European Society of Paediatric Radiology Computed Tomography and Dose Task Force : European guidelines on diagnostic reference levels for paediatric imaging

The recent European Council Directive 2013/59/EURATOM requires the establishment of diagnostic reference levels (DRLs) to optimise radiation dose in diagnostic and interventional radiology procedures. At the time this directive was enacted, just a few European countries had already set paediatric DRLs and many of these were outdated. For this reason, the European Commission launched a project addressing European Guidelines on Diagnostic Reference Levels for Paediatric Imaging that was awarded to a consortium led by the European Society of Radiology with the collaboration of the European Society of Paediatric Radiology and other European stakeholders involved in the radiation protection of children. The main aims of this project were to establish European DRLs to be used by countries without their own national paediatric DRLs and to provide a consistent method to establish new DRLs in the future. These European guidelines have been very recently endorsed by the European Commission and published in issue N degrees 185 of the Radiation Protection series. The purpose of this article is to introduce these guidelines to the wide community of paediatric radiologists.Peer reviewe

Impact ionization processes in the steady state of a driven Mott insulating layer coupled to metallic leads

We study a simple model of photovoltaic energy harvesting across a Mott insulating gap consisting of a correlated layer connected to two metallic leads held at different chemical potentials. Upon driving the layer with a time periodic electric field a particle current is induced from the low-energy to the high-energy lead. We address in particular the issue of impact ionization, whereby a particle photoexcited to the high-energy part of the upper Hubbard band uses its extra energy to produce a second particle-hole excitation. We find a drastic increase of the photocurrent upon entering the frequency regime where impact ionization is possible. At large values of the Mott gap, where impact ionization is energetically not allowed, we observe a suppression of the current and a piling up of charge in the high-energy part of the upper Hubbard band. Our study is based on a Floquet-DMFT treatment with the so-called auxiliary master equation approach as impurity solver. We verify that an approximation, whereby the self-energy is taken diagonal in the Floquet indices, is appropriate for the parameter range we are considering.Comment: 11 pages, 8 figures. Comments and suggestions welcome

Computer Aided Diagnosis of Clustered Microcalcifications Using Artificial Neural Nets

Objective: Development of a fully automated computer application for detection and classification of clustered microcalcifications using neural nets. Material and Methods: Mammographic films with clustered microcalcifications of known histology were digitized. All clusters were rated by two radiologists on a 3 point scale: benign, indeterminate and malignant. Automated detected clustered microcalcifications were clustered. Features derived from those clusters were used as input to 2 artificial neural nets: one was trained to identify the indeterminate clusters, whereas the second ANN classified the remaining clusters in benign or malignant ones. Performance evaluation followed the patient-based receiver operator characteristic analysis. Results: For identification of patients with indeterminate clusters a an Az-value of 0.8741 could be achieved. For the remaining patients their clusters could be classified as benign or malignant at an Az-value of 0.8749, a sensitivity of 0.977 and specificity of 0.471. Conclusions: A fully automated computer system for detection and classification of clustered microcalcifications was developed. The system is able to identify patients with indeterminate clusters, where additional investigations are recommended, and produces a reliable estimation of the biologic dignity for the remaining ones

Three-dimensional imaging of the larynx for pre-operative planning of laryngeal framework surgery

Modern laryngeal framework surgery (LFS) requires an exact understanding of the laryngeal biomechanics and precise pre-operative planning, for which bi-planar imaging is not sufficient. The aim of the study was to test whether MIMICS®, a commercially available software package for three-dimensional (3D) rendering of high-resolution computerised tomography (HRCT), is suitable for 3D imaging of the larynx, analysis of laryngeal biomechanics and pre-operative planning. We examined four cadaver larynx and one patient larynx. In the five larynges, all relevant structures and landmarks could be 3D visualised. Superimposing of two HRCT scans shows that when the arytenoids move from ‘respiration' to ‘phonation', they perform a rotating, translating and tilting motion. Moreover, we could demonstrate that the vocal fold elongates by 7% with cricothyroid approximation. We conclude that MIMCS® is well suited for 3D imaging of the larynx, analysis of laryngeal biomechanics and pre-operative planning of LFS procedure

DICOM for EIT

With EIT starting to be used in routine clinical practice [1], it important that the clinically relevant information is portable between hospital data management systems. DICOM formats are widely used clinically and cover many imaging modalities, though not specifically EIT. We describe how existing DICOM specifications, can be repurposed as an interim solution, and basis from which a consensus EIT DICOM ‘Supplement’ (an extension to the standard) can be writte

Cross-sectional chest circumference and shape development in infants

Objective: This study investigates the development of the thoracic cross-section at the nipple line level during the early stages of life. Unlike the descriptive awareness regarding chest development course, there exist no quantitative references concerning shape, circumference and possible dependencies to age, gender or body weight. The proposed mathematical relations are expected to help create guidelines for more realistic modelling and potential detection of abnormalities. One potential application is lung electrical impedance tomography (EIT) monitoring where accurate chest models are crucial in both extracting reliable parameters for regional ventilation function and design of EIT belts. Despite their importance, such reference data is not readily available for the younger age range due to insufficient data amid the regulations of neonatal imaging. Results: Chest circumference shows the highest correlation to body weight following the relation fx=18.3735ln0.0012x+2.1010 where x is the body weight in grams and f(x) is the chest circumference in cm at the nipple line level. No statistically significant difference in chest circumference between genders was detected. However, the shape indicated signs of both age and gender dependencies with on average boys developing a more rectangular shape than girls from the age of 1 years and 9 months

Torso shape detection to improve lung monitoring

Newborns with lung immaturity often require continuous monitoring and treatment of their lung ventilation in intensive care units, especially if born preterm. Recent studies indicate that Electrical Impedance Tomography (EIT) is feasible in newborn
 infants and children, and can quantitatively identify changes in regional lung aeration and ventilation following alterations to respiratory conditions. Information on the patient-specic shape of the torso and its role in minimizing the artefacts in the
 reconstructed images can improve the accuracy of the clinical parameters obtained from EIT. Currently, only idealized models or those segmented from CT scans are usually adopted. This study presents and compares two methodologies that can
 detect the patient-specic torso shape by means of wearable devices based on: (1) previously reported bend sensor technology and (2) a novel approach based on the use of accelerometers. The reconstruction of different phantoms, taking into account
 anatomical asymmetries and different sizes, are produced for comparison. As a result, the accelerometers are more versatile than bend sensors, which cannot be used on bigger cross-sections. The computational study estimates the optimal number of
 accelerometers required in order to generate an image reconstruction comparable to the use of a CT scan as the forward model. Furthermore, since the patient position is crucial to monitoring lung ventilation, the orientation of the phantoms is automatically
 detected by the accelerometer-based method. [Abstract copyright: © 2018 Institute of Physics and Engineering in Medicine.

Pediatric radius torus fractures in x-rays—how computer vision could render lateral projections obsolete

It is an indisputable dogma in extremity radiography to acquire x-ray studies in at least two complementary projections, which is also true for distal radius fractures in children. However, there is cautious hope that computer vision could enable breaking with this tradition in minor injuries, clinically lacking malalignment. We trained three different state-of-the-art convolutional neural networks (CNNs) on a dataset of 2,474 images: 1,237 images were posteroanterior (PA) pediatric wrist radiographs containing isolated distal radius torus fractures, and 1,237 images were normal controls without fractures. The task was to classify images into fractured and non-fractured. In total, 200 previously unseen images (100 per class) served as test set. CNN predictions reached area under the curves (AUCs) up to 98% [95% confidence interval (CI) 96.6%–99.5%], consistently exceeding human expert ratings (mean AUC 93.5%, 95% CI 89.9%–97.2%). Following training on larger data sets CNNs might be able to effectively rule out the presence of a distal radius fracture, enabling to consider foregoing the yet inevitable lateral projection in children. Built into the radiography workflow, such an algorithm could contribute to radiation hygiene and patient comfort

Model selection based algorithm in neonatal Chest EIT

This paper presents a new method for selecting a patient specific forward model to compensate for anatomical variations in electrical impedance tomography (EIT) monitoring of neonates. The method uses a combination of shape sensors and absolute reconstruction. It takes advantage of a probabilistic approach which automatically selects the best estimated forward model fit from pre-stored library models. Absolute/static image reconstruction is performed as the core of the posterior probability calculations. The validity and reliability of the algorithm in detecting a suitable model in the presence of measurement noise is studied with simulated and measured data from 11 patients. The paper also demonstrates the potential improvements on the clinical parameters extracted from EIT images by considering a unique case study with a neonate patient undergoing computed tomography imaging as clinical indication prior to EIT monitoring. Two well-known image reconstruction techniques, namely GREIT and tSVD, are implemented to create the final tidal images. The impacts of appropriate model selection on the clinical extracted parameters such as center of ventilation and silent spaces are investigated. The results show significant improvements to the final reconstructed images and more importantly to the clinical EIT parameters extracted from the images that are crucial for decision-making and further interventions