to recognize the signs and symptoms of exposure to class (A) biological agents in less than half of the hospitals. Eight of the hospitals had antidotes and prophylactics to manage chemical incidents, but only half of them had radiation detection instruments. Personal protective equipment was available in all hospitals, but rapid access to stockpiles of medications was available in only half of them. Government hospitals in Riyadh demonstrated insufficient CBRN preparedness as per the CBRNE Plan Checklist. Overall, there was a lack of preemptive planning, application of pre-established policies and procedures, and adequate staff training. Furthermore, several hospitals had insufficient stockpiles of medications and in concrete plans on accessing government stockpiles in the case of an emergency. Therefore, their staffs should be trained to manage CBRN emergencies, and local drills should be conducted to improve their preparedness.

Academic program recommendations for graduate degrees in medical physics: AAPM Report No. 365 (Revision of Report No. 197).

Academic program recommendations for graduate degrees in medical physics: AAPM Report No. 365 (Revision of Report No. 197).

Simultaneous, Robot-Compatible γ-Ray Spectroscopy and Imaging of an Operating Nuclear Reactor

The design and test of a robot-compatible, radiation detection instrument providing simultaneous $\gamma $ -ray imaging and $\gamma $ -ray spectroscopy is described. The sensing system comprises a cerium bromide inorganic scintillation detector and a cylindrical, lead slot collimator that is configured with a robot-compatible, on-board data acquisition system. The mount for the sensor is a lightweight, bespoke 3-axis gimbal actuated by servos for pan, tilt and rotation of the collimator for imaging capability. This paper discusses the integration of this relatively low-cost radiation detection apparatus with a commercially available, Robot-Operating-System-controlled robotic platform (a Clearpath Robotics™ Jackal). The detection system is compliant with the power and mass payload constraints of the robot. Its performance has been evaluated by means of two practical examples: a) measurements in a laboratory environment to assess the ability of the system to resolve two caesium-137 point sources, and b) deployment at the Jožef Stefan Institute TRIGA Mark II research reactor to assess the ability of the system to characterise the $\gamma $ -ray emission at 1 kW from a horizontal tangential beam port in the reactor hall and from the reactor sample pool above the core.

GUIMesh: A tool to import STEP geometries into Geant4 via GDML

Detailed radiation analysis of instruments flown in space is critical to ensure mission safety, often requiring the use of state-of-the-art particle transport simulation tools. Geant4 is one of the most powerful toolkits to simulate the interaction and the passage of particles through matter, but it is not prepared to receive Standard for The Exchange of Product data (STEP) files, the most versatile Computer-Aided Design (CAD) format, as input, requiring previous conversion to other CAD formats. This may lead to loss of detail and under or overestimation of the quantities under study, especially when the instruments have complex shapes, and/or a large number of volumes. Though several solutions have been proposed to import complex geometries from STEP files into Geant4, so far, only commercial options are available. In this paper we present a new tool, GUIMesh, that embeds FreeCAD libraries, an open-source CAD editor, to tessellate volumes, and convert them to Geometry Description Markup Language (GDML), a Geant4 readable format, in a straightforward way. Several degrees of freedom are given to the user regarding mesh precision and choice of material. Different geometries were tested for material definition, geometry and navigation errors, and the method used was successfully validated. Program SummaryProgram Title: GUIMeshProgram Files doi: http://dx.doi.org/10.17632/c3c9xbspzp.1Licensing provisions: GNU General Public License 3 (GPLv3)Programming language: PythonNature of problem: No open-source software allows to import STEP geometries intro Geant4, one of the most powerful toolkits to simulate radiation interaction with matter. Since CAD software is extensively used in the design of particle and radiation detection instruments, it is highly desirable for physicists that STEP geometries can be imported to Geant4 with little effort instead of having to code structures made of a very large number of solid volumes which are difficult to accurately reproduce with Geant4 C++ classes.Solution method: STEP geometries are converted to tessellated volumes (with some margin of error) using FreeCAD libraries. A Python script then writes GDML files based on the results allowing users to import these geometries with Geant4. A graphical user interface provides several options to the user, including material assignment and mesh precision setting for each volume.

Materials for Gamma-Ray Spectrometers: Inorganic Scintillators

Scintillation detectors constitute an important branch of radiation detection instrumentation. The discovery of the inorganic scintillating compound thallium-activated sodium iodide (NaI:Tl) in 1948 was key to the production of the first practical gamma-ray spectrometer. Since that time, numerous inorganic scintillators have been discovered and studied. Many of the more successful inorganic scintillators are described, including discussion of their properties and performance, in this article.

Measurements of Scatter Peaks in 137Cs and 60Co Sources.

Results from tests of radiation detection instruments with radionuclide identification capabilities will depend on the sources used for the tests. Radionuclide identification detectors are designed to measure photons and provide an identification of the source being measured. High-resolution spectra need to be acquired to determine all the observable peaks in the source spectra before testing these types of instruments. These peaks may be due to impurities and/or scatter peaks in the sources. This paper discusses the issues encountered with the response of a radioisotope identification device due to scatter peaks in one type of source used for testing. In addition, it provides spectra for different source types and source constructions to compare the differences in scatter, allowing for a better source type selection for instrument testing.

Ligand-Mediated Control of Dopant Oxidation State and X-ray Excited Optical Luminescence in Eu-Doped LaOCl.

The development of an expanded palette of X-ray phosphors is a critical imperative for applications in medical imaging, radiation detection, and scientific instrumentation. The rational design of X-ray phosphors has been stymied by the absence of fundamental understanding of activation channels, sensitization mechanisms, and recombination pathways induced upon high-energy excitation of luminescent centers. In this article, we describe the preparation of Eu-doped LaOCl nanocrystals based on the condensation of molecular precursors. The synthetic route allows for control of the oxidation state of the incorporated Eu-atoms based on ligand-induced oxidation or reduction of the Eu-precursors. Nanocrystals exhibiting blue and red X-ray excited optical luminescence are developed by tuning the oxidation state of europium ions incorporated within the LaOCl nanocrystal matrix. Pronounced modulation of the intensity of the optical luminescence is evidenced at and near the giant resonance absorption of the host matrix as a result of distinctly divergent recombination channels. Resonant excitation results in recombination via Auger electron ionization and relaxation of a single electron-hole pair, whereas excitation away from the giant resonance results in thermalization of "hot" electron-hole pairs, while launching cascades of energy transfer, excitation, and radiative recombination events at the Eu-luminescent centers. Mechanistic elucidation and the development of a generalizable synthetic route starting from molecular precursors paves the way to an expanded palette of X-ray phosphors.

Enhanced Scintillation Light Extraction Using Nanoimprinted Photonic Crystals

The extraction of scintillation light from a crystal with high efficiency and low time jitter is vital for realizing much-needed gains in the performance of numerous radiation detection and imaging instruments that are vital components in medical imaging, industrial, and homeland security applications for the detection, localization, and energy classification of X-rays, $\gamma $ -rays, or neutrons. Nanostructures such as photonic crystals (PhCs) maximize extraction of usable scintillation light that is otherwise lost when a high refractive index (RI) scintillator is coupled to a photodetector with low RI window. The PhC gradually changes the RI between the scintillator and photodetector, thereby substantially improving the light extraction efficiency, as well as the energy resolution (ER) and timing resolution. Here, we report on improvements in the light extraction and ER of inorganic scintillators using PhCs nanoimprinted in high RI polymers. Details of the design, fabrication, and characterization of the PhCs, the high RI polymers, and their impact on scintillator performance are presented here.

Some key issues of X/gamma-ray detection in space

Space as a frontier of scientific exploration and discovery, basic and extreme environment engineering research laboratory has its own unique advantages. In the study of space science exploration, whether it is a natural physical phenomenon research, or outside resources, disaster and security application, X/gamma-ray detection has become an indispensable necessity. There are many unsolved mysteries of science of nature, its exploration and research are closely related to X/gamma-ray radiation detection, key scientific issues are: supernovae, black hole formation, Lunar and planetary evolution and the origin of the universe, dark matter and dark energy; and outer space resources available; national security and space research, and so on. In addition, the space X/gamma-ray radiation detection research and application is different from the ground-based observation, as launches and space environment requirements, space radiation detection instruments not only have good performance, but also should have a high and reliable quality. Therefore, there are some of key technical problems to be overcome. This paper consists of three main parts. In the first part, described as an integrated lab space has in the radiation field, high vacuum, microgravity, comprehensive and wide field of view, and other features, the peaceful use of space will bring enormous benefits for human development and wide space, and given in table development status in worldwide, it describes several big space nations to solve the scientific fundamental problems and key technical challenges, made a series of research strategy or projects, and gradually promote the implementation. Highlight five trends that are targeted to explore unknown space science and to develop deep space: the first is exploring the unknown space science, developing deep space exploration; the second is challenging human innovation, which is the development of advanced space technology and detection technology; the third is based on advanced intelligent robots for leading development of manned space; the fourth is to target the near-Earth orbit exploration, made innovation in methods and ways to use outside resources; the fifth point is looking for potential business opportunities. In the second section, highlights the fundamental scientific problems in the space X/gamma-ray detection, including cosmic gamma-ray bursts, black holes, neutron stars and Supernova remnants, such as dark matter and dark energy. Meanwhile, also pointed to the space environment, planetary evolution, space electromagnetic hazards, multidisciplinary issues such as ex-territorial resources available. In order to achieve some of the fundamental science goals designed, key technologies and processes in space experiments need to be addressed. In the third part, the space X/gamma ray radiation detection key technical challenges are described. Different science targets relay on different experiment requirements, needs of key technology are different. General speaking, physical parameters of a space radiation detection experiment include charge particles discrimination, energy detection, and flux, azimuth, angle, time, position detection as well. Usually, space radiation detection instrument has high sensitivity, and large effective area, and more pixel; low noise, and high speed of read out electronics, and mass data processing transmission; precision pointing and distance sensing and perception, and in-orbit calibration, extreme environment survival function; reliable software implementation, channel number also often from several ten of channels to around million. Technical problems to be solved are following: (1) high performance detectors (high sensitivity, pixels or micro-strip type); (2) low-noise, low-powerdissi- pation, multichannel, lightweight, multi-purpose ASICs; (3) high quality components, including devices; (4) test and alignment, special nuclear materials processing technologies; (5) calibration equipments and instruments. Future prospects of space radiation physics research and application are very broad and promising. In comparison with the United States, Russia, Europe, Japan and other space technology power nations than started late in China, less investment, weak industrial base, is relatively backward, especially, X/gamma-ray detection and application of relatively weak basis, should pay more attention to, and increase investment and support efforts to make China a scientific power in space exploration.

Radioactive Iodine Therapy of Differentiated Thyroid Carcinoma: Redesigning the Paradigm.

Radioactive iodine therapy has evolved over the past 70 years from treatment of known metastatic thyroid carcinoma to include adjuvant use to decrease the incidence of recurrent disease and to ablation of normal remnant tissue following thyroidectomy, even for minimal tumor involvement. Advances in laboratory testing, development of drugs useful in radioiodine treatment, as well as advances in radiation detection and imaging instrumentation, have progressively improved the utility of radioiodine therapy of differentiated thyroid carcinoma. Guidelines have proliferated and they have become more detailed and complex. This trend is likely to continue as the science and technology involved increases in sophistication and efficacy.

Use of Transportable Radiation Detection Instruments to Assess Internal Contamination From Intakes of Radionuclides Part I: Field Tests and Monte Carlo Simulations.

The detonation of a radiological dispersion device or other radiological incidents could result in the dispersion of radioactive materials and intakes of radionuclides by affected individuals. Transportable radiation monitoring instruments could be used to measure photon radiation from radionuclides in the body for triaging individuals and assigning priorities to their bioassay samples for further assessments. Computer simulations and experimental measurements are required for these instruments to be used for assessing intakes of radionuclides. Count rates from calibrated sources of Co, Cs, and Am were measured on three instruments: a survey meter containing a 2.54 × 2.54-cm NaI(Tl) crystal, a thyroid probe using a 5.08 × 5.08-cm NaI(Tl) crystal, and a portal monitor incorporating two 3.81 × 7.62 × 182.9-cm polyvinyltoluene plastic scintillators. Computer models of the instruments and of the calibration sources were constructed, using engineering drawings and other data provided by the manufacturers. Count rates on the instruments were simulated using the Monte Carlo radiation transport code MCNPX. The computer simulations were within 16% of the measured count rates for all 20 measurements without using empirical radionuclide-dependent scaling factors, as reported by others. The weighted root-mean-square deviations (differences between measured and simulated count rates, added in quadrature and weighted by the variance of the difference) were 10.9% for the survey meter, 4.2% for the thyroid probe, and 0.9% for the portal monitor. These results validate earlier MCNPX models of these instruments that were used to develop calibration factors that enable these instruments to be used for assessing intakes and committed doses from several gamma-emitting radionuclides.

Effects of Proton Radiation on Noise Performance in Solid-State Photomultipliers

Solid-state photomultiplier (SSPM) devices are a viable alternative to photomultiplier tubes for nuclear and space radiation detection and science instruments. Noise terms such as dark noise, cross talk, after-pulsing, and their radiation sensitivity directly affect the photodetector performance for harsh environment applications. This paper presents the results from proton radiation-hardness tests conducted for two sets of SSPMs designed and fabricated in two different commercial complementary metal oxide silicon (CMOS) processes: $0.18\hbox{-}\mu\text{m}$ and $0.8 \mu\text{m}$ . Following proton exposures to the SSPMs at 100 krad, 500 krad and 1 Mrad, the measured proton induced dark noise at unity gain is higher in $0.18\hbox{-}\mu\text{m}$ SSPMs, but the dark current in Geiger mode is higher in $0.8 \mu\text{m}$ devices. The results and analysis suggest a higher proton-induced surface/sidewall dark current than bulk dark current in $0.18\hbox{-}\mu\text{m}$ samples. The proton induced bulk defect densities are similar between $0.18\hbox{-}\mu\text{m}$ and $0.8 \mu\text{m}$ SSPMs. Reasonable excess noise measurement results were obtained in $0.18\hbox{-}\mu\text{m}$ SSPM samples, and inter-pixel cross talk and after-pulsing remain statistically unchanged after proton exposure. The radiation insensitivity of after-pulsing noise suggests that shallow trap density responsible for after-pulsing is not significantly affected by proton irradiations in these CMOS high gain photodetectors.

Response of the Li-7-enriched Cs2LiYCl6:Ce (CLYC-7) scintillator to 6–60 MeV neutrons

We discuss a test campaign designed to irradiate the 7Li-enriched Cs2LiYCl6:Ce3+ (CLYC-7) scintillator with 6–60MeV neutrons using the cyclotron located at the Crocker Nuclear Laboratory in Davis, CA. CLYC-7 is a newly developed scintillator that exhibits the ability to make good γ-ray measurements and has the ability to detect and discriminate fast neutrons via pulse shape discrimination (PSD) while functioning as a spectrometer. This allows a single detector to make good measurement of both stimuli simultaneously. The response of this scintillation detector has been investigated below 20MeV [1] but has yet to be explored for energies greater than 20MeV. Understanding the spectral and pulse shape response across a broad energy range is important for any radiation detection instrumentation capable of detecting multiple species. At the highest energies sampled, the CLYC-7 PSD demonstrated not only the standard electron/proton separation expected in a mixed γ/n field but the ability to discriminate locally produced deuterons, tritons and α particles. We show the results from the four different neutron beam energies sampled during the experiment. Lastly, we present the results obtained for relating the light output equivalence between electrons and protons/deuterons.

Sweating the Small Stuff: Pitfalls in the Use of Radiation Detection Instruments

Nuclear medicine technologists use nonimaging radiation detection instruments on a daily basis and routinely assess their performance in several ways. These instruments are simple to operate compared with imaging instruments but are also susceptible to misuse. After reviewing the theoretic basis for common mistakes and the importance of routine quality control, this continuing education article discusses pitfalls in the operation of dose calibrators, survey meters, scintillation detectors, and semiconductors. The article also reviews quality control procedures and ways in which these can be performed incorrectly. The goal of the article is to help technologists to spot and correct problems before they lead to errant results.

Improving Consistency in the Radiation Fields Used During Testing of Radiation Detection Instruments for Homeland Security Application

Improving Consistency in the Radiation Fields Used During Testing of Radiation Detection Instruments for Homeland Security Application

MO‐F‐134‐02: Project‐Based Learning ‐ Expanding Course Content with a Broad‐Scope Project

Purpose: We set out to revise/improve the Radiation Detection Instrumentation and Data Analysis course at our institution due to negative student evaluations of this course. Initially, we began with changes to the syllabus, adding important topics that were not being covered and expanding the teaching faculty to include board‐certified physicists with practical clinical experience. Although this led to improved student course evaluations compared to the previous years, we were still not satisfied that enough material was being covered in the course. Because the time in the semester was limited, we considered alternative teaching methodologies in an effort to broaden the scope of the course. Methods: We implemented project‐based learning because it allowed us to keep instructor‐led lectures, which provide the students with fundamental knowledge that we believe essential for a core course. We also expanded the breadth of the topics covered in the course through assignment of a class project. The class project broadly aims to provide opportunities for each group of students to investigate meaningful real‐world topics related to radiation detection in medical physics. For this assignment, the students assume the role of director of the medical physics radiation therapy department at a comprehensive cancer treatment center and are asked to develop a capital equipment list of detectors and associated equipment to perform all necessary QA for this department. They are expected to submit a detailed report and give a presentation to the class. Results: The class project was first assigned in 2010 and has been required every year since. The project has increased the breadth of the course and student course evaluations have improved (82% positive compared to 36% positive). Conclusion: Overall, our students are learning more material in the revamped course and are exposed to one of the many facets of a career in clinical medical physics.

Recommendations for Improving Consistency in the Radiation Fields Used During Testing of Radiation Detection Instruments for Homeland Security Applications.

Several measurements and calculations were performed to illustrate the differences that can be observed in the determination of exposure rate or ambient dose equivalent rate used for testing radiation detection systems against consensus standards. The large variations observed support our recommendation that better consistency in the test radiation fields can be achieved by specifying the source activity and testing distance instead of the field strength.

Simulated spatially dependent transient kinetics analysis of the Oak Ridge Y12 plant criticality excursion

In June 1958 an accidental nuclear excursion occurred in the C-1 Wing of building 9212 in a process facility designed to recover enriched Uranium U(93) from various solid wastes. The accident was caused by the inadvertent flow of enriched uranyl nitrate into a 55 gallon drum which established a prompt critical nuclear excursion. Following the initial fission spike the nuclear system oscillated in power. The reaction was eventually terminated by the additional water which was flowing into the drum. The criticality excursion was estimated to have lasted approximately 20 min based upon nearby radiation measurement equipment with an estimated total fission yield of 1.3 × 1018 fissions of which the first fission spike contributed 6 × 1016 fissions.The traces from the radiation measurement devices indicated that most of the fissions occurred in the first 2.8 min, in which case the average power required for the observed fission yield was approximately 220 kW. After the first 2.8 min the system was postulated to have boiled causing a sharp decrease in density and reactivity of the system. This boiling probably reduced the power output from the system to a low level for the final 18 min of the excursion. This paper will aim to investigate the subsequent evolution of the Y12 excursion using the fundamentally based spatially dependent neutron/multiphase CFD kinetics simulation tool - FETCH. The reconstruction of the Y12 excursion using FETCH will follow the evolution of the excursion up until the uranyl nitrate starts to boil. The results of the FETCH simulation are presented and compared against the known measurements of the excursion from the radiation detection instruments located near the drum.

Measurements for the Development of a Simulated Naturally Occurring Radioactive Material.

Nineteen different commercially available samples containing naturally occurring radioactive materials (NORM) (i.e., natural uranium, thorium, radium and potassium) were investigated, including zircon sand, cat litter, roofing tiles, ice melt and fertilizer among others. A large variation in isotopic composition was observed across the measured samples. As a result of this observation, a need was identified to develop and implement the use of a simulated NORM sample to serve as a reference standard sample containing naturally occurring radioactive elements. The purpose of the simulated NORM sample would be to simulate typical samples containing NORM to be used for testing radiation detection instruments against ANSI/IEEE and IEC document standards requirements. The design and construction of the proposed new simulated NORM sample and the subsequent energy spectra characterization measurements are presented as part of this work.