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Introduction: Diagnostic reference levels (DRLs) are typical dose levels for medical imaging examinations for groups of standard‐sized patients or standard phantoms for broadly defined types of equipment used as a tool to aid optimisation of protection for medical exposures. Currently, there are no paediatric DRLs for conventional radiography (i.e. general X‐rays) published in Australia. The aim of this study was to establish typical radiation doses and risks that are representative of those delivered for commonly performed X‐ray projections for a 5‐year‐old/20 kg child using a 5‐year‐old anthropomorphic 'bone fracture' phantom in three dedicated paediatric radiology departments in Victoria. Methods: A total of 20 projection images were acquired for a standard 5‐year‐old/20 kg phantom using digital radiography X‐ray equipment. The air kerma‐area product (KAP) measured at each centre by a KAP metre, which was calibrated to a national primary standard, was considered to represent the median value for that centre for each X‐ray projection. Organ doses and effective dose were estimated using PCXMC software, and risks of radiation‐induced cancer and radiation‐induced death were calculated based on the BEIR VII report. Results: The typical doses for the individual X‐ray projections ranged from 3 mGy•cm2 to 86 mGy•cm2, whilst the effective doses ranged from 0.00004 to 0.07 mSv. The radiation risks were 'minimal' to 'negligible'. Conclusion: The estimation of typical radiation doses and associated risks for a 5‐year‐old/20 kg phantom study provides reference values for guidance and is a first step in assisting optimisation at other institutions until national DRLs, based on patient data from the clinical setting, are published. [ABSTRACT FROM AUTHOR]

Background: A series of 31 radiographs is recommended by the Royal College of Radiologists (RCR) when investigating suspected physical abuse (SPA). Objective: To determine the radiation dose delivered for skeletal surveys performed for SPA in Victorian radiology departments based on their local protocols. Materials and methods: A 5-year-old paediatric bone fracture phantom was radiographed at five radiology sites using both the RCR recommended protocol and, where applicable, the local departmental SPA protocol. The radiation doses were measured and recorded. These were scaled down to estimate the effective radiation doses for a 2-year-old child at each site and the associated radiation risks estimated. Results: The median effective dose for all radiographic projections in the RCR skeletal survey radiographic series was 0.09 mSv. The estimated risk of radiation-induced cancer and radiation-induced death from cancer for 2-year-old children is classified as "very low," with girls having a higher risk than boys. Conclusion: The median effective radiation dose for the RCR skeletal survey for imaging in SPA was 0.09 mSv resulting in a "very low" additional risk of radiation-induced cancer. The authors will now aim to ascertain whether whole-body CT skeletal survey can replace the radiographic series for imaging in SPA while maintaining a comparable radiation dose. [ABSTRACT FROM AUTHOR]

The production, application, and/or measurement of polarised X-/gamma rays are key to the fields of synchrotron science and X-/gamma-ray astronomy. The design, development and optimisation of experimental equipment utilised in these fields typically relies on the use of Monte Carlo radiation transport modelling toolkits such as Geant4. In this work the Geant4 "G4LowEPPhysics" electromagnetic physics constructor has been reconfigured to offer a best set of electromagnetic physics models for studies exploring the transport of low energy polarised X-/gamma rays. An overview of the physics models implemented in "G4LowEPPhysics", and it's experimental validation against Compton X-ray polarimetry measurements of the BL38B1 beamline at the SPring-8 synchrotron (Sayo, Japan) is reported. "G4LowEPPhysics" is shown to be able to reproduce the experimental results obtained at the BL38B1 beamline (SPring-8) to within a level of accuracy on the same order as Geant4's X-/gamma ray interaction cross-sectional data uncertainty (approximately ± 5 %). [ABSTRACT FROM AUTHOR]

External fixation is a common tool in the treatment of complex fractures, correction of limb deformity, and salvage arthrodesis. These devices typically incorporate radio-opaque metal rods/struts connected at varying distances and orientations between rings. Whilst the predominant imaging modality is plain film radiology, computed tomography (CT) may be performed in order for the surgeon to make a more confident clinical decision (e.g. timing of frame removal, assessment of degree of arthrodesis). We used a fractured sheep leg to systematically assess CT imaging performance with a Discovery CT750 HD CT scanner (GE Healthcare) to show how rod coupling in both traditional Ilizarov and hexapod frames distorts images. We also investigated the role of dual-energy CT (DECT) and metal artefact reduction software (MARS) on the visualisation of the fractured leg. Whilst mechanical reasons predominantly dictate the rod/strut configurations when building a circular frame, rod coupling in CT can be minimised. Firstly, ideally, all or all but one rod can be removed during imaging resulting in no rod coupling. If this is not possible, strategies for configuring the rods to minimise the effect of the rod coupling on the region of interest are demonstrated, e.g., in the case of a four-rod construct, switching the two anterior rods to a more central single one will achieve this goal without particularly jeopardising mechanical strength for a short period. It is also shown that the addition of DECT and MARS results in a reduction of artefacts, but also affects tissue and bone differentiation. [ABSTRACT FROM AUTHOR]

A C++/OpenCL software platform for emission image reconstruction of data from pinhole cameras has been developed. The software incorporates a new, accurate but computationally costly, probability distribution function for operating on list-mode data from detector stacks. The platform architecture is more general than previous works, supporting advanced models such as arbitrary probability distribution, collimation geometry and detector stack geometry. The software was implemented such that all performance-critical operations occur on OpenCL devices, generally GPUs. The performance of the software is tested on several commodity CPU and GPU devices. [ABSTRACT FROM AUTHOR]

An AGATA symmetric, coaxial, high-purity germanium (HPGe) detector has been scanned in coincidence mode. Charge pulse shapes from the 36-fold segmented outer contacts and center contact were stored for events at more than 2000 precisely determined 3-D interaction positions spread over ten depths (z). A database (basis) of the 37 average experimental pulse shapes at each position was generated. The electric field simulation code Multi Geometry Simulation (MGS) was used to generate the pulse shapes for the geometry on a 1.0-mm cubic grid. A minimization between the experimental pulse shapes at each position and the MGS basis yielded mean displacements of between 1.5 and 3.0 mm in the x-y plane. The vectors of these displacements were biased in the direction of the center of the detector. This effect is attributed to cross-talk. The maximum level of derivative cross-talk was measured and shown to be 534%ns. However due to the lack of a global clock in the acquisition system, it could not be accounted for throughout the basis. [ABSTRACT FROM AUTHOR]

Purpose: The skeletal survey X-ray series is the current ‘gold standard’ when investigating suspected physical abuse (SPA) of children, in addition to a non-contrast computed tomography (CT) brain scan. This systematic literature review synthesised findings of published research to determine if low dose computed tomography (LDCT) could detect subtle fractures and therefore replace the skeletal survey X-ray series in the investigation of SPA in children aged under 3 years.Five electronic databases and grey literature were systematically searched from their inception to 28 April 2022. Primary studies were included where the population comprised paediatric patients up to 16 years and LDCT was used to detect fractures associated with SPA. Studies involving imaging investigations of the head, standard dose CT examinations or accidental trauma were excluded.Three studies met the inclusion criteria, all of which were case series. These studies did not report many of the criteria required to compare the accuracy of LDCT to X-ray, i.e. they did not meet the criteria for a diagnostic accuracy test. Therefore, it is difficult to conclude from the case series if LDCT is accurate enough to replace X-rays.Due to the gap in current literature, a phantom study and subsequent post-mortem CT study are recommended as the primary investigative methods to assess the ability of low-dose CT to identify the subtle fractures associated with SPA and to calculate how low the achievable CT dose can be.Methods: The skeletal survey X-ray series is the current ‘gold standard’ when investigating suspected physical abuse (SPA) of children, in addition to a non-contrast computed tomography (CT) brain scan. This systematic literature review synthesised findings of published research to determine if low dose computed tomography (LDCT) could detect subtle fractures and therefore replace the skeletal survey X-ray series in the investigation of SPA in children aged under 3 years.Five electronic databases and grey literature were systematically searched from their inception to 28 April 2022. Primary studies were included where the population comprised paediatric patients up to 16 years and LDCT was used to detect fractures associated with SPA. Studies involving imaging investigations of the head, standard dose CT examinations or accidental trauma were excluded.Three studies met the inclusion criteria, all of which were case series. These studies did not report many of the criteria required to compare the accuracy of LDCT to X-ray, i.e. they did not meet the criteria for a diagnostic accuracy test. Therefore, it is difficult to conclude from the case series if LDCT is accurate enough to replace X-rays.Due to the gap in current literature, a phantom study and subsequent post-mortem CT study are recommended as the primary investigative methods to assess the ability of low-dose CT to identify the subtle fractures associated with SPA and to calculate how low the achievable CT dose can be.Results: The skeletal survey X-ray series is the current ‘gold standard’ when investigating suspected physical abuse (SPA) of children, in addition to a non-contrast computed tomography (CT) brain scan. This systematic literature review synthesised findings of published research to determine if low dose computed tomography (LDCT) could detect subtle fractures and therefore replace the skeletal survey X-ray series in the investigation of SPA in children aged under 3 years.Five electronic databases and grey literature were systematically searched from their inception to 28 April 2022. Primary studies were included where the population comprised paediatric patients up to 16 years and LDCT was used to detect fractures associated with SPA. Studies involving imaging investigations of the head, standard dose CT examinations or accidental trauma were excluded.Three studies met the inclusion criteria, all of which were case series. These studies did not report many of the criteria required to compare the accuracy of LDCT to X-ray, i.e. they did not meet the criteria for a diagnostic accuracy test. Therefore, it is difficult to conclude from the case series if LDCT is accurate enough to replace X-rays.Due to the gap in current literature, a phantom study and subsequent post-mortem CT study are recommended as the primary investigative methods to assess the ability of low-dose CT to identify the subtle fractures associated with SPA and to calculate how low the achievable CT dose can be.Conclusion: The skeletal survey X-ray series is the current ‘gold standard’ when investigating suspected physical abuse (SPA) of children, in addition to a non-contrast computed tomography (CT) brain scan. This systematic literature review synthesised findings of published research to determine if low dose computed tomography (LDCT) could detect subtle fractures and therefore replace the skeletal survey X-ray series in the investigation of SPA in children aged under 3 years.Five electronic databases and grey literature were systematically searched from their inception to 28 April 2022. Primary studies were included where the population comprised paediatric patients up to 16 years and LDCT was used to detect fractures associated with SPA. Studies involving imaging investigations of the head, standard dose CT examinations or accidental trauma were excluded.Three studies met the inclusion criteria, all of which were case series. These studies did not report many of the criteria required to compare the accuracy of LDCT to X-ray, i.e. they did not meet the criteria for a diagnostic accuracy test. Therefore, it is difficult to conclude from the case series if LDCT is accurate enough to replace X-rays.Due to the gap in current literature, a phantom study and subsequent post-mortem CT study are recommended as the primary investigative methods to assess the ability of low-dose CT to identify the subtle fractures associated with SPA and to calculate how low the achievable CT dose can be. [ABSTRACT FROM AUTHOR]

Background: Cough is a defense mechanism that protects the airways and lungs in response to airway irritation. The sensory neurons involved in detecting airway irritants and the neural pathways mediating cough share similarities with those that encode pain from the body. Painful conditioning stimuli applied to one body site are known to reduce the perception of pain at another. However, whether the neural regulation of cough is influenced by painful stimuli is not known.Research Question: What are the behavioral and neural outcomes of painful conditioning stimuli on urge-to-cough (UTC) and cough evoked by inhaled capsaicin?Study Design and Methods: Sixteen healthy participants underwent psychophysical testing and functional MRI while completing a series of capsaicin inhalations to induce UTC and cough. The responses associated with capsaicin inhalation without pain were compared with those after the application of painful conditioning stimuli.Results: Significant decreases were seen behaviorally of 18.7% ± 17.3% (P < .001) and 47.0% ± 30.8% (P < .001) in participants' UTC ratings and cough frequencies, respectively, during the application of pain. UTC ratings were reduced by 24.2% ± 36.5% (P < .005) and increased by 67% ± 40% (P < .001) for capsaicin and saline inhalation, respectively, during the scanning session. Painful conditioning stimuli were associated with widespread decreases in regional brain responses to capsaicin inhalation (P < .001). Several brain regions showed levels of reduced activation attributable to painful conditioning that correlated with related changes in behavioral responses during scanning (R2 = 0.53).Interpretation: Pain-related decreases of cough and UTC are accompanied by widespread changes in brain activity during capsaicin inhalation, suggesting that pain can modify the central processing of inputs arising from the airways. A mechanistic understanding of how cough and pain processing interact within the brain may help develop more effective therapies to reduce unwanted coughing. [ABSTRACT FROM AUTHOR]

Purpose: Advances in additive manufacturing processes are enabling the fabrication of surrogate bone structures for applications including use in high‐resolution anthropomorphic phantoms. In this research, a simple numerical model is proposed that enables the generation of microarchitecture with similar statistical distribution to trabecular bone. Methods: A human humerus, radius, ulna, and several vertebrae were scanned on the Imaging and Medical beamline at the Australian Synchrotron and the proposed numerical model was developed through the definition of two complex functions that encode the trabecular thickness and position‐dependant spacing to generate volumetric surrogate trabecular structures. The structures reproduced those observed at 19 separate axial locations through the experimental bone volumes. The applicability of the model when incorporating a two‐material approximation to absorption‐ and phase‐contrast CT was also investigated through simulation. Results: The synthetic structures, when compared with the real trabecular microarchitecture, yielded an average mean thickness error of 2 μm, and a mean difference in standard deviation of 33 μm for the humerus, 24 μm for the ulna and radius, and 15 μm for the vertebrae. Simulated absorption‐ and propagation‐based phase contrast CT projection data were generated and reconstructed using the derived mathematical simplifications from the two‐material approximation, and the phase‐contrast effects were successfully demonstrated. Conclusions: The presented model reproduced trabecular distributions that could be used to generate phantoms for quality assurance and validation processes. The implication of utilizing a two‐material approximation results in simplification of the additive manufacturing process and the generation of synthetic data that could be used for training of machine learning applications. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: An immersive virtual reality (VR) simulation clinic with dynamic patient interaction and communication was developed to facilitate the training of medical radiation science students. The software “CETSOL VR Clinic” was integrated into the Medical Imaging programme at Monash University in 2016 in order to benchmark student experiences against existing simulation techniques (Shaderware™). Methods: An iterative approach to development, based on two cycles of user feedback, was used to develop and refine the simulated clinical environment. This environment uses realistic 3D models, embedded clinical scenarios, dynamic communication, 3D hand gesture interaction, gaze and positional stereoscopic tracking and online user capabilities using the Unity™ game and physics engines. Students’ perceptions of educational enhancement of their positioning skills following the use of the simulation tools were analysed via a 5‐point Likert scale questionnaire. Results: Student perception scores indicated a significant difference between simulation modalities in favour of the immersive CETSOL VR Clinic, χ2 (4, N = 92) = 9.5, P‐value <0.001. Conclusion: Student perception scores on improvement of their clinical and technical skills were higher for the hand‐positioning tasks performed with the CETSOL VR Clinic™ than with the comparative benchmark simulation that did not provide dynamic patient interaction and communication. [ABSTRACT FROM AUTHOR]

Laplacian Erosion, an image deblurring technique for multi-plane Gamma-cameras, has been developed and tested for planar imaging using a GEANT4 Monte Carlo model of the Pixelated Emission Detector for RadioisOtopes (PEDRO) as a test platform. A contrast and Derenzo-like phantom composed of ^125I were both employed to investigate the dependence of detection plane and pinhole geometry on the performance of Laplacian Erosion. Three different pinhole geometries were tested. It was found that, for the test system, the performance of Laplacian Erosion was inversely proportional to the detection plane offset, and directly proportional to the pinhole diameter. All tested pinhole geometries saw a reduction in the level of image blurring associated with the pinhole geometry. However, the reduction in image blurring came at the cost of signal to noise ratio in the image. The application of Laplacian Erosion was shown to reduce the level of image blurring associated with pinhole geometry and improve recovered image quality in multi-plane Gamma-cameras for the targeted radiotracer ^125I. [ABSTRACT FROM AUTHOR]

The Pixelated Emission Detector for RadiOisotopes (PEDRO) is a hybrid imaging system designed for the measurement of single photon emission from small animal models. The proof-of-principle device consists of a Compton-camera situated behind a mechanical collimator and is intended to provide optimal detection characteristics over a broad spectral range, from 30 to 511 keV. An automated routine has been developed for the optimization of large-area slits in the outer regions of a collimator which has a central region allocated for pinholes. The optimization was tested with a GEANT4 model of the experimental prototype. The data were blurred with the expected position and energy resolution parameters and a Bayesian interaction ordering algorithm was applied. Images were reconstructed using cone back-projection. The results show that the optimization technique allows the large-area slits to both sample fully and extend the primary field of view (FoV) determined by the pinholes. The slits were found to provide truncation of the back-projected cones of response and also an increase in the success rate of the interaction ordering algorithm. These factors resulted in an increase in the contrast and signal-to-noise ratio of the reconstructed image estimates. Of the two configurations tested, the cylindrical geometry outperformed the square geometry, primarily because of a decrease in artifacts. This was due to isotropic modulation of the cone surfaces, that can be achieved with a circular shape. Also, the cylindrical geometry provided increased sampling of the FoV due to more optimal positioning of the slits. The use of the cylindrical collimator and application of the transmission function in the reconstruction was found to improve the resolution of the system by a factor of 20, as compared to the uncollimated Compton camera. Although this system is designed for small animal imaging, the technique can be applied to any application of single photon imaging. [ABSTRACT FROM AUTHOR]

Machine learning (ML) techniques are increasingly being used in clinical medical imaging to automate distinct processing tasks. In post-mortem forensic radiology, the use of these algorithms presents significant challenges due to variability in organ position, structural changes from decomposition, inconsistent body placement in the scanner, and the presence of foreign bodies. Existing ML approaches in clinical imaging can likely be transferred to the forensic setting with careful consideration to account for the increased variability and temporal factors that affect the data used to train these algorithms. Additional steps are required to deal with these issues, by incorporating the possible variability into the training data through data augmentation, or by using atlases as a pre-processing step to account for death-related factors. A key application of ML would be then to highlight anatomical and gross pathological features of interest, or present information to help optimally determine the cause of death. In this review, we highlight results and limitations of applications in clinical medical imaging that use ML to determine key implications for their application in the forensic setting. [ABSTRACT FROM AUTHOR]