44Sc production from enriched 47TiO2 targets with a medical cyclotron

44Sc is a β+-emitter which has been extensively studied for nuclear medicine applications. Its promising decay characteristics [t1/2 = 3.97 h, E [Formula: see text] = 632 keV (94.3%), Eγ = 1157 keV (99.9%); 1499 keV (0.91%)] make it highly attractive for clinical PET imaging, offering an alternative to the widely used 68Ga [t1/2 = 67.7 min, E [Formula: see text] = 836 keV (87.7%)]. Notably, its nearly fourfold longer half-life opens avenues for applications with biomolecules having extended biological half-lives and enables the centralized distribution of 44Sc radiopharmaceuticals. An additional advantage of employing 44Sc as a diagnostic radioisotope lies in its counterpart, the β--emitter 47Sc, which is currently under investigation for targeted radiotherapy. Together, they form an ideal theranostic pair, providing a comprehensive solution for both diagnostic imaging and therapeutic applications in nuclear medicine. At the Bern medical cyclotron, a study to optimize the production of scandium radioisotopes is currently ongoing. In this context, proton irradiation of titanium targets has been investigated, exploiting the reactions 47Ti(p,α)44Sc and 50Ti(p,α)47Sc. This approach enables the production of Sc radioisotopes within a single PET medical cyclotron facility, employing identical chemical procedures for target preparation and post-irradiation processing. In this paper, we report on cross-section measurements of the 47Ti(p,α)44Sc nuclear reaction using 95.7% enriched 47TiO2 targets. On the basis of the obtained results, the production yield and purity were calculated to assess the optimal irradiation conditions. Production tests were performed to confirm these findings.

Fast neutron induced reaction cross sections on natural manganese and tantalum

The cross sections for the 55Mn(n,2n)54Mn, 181Ta(n,2n)180gTa, and 181Ta(n,p)181Hf reactions were measured to be 705.1 ± 26.1 mb at 14.0 MeV, 1362.7 ± 87.2 mb at 13.6 MeV, and 2.31 ± 0.09 mb at 13.6 MeV, respectively, by using an off-line γ-ray spectroscopic technique. The neutrons were produced via the 3H(d,n)4He reaction. The monitor reactions 27Al(n,α)24Na and 93Nb(n,2n)92mNb were used for neutron flux determination. The results from the present work were compared with those of the literature and the evaluated data from ENDF/B-VIII.0, JEFF-3.3, JENDL-5, CENDL-3.2, and BROND-3.1 libraries. Besides, the cross sections were also estimated with the TALYS-1.96 nuclear model code using different level density models for a better description of the present work and literature data. The present experimental results were found to be in good agreement with most of the available literature data and with the evaluated data.

Cross-section measurement of thulium radioisotopes with an 18 MeV medical PET cyclotron for an optimized 165Er production

165Er is a pure Auger-electron emitter with promising characteristics for therapeutic applications in nuclear medicine. The short penetration path and high Linear Energy Transfer (LET) of the emitted Auger electrons make 165Er particularly suitable for treating small tumor metastases. Several production methods based on the irradiation with charged particles of Er and Ho targets can be found in the literature. In this paper, we report on the study of 165Er indirect production performed via the 166Er(p,2n)165Tm →165Er reaction at the 18 MeV Bern medical cyclotron. Despite the use of highly enriched 166Er2O3 targets, several Tm radioisotopes are produced during the irradiation, making the knowledge of the cross sections involved crucial. For this reason, a precise investigation of the cross sections of the relevant nuclear reactions in the energy range of interest was performed by irradiating Er2O3 targets with different isotopic enrichment levels and using a method based on the inversion of a linear system of equations. For the reactions 164Er(p, γ)165Tm, 166Er(p,n)166Tm, 166Er(p, γ)167Tm, 167Er(p,3n)165Tm, 167Er(p, γ)168Tm, 168Er(p,2n)167Tm and 170Er(p,3n)168Tm, the nuclear cross section was measured for the first time. From the results obtained, the production yield and purity of the parent radioisotope 165Tm were calculated to assess the optimal irradiation conditions. Several production tests with solid targets were performed to confirm these findings.

Optimized production of 67Cu based on cross section measurements of 67Cu and 64Cu using an 18 MeV medical cyclotron

RadioNuclide Therapy (RNT) in nuclear medicine is a cancer treatment based on the administration of radioactive substances that specifically target cancer cells in the patient. These radiopharmaceuticals consist of tumor-targeting vectors labeled with β^-, α, or Auger electron-emitting radionuclides. In this framework, ⁶⁷Cu is receiving increasing interest as it provides β^--particles accompanied by low-energy γ radiation. The latter allows to perform Single Photon Emission Tomography (SPECT) imaging for detecting the radiotracer distribution for an optimized treatment plan and follow-up. Furthermore, ⁶⁷Cu could be used as therapeutic partner of the β⁺-emitters ⁶¹Cu and ⁶⁴Cu, both currently under study for Positron Emission Tomography (PET) imaging, paving the way to the concept of theranostics. The major barrier to a wider use of ⁶⁷Cu-based radiopharmaceutical is its lack of availability in quantities and qualities suitable for clinical applications. A possible but challenging solution is the proton irradiation of enriched ⁷⁰Zn targets, using medical cyclotrons equipped with a solid target station. This route was investigated at the Bern medical cyclotron, where an 18 MeV cyclotron is in operation together with a solid target station and a 6-m-long beam transfer line. The cross section of the involved nuclear reactions were accurately measured to optimize the production yield and the radionuclidic purity. Several production tests were performed to confirm the obtained results.

Sub-keV corrections to binary encounter cross section models for electron ionization of liquid water with application to the Geant4-DNA Monte Carlo code

INTRODUCTION

The electron ionization cross section of water is one of the most important input in Monte Carlo studies of cellular radiobiological effects. Analytical cross section models of the binary-encounter type have the potential of reducing simulation time and facilitate application to a variety of biological materials (other than water). The Binary-Encounter-Bethe (BEB) and Binary-Encounter-Dipole (BED) models of NIST are perhaps the most popular of such models giving reliable results for atoms and molecules in the gas-phase over a wide energy range. However, the use of such models to sub-keV electron energies in liquid water raises concerns due to the neglect of condensed phase effects that leads to a significant overestimation when compared to medium-specific dielectric models.

PURPOSE

To modify the BEB and BED models towards better agreement with the recommended low-energy dielectric model of Geant4-DNA (Option 4). To implement the new modifications to the existing BEB model of the Option 6 physics constructor of Geant4-DNA and re-evaluate fundamental transport quantities for sub-keV electrons.

METHODS

In analogy to a Yukawa potential a simple, yet physically-motivated, modification of the Burgess correction term is proposed to account for the reduction of the Coulomb interaction due to the polarizability of the target. The magnitude of the correction is guided by the dielectric-based ionization cross section implemented in Option 4.

RESULTS

Differential, total and stopping ionization cross sections for low-energy electrons in liquid water are presented. When combined with the Vriens correction (which is not included in Option 6), the proposed modification to the BEB and BED models brings the ionization and stopping cross sections in much better agreement against those used in the Option 4 dielectric model of Geant4-DNA, with up to 30% and 10% deviation, respectively. Implementation of the new correction to the Option 6 constructor of Geant4-DNA and re-evaluation of fundamental transport quantities, such as electron penetration ranges and dose-point-kernels, reduced the discrepancies from Option 4 at sub-keV energies from 20 to 100% (or more) to well below 10% in most cases.

CONCLUSIONS

A simple modification to the BEB and BED analytic models was found to improve their performance for sub-keV electrons in liquid water medium. Implementation of the new modification to the Option 6 constructor of Geant4-DNA significantly improved the agreement with the recommended low-energy Option 4 constructor for a variety of fundamental quantities related to electron transport.

Estimations for (n,α) reaction cross sections at around 14.5MeV using Levenberg-Marquardt algorithm-based artificial neural network

Prediction of neutron-induced reaction cross-sections at around the 14.5 MeV neutron energy is crucial to calculate nuclear transmutation rates, nuclear heating, and radiation damage from gas formation in fusion reactor technology In this research, the new approach of (n,α) reaction cross-section is presented. It has been assessed by utilizing the artificial neural network (ANN) when compared to more advanced algorithms, the Levenberg-Marquardt algorithm-based ANN can be exceedingly fast. The correlation coefficients for a training R-value of 0.99283, a validation R-value of 0.991190, a testing R-value of 0.97337, and an overall R-value of 0.98515 demonstrate that Levenberg-Marquardt algorithm-based ANN is well suited for this purpose. . The obtained results were compared to theoretical calculations of TALYS 1.95 nuclear code. As a consequence, it has been demonstrated that the ANN model can be used to determine the systemic study for (n, α) reaction cross-sections.

Cross-section measurement for an optimized 61Cu production at an 18 MeV medical cyclotron from natural Zn and enriched 64Zn solid targets

The availability of novel medical radionuclides is a key point in the development of personalised nuclear medicine. In particular, copper radioisotopes are attracting considerable interest as they can be used to label various molecules of medical interest, such as proteins and peptides, and offer two of the most promising true theranostic pairs, namely ⁶¹Cu/⁶⁷Cu and ⁶⁴Cu/⁶⁷Cu. Although ⁶⁴Cu (t_1/2 = 12.7006 h, β⁺: 17.6%, β^-: 38.5%) is nowadays the most commonly used as a diagnostic radionuclide, ⁶¹Cu (t_1/2 = 3.339 h, β⁺: 61%) features more favourable nuclear properties, such as a higher positron decay fraction and the absence of β^- emissions. To date, the production of ⁶¹Cu has been carried out irradiating highly enriched ⁶¹Ni targets with a low energy proton beam. However, the use of the very expensive ⁶¹Ni targets requires an efficient recovery of the target material and makes this method quite inconvenient. Another promising production route is the proton irradiation of natural Zn or enriched ⁶⁴Zn targets, exploiting the (p,α) nuclear reaction. Along this line, a research program is ongoing at the Bern medical cyclotron, equipped with an external beam transfer line and a solid target station. In this paper, we report on cross-section measurements of the ⁶⁴Zn(p,α)⁶¹Cu nuclear reaction using natural Zn and enriched ⁶⁴Zn material, which served as the basis to perform optimized ⁶¹Cu production tests with solid targets.

First principles calculation for generating new thermal neutron scattering data for Zirconium hydride

Lattice parameters of materials have the same magnitude as the energy of thermal neutrons in reactors, which directly affects the neutron cross section and its energy. While they are thermalized, incident neutrons can lose or gain energy during their interactions with materials components. Since several decades, methods and models were developed in the aim to generate nuclear data sub-libraries required in correcting neutrons interactions cross sections at thermal energies. However, very few experimental works were dedicated to this field. In this paper we focus our efforts on reviewing the theoretical models and their adequacy in describing thermal scattering events in the aim of proposing new formalisms to calculate the density of states (DOS) and phonon responses of zirconium hydride material, which constitutes an important moderator of neutrons in TRIGA reactors fuel elements. Generally the effects of thermal scattering are provided in nuclear data evaluations by a thermal sub-library ENDF file 7. Data in file 7 are described by the known thermal scattering law S(α,β) which is a function of momentum transfer and energy transfer parameters α and β respectively. The thermal scattering law has been used to calculate the double differential cross sections and the corresponding results are presented. Although the comparison with other models shows satisfactory results, no previously personalized use of data may be the raison of its usefulness in some cases and not in others.

Optimization of ultraviolet Raman spectroscopy for trace explosive checkpoint screening

Raman spectroscopy has long been considered a gold standard for optically based chemical identification, but has not been adopted in non-laboratory operational settings due to limited sensitivity and slow acquisition times. Ultraviolet (UV) Raman spectroscopy has the potential to address these challenges through the reduction of fluorescence from background materials and increased Raman scattering due to the shorter wavelength (relative to visible or near-infrared excitation) and resonant enhancement effects. However, the benefits of UV Raman must be evaluated against specific operational situations: the actual realized fluorescence reduction and Raman enhancement depend on the specific target materials, target morphology, and operational constraints. In this paper, the wavelength trade-space in UV Raman spectroscopy is evaluated for one specific application: checkpoint screening for trace explosive residues. The optimal UV wavelength is evaluated at 244, 266, and 355 nm for realistic trace explosive and explosive-related compound (ERC) residues on common checkpoint materials: we perform semi-empirical analysis that includes the UV penetration depth of common explosive and ERCs, realistic explosive and ERC residue particle sizes, and the fluorescence signal of common checkpoint materials. We find that while generally lower UV wavelength provides superior performance, the benefits may be significantly reduced depending on the specific explosive and substrate. Further, logistical requirements (size, weight, power, and cost) likely limit the adoption of optimal wavelengths. Graphical abstract.

Characterizing the Two-photon Absorption Properties of Fluorescent Molecules in the 680-1300 nm Spectral Range

Two-photon laser scanning microscopy (2PLSM) is a state-of-the-art technique used for non-invasive imaging deep inside the tissue, with high 3D resolution, minimal out-of-focus photodamage, and minimal autofluorescence background. For optimal application of fluorescent probes in 2PLSM, their two-photon absorption (2PA) spectra, expressed in absolute cross sections must be characterized. Excitation at optimum wavelength will make it possible to reduce the laser power and therefore minimize photodamage. Obtaining 2PA spectra and cross sections requires correcting the two-photon excited fluorescence signals for a combination of laser properties, including the beam spatial profile, pulse duration, and absolute power, at each wavelength of the tuning range. To avoid such tedious day-to-day laser characterization required in the absolute measurement method, a relative method based on independently characterized 2PA reference standards is often used. By carefully analyzing the available literature data, we selected the most reliable standards for both the 2PA spectral shape and cross section measurements. Here we describe a protocol for measuring the 2PA spectral shapes and cross sections of fluorescent proteins and other fluorophores with the relative fluorescence method using these reference standards. Our protocol first describes how to build an optical system and then how to perform the measurements. In our protocol, we use Coumarin 540A in dimethyl sulfoxide and LDS 798 in chloroform for the spectral shape measurements to cover the range from 680 to 1300 nm, and Rhodamine 590 in methanol and Fluorescein in alkaline water (pH 11) for the absolute two-photon cross section measurements.

Activation cross sections of proton induced nuclear reactions on palladium up to 80MeV

Activation cross sections of proton induced nuclear reactions on palladium were measured up to 80MeV by using the stacked foil irradiation technique and gamma ray spectrometry. The beam intensity, the incident energy and the energy degradation were controlled by a method based on flux constancy via normalization to the excitation functions of monitor reactions measured in parallel. Excitation functions for direct and cumulative cross-sections were measured for the production of (104m,104g,105g,106m,110m)Ag, (100,101)Pd, (99m,99g,100,101m,101g,102m,102g,105)Rh and (103,97)Ru radioisotopes. The cross section data were compared with the theoretical predictions of TENDL-2014 and -2015 libraries. For practical applications thick target yields were derived from the measured excitation functions. Application in the field of medical radionuclide production is shortly discussed.

Automated high-content morphological analysis of muscle fiber histology

In the search for a cure for many muscular disorders it is often necessary to analyze muscle fibers under a microscope. For this morphological analysis, we developed an image processing approach to automatically analyze and quantify muscle fiber images so as to replace today's less accurate and time-consuming manual method. Muscular disorders, that include cardiomyopathy, muscular dystrophies, and diseases of nerves that affect muscles such as neuropathy and myasthenia gravis, affect a large percentage of the population and, therefore, are an area of active research for new treatments. In research, the morphological features of muscle fibers play an important role as they are often used as biomarkers to evaluate the progress of underlying diseases and the effects of potential treatments. Such analysis involves assessing histopathological changes of muscle fibers as indicators for disease severity and also as a criterion in evaluating whether or not potential treatments work. However, quantifying morphological features is time-consuming, as it is usually performed manually, and error-prone. To replace this standard method, we developed an image processing approach to automatically detect and measure the cross-sections of muscle fibers observed under microscopy that produces faster and more objective results. As such, it is well-suited to processing the large number of muscle fiber images acquired in typical experiments, such as those from studies with pre-clinical models that often create many images. Tests on real images showed that the approach can segment and detect muscle fiber membranes and extract morphological features from highly complex images to generate quantitative results that are readily available for statistical analysis.