Radiation, Volume 2, Issue 2 (June 2022) – 6 articles

In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes is presented. In particular, the investigations using HP-Ge spectrometry and Hf-based crystal scintillators are focused; the potentiality and the results of the “source = detector” approach are underlined. In addition, a short introduction concerning the impact of such kind of research in the context of astroparticle and nuclear physics is pointed out. In particular, the study of $\alpha$ decay and double beta decay of ${}^{174}$Hf, ${}^{176}$Hf, ${}^{177}$Hf, ${}^{178}$Hf, ${}^{179}$Hf, ${}^{180}$Hf isotopes either to the ground state or to the lower bounded levels have been discussed. The observation of $\alpha$ decay of ${}^{174}$Hf isotope to the ground state with a T${}_{1/2}=7.0\left(1.2\right)\times {10}^{16}$ y is reported and discussed. No decay was detected for $\alpha$ decay of ${}^{174}$Hf isotope at the first excited level of daughter and of ${}^{176}$Hf, ${}^{177}$Hf, ${}^{178}$Hf, ${}^{179}$Hf, ${}^{180}$Hf isotopes either to the ground state or to the lower bounded levels. The T${}_{1/2}$ lower limits for these decays are at the level of ${10}^{16}$–${10}^{20}$ y. Nevertheless, the T${}_{1/2}$ lower limits for the transitions of ${}^{176}$Hf$\to {}^{172}$Yb ($0^{+}\to 0^{+}$) and ${}^{177}$Hf$\to {}^{173}$Yb ($7/2^{-}\to 5/2^{-}$) are near to the theoretical predictions, giving hope to their observation in the near future. All the other experimental limits ($\sim {10}^{16}$–10${}^{20}$ y) are absolutely far from the theoretical expectations. The experiments investigating the $2ϵ$ and $ϵ{\beta }^{+}$ processes in ${}^{174}$Hf are also reported; the obtained half-life limits are set at the level of ${10}^{16}$–${10}^{18}$ y. Moreover, we estimate the T${}_{1/2}$ of $2\nu 2ϵ$ of ${}^{174}$Hf decay at the level of (0.3–6) × ${10}^{21}$ y (at now the related measured lower limit is $7.1\times {10}^{16}$ y). Full article

The aim of this work was to test polyamines as potential natural substrates of the Acinetobacter baumannii chlorhexidine efflux protein AceI using near-UV synchrotron radiation circular dichroism (SRCD) spectroscopy. The Gram-negative bacterium A. Baumannii is a leading cause of hospital-acquired infections and an important foodborne pathogen. A. Baumannii strains are becoming increasingly resistant to antimicrobial agents, including the synthetic antiseptic chlorhexidine. AceI (144-residues) was the founding member of the recently recognised PACE family of bacterial multidrug efflux proteins. Using the plasmid construct pTTQ18-aceI(His₆) containing the A. baumannii aceI gene directly upstream from a His₆-tag coding sequence, expression of AceI(His₆) was amplified in E. coli BL21(DE3) cells. Near-UV (250–340 nm) SRCD measurements were performed on detergent-solubilised and purified AceI(His₆) at 20 °C. Sample and SRCD experimental conditions were identified that detected binding of the triamine spermidine to AceI(His₆). In a titration with spermidine (0–10 mM), this binding was saturable and fitting of the curve for the change in signal intensity produced an apparent binding affinity (K_D) of 3.97 ± 0.45 mM. These SRCD results were the first experimental evidence obtained for polyamines as natural substrates of PACE proteins. Full article

The purpose of this study was to assess organ dosimetry and clinical use of [¹²⁴I]I-NM404, a radiotheranostic alkylphosphocholine (APC) analog, for accurate detection and characterization of a wide variety of solid primary and metastatic malignancies anywhere in the body. Methods: Patterns of [¹²⁴I]I-NM404 uptake were quantitatively analyzed and qualitatively compared with [¹⁸F]FDG PET/CT in 14 patients (median age, 61.5 years; 7 males, 7 females) with refractory metastatic cancer who were enrolled in one of two Phase I imaging studies. Primary cancer types included bronchogenic (n = 7), colorectal (n = 1), prostate (n = 1), triple-negative breast (n = 1), head and neck (n = 2), pancreatic (n = 1) carcinoma, and melanoma (n = 1). Patients were administered [¹²⁴I]I-NM404 and imaged via PET/CT at 1–2, 4–6, 24, and 48 h and at 5–10 days post injection, from top of the skull to mid-thigh. Volumes of interest were drawn over lungs, heart, liver, kidneys, and whole body for dosimetry estimation using OLINDA 1.1 Representative metastatic index lesions were chosen when applicable for each case with active sites of disease to calculate maximum and mean tumor-to-background ratios (TBRmax, TBRmean), using the adjacent normal organ parenchyma as background when possible. Results: Administrations of [¹²⁴I]-NM404 were safe and well-tolerated. The organs with the highest estimated absorbed dose (mean ± SD) were the lungs (1.74 ± 0.39 mSv/MBq), heart wall (1.52 ± 0.29 mSv/MBq), liver (1.28 ± 0.21 mSv/MBq) and kidneys (1.09 ± 0.20 mSv/MBq). The effective dose was 0.77 ± 0.05 mSv/MBq. Preferential uptake within metastatic foci was observed with all cancer subtypes, TBRmax ranged from 1.95 to 15.36 and TBRmean ranged from 1.63 to 6.63. Robust sensitive imaging of lesions was enhanced by delayed timing (2–6 days after single injection of [¹²⁴I]I-NM404, respectively) due to persistent tumor retention coupled with progressive washout of background activity. NM404 uptake was evident in pulmonary, nodal, skeletal, CNS, and other metastatic sites of disease. Radiation related injury or necrosis were NM404 negative, whereas certain small number of metastatic brain lesions were false negative for NM404. Conclusions: In addition to being well tolerated, selective tumor uptake of NM404 with prolonged retention was demonstrated within a broad spectrum of highly treated metastatic cancers. Full article

The UK, and other countries worldwide, have benefited from nuclear energy to provide a low-carbon power source to fuel their increasing populations and industrial growth. In support of the extensive end-of-life decommissioning activities ongoing globally, as well as to enable accident clean-up and nuclear security/monitoring provisions; systems are necessary to rapidly and accurately detect and attribute the nature of any nuclear and/or radioactive materials. To facilitate the utilisation of the increasing suite of miniaturised radiation sensor systems for a range of largely robotic (whether aerial, underwater or ground-based) deployment applications, without the issue of being ’tethered’ to a specific vendor or system, an open-source and compact python module has been developed. Within this readily integrable code-base designed for incorporation into wider software architectures (such as the Robotic Operating System, or ROS), gamma-ray spectroscopy data are recorded in real-time and processed with a peak identification procedure once sufficient data has been recorded. Iterative peak-fitting is applied to determine the isotopic compositions of the incident radiation. The stand-alone application comprises two connected components: a small detector-specific module (or wrapper) that translates a detector’s serial output into the desired format, ahead of the main analysis function. Second, a photopeak identification is performed through an algorithm which uses the second derivative of the spectrum. The peaks identified are subsequently labelled by the program, utilizing the properties of all the mathematically detected/derived peaks, and finally output in a user-defined format for subsequent usage. Full article

Nkamouna-Kongo is a cobalt–nickel deposit located in Lomié, Eastern Cameroon. Mining creates radiation exposure pathways that must be considered in risk management scenarios. RESRAD-ONSITE and RESRAD-BIOTA, developed by the US DOE, assess contaminated sites by deriving cleanup criteria and estimating the radiation dose and risk associated with residual radioactive materials using site-specific parameters. This paper evaluated the radiation dose in biota and the health risk from exposure to naturally occurring radionuclides. The activity of ²²⁶Ra, ²³²Th, and ⁴⁰K was determined by γ-spectrometry. The internal doses were 2.13 × 10⁻⁰⁷, 1.42 × 10⁻⁰⁶, and 8.38 × 10⁻⁰⁵ Gy d⁻¹ for animals and 2.38 × 10⁻⁰⁷, 2.04 × 10⁻⁰⁶, and 9.07 × 10⁻⁰⁵ Gy d⁻¹ for plants. The maximum total dose of 0.7234 mSv yr⁻¹ was obtained at t = 1 year. The external dose contribution obtained at t = 1 year for all nuclides summed and all component pathways was 0.4 mSv yr⁻¹, above the background radiation dose limit of 2.5 × 10⁻⁰¹ mSv yr⁻¹. A maximum cancer risk of 1.36 × 10⁻⁰³ was observed at t = 1 year. It was also shown in the RESRAD calculations that the total cancer morbidity risks from plant ingestion, radon (independent of water), and external gamma exposure pathways were greater than those from other exposure pathways. The high risk calculated for ²²⁶Ra relative to ²³²Th and ⁴⁰K makes it the primary human health concern in the study area. The use of a 1 m cover thickness would remediate the contaminated site to a dose on the order of 10⁻⁵ mSv yr⁻¹ for a period of 0 to 100 years. The values of these doses are below the US DOE recommended limits. Full article

The step-and-shoot (SS) mode and continuous mode are currently used for single-photon emission computed tomography (SPECT) scan mode, and a new scan mode that combines both modes, step-and-shoot plus continuous (SSC) mode, was developed. It is expected to allow a shorter scan time and lower injected dose because the SSC mode is more sensitive than the SS mode. We confirmed the image quality of this scan mode, including various quantitative correction methods for scatter (SC), attenuation (AC), and resolution recovery (RR) in a phantom study and clinical case study. Image quality was evaluated by the count, contrast-to-noise ratio (CNR), and percent of the coefficient of variation (%CV). Independent of the correction methods, the count, CNR, and %CV of the SSC mode were superior to those of the SS mode. The ACSCRR was the best method, with a maximum increased rate of 66.4% in counts and 57.8% in CNR for the 13-mm sphere and 19.6% in CNR for other sphere sizes. The %CV for the SSC mode was the best for AC and ACRR, which was at 15.1%. With regards to attaining short bone SPECT scan time, the combination of the SSC mode and ACRR or ACSCRR demonstrated the best physical performance. Full article