Gradient-echo (GRE) sequences form echoes by reversing gradient-induced dephasing without a 180 degrees refocusing RF pulse, enabling rapid image acquisition with short repetition time (TR) and echo time (TE). Because static field inhomogeneity and susceptibility effects are not refocused, GRE signals are sensitive to T2* decay. This paper first reviews the signal formation mechanism of GRE from a k-space perspective, then proposes a classification framework based on transverse-coherence handling across repeated RF cycles and on the steady-state signal components that contribute to image formation, and finally summarizes the clinical applications of each sequence family in a systematic manner. The proposed classification and summary may serve as a useful reference for selecting and applying GRE imaging techniques.

A high-fidelity electron-source Monte Carlo model of a mobile C-arm fluoroscopy system was developed using Particle and Heavy Ion Transport code system (PHITS) to evaluate scattered radiation and calculation acceleration. Electrons were injected into the X-ray tube target, and energy spectra, dose profiles, and scattered doses around the tube head and in the room were calculated. Simulated spectra Simulated spectra agreed with the measured spectra with a root mean square error of 0.06 or less, and the simulation-to-measurement ratios of the scattered air kerma from the electron-source simulations were within 20

This study determined the holder correction factors (HCFs) for the new electron-holder to assess its use for photon beams within the IAEA/WHO postal dosimetry audits. MC simulations were used for photon beam qualities (6-18 MV), and were experimentally validated. MC simulations were first validated for the legacy photon-holder. The HCFs from the simulations ranged from 1.001 to 1.005 with the largest uncertainty of 0.24%. The experimentally validated HCFs ranged from 1.002 to 1.007 with uncertainties reaching up to 0.12%. This supports the adoption of a single, universal holder for photon and electron dosimetry audits, offering potential benefits in operational efficiency.​

Occupational radiation exposure among medical staff remains a critical concern, underscoring the importance of effective radiation-protection education. This study aimed to develop and evaluate educational materials incorporating an augmented reality (AR) application to visualise scattered-radiation distributions during radiological procedures. The educational program comprised a 20-item true/false quiz, a questionnaire based on the Attention, Relevance, Confidence, and Satisfaction (ARCS) motivational model, and open-ended questions assessing perceived strengths and weaknesses. Pre- and post-training quiz scores demonstrated an improvement of approximately 10% in the overall correct-response rate, indicating measurable gains in factual knowledge related to scattered radiation and radiation protection. ARCS scores reflected high levels of learner motivation, with mean ratings of 3.98 for Attention, 3.99 for Relevance, 4.06 for Confidence, and 4.08 for Satisfaction on a five-point scale. Free-text responses suggested that visualising scattered radiation with AR facilitated a more concrete understanding of its spatial distribution and the effectiveness of protective measures. However, both ARCS feedback and open-ended comments indicated that the training content was dense and that the exercise workload was perceived as burdensome. Participants also reported usability challenges related to the application interface. Overall, the findings suggest that the AR-based educational materials can enhance both learner motivation and conceptual understanding of radiation protection, although further refinement of scenario design and interface usability is required to optimise learning efficiency and user experience.

Caregivers may be at risk of exposure to scattered radiation during paediatric chest computed tomography (CT) examinations. This study re-evaluated the effects of physical shielding on paediatric chest CT under controlled experimental conditions using an anthropomorphic paediatric phantom, with an emphasis on the organ dose distribution, scattered radiation relevant to caregivers, and image quality. The phantom was scanned using two CT protocols: with and without bismuth shielding applied to the anterior chest region. Organ doses were measured using real-time scintillation detectors placed in multiple internal organs at the anterior chest surface location corresponding to the breast. Scattered radiation was assessed at caregiver-relevant positions adjacent to the CT gantry using personal dosimeters positioned at the thyroid, eye, abdominal, and gonadal levels. Image quality was evaluated through region-of-interest-based analyses, including the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and Hounsfield unit line profile assessments. The results demonstrated that physical shielding primarily altered the dose distribution in the anterior thoracic regions, including a marked reduction in the breast dose, while doses to the posterior and distant organs were minimally affected. In addition, scattered radiation measurements indicated reduced exposure at caregiver-relevant locations when shielding was applied. Quantitative image analysis showed that shielding-induced changes in the SNR and CNR were measurable but did not compromise the interpretability of the lung parenchyma and other diagnostically relevant regions under controlled conditions. Under these conditions, without automatic exposure control (AEC), physical shielding modified the anterior organ dose distribution and reduced scattered radiation while preserving stable image characteristics. Although the routine clinical use of physical shielding is not advocated, these findings provide quantitative reference data to clarify its potential benefits and limitations in paediatric-specific contexts and support further investigations incorporating AEC and clinical image validation.

This study evaluates organ doses from ¹⁸F-FDG whole-body PET-CT using the phantom–based software PARaDIM and patient image–based software RT-PHITS and compares with reference data from ICRP Publication 128. Absorbed dose coefficients (mGy/MBq) were calculated using ICRP Publication 145 mesh-type phantoms in PARaDIM and 20 patient datasets (10 male, 10 female) from ‘The Cancer Imaging Archives’ website in RT-PHITS. Organs were segmented in 3D Slicer, and dose coefficients were derived after physical decay correction of the resultant dose rates (mGy/s). The patient cohort (n = 20; 10 males, 10 females) had an average age of 52.1 years, height of 172.1 cm, weight of 76.65 kg, and total administered activity of 306.55 MBq. Absorbed dose coefficients from PARaDIM and RT-PHITS ranged from 0.01 to 0.07 mGy/MBq. RT-PHITS showed acceptable agreement with ICRP 128 and PARaDIM for most organs, except for the urinary bladder and heart wall. Standard deviations (SD) for RT-PHITS urinary bladder doses were 0.04 relative to ICRP 128 and 0.12 relative to PARaDIM; heart wall SDs were 0.016 and 0.014, respectively. Overall, RT-PHITS organ doses yielded an average SD of 0.0073, with the highest deviation in the heart wall. The results indicate that anatomical differences lead to measurable variations between the generalized and individualized dosimetry methodologies. Because a consistent physical decay model of 18F was used, these variations primarily reflect structural and geometric factors. This study provides a framework for advancing individualized dosimetry approaches and supports future developments in cumulative exposure assessments and potential theranostic applications.

This study aims to quantitatively evaluate the photoneutrons produced by each accessory of the accelerator head using Monte Carlo simulation. First, the elements simulated in MCNP6 are tungsten, with a density of 19.25 g/cm3, and copper, with 8.96 g/cm3. Second, the accessories include a primary collimator, jaw, flattening filter, and single/composite targets, vary depending on the photon beam energy. The neutron energy spectrum was obtained using the F2 tally function on the sphere’s surface with a field size of 10 × 10 cm2. Additionally, the contribution of neutron generation from each accessory in the head part was analyzed. As a result, neutron generation was observed in the 15–20 MeV energy range, reflecting the threshold energy for the photonuclear interaction of each element. At lower photon beams (8 and 10 MeV), the target consists only of copper. More than 75

In medical settings, radiation exposure among radiation workers is a significant concern, and understanding radiation protection is crucial. We developed and evaluated radiation protection educational materials using an augmented reality application for visualizing scatter radiation. The evaluation included a true/false quiz, a questionnaire based on the ARCS (Attention, Relevance, Confidence, and Satisfaction) model, and open-ended responses. The correct response rates for the true/false quiz were 65.5% and 72.4% for two questions regarding the effect of C-arm angle changes on scatter radiation distribution. The correct response rate for all other questions was 100%. Understanding how changes in C-arm angles specifically affect angiographic procedures proved more challenging than other topics. The ARCS model evaluation of learning motivation revealed average scores of 4.15 for Attention, 3.91 for Relevance, 3.93 for Confidence, and 4.28 for Satisfaction in the scale 5.00.These results suggest that the developed materials are effective in enhancing motivation. However, open-ended responses identified areas for improvement in the application's usability, particularly regarding ease of operation. While the materials successfully enhance motivation, further refinements are needed to address the variation in correct response rates across different scenarios and the usability challenges of the application.

This study proposes a method for real-time visualization of scatter radiation using a high-sensitivity CMOS camera with a pinhole collimator, within the energy range relevant to diagnostic imaging. Additionally, Monte Carlo simulations were employed to validate whether the measured data accurately represent actual scatter radiation. A real-time scatter radiation imaging system was developed using a CMOS camera, CsI scintillator, and pinhole collimator. Various parameters, including pinhole diameter and exposure time, were evaluated to identify the optimal configuration. Monte Carlo simulations were used to compare the measured data against the simulated scatter radiation distribution. The system successfully visualized scatter radiation sources with high spatial resolution. The optimal parameters were identified as a 2 mm pinhole diameter and 50 ms exposure time, balancing image clarity and efficiency. The measured data closely matched the simulation results, confirming the accuracy of the system. The proposed system offers significant potential for enhancing radiation protection in clinical settings by enabling real-time visualization of scatter radiation. It is expected to contribute to safer working environments and more effective radiation safety management during diagnostic procedures.

A 3D-printed bolus is being developed to deliver accurate doses to superficial cancers. In this study, flexible thermoplastic filaments, specifically PLA , TPU , PETG , and HIPS, were fabricated into boluses and then compared to commercial bolus for the variation of the dose elevation region of photon beams. The experimental results indicate that the maximum dose depth is similar, and the consistent trend of the percentage depth dose confirms the potential usage as a build-up bolus.

This study quantitatively evaluated the source term of a linear accelerator according to target thickness for a 6-20 MeV electron beam using MCNP6. The elements of the target were tungsten and copper, and a composite target and single target were simulated by setting different thickness parameters depending on energy. The accumulation of energy generated through interaction with the collided target was evaluated at 0.1-mm intervals, and F6 tally was used. The results indicated that less than 3% reference error was maintained according to the MCNP recommendations. At 6, 8, 10, 15, 18, and 20 MeV, the energy accumulation peaks identified for each target were 0.3 mm in tungsten, 1.3 mm in copper, 1.5 mm in copper, 0.5 mm in tungsten, 0.5 mm in tungsten, and 0.5 mm in tungsten. For 8 and 10 MeV in a single target consisting only of copper, the movement of electrons was confirmed at the end of the target, and the proportion of escaped electrons was 0.00011% and 0.00181%, respectively.

The purpose of the study was to evaluate the radiation dose in High-Definition Reference Korean-Man phantom according to the lead equivalent in the protection devices using MCNPX. The tube voltage and current are 80–100 kV and 15 mAs, respectively, and the exposure time is 7–10 min. The range of lead equivalent of the protection devices worn by the operator phantom is 0–0.50 mmPb with the internal of 0.05 mmPb. The radiation dose indirect calculation method, the NDD(k), and variance reduction techniques are applied. The average error rate of the absorbed dose in each organ was 12.88% at 80 kV and 7.41% at 100 kV. Among the organs, the doses by the gonads (testis) and bladder accounted for 58.91%, resulting from close proximity to the table height, the origin of the scattered radiation. In case of evenly distributed bone surfaces throughout the body, it was 25.66%. This study quantitatively reports that after 0.25 mmPb lead equivalent of radiation protection devices commonly used in the clinical interventional procedure, TACE, the decrease in effective dose begins to slow down and become constant.

The purpose of this work is to optimize the number of holes in each layer with the Monte Carlo simulation tool, GATE, within reasonable error, a variable collimator of the non-replaceable methods that makes up for pinhole collimator’s shortcomings. The material is tungsten and the detector size is 25.8 × 25.8 × 3.0 mm3 GAGG with 0.7 × 0.7 × 3.0 mm3 pixels arranged in 29 × 29 × 1 and performance is evaluated based on the field-of-view, sensitivity, and spatial resolution by magnification for the point source 137Cs. Simulation results were designed to optimize the five layers from 44, 55, 11, 55, 44 to 6, 9, 3, 9, and 6 to meet the feasibility of manufacturing collimators. We also confirmed performance errors of 5.7% sensitivity and 5.2% spatial resolution compared to using an ideal variable collimator for all parameters, such as specific purposes and magnification scale. Through these results, we propose an environmental monitoring system that can be used for diversified radiation disasters by enabling image magnification and transforming the shape of the collimator.

The purpose of this study is to perform radiation monitoring by acquiring gamma images and real-time optical images for 99mTc vial source using charge couple device (CCD) cameras equipped with the proposed compact gamma camera. The compact gamma camera measures 86 x 65 x 78.5 mm3 and weighs 934 g. It is equipped with a metal 3D printed diverging collimator manufactured in a 45 & DEG; field of view (FOV) to detect the location of the source. The circuit's system uses system-on-chip (SoC) and field programmable-gate-array (FPGA) to establish a good connection between hardware and software. In detection modules, the photodetector (multi-pixel photon counters) is tiled at 8 x 8 to expand the activation area and improve sensitivity. The gadolinium aluminium gallium garnet (GAGG) measuring 0.5 x 0.5 x 3.5 mm3 was arranged in 38 x 38 arrays. Intrinsic and extrinsic performance tests such as energy spectrum, uniformity, and system sensitivity for other radioisotopes, and sensitivity evaluation at edges within FOV were conducted. The compact gamma camera can be mounted on unmanned equipment such as drones and robots that require miniaturization and light weight, so a wide range of applications in various fields are possible. & COPY; 2023 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

A lead is mainly used for radiation shielding owing to high density and atomic number, but lead is a harmful substance and has disadvantages such as heavy weight and toxicity. In this study, each material chosen is tellurium trioxide (TeO3), tin dioxide (SnO2), gadolinium oxide (Gd2O3), bismuth trioxide (Bi2O3), and tungsten dioxide (WO2). Monte Carlo simulation has been carried out for calculating half-layer value and linear attenuation coefficient as shielding parameters. In addition, feasibility was evaluated by comparing lead dioxide (PbO2) with lead-free oxide one following the weight and thickness in the simulation as using various shielding performance. A result indicated that gadolinium oxide (Gd2O3) has the most lightweight value in the shielding performance of 50%, 70%, and 90% of 120 kV and 150 kV. It expected to reduce radiation dose with lightweight and provide basic data to develop the apron using proper material powder.

Environmental radiation monitoring is required to protect from the effects of radiation in industrial fields such as nuclear power plant (NPP) monitoring, and various gamma camera systems are being developed. The purpose of this study is to optimize parameters of a diverging collimator composed of pure tungsten for compactness and lightness through Monte Carlo simulation. We conducted the performance evaluation based on spatial resolution and signal-to-noise ratio for point source and obtained gamma images and profiles. As a result, optimization was determined at a collimator height of 60.0 mm, a hole size of 1.5 mm, and a septal thickness of 1.0 mm. Also, the full-width-at-half-maximum was 3.5 mm and the signal-to-noise ratio was 53.5. This study proposes a compact 45° diverging collimator structure that can quickly and accurately identify the location of the source for radiation monitoring.

Mammography is one of the most important test techniques for screening and diagnostic examinations of breast diseases. Recently, the incidence of breast cancer has increased and the demand for mammography is increasing through the cancer screening programs in each country. Therefore, research on shielding materials is actively being pursued to reduce radiation exposure during mammography. The purpose of this study is to verify and compare the GATE simulation and experiment in terms of the shielding performance under the experimental conditions of tube voltage (25, 30, 35 kVp) and silicon thickness (1, 2, 3, 4, 5, 6 mm). Through MCNP simulation, the absorbed dose reduction rate of breast tissue according to tube voltage/silicon shielding thickness is presented. The GATE simulation and experimental results were within the error range of 0.07 to 1.42 % under all conditions. In addition, through simulations and experiments, it was confirmed that silicon can offer more than 80 % shield regardless of automatic exposure control (AEC) of mammography equipment when 5 mm of silicon is used. Therefore, the results of the study can serve as useful basic data for the development of a shielding suit or shield that can reduce the exposure of other surrounding tissues due to scattered rays during mammography.

The purpose is to develop gamma cameras to monitor the environment using diverging collimators designed to respond to 131I through Geant4 application for tomographic emission (GATE) tool. The detector system is 50.0 $$\times$$ 50.0 $$\times$$ 3.5 mm3 and contains gadolinium aluminum gallium garnet crystals with a 62 $$\times$$ 62 array. Our results were obtained by classifying the parameters as general purpose, high sensitivity, and high resolution; we also evaluated the extent of improvement in performance compared to a pinhole collimator. The minimum collimator height to remove an in-image artifact was 45.0 mm, and the reference full width at half maximum (FWHM) was set to about 3.0 mm for general-purpose use; the general-purpose parameters were a collimator height of 50.0 mm, hole size of 1.0 mm, and septal thickness of 0.4 mm. The high-sensitivity parameters were 45.0, 1.2, and 0.4 mm; the high-resolution parameters were 50.0, 1.0, and 0.8 mm, and the FWHM was 3.06, 3.99, and 2.38 mm, respectively. Our comparison showed a relatively constant performance regardless of the point source location in the field of view.

A new detector was designed to improve the spatial resolution of positron emission tomography (PET) and acquire digital coordinates of the detector"s scintillation pixels. In order to solve the spatial resolution deterioration phenomenon due to parallax error occurring outside the field of view (FOV), a method of measuring the depth of interaction was developed, and this was accomplished with the acquisition of digital coordinates. A detector using a 4 × 4 × 2 GAGG scintillator was designed using the DETECT2000 simulation tool to acquire digital coordinates of the scintillation pixels and measure the depth of interaction of the two layers. A gamma-ray reaction was generated in all the scintillation pixels, and the signals were obtained from SiPM pixels in a 4 × 4 array. The 16-channels of optical sensor signals were reduced to signals of 4 channels, and these were calculated as a ratio of each signal. The ratio of the signal was obtained from all the flash pixels, and the position was obtained as digital coordinates by comparing it with the ratio of the signal by the gamma ray response generated at the new position. In order to evaluate the accuracy of acquiring the digital coordinates and the accuracy of the layer where the scintillation pixel in which the scintillator and the gamma ray reacted, a signal was obtained by generating a gamma ray response for the entire length of each scintillation pixel. Gamma-ray reactions were generated at intervals of 0.2 mm from 0.1 mm to 19.9 mm. The obtained signals through these reactions were compared with the signals of each scintillation pixel obtained in advance. Then, the accuracy of measured positions on the X, Y, and Z axes were evaluated. The accuracy of both the X and Y axis showed perfect results, and the accuracy of the Z axis was 91.46 %.