Internal Conversion Electrons Research Articles

Assessing DNA damage and relative biological effectiveness of the secondary electrons in gadolinium neutron capture therapy using an adapted Geant4-DNA

The aim of this study is to assess the impact of internal conversion (IC) and Auger electrons released during gadolinium neutron capture therapy (157GdNCT) on the amount of DNA damage induced and the relative biological effectiveness (RBE) across varying cellular structures and types. We developed cell models that featured simplified chromosome geometries with diverse shapes and base pair densities, utilizing the Geant4-DNA package. The RBE values of these secondary electrons were determined based on the DNA double-strand breaks (DNA-DSBs) endpoint. The findings revealed that the more the distribution of gadolinium is concentrated in the nucleus, the greater the degree of DNA damage. In the cytoplasm, the influence of secondary electrons on DNA damage were not related to cell shape. However, when the secondary electrons were distributed in the nuclear membrane, the RBE of the secondary electrons was affected by the cell shape. When there is a greater difference in base pair density, more pronounced discrepancies in the yield of DSBs are evident. As the base pair density decreased, the yield of DSBs increased. Furthermore, the yield of DSBs exceeded 8.63 ± 0.33 DSBs/Gy/Gbp under different influencing factors. The RBE range of IC electrons and Auger electrons released from 157GdNCT based on DNA-DSBs endpoints was found to be between 0.8 and 1.6.

Standardization of 109Cd Using CIEMAT/NIST Method and Internal Conversion Electron Counting

Standardization of 109Cd Using CIEMAT/NIST Method and Internal Conversion Electron Counting

PRINCEPS: Towards the Automation of Simultaneous \(\gamma \)-ray and Internal Conversion Electron Analysis

PRINCEPS: Towards the Automation of Simultaneous \(\gamma \)-ray and Internal Conversion Electron Analysis

New results on the decay spectroscopy of 254No with GABRIELA@SHELS

The structure of the nucleus has been studied for more than 20 years: the last publications on its decay spectroscopy are from LBNL [1], GSI [2], JYFL [3] and ANL [4]. Four decay schemes featuring two isomers have been published and are interpreted differently in terms of excitation energy and decay scheme of the 2 nd isomer and configuration assignments of both K-isomers. These discrepancies have triggered new experiments including this one, performed with the GABRIELA [5, 6] array, at the focal plane of the SHELS [7] separator at the FLNR, Dubna. The first part of this proceeding will present the experimental setup and the analysis techniques used to reveal the electromagnetic decay of the known isomers in 254No. The second part will focus on the new results obtained with more than 1 million 254No nuclei implanted in the focal plane detector. In particular, the internal conversion electron spectrum observed in the decay of the 8− K-isomer has revealed the presence of a strong transition, most likely E0, suggesting low-lying shape coexistence in this nucleus as predicted in [8, 9]. The γ-ray spectrum obtained from the decay of the short-lived 170 μs isomer has revealed new γ-ray lines putting in doubt the previous interpretations about this isomer decay.

Emergence of triaxiality in 74Se from electric monopole transition strengths

The structure of 74Se at low energy was investigated via spectroscopy of internal conversion electrons at the INFN Legnaro National Laboratories (LNL). A set of internal K-conversion coefficients and monopole transition strengths was measured. A large ρ2(E0;22+→21+)⋅103=210(130) value was deduced. This result, in addition to a low upper limit for the 03+→02+ electron transition, casts in doubt a simple interpretation of the 74Se low-lying structure, in particular the recently proposed spherical, vibrational character. New microscopic beyond-mean-field calculations generally agree with the experimental results and are capable of producing a large ρ2(E0;22+→21+) value, even if still a factor ≈7 smaller than the experiment. Triaxiality and a complex shape-coexistence and mixing scenario seem responsible for this unexpected experimental result.

Gold Nanorods as Radiopharmaceutical Carriers: Preparation and Preliminary Radiobiological In Vitro Tests

Low-energy electrons (Auger electrons) can be produced via the interaction of photons with gold atoms in gold nanorods (AuNRs). These electrons are similar to those emitted during the decay of technetium-99m (99mTc), a radioactive nuclide widely used for diagnostics in nuclear medicine. Auger and internal conversion (IC) electron emitters appropriately targeted to the DNA of tumors cells may, therefore, represent a new radiotherapeutic approach. 99mTc radiopharmaceuticals, which are used for diagnosis, could indeed be used in theragnostic fields when loaded on AuNRs and delivered to a tumor site. This work aims to provide a proof of concept (i) to evaluate AuNRs as carriers of 99mTc-based radiopharmaceuticals, and (ii) to evaluate the efficacy of Auger electrons emitted by photon-irradiated AuNRs in inducing radio-induced damage in T98G cells, thus mimicking the effect of Auger electrons emitted during the decay of 99mTc used in clinical settings. Data are presented on AuNRs’ chemical characterization (with an aspect ratio of 3.2 and Surface Plasmon Resonance bands at 520 and 680 nm) and the loading of pharmaceuticals (after 99mTc decay) on their surface. Spectroscopic characterizations, such as UV-Vis and synchrotron radiation-induced X-ray photoelectron (SR-XPS) spectroscopies, were performed to investigate the drug–AuNR interaction. Finally, preliminary radiobiological data on cell killing with AuNRs are presented.

Experimental determinations of the energy of the 9.4 keV (M1+E2) nuclear transition in 83Kr and the Kr electron binding energies in different matrices by ICES method

An energy value of 9406.3(5) eV was determined for the 9.4 keV (M1+E2) nuclear transition in 83Kr by the internal conversion electron spectrometry method. This value agrees within 1σ with the most precise values determined previously for which their weighted mean amounts to 9405.9(2) eV. A value of 22745.3(2) eV was obtained directly from our experimental data for the energy difference between the 32.1 keV and 9.4 keV transitions in 83Kr. Electron binding energies (related to the Fermi level) on the K, L, and M1,2,3 subshells of Kr implanted into a polycrystalline Pt matrix were also derived. They were found to be lower by weighted mean values of 11.6(4) and 1.7(6) eV compared to those for free Kr atoms and for Kr in an evaporated 83Rb layer on Al backing, respectively, and higher by a weighted mean value of 2.9(2) eV than the binding energies in Kr in an evaporated layer on polycrystalline Pt backing.

Analysis of a neutron-induced conversion electron spectrum of gadolinium

A 100-nm-thick gadolinium layer deposited on a pixelated silicon sensor was activated in a neutron field to measure the internal conversion electron (ICE) spectrum generated by neutron capture products of 155Gd and 157Gd. The experiment was performed at the ISIS neutron and muon facility, using a bespoke version of the HEXITEC spectroscopic imaging camera. Signals originating from internal conversion electrons, Auger electrons, x rays and gamma rays up to 150 keV were identified. The ICE spectrum has an energy resolution of 1.8–1.9 keV at 72 keV and shows peaks from the K, L, M, N+ ICEs of the 79.51 keV and 88.967 keV 2+-0+ gamma transitions from the first excited states in 158Gd and 156Gd, respectively, as well as the K ICEs of the 4+-2+ transitions at 181.931 keV and 199.213 keV from the respective second excited states. Spectrum analysis was performed using a convolution of a Gaussian with exponential functions at the low and high energy side as the peak shaping function. Relative ICE intensities were derived from the fitted peak areas and compared with internal conversion coefficient (ICC) values calculated from the BrIcc database. Relative to the dominant L shell contribution, the K ICE intensity conforms to BrIcc and the M, N, O+ ICE intensities are somewhat higher than expected.

Update and Extension of Release Criteria for Canine 117m Sn Treatments.

Tin-117 m ( 117m Sn) is used to treat dogs with osteoarthritic joints by radiosynoviorthesis. The internal conversion and Auger electrons emitted by the 117m Sn provide the therapeutic effect. Sn-117 m also emits x rays and gamma rays, of which the most significant is 158.6 keV. Accurate information regarding the interactions of a person with a treated dog is needed to determine the person's total dose and thus regulatory compliance; i.e., a time and motion study. Prior studies have characterized the radiation field emitted by a treated dog, determined the effective dose rates to a person based on those radiation fields, and evaluated dog-human interactions. These studies have been tied together to calculate the prospective dose to the owner of a treated dog. The behavior modifications needed to comply with public dose limits were identified, and a template for written instructions limiting dose was developed. Further calculations based on the written instructions were made to determine the necessary duration of the instructions. The result is guidance that may be used by veterinary practitioners to release treated dogs in accordance with the public dose limits.

DICE: Apparatus for Detection of Internal Conversion Electrons

An apparatus for the Detection of Internal Conversion Electrons (DICE) has been built and commissioned at Johannes Gutenberg University Mainz (JGU) for the study of recoil ion sources of 239Pu, which emit 235mU nuclei that deexcite to the ground state by emitting low-energy internal conversion (IC) electrons. We present an overview of DICE and its commissioning with 207Bi and 235mU electron sources, demonstrating that DICE allows the detection and counting of IC electrons from 235mU deexcitation. Our preliminary 235mU half-life of ≈ 26 min agrees with literature. DICE is thus an interesting tool to broaden analytical capabilities for recoil ion source characterization via studies of the peculiar decay of 235mU.

Precise conversion electron intensities of low energy gamma transitions for efficiency calibration of electron detectors

Precise energies and relative intensities of gamma transitions and conversion electrons in the electron capture decay of 153Gd have been determined independently with our well-tested and optimized gamma and electron spectrometers - a large-volume (60 cc) HPGe detector and a mini-orange electron transporter paired to a Si(Li) detector, respectively. The experimental internal conversion coefficients of the gamma transitions in 153Eu have been determined using Normalized Peak to Gamma method and compared with the theoretical values adopted by Nuclear Data Sheets to assign multipolarities of all the transitions. The precise internal conversion electron intensities of the low energy transitions can be used as standards for calibration purposes of electron detectors and spectrometers.

Improved measurement of the 02+→01+E0 transition strength for Se72 using the SPICE spectrometer

The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton drip line. In this work, a study of $^{72}\mathrm{Se}$ by internal conversion electron and $\ensuremath{\gamma}$-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the ${0}_{2}{}^{+}$ state were performed, yielding a determination of ${\ensuremath{\rho}}^{2}(E0;{0}_{2}{}^{+}\ensuremath{\rightarrow}{0}_{1}{}^{+})=29(3)$ milliunits. Two-state mixing calculations were performed that highlighted the importance of interpretation of such $E0$ strength values in the context of shape coexistence.

Dosimetry assessment of theranostic Auger-emitting radionuclides in a micron-sized multicellular cluster model: A Monte Carlo study using Geant4-DNA simulations

The present work is aimed at improving the multicellular dosimetry of several Auger radionuclides of interest for targeted cancer therapy, including 99mTc, 111In, 123I, 125I, and 201Tl. For this purpose, using the Geant4-DNA Monte Carlo code, a cluster of 13 similar spherical cells with a hexagonal packed arrangement was modeled, and the mean absorbed doses per unit cumulated activity (S-values) were calculated by considering two target←source configurations, cell←cell and nucleus←nucleus. The obtained ratios of cross-dose to self-dose S-value in terms of the distance between the source and target regions were evaluated and also compared to those estimated by the Medical Internal Radiation Dose (MIRD) method. Besides, the contribution of the Coster-Kronig, Auger and internal conversion electrons to the S-values was provided for each radionuclide. According to the results, it can be concluded that in contrast to self-absorption, the cross-absorption due to the Auger-emitters has not a significant role in the total energy deposition within a cell in the cluster.

Proliferation protection of uranium due to the presence of U-232 decay products as intense sources of hard gamma radiation

The objectives of the article are (1) to show the nuclear and physical causes of hard γ-quanta in the U-232 decay chain, (2) to propose tactics for handling uranium containing U-232, and (3) to assess the efficiency of its protective γ-barrier against uncontrolled proliferation. The authors show the general picture of the decay chains of U-232 nuclide transformations, on which the protection of uranium from its uncontrolled proliferation is based. During the decay of nuclei, their emission of α- or β-particles is only the first stage of the most complex process of rearrangement of both the internal structure of the nucleus itself, which consists in the rearrangement of the neutron and proton shells and the levels of its excitation, and in the rearrangement of the electron shells of the atom. As a rule, the daughter nucleus is in a highly excited state, which is removed by the emission of hard γ-quanta and internal conversion electrons. After the second case, the remaining excitation of the atom is removed by the emission of characteristic γ-quanta and Auger-electrons with characteristic γ-quanta. In addition, explanations are given for the quantum-mechanical reasons for the hard γ-radiation of Tl-208 and Bi-212, which complete the U-232 decay chain. The authors also proposed a tactic for handling uranium containing uranium-232. Since the hard γ-quanta of Tl-208 and Bi-212 appear only at the end of the U-232 decay chain, after its chemical purification from its decay products, U-232 itself does not pose a radiation hazard; therefore, at this time it is advisable to conduct all necessary operations for transporting the material to the plant, fabricating uranium-based fuel containing U-232, and transporting this fuel to the nuclear facility where it will be used.

A method for quickly subtracting the contributions from 182Ta and 94Nb in activity measurement of 93mNb in reactor neutron environment

Niobium is one of the most important neutron dosimeters used outside of the reactor. Owing to the fluorescence effects of 182Ta and 94Nb radionuclides, it is a problem to quickly obtain the activity of 93mNb which produced by the neutron inelastic scattering of Nb. To solve this problem, a fast estimating method based on the Monte Carlo simulation is proposed. All the contributions from fluorescence effects that induced by gamma-rays, beta-rays and internal conversion electrons of the radionuclides in the niobium sample were considered. The comparison results demonstrated that the deviation is less than 8.0% between the calculated and the experimental activities. It shows that the contribution of radionuclide by fluorescence effects in activity measurement of the niobium sample can be subtracted quickly using this method, based just once experimental measurement.

Electric monopole transitions and structure of low-spin states in Pd106

Structures in the $^{106}\mathrm{Pd}$ nucleus have been studied in the $\mathrm{EC}/{\ensuremath{\beta}}^{+}$ decay of $^{106}\mathrm{Ag}$ at the INFN Legnaro National Laboratories using the Spes Low-energy Internal Conversion Electron Spectrometer (SLICES). The K-conversion coefficients and the electric monopole transition strengths, between low-lying ${2}^{+}$ and ${0}^{+}$ states, have been studied. These experimental data combined with the results from conversion electron measurement on $^{104}\mathrm{Pd}$ previously performed by the Florence spectroscopy group were compared with the theoretical values calculated in the framework of the interacting proton-neutron boson model. Good agreement between experimental and theoretical values is found when interpreting the ${0}_{3}^{+}$ level as an intruder state.

Photo-Driven Delivery of 125I-Labeled Nanomicelles for Nucleus-Targeted Internal Conversion Electron-Based Cancer Therapy.

As a kind of high linear energy transfer (LET) radiation, internal conversion electrons are emitted from some radionuclides, such as 125I, triggering severe DNA damage to tumor cells when transported into the nucleus. Herein, we develop a curcumin-loaded nanomicelle composed of a photosensitizer chlorin e6 (Ce6) and amphiphilic poly(ethylene glycol) (poly(maleic anhydride-alt-1-octadecene)-poly(ethylene glycol) (C18-PMH-PEG)) to deliver 125I into the nucleus under 660 nm laser irradiation, leading to the optimized imaging-guided internal conversion electron therapy of cancer. Ce6-containing nanomicelles (Ce6-C18-PEG) self-assemble with nucleus-targeted curcumin (Cur), obtaining Ce6-C18-PEG/Cur nanoparticles. After labeling Cur with 125I, Ce6-C18-PEG/Cur enables single-photon emission computed tomography and fluorescence imaging of the tumor, serving as a guide for follow-up laser irradiation. Notably, the 660 nm laser-triggered photodynamic reaction of Ce6 optimizes the delivery of Ce6-C18-PEG/125I-Cur at various stages, including tumor accumulation, cellular uptake, and lysosome escape, causing plenty of 125I-Cur to enter the nucleus. By this strategy, Ce6-C18-PEG/125I-Cur showed optimal antitumor efficacy and high biosafety in mice treated with local 660 nm laser irradiation using efficient energy deposition of internally converted electrons over short distances. Therefore, our work provides a novel strategy to optimize 125I delivery for tumor treatment.

Evidence of high- K isomerism in No154102256

Isomeric states in $^{256}\mathrm{No}$ were investigated using internal conversion electron and $\ensuremath{\gamma}$-ray spectroscopy with the GABRIELA detection system at the focal plane of the SHELS recoil separator, at the Flerov Laboratory for Nuclear Research (FLNR, JINR, Dubna). The nuclei of interest were produced using the highly asymmetric fusion-evaporation reaction $^{238}\mathrm{U}(^{22}\mathrm{Ne},4n)^{256}\mathrm{No}$. The emission of internal conversion electrons and $\ensuremath{\gamma}$ rays occurring between a $^{256}\mathrm{No}$ implantation and a subsequent $\ensuremath{\alpha}$-decay event were studied, resulting in the observation of high-$K$ isomerism in this nobelium isotope. The nature of the isomeric states is discussed in terms of possible two- and four-quasiparticle structures.

SLICES: Spes Low-energy Internal Conversion Electron Spectrometer

The Spes Low-energy Internal Conversion Electron Spectrometer (SLICES) is a new electron spectrometer designed to perform off-beam measurements at the beta decay station of the SPES facility at the Legnaro National Laboratories (LNL). SLICES consists of a large area Si(Li) detector cooled at −150 °C and a magnetic transport system. Four permanent N52 magnets, located around a central photon shield focus the electrons on the detector. In this paper, a detailed description of the SLICES components is presented. The strength of the measured magnetic field has been compared with calculations. The efficiency of the apparatus has been simulated and compared with the experimental data obtained using a radioactive 207Bi source. The commissioning of the spectrometer at the CN accelerator at LNL is also presented.

The first experimental evidence for the (M1 + E2) mixed character of the 9.2 keV transition in 227Th

The 9.2 keV nuclear transition in 227Th was studied in the β−-decay of 227Ac by means of the internal conversion electron spectroscopy to clarify the spin-parity assignment of the ground state and the two lowest excited states of 227Th. The transition multipolarity was proved to be of mixed character M1 + E2 and the spectroscopic admixture parameter δ2(E2/M1)=0.695±0.248 (|δ(E2/M1)|=0.834±0.149) was determined. Nonzero value of δ(E2/M1) questioned the present theoretical interpretation of low-lying levels of 227Th. Calculations performed prefer the 1/2+, 3/2+, and 3/2+ sequence instead of the adopted 1/2+, 5/2+ and 3/2+ one for the 0.0, 9.2, and 24.3 keV levels, respectively.