Abstract: Synchrotron radiation light source has been successfully used in material science, biomedicine, and other fields because of its high intensity, good monochromaticity, and excellent coherence and collimation. In recent years, the source has significantly expedited the advancement of medical applications. High contrast and spatial-temporal resolution images based on synchrotron radiation X-ray have been obtained, presenting innovative opportunities for precise clinical diagnosis and therapy. In this review, we first delineate the characteristics of synchrotron radiation beamlines, then conclude recent breakthroughs in synchrotron X-ray imaging and radiotherapy for various clinical applications, particularly for heart, breast, lung, bone, and brain conditions. Novel synchrotron radiation X-ray radiotherapy treatments, including microbeam and stereotactic radiotherapy, have shown great potential for clinical application by enabling more precise and low-dose treatments. Synchronized radiation techniques are projected to redefine diagnostic criteria for imaging and therapeutic options for resistant cancer, offering immense potential for medical applications.

Abstract: Blood concentrations of essential trace elements can be used to diagnose conditions and diseases associated with excess or deficiency of these elements. Inductively coupled plasma mass spectrometry (ICP-MS) has been employed for such measurements, but maintenance and operation costs are high. XRF detectability in cutaneous blood of iron (Fe), copper (Cu), zinc (Zn), and selenium (Se) was assessed as alternative to ICP-MS. Three phantoms were made up of two polyoxymethylene (POM) plastic cylindrical cups of 0.6-mm and 1.0-mm thick walls and a 5.3-mm diameter POM cylindrical insert. Six water solutions of Fe in 0 to 500 mg/L and Cu, Zn, and Se in 0 to 50 mg/L concentrations, were poured into the phantoms to simulate x-ray attenuation of skin. Measurements using an integrated x-ray tube and polycapillary x-ray lens unit generated 24 calibration lines. Detection limit intervals in mg/L were: (36, 100), (14, 40), (3.7, 10), and (2.1, 3.4) for Fe, Cu, Zn, and Se, respectively. Fe was the only element with detection limits lower than its 480 mg/L median human blood concentration. Estimated radiation dose and equivalent dose to skin were below those of common radiological procedures. Applications will require further instrumental development, and finding a calibration method.

Abstract: This study proposes an innovative methodology that combines experimental microCT imaging with Monte Carlo irradiation simulations using the PENELOPE code aimed at enabling detailed analyses of different features involved in the irradiation processes along with elemental mapping, as required for X-ray fluorescence imaging of in vivo samples. By examining the relationship between signal-to-noise ratio (SNR) and absorbed dose (D), a mathematical approach was proposed to determine critical points where their rates of change are equal. Thus, allowing to identify optimal concentrations of gold dispersions to the specific simulated system of interest, where the signal quality efficiently improves as weighted in relation to the absorbed dose. The proposed methodology has been applied to a typical small animal (rat) microCT that was further used by the computationally implemented model to infuse the animal kidneys by different amounts of gold. For the K_(α_1 ), K_(α_2 ), and K_(β_1 ) lines, these critical concentrations were found to be 0.78 %, 1.32 %, and 0.32 % w/w, respectively, while no such behavior was identified for the K_(β_2 ) line under the given configuration considered as a representative/typical small animal infused with Au-based agents. The obtained results highlight the methodology's ability to optimize the balance between the absorbed dose and corresponding SNR, obtaining high-quality images without compromising in vivo samples due to excessive radiation exposure. Moreover, the proposed methodology provides high-resolution structural imaging and detailed elemental mapping, facilitating the analysis of detection limits along with the overall system performance. These findings confirm the robustness and reliability of the approach, offering a valuable tool for refining X-ray spectroscopy imaging processes and advancing X-ray fluorescence-based tomography techniques.

Abstract: Diagnostic Reference Levels (DRL) in digital mammography were determined from 31,040 digital mammography images acquired from diagnostic and screening examination data from eight state-managed mammography centres/units in the Republic of North Macedonia (RM). The main objective is to establish a Diagnostic Reference Level for mammography examinations at different ranges of breast thickness. Materials and methods: ~30,000 mammography images were used to evaluate Mean Glandular Dose (MGD), and Compressed Breast Thickness (CBT)for each projection, craniocaudal (CC) and mediolateral oblique (MLO). The stratified DRL was derived by calculating the 75th percentile of the MGD across all the samples at various CBT ranges for both projections. Results and Discussion: The overall median MGDs, minimum, and maximum were calculated to be 1.15 mGy, 0.1 mGy, and 9.93 mGy, respectively. As the CBT increased from 7 to 120 mm, the 75th percentile of the MGD increased from 0.94 mGy to 3.67 mGy for CC, and from 0.44 mGy to 4.91 mGy for MLO projections. Conclusion: The study established local DRLs for the digital mammography systems at the 75th percentile, which compared well with the values reported by other countries/regions. The DRL defined per CC and MLO image view for a specific CBT indicated that at least one mammography facility needs optimization.

Abstract:

In this work, a first trial of a method has been developed to estimate the average annual indoor radon activity concentration from three-week short-term measurements using active radon-222 measuring devices, considering relevant influencing parameters. 24 long-term measurements (6 months) and 50 short-term measurements (3 weeks) were carried out in 24 indoor spaces in private houses in four Austrian federal states between October 2022 and July 2023. At the same time as the short-term measurements, ambient parameters (outside and inside temperature, air pressure inside, outside, air humidity inside, outside, wind speed, wind direction, amount of precipitation) were also recorded to investigate their influence on the measured radon-222 activity concentrations. Building and usage data of the indoor spaces examined were also collected. Based on the evaluation of the radon-222 measurements carried out, a first guideline was developed for estimating the annual mean value of the radon-222 activity concentration from short-term measurements lasting around three weeks. Using further measurements and advanced physical-statistical methods, it would be possible to test, validate and improve the generalization of the method to indoor spaces and to further improve the functional relationships.

Abstract: The interest in Boron Neutron Capture Therapy (BNCT) has been recently increasing thanks to the latest advancements in accelerator technology which allow to generate the required neutron field from accelerator facilities that could be hosted in hospitals or clinical centres. BNCT is a form of radiation therapy which relies on the highly localised and enhanced biological effects of the boron-10 (B-10) neutron capture (BNC) reaction products to selectively kill cancer cells. The BNC products are low-energy alpha and lithium ions, which are characterised by a high Linear Energy Transfer (LET) and a very short range lower than 9?m. The energy deposition and interaction with critical biological target such as DNA molecules is therefore strongly dependent on the B-10 spatial micro-distribution into the cells. In this framework, the Fluorescent Nuclear Track Detectors (FNTD) could be a promising device for the visualisation of the ion traversals induced in BNCT. FNTD consists of a fluorescent single-crystal aluminium oxide doped with carbon and magnesium, coupled with a Confocal Laser Scanning Microscopy (CLSM) read-out. Its biocompatibility allows to deposit and grow cells samples on its surface. If a layer of borated cells is deposited and irradiated by a neutron field, the energy deposited by the BNC products and their trajectories can be measured by analysing the corresponding track spots induced at different depths of the detector. This allows to reconstruct the position where the measured particles were generated, hence the micro-distribution of B-10. A FNTD was tested in three irradiation conditions to study the feasibility of FNTD for BNCT applications. The device was firstly irradiated by the alpha particles emitted by an Am-241 source (with energy of about 5.5 MeV). The same radiation field moderated by a 23?m layer of Mylar was then used to obtain alpha particles with a lower energy of about 2.5 MeV, thus closer to BNC products. Finally, the FNTD was tested at the University of Pavia’s LENA (Applied Nuclear Energy Laboratory) under a thermal neutron beam. A standard reference material (SRM) consisting of boron implanted on a silicon wafer was placed on the detector surface to reproduce a typical BNCT radiation field. The FNTD allowed to successfully measure the correct alpha particles range and mean penetration depth expected for all the radiation fields employed. This work proved the feasibility of FNTD to reconstruct the tracks of the alpha particles produced in typical BNCT conditions. Hence, FNTD will allow to measure the intra-cellular micro-distribution of B-10, bringing a significant contribution to the advancement of BNCT research. With this purpose, further experiments at LENA irradiating borated cell samples are planned.

Abstract: The image quality index for whole-body bone scintigraphy has traditionally relied on the total count (Total-C) with a threshold of ≥1.5 mc. However, Total-C measurements are susceptible to variability owing to urine retention. This study aimed to develop a skeletal count (Skel-C)-based index, focusing exclusively on bone regions, to improve the accuracy of image analysis in bone scintigraphy. All cases included herein were Total-C≥1.5 mc. Thresholds were set for Skel-C (0.9–1.2 mc) and Total-C (1.75–2.25 mc); patients were grouped according to whether they were above or below these thresholds. The group including all cases was defined as the Total-C 1.5 high group. Sensitivity and specificity were calculated for each group, and receiver operating characteristic analyses and statistical evaluations were conducted. The specificity of the Skel-C < 0.9 mc group was significantly lower than that of the Skel-C ≥ 0.9 mc group and the Total-C 1.5 high group. These findings highlight the importance of achieving Skel-C ≥ 0.9 mc and suggest that Total-C alone is insufficient for reliable image assessment.

Abstract: Effective dose calculation is essential for optimizing Gamma Knife (GK) stereotactic radiosurgery (SRS) treatment plans. Modern GK systems allow independent sector activation, enabling complex dose distributions per shot. This study presents a dose approximation method designed to account for shot flexibility and generate 3D dose external to GammaPlan. A treatment plan was created with the TMR10 calculation for individual sector activations using a Radiosurgery Head Phantom. The resulting dose arrays established a basis set of sector-specific distributions, which were then refer-enced by shot parameters from the plan, allowing dose accumulation through superposition. This superposition approximation (SA) was compared to the original TMR10 using Dice Similarity Co-efficient (DSC), 95% Hausdorff Distance (HD95), and GK deliverability metrics: coverage, selec-tivity, and gradient index, across an isodose normalization range from 10% to 90%. In a cohort of 30 patients with 71 targets, strong agreement was observed between TMR10 and SA in the clinically used 50-60% isodose range, with DSC above 85% and HD95 under 2.18mm. Average differences for coverage, selectivity, and gradient index were 0.014, 0.008, and 0.118, respectively. This method accurately approximates TMR10 calculations within clinically relevant ranges, offering an external tool to assess 3D dose distributions for GK treatment plans.

Abstract: Background: Accurate reconstruction and quantification in post-therapy SPECT/CT imaging of 166Ho microspheres for hepatic malignancies is crucial for treatment evaluation. This present study aimed to explore the impact of the OSEM reconstruction parameters on SPECT/CT image features for dose distribution determination, using Hybrid Recon™ (Hermes Medical Solutions AB) and full Monte Carlo (MC) collimator modeling. Methods: Image quality and activity quantification were evaluated using Jaszczak and PTW SPECT/PET body phantoms. Siemens Symbia Intevo Bold and Symbia Pro.specta camera models were used for imaging. Datasets were reconstructed using OSEM (varying number of iterations) with and without full MC collimator modeling. Contrast recovery coefficients (QH), coefficients of variation (CV), calibration factors (CF) and activity recovery coefficients (ARC) were calculated and used to evaluate image quality and activity quantification. Results: The reconstruction method that provided the higher QH and ARCs in both studied systems/phantoms was the one applying 5 iterations and 15 subsets, incorporating full Monte Carlo collimator modeling. CF were (14.5±0.6) cps/MBq and (15.4±0.5) cps/MBq for the Siemens Symbia Intevo Bold and Symbia Pro.specta, respectively, corresponding to Jaszczak and PTW SPECT/PET body phantoms. The two analytical approaches used to fit the ARCs data confirmed the expected activity underestimation in small volumes due to partial volume effect (PVE) and the validity of the results in two different scanners and phantoms. Conclusions: For post-SIRT 166Ho SPECT/CT imaging, OSEM (5 iterations, 15 subsets) with full Monte Carlo collimator modeling provided superior quantification results. The determination of CF and ARC is vital for accurate quantification of 166Ho and should be always considered.

Abstract: The use of Very High Energy Electron (VHEE) beams, with energies between 50 and 400 MeV, has drawn considerable interest in radiotherapy due to their deep tissue penetration, sharp beam edges, and low sensitivity to tissue density. VHEE beams can be precisely steered with magnetic components, positioning VHEE therapy as a cost-effective option between photon and proton therapies. However, clinical implementation of VHEE Therapy (VHEET) requires advances in several areas: developing compact, stable, and efficient accelerators; creating sophisticated treatment planning software; and establishing clinically validated protocols. In addition, the perspective of VHEE to access ultra-high dose-rate regime presents a promising avenue to practical integration of FLASH radiotherapy of deep tumors and metastases with VHEET (FLASH-VHEET), enhancing normal tissue sparing while maintaining the inherent dosimetric advantages of VHEET. However, FLASH-VHEET systems require validation of time-dependent dose parameters, thus introducing additional technological challenges. Here we discuss recent progress in VHEET research, focusing on both conventional and FLASH modalities, and covering key aspects including dosimetric properties, radioprotection, accelerator technology, beam focusing, radiobiological effects, and clinical outcomes. Furthermore, we provide a comprehensive analysis of initial VHEET in silico studies on coverage across various tumor sites.

Abstract: Ambient dose rate surveying has the objective, in most cases, to quantify terrestrial radiation levels. This is true in particular for Citizen Monitoring projects. Readings of detectors, which do not provide spectrally resolved information, such as G-M counters, are the sum of contributions from different sources, including cosmic radiation. To estimate the terrestrial component, one has to subtract the remaining ones. In this paper, we investigate the cosmic response of two particular monitors, the bGeigie Nano which has been used extensively in the Safecast Citizen Monitoring project and its upgraded version, the new CzechRad which uses the same G-M detector, and show how the local contribution of cosmic radiation can be estimated.

Abstract: In the framework of the H2020 CLEANDEM project a small robotic vehicle was equipped with a series of different sensors, developed for the preliminary inspection of areas possibly contaminated by radiation. Such unmanned inspection allows to identify dangerous locations prior to the possible start of human operations. One of the developed devices, named MiniRadMeter, is a compact, low-cost sensor to perform gamma and neutron radiation field mapping of the environment. The MiniRadMeter was successfully tested in a simulated field mission with four "hidden" radioactive sources and a neutron generator. In this work we describe the test procedure and the results, also supported by the outcome of dedicated Monte Carlo simulations.

Abstract: Muon tomography leverages cosmic muons’ exceptional penetration capabilities to reconstruct detailed tomographic images via multiple Coulomb scattering interactions, making it invaluable for detecting High-Z materials critical to homeland security. This study introduces the Slope Intercept (SI) algorithm, a novel approach for rapid and precise tomographic image reconstruction. Implemented using Geant4 simulations in a standard-sized container tomography station, SI demonstrates superior performance in speed and simplicity compared to traditional methods. While the imaging results of SI and the Point of Closest Approach (POCA) algorithm are nearly identical, the SI algorithm is simpler to implement, requires shorter CPU time, and exhibits a smaller margin of error. Its computational efficiency and simplicity make it a robust alternative to the POCA algorithm. These findings highlight SI’s suitability for applications demanding robust imaging and efficient data processing, which are crucial for advancing security measures and scientific research.

Abstract: Background and Objective: To examine the effect of ordered subset expectation maximization (OSEM) parameters on the quantitative image quality of cardiac SPECT images in two different frequently used SPECT cameras and determine the optimal settings for producing images of best diagnostic quality. Another objective was to assess if different cameras produced a significant change in optimal parameters and levels of detectability. Methods: The optimization of OSEM iterative reconstruction algorithm was carried out by comparing image quality metrics, namely, contrast-to-noise ratio (CNR) and defect contrast across 12 OSEM subset-iteration combinations to find the best choice for cardiac perfusion SPECT images. Eight frames were reconstructed using the SIMIND Monte Carlo Simulation package. An activity of 370 MBq (10mCi) and projection acquisition interval of 20 seconds per projection were used. Attenuation (AC) and scatter corrections (SC) were performed in this study for all images. Results: The 16-2 subset-iteration combination yielded the highest CNR and defect contrast values for both cameras. The difference between CNR values for two cameras was found to be around 5% only. Conclusions: Monte Carlo simulations can be useful to investigate how quantitative image quality behaves with respect to reconstruction parameters and correction algorithms in a controlled environment. The found optimum is similar to values reported in previous findings. In this study, the use of different camera brands did not affect the optimum. The quantitative detectability measures were also very similar.

Abstract: A high-gain broadband circularly polarized crossed dipole antenna is designed. This antenna utilizes two pairs of cross dipoles and a pair of phase delay lines to form circularly polarized radiation. Open-circuit stubs are loaded on the four arms of these two pairs of cross dipoles to introduce new circularly polarized resonating frequency. A rectangular ring patch is introduced directly below the cross dipoles to form the third circularly polarized resonating frequency, thereby broadening the axial ratio bandwidth of the antenna. In addition, metal posts are loaded at the four right angles of the rectangular ring patch to increase the antenna gain. Measurement results show that the antenna achieves a 3dB axial ratio bandwidth of 29.2% (1.9 GHz-2.55 GHz) and maintains a gain of 7.5 dB within the passband, exhibiting good circularly polarized radiation performance.

Abstract: Alpha emitters like plutonium pose severe health risks when ingested, damaging DNA and potentially causing cancer. Traditional detection methods require proximity within millimeters of the contamination source, presenting safety risks and operational inefficiencies. Long-range detection through alpha radioluminescence (RL) offers a promising alternative. However, most of the previous experiments have been carried out under controlled conditions that preclude the overwhelming effect of ambient light. This study demonstrates successful detection of a 3 MBq alpha emitter in an open environment using a newly developed, lightweight compact alpha camera. This camera incorporates a deep-cooled CCD and a specially designed lens system with a low f-number to maximum the signal intensity. The lens was also designed to minimize blue shift effects of filters. Nighttime imaging was achieved with a dual-filter system using a sandwich filters assembly centered at 337 nm and 343 nm for capturing alpha RL and subtracting background light, respectively. At night, the alpha source was detected from 1 meter away within one minute. The system was also evaluated under simulated urban lighting conditions. For daytime imaging, a stack of tilted 276 nm short pass filters minimized sunlight interference, enabling clear detection of the alpha source at 70 cm within 10 minutes under indirect sunlight. This research not only underscores the viability of long-range optical detection of alpha emitters for environmental monitoring and scientific research but also highlights its ability to enhance nuclear safety and public health in real-world settings.

Abstract: Spectral photon counting cone-beam CT imaging is challenged by individual pixel response behaviour, which leads to noisy projection images and subsequent image artefacts like rings. Existing methods to correct for this either use calibration measurements, like signal-to-thickness calibration (STC), or perform post-processing ring artefact correction of sinogram data or scan reconstructions, without taking the pixel response explicitly into account. Here we present a novel post-processing method (DAC-shifting), which explicitly measures the current pixel response using flat field images, and subsequently corrects the projection data. The DAC-shifting method was evaluated with a repeat series of spectral photon counting imaging (Medipix3) of a phantom with different density inserts, and in iodine K-edge imaging. The method was also compared against PMMA based STC. The DAC-shifting method was shown to be effective in correcting individual pixel response, and was robust against detector instability. On the contrary, STC correction showed varying results, which was almost as good as DAC-shifting when data was acquired just after STC calibration, but worse with larger time differences. In K-edge imaging, DAC-shifting provides a sharper attenuation peak, and more uniform CT values, which is expected to benefit iodine concentration quantification.

Abstract: This paper presents a wideband dual-polarized dipole antenna structure operating at 1.7-3.8 GHz (76.4%). For a traditional 4G dipole antenna which covers the band 1.71 GHz- 2.69 GHz, it’s difficult to maintain the satisfactory impedance matching and normal stable radiation patterns within the 5G sub-6 GHz band 3.3-3.8 GHz, which mainly due to the fixed antenna height is no longer a quarter-wavelength. To solve this, a connected-ring-shaped metasurface structure is proposed and deployed to operate as an artificial magnetic conductor (AMC). As a result, stable antenna radiation patterns are obtained within the whole band 1.7-3.8 GHz. For verification, this wideband dipole antenna using AMC is implemented and tested. The measured results show that the proposed antenna has an impedance bandwidth of 80.7% (1.7-4.0 GHz). It has an average measured in-band realized gain of 7.0±1.0 dBi and a stable 70∘±5∘ half power beam width (HPBW) within the 4G/5G-sub 6GHz bands 1710-2690 MHz and 3300-3800 MHz.

Abstract: This paper presents a compact wideband circularly polarized cross dipole antenna with low-pass filter response. It consists of two pairs of folded crossed dipole arms printed separately on both sides of the top substrate, and the two dipole arms on the same surface are connected by an annular phase-shifting delay line to generate circular polarization. A bent metal square ring and four small metal square rings around the cross dipoles are employed to introduce new resonant frequencies, effectively extending the impedance and axial ratio bandwidth. Four square patches printed on the middle substrate are connected to the ground plane by the vertical metal plates, in order to reduce the antenna height. Thus, a compact wideband circularly polarized antenna is realized. In addition, a transmission zero can be introduced at the upper frequency stopband by the bent metal square rings, without using extra filter circuits. For verification, the proposed model is implemented and tested. The overall size of the model is 90mm×90mm×33mm(0.37λ0×0.37λ0×0.14λ0, λ0 denotes the center operating frequency). The measured impedance bandwidth and 3 dB axial ratio bandwidth are 53.3% and 41%, respectively. More than 15 dB upper-band radiation suppression level is realized, indicating a good low-pass filter response.

Abstract: This study assessed the performance of low-dose CT lung scans across various acquisition parameters and examined the impact of iterative reconstruction (IR) algorithms on image quality for lung cancer screening. The performance of multi-slice CT scanners was assessed by using a Catphan 600 phantom, specifically within the CTP404 test module that contains materials like Teflon, Delrin, Acrylic, Polystyrene, LDPE, PMP, Air, and water. Three protocols were selected and categorized into standard, low dose, and ultra-low dose. The standard protocol featured a tube voltage of 100 kVp for single-detector CT, a pitch of 0.75, detector collimation of 0.60 mm, and a gantry rotation time of 0.33 seconds, with 5 mm slice thickness. Images were reconstructed using standard kernels like B80f and 170f, combined with either FBP or various IR algorithms. Findings indicated that the noise power spectrum (NPS) peak value (HU2mm2) increased with higher IR levels, with FBP showing the highest peak. Additionally, NPS spatial frequency diminished as IR levels rose. Optimizing contrast and spatial resolution for both background and regions of interest involved adjusting the target transfer function (TTF) and contrast-to-noise ratio (CNR), crucial for protocol optimization. Proper adjustment of IR levels is vital, as higher levels can alter image texture and affect NPS spatial frequency. The results of this study showed that the use of IR algorithms in low-dose CT lung scans significantly improved image quality, particularly in terms of noise reduction and spatial resolution. However, the choice of acquisition parameters also played a crucial