Different Types Of Radiation Research Articles

Neutron detectors in proton therapy: Calibration, operational in situ verification, and comparison with Monte Carlo simulation

The number of proton therapy centers is continuing to increase and the use of suitable neutron detectors is essential in the field of radiation protection to ensure a safe working environment. The neutrons present in proton therapy centers range from thermal neutrons to neutrons with the maximum energy of the irradiated proton beam. Therefore, the neutron detectors must be of extended-range. The first aim of the study is to develop a robust and easy-to-implement method to operationally verify the neutron detectors in a proton therapy facility. The neutron field generated in the facility under specific conditions was used as the neutron reference source against which the neutron detectors were evaluated. For this purpose, an analysis of the detectors' uncertainties and the establishment of indicators that report the correct status of the detectors was performed. In addition, the experiment was characterized in TOPAS (a Monte Carlo toolkit based on Geant4) to validate the experimentally measured data and vice versa. The WENDI-II and LUPIN-II responses were determined in TOPAS. Both detectors were calibrated in an accredited laboratory and the simulation of this calibration in Monte Carlo was performed. An estimated uncertainty of 13.1% (k = 2) was found for the results of the operational verification of the WENDI-II and LUPIN-II detectors. Thus, for the neutron detectors, the investigation interval is the range between 13.1% and 17.2% (k = 3) while the intervention level is set at 17.2%. An overall agreement (within 61%) was obtained among neutron H∗(10) values calculated with TOPAS and H∗(10) measured for the operational verification of the detectors. The calibration factor for WENDI-II coincides with that indicated by the manufacturer, although a discrepancy of 19% was found for LUPIN-II. The verification method for neutron detectors, studied for two different types of irradiations (a single energy and an energy sweep irradiation), is sufficiently conservative to ensure the correct operation of the equipment, fully complies with international recommendations (i.e. IEC 61005:2014) and can be applied in other proton therapy facilities.

Design and Performance of an InAs Quantum Dot Scintillator with Integrated Photodetector.

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD's emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30-60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 1014 cm-2 dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells.

Identification of conditions for ultrasonic effect on gas-dispersed medium and creation of radiators to increase the efficiency of coagulation in devices with swirling flow

Relevance. The presence and uncontrolled distribution of aerosols of various substances in the air, which have a negative impact on humans, flora and fauna. This problem is especially acute in the extraction, processing and combustion of georesources. The most effective way to solve the problem is the use of high-intensity ultrasonic vibrations, the effect of which on aerosols causes convergence and agglomeration of small particles into large ones. However, at low concentrations, the particle coagulation efficiency is not sufficient to increase the recovery rate of gas treatment equipment. Therefore, there is a need to find new ways to optimize ultrasonic equipment for coagulation of fine particles in order to increase its efficiency. Aim. To determine the optimal conditions for ultrasonic influence on a swirling gas-dispersed flow, ensuring maximum efficiency of agglomeration of highly dispersed particles. Carrying out comparative studies of coagulation of particles when exposed to ultrasonic fields generated by different types of radiators and their combined effects will make it possible to determine the effectiveness of ultrasonic coagulation and the optimal design scheme of ultrasonic exposure. Objects. Coagulation of particles under ultrasonic impact, formed by various types of radiators. Methods. Computer modeling of the generated ultrasonic field using the finite element method using harmonic acoustic analysis. Finite element modeling and design of disk radiators using modal analysis. To determine the characteristics of the aerosol, a Malvern Spraytec Particle Analyzer was used. Results. The results of calculations and experiments have shown that the use of an extended ultrasonic tubular radiator operating on a bending-diametric mode of vibration and forming a ring standing wave with a sound pressure level of 162–165 dB as the main source of ultrasonic impact for devices with swirling flows may be the most energy efficient. Further increase in the efficiency of coagulation can only be achieved by the combined action of a tubular radiator and a longitudinally oscillating radiator. This significantly modifies the field structure and provides not only an increase in the sound pressure level (up to 167 dB), but also in the number of formed nodal surfaces (up to 44).

Unveiling the shielding potential: Exploring photon and neutron attenuation in a novel lead-free XCr2Se4 chalcogenide Spinals alloys with MCNP 4C code

The study covers shielding properties of three promising lead-free XCr2Se4 alloys, where X represents Mn, Cu, or Ag, across a spectrum of energies between 0.02 MeV and 15 MeV. MCNP4C was employed to simulate the mass attenuation coefficient (MAC) for the three selected alloys. After being prepared using the conventional solid-state reaction method, the samples displayed densities ranging from 5.45 g cm−3to 6.22 g cm−3. The simulated results obtained from the MCNP4C are then benchmarked with data obtained using different software such as Phy-X, Py-MLBUF, EPIXS, and GRASP. Upon comparing the acquired results with the Phy-X data, a notable correlation was observed with a relative difference ranging from 0.11% to 8.57%. The accuracy of the simulated data was additionally validated through the Kolmogorov-Smirnov test. From the simulated MAC, different ionizing radiation shielding properties including linear attenuation coefficient (LAC), half-value layer (HVL), mean-free path (MFP), transmission factor (TF), radiation protection efficiency (RPE), and fast neutron removal cross section (FNRCS) were calculated to provide a comprehensive analysis of the samples' efficacy in dealing with different types of radiation. The LAC for neutrons at different energies is also examined. HVL analysis indicates the radiation-blocking capacity of the samples. The TF shows the alloys’ ability to either permit or restrain the transfer of radiation. Additionally, RPE and FNRCS give indication of the shielding potential of the studied samples. This study is important for nuclear physicians and researchers and serves as useful data for the development of superior shielding materials.

A comprehensive review of radiation shielding concrete: Properties, design, evaluation, and applications

AbstractThis review paper provides a comprehensive analysis of radiation shielding concrete, covering its properties, design, evaluation, and applications. It begins with an introduction, stating the objective and scope. The paper explores radiation shielding basics, including ionizing radiation, shielding principles, and materials used for shielding. Concrete's properties relevant to shielding, radiation attenuation mechanisms, and factors affecting its efficiency are discussed. Different types of radiation shielding concrete are examined, along with their applications. The design and formulation of shielding concrete, including mix proportions, optimization techniques, and quality control, are presented. Evaluation methods and standards are discussed. Lastly, challenges, future directions, and emerging technologies are outlined. This review paper serves as a valuable resource for professionals involved in radiation shielding. The review on radiation shielding concrete highlighted its effectiveness in attenuating ionizing radiation, emphasizing material composition, density, and thickness as key design factors. Evaluation methods, such as gamma spectroscopy and Monte Carlo simulations, are discussed, demonstrating its versatile applications in nuclear facilities, healthcare, and space exploration.

CYRAD: a translational study assessing immune response to radiotherapy by photons or protons in postoperative head and neck cancer patients through circulating leukocyte subpopulations and cytokine levels

BackgroundRadiotherapy has both immunostimulant and immunosuppressive effects, particularly in radiation-induced lymphopenia. Proton therapy has demonstrated potential in mitigating this lymphopenia, yet the mechanisms by which different types of radiation affect the immune system function are not fully characterized. The Circulating Immunes Cells, Cytokines and Brain Radiotherapy (CYRAD) trial aims to compare the effects of postoperative X-ray and proton radiotherapy on circulating leukocyte subpopulations and cytokine levels in patients with head and neck (CNS and ear nose throat) cancer.MethodsCYRAD is a prospective, non-randomized, single-center non interventional study assessing changes in the circulating leukocyte subpopulations and cytokine levels in head and neck cancer patients receiving X-ray or proton radiotherapy following tumor resection. Dosimetry parameters, including dose deposited to organs-at-risk such as the blood and cervical lymph nodes, are computed. Participants undergo 29 to 35 radiotherapy sessions over 40 to 50 days, followed by a 3-month follow-up. Blood samples are collected before starting radiotherapy (baseline), before the 11th (D15) and 30th sessions (D40), and three months after completing radiotherapy. The study will be conducted with 40 patients, in 2 groups of 20 patients per modality of radiotherapy (proton therapy and photon therapy). Statistical analyses will assess the absolute and relative relationship between variations (depletion, recovery) in immune cells, biomarkers, dosimetry parameters and early outcomes.DiscussionPrevious research has primarily focused on radiation-induced lymphopenia, paying less attention to the specific impacts of radiation on different lymphoid and myeloid cell types. Early studies indicate that X-ray and proton irradiation may lead to divergent outcomes in leukocyte subpopulations within the bloodstream. Based on these preliminary findings, this study aims to refine our understanding of how proton therapy can better preserve immune function in postoperative (macroscopic tumor-free) head and neck cancer patients, potentially improving treatment outcomes.Protocol versionVersion 2.1 dated from January 18, 2023.Trial registrationThe CYRAD trial is registered from October 19, 2021, at the US National Library of Medicine, ClinicalTrials.gov ID NCT05082961.

Characterization of Molecular Subtypes of Rat Mammary Cancer and Their Association With Environmental Exposures.

Breast cancer is a heterogeneous disease with many subtypes, and the association between these subtypes and exposure to environmental factors such as radiation remains controversial. Although the rat is used widely for research into human breast cancer, the heterogeneity and subtype definitions are unclear. Here, we leveraged an archive of rat mammary cancer samples and gene expression microarray data to classify tumors and examine their association with exposures. Eighty-four mammary cancer and 12 normal mammary tissue samples were obtained from previous experiments in which rats were exposed to different types of radiation, chemical carcinogens, and diets. Tumors were then subjected to immunohistochemical (IHC) analysis of conventional biomarkers, as well as gene expression profiling; they were then classified by three approaches based on IHC results, the PAM50 classifier algorithm, and unsupervised clustering of gene expression profiles. IHC identified four subtypes (luminal A-like, luminal B-like 1, luminal B-like 2, and triple-negative), while PAM50 identified six (luminal A, luminal B, basal-like, HER2-enriched, normal-like, and claudin-low). Unsupervised clustering divided the tumors into three large, statistically significant, groups (named "luminal A", "luminal B", and "non-luminal" clusters). The results of the three approaches were significantly associated with each other. Exposure to radiation and chemical carcinogens during post-pubertal development was significantly associated with an increased risk of developing luminal A tumors, whereas exposure to a high corn-oil diet was associated with a higher likelihood of luminal B tumors. Rat mammary cancer subtypes resemble those in humans and are related to environmental factors.

Quantifying local lattice distortions in refractory high-entropy alloys

Severe local lattice distortions (LLDs), originating from the size mismatch among atoms, have been proposed as one of the key mechanisms responsible for the excellent mechanical properties of bcc-structured high-entropy alloys (HEAs). They have also been connected to phase stability, as well as physical properties such as electrical conductivity. Experimental measurements of LLDs are, however, difficult and often ambiguous. Analysis of total scattering data in real space has been proposed to provide a uniquely suitable probe of LLDs, but its widespread application and validation are still limited. We conduct a thorough study of LLD measurements in refractory high-entropy alloys (RHEAs) using small-box pair distribution function (PDF) analysis. We start by reexamining existing literature data using a recently proposed coherent theoretical framework to demonstrate that LLDs in RHEAs can indeed be considered as severe and can be reliably measured even in the absence of known thermal components. We perform total scattering experiments of a typical RHEA (HfNbTaTiZr) using both x-rays and neutrons, and show that real-space PDF analysis of data from different types of radiation gives consistent values of LLDs. The results are also in good agreement with the values derived from reciprocal-space data. Finally, through simulation and analysis of theoretical two-phase PDFs, we demonstrate that the effect of the chemical segregation in the investigated RHEA on the measured LLDs is limited when dealing with comparatively large LLDs. The results show that PDF analysis using small-box modeling provides a fast and reliable tool for measuring LLDs in RHEAs, which makes it ideal for analysis of large data sets from time-resolved measurements. Published by the American Physical Society 2024

Spectroscopic performance of Low-Gain Avalanche Diodes for different types of radiation

LGADs (Low-Gain Avalanche Diodes or Detectors) are a type of silicon Avalanche Photo-Diodes originally developed for the fast detection of minimum ionizing particles in high-energy physics experiments. Thanks to their fast timing performance, the LGAD paradigm enables detectors to accurately measure minimum ionizing particles with a timing resolution of a few tens of picoseconds. Such a performance is due to a thin substrate and the presence of a moderate signal gain. This internal gain of a few tens is enough to compensate for the reduced charge deposition in the thinner substrate and the noise of fast read-out systems. While LGADs are optimized for the detection of minimum ionizing particles for high-energy particle detectors, it is critical to study their performance for the detection of different types of particle, such as X-rays, gamma-rays, or alphas. In this paper, we evaluate the gain of three types of LGADs: two devices with different geometries and doping profiles fabricated by Brookhaven National Laboratory, and one fabricated by Hamamatsu Photonics with a different process.Since the gain in LGADs depends on the bias voltage applied to the sensor, pulse-height spectra have been acquired for bias voltages spanning from the depletion voltage up to the breakdown voltage. The signal-to-noise ratio of the generated signals and the shape of their spectra allow us to probe the underlying physics of the multiplication process.

Biodosimetry of ionizing radiations at different LET levels through cytogenetic endpoints in Allium cepa meristems

- This paper aims to enhance our understanding of the effects of ionizing radiation using radiobiology and biodosimetry techniques applied to living plant organisms. Plants are particularly suitable for this purpose as they are highly sensitive to detecting potential genotoxic agents in the environment and their use allows us to avoid using animals in research in compliance with the 3R principle. Currently, the onion (Allium cepa) is recognized as a valid model for the analysis of environmental pollutants but has been relatively unexplored as an indicator of radiation exposure. In this study, analyses of the genotoxicity of X and alpha radiation were conducted using the micronucleus test and mitotic index analysis. Our results indicate that Allium cepa can be considered a valid alternative model to animal use for assessing the effects of ionizing radiation. In particular, it was found that alpha radiation caused significant damage, as evidenced by an increased number of micronuclei, which was 20 times higher compared to X-ray radiation. This was further confirmed through the observation of the effective dose parameter, as determined by the analysis of various weight factors associated with different types of radiation.

On Approach for Analysis of Distribution of Temperature During Effects of Radiation on Biological Tissues

Different types of irradiation take essential role in biological processes directly related to human health. Currently they are widely using in clinical practice. In this situation one can find several works to determine therapeutic effects, which were obtained by actions of the irradiation on living organisms. One type of irradiation of tissues of the considered organisms is electromagnetic radiation. A consequence of the radiation tissues of organisms is their heating. In this paper we introduce a model and an analytical approach to analyze distribution of temperature at effect of radiation on biological tissues. We consider a possibility to control of heat transport in biological tissues by choosing of conditions of heating. Also we present an analytical approach for analysis of the obtained model. The approach takes into account changing of parameters of the considered processes on coordinate and time as well as their nonlinearity.

A comprehensive research on γ-ray and particle radiation interaction parameters of Cerium doped heavy oxide inorganic scintillators

In this study, the interaction cross sections of heavy oxide scintillators, which have a very important place in high energy physics research, with photon and particle radiation were comparatively investigated. In this context, the interaction parameters of six different Ce-doped heavy oxide scintillators were obtained using updated software. The interactions of photons with energies between 1 keV and 100 GeV with scintillators were evaluated in the light of the results produced by the Phy-X/PSD software. In addition to the continuous energy range, calculations were also made on the photon energies emitted with the highest probability of emission from sources 241Am (59.54 keV), 133Ba (356 keV), 22Na (511 and 1280 keV), 137Cs (662 keV) and 152Eu (1460 keV). Additionally, evaluations of energy absorption build-up factors valid under broad beam conditions are also included in this study. Fast neutron absorption cross sections and changes in the range (R) values for heavy particle radiation in the range of 1 keV–20 MeV were also determined with SRIM and ESTAR software. All data obtained depending on energy are explained according to the mass percentages of Lu, Gd, Hf, Y, Al and O elements in the scintillators. The highest interaction cross section for photons was obtained in the Lu2Gd2SiO5 (Ce 0.3%) scintillator (HOS2). The interaction cross section of this scintillator was obtained as 3.115 and 0.042 cm2/g at 0.1 MeV and 10 MeV photon energies, respectively. On the other hand, the highest cross-sections of the fast neutrons were observed in the scintillator (HOS5) containing GdAlO3 (Ce 1.0%) as 0.148 cm−1. This difference in neutron radiation has been explained by calculating the individual attenuation abilities of the elements in the structures. It is hoped that the data obtained will guide researchers working on the detection of different types of radiation.

ОЦЕНКА РАДИАЦИОННОГО РИСКА СМЕРТИ ОТ СЕРДЕЧНО-СОСУДИСТЫХ ЗАБОЛЕВАНИЙ ЛИКВИДАТОРОВ ПОСЛЕДСТВИЙ АВАРИИ НА ЧАЭС – РАБОТНИКОВ ПРЕДПРИЯТИЙ АТОМНОЙ ПРОМЫШЛЕННОСТИ ПО ДАННЫМ О ДОЗАХ РАЗЛИЧНЫХ ВИДОВ ОБЛУЧЕНИЯ

Background: Assessment of the risk of death from circulatory system diseases due to radiation exposure in liquidators of the Chernobyl accident consequences (hereinafter referred to as liquidators) using data on doses of various types of exposure. Material and methods: The work used the information base of the Industry Register of persons exposed to radiation as a result of the accident at the Chernobyl nuclear power plant (hereinafter referred to as the register), nuclear industry workers. The radiation risk assessment study included men - 12,706 liquidators who had data on external emergency radiation doses when working in the 30 km Chernobyl NPP zone, 1,327 of them had data on occupational radiation doses. Poisson regression was chosen as the statistical model of risk. The study covers the period from 1987 to 2021. During the observation period, the register accumulated 304,023 person/years. The majority of the register in 1986 was made up of men – 84.7 %, women – 15.3 %. Results: When data on doses of different types of radiation are used to calculate doses, different results of excess relative risk are obtained. Only the total radiation dose (occupational, emergency, medical, natural) can provide correct results for calculating the radiation risk of death from radiation-induced diseases. Conclusion: The prospect of research should be considered to be filling the information base of the Industry Register with data on doses of all types of radiation.

Development of a phoswich detector utilizing bismuth germanate crystal scintillator and polyethylene naphthalate scintillation film

In this study, we present the development of a phoswich detector system employing a Bismuth Germanate (BGO) crystal scintillator in combination with a Polyethylene naphthalate (PEN) film plastic scintillator. Phoswich detectors can contribute to various applications, including radiation monitoring, medical imaging, and nuclear physics experiments, due to their ability to discriminate between different types of radiation. The thin PEN film is sensitive to α and β radiation, while the BGO scintillator exhibits good γ radiation detection efficiency. The incident radiation type and its energy can be determined by analyzing the difference in decay times between these two scintillators. This paper presents an analysis of the detector’s response to α, β, and γ radiation, and the particle tagging efficiencies are to be over 99.9%, 92%, and 99.8%, respectively.

Epigenetic factors of the effect of UV-C and X-ray presowing seeds radiation exposure in Matricaria chamomilla L. genotypes

In a series of experiments using both X-ray and UV-C radiation exposure a parallel study of several pharmacological characteristics of the Matricaria chamomilla L. genotype group was carried out. The data concerning the changes in the productivity of pharmacological raw materials and stimulation of the synthesis of low molecular weight antioxidants as markers of secondary metabolism induction have been published earlier. In this study, the data on the relationship between the stimulation of the synthesis of secondary metabolites under different types of irradiation and the epigenetic changes in the plant organism are presented. It was shown that DNA methylation was switched to the de novo mode in plants of all studied genotypes of M. chamomilla under both types of irradiation. That indicates changes in the epigenetic program of the plant organism. Comparison of the epigenetic pattern between control and irradiated samples, based on the difference in DNA methylation patterns in terms of a statistical indicator, shows that there is no unambiguous relationship between the epigenetic changes and increasing yield of antioxidant synthesis. This is additional evidence of the diversity of metabolic rearrangements and adaptive strategies of the plant organism under radiation exposure even within one species.

Hausdorf dimension of typical very low frequency chorus emissions and verification of their excitation mechanism

A quantitative study of the degree of complexity of electromagnetic VLF chorus emissions in the region of their excitation near the local minimum of the magnetic field outside the plasmasphere was carried out using modern mathematical tools. From the vast observational data collected during the Van Allen Probe mission, typical examples of chorus have been selected for which high-resolution digitized data are available. The original program was used to calculate the Hausdorff dimension of long numerical sequences. In all cases, the dimension turned out to be non-integer, which indicates the complex dynamics of the system. During the calculations, jumps in dimension were noted, including its decrease by about a factor of two for a fragment of a burst of chorus. The obtained results are important for confirming the mechanism of excitation of chorus by amplifying short noise pulses and for substantiating the possibility of automatic identification of electromagnetic radiation of different types.

Exploring the impact of gamma rays and electron beam irradiation on physico-mechanical properties of polymers & polymer composites: A comprehensive review

Ionizing radiations are a unique and powerful means of modifying physico-mechanical properties of various polymers and composites. Modification of properties by irradiation technique has become a pioneer area of research due to its extraordinary results and toxic-free route. Many studies revealed that radiations act differently on polymers and composites. At the optimal radiation dose; various mechanical properties such as tensile, compression, impact and flexural strength/modulus were improved upto some extent. This paper gives a clear overview of different types of radiations used for altering the properties of polymers and its composites reinforced with natural and synthetic fillers. Furthermore, the current area of research has been documented in this review. In nutshell, high-energy gamma rays and electron beam act a promising technology and bettter alternative of traditionally used chemical methods to modify various chemical and physico-mechanical aspects of commerical available polymers and composites.

Optimization of a Photobiomodulation Protocol to Improve the Cell Viability, Proliferation and Protein Expression in Osteoblasts and Periodontal Ligament Fibroblasts for Accelerated Orthodontic Treatment.

Numerous pieces of evidence have supported the therapeutic potential of photobiomodulation (PBM) to modulate bone remodeling on mechanically stimulated teeth, proving PBM's ability to be used as a coadjuvant treatment to accelerate orthodontic tooth movement (OTM). However, there are still uncertainty and discourse around the optimal PBM protocols, which hampers its optimal and consolidated clinical applicability. Given the differential expression and metabolic patterns exhibited in the tension and compression sides of orthodontically stressed teeth, it is plausible that different types of irradiation may be applied to each side of the teeth. In this sense, this study aimed to design and implement an optimization protocol to find the most appropriate PBM parameters to stimulate specific bone turnover processes. To this end, three levels of wavelength (655, 810 and 940 nm), two power densities (5 and 10 mW/cm2) and two regimens of single and multiple sessions within three consecutive days were tested. The biological response of osteoblasts and periodontal ligament (PDL) fibroblasts was addressed by monitoring the PBM's impact on the cellular metabolic activity, as well as on key bone remodeling mediators, including alkaline phosphatase (ALP), osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANK-L), each day. The results suggest that daily irradiation of 655 nm delivered at 10 mW/cm2, as well as 810 and 940 nm light at 5 mW/cm2, lead to an increase in ALP and OPG, potentiating bone formation. In addition, irradiation of 810 nm at 5 mW/cm2 delivered for two consecutive days and suspended by the third day promotes a downregulation of OPG expression and a slight non-significant increase in RANK-L expression, being suitable to stimulate bone resorption. Future studies in animal models may clarify the impact of PBM on bone formation and resorption mediators for longer periods and address the possibility of testing different stimulation periodicities. The present in vitro study offers valuable insights into the effectiveness of specific PBM protocols to promote osteogenic and osteoclastogenesis responses and therefore its potential to stimulate bone formation on the tension side and bone resorption on the compression side of orthodontically stressed teeth.

Energetic processing of thioacetamide in cryogenic matrices.

There is an ongoing debate on the apparent depletion of sulfur in the interstellar medium (ISM) compared to its universal abundance; therefore, the investigation of sulfurous compounds at low temperatures is of utmost importance. This work aims to study thioacetamide, H3C-C(=S)-NH2, in low-temperature inert Ar and para-H2 matrices by IR spectroscopy. The samples have been exposed to various sources of irradiation, such as Lyman-α or laser UV photons as well as energetic electrons. Using different host materials enabled assessing the matrix's impact on precursor decomposition. The response of the molecule to different types of irradiation has also been evaluated. The existence of three main decomposition channels were deduced: formation of (i) CH3, CH4, and HNCS; (ii) H2S and H2C=C=NH; and (iii) NH3 and H2C=C=S. The H3C-CN and H3C-NC isomers of H2C=C=NH could also be identified. Secondary products such as HNC and HCN were also detected in the quantum solid para-H2 in contrast to the more rigid Ar matrix. The listed decomposition products have been observed in the ISM, with the exception of H2C=C=NH and H3C-NC. The results point to the potential sensitivity of the precursor molecule to energetic radiation in space environments. Finally, the findings of this work will serve as a foundation for future irradiation experiments using the astrochemically more relevant pure thioacetamide ice.

Essentials of Theranostics: A Guide for Physicians and Medical Physicists.

Radiopharmaceutical therapies (RPTs) are gaining increased interest with the recent emergence of novel safe and effective theranostic agents, improving outcomes for thousands of patients. The term theranostics refers to the use of diagnostic and therapeutic agents that share the same molecular target; a major step toward precision medicine, especially for oncologic applications. The authors dissect the fundamentals of theranostics in nuclear medicine. First, they explain the radioactive decay schemes and the characteristics of emitted electromagnetic radiation used for imaging, as well as particles used for therapeutic purposes, followed by the interaction of the different types of radiation with tissue. These concepts directly apply to clinical RPTs and play a major role in the efficacy and toxicity profile of different radiopharmaceutical agents. Personalized dosimetry is a powerful tool that can help estimate patient-specific absorbed doses, in tumors as well as normal organs. Dosimetry in RPT is an area of active investigation, as most of what we know about the relationship between delivered dose and tissue damage is extrapolated from external-beam radiation therapy; more research is needed to understand this relationship as it pertains to RPTs. Tumor heterogeneity is increasingly recognized as an important prognostic factor. Novel molecular imaging agents, often in combination with fluorine 18-fluorodeoxyglucose, are crucial for assessment of target expression in the tumor and potential hypermetabolic disease that may lack the molecular target expression. ©RSNA, 2023 Test Your Knowledge questions are available in the supplemental material.