New automated fluoroscopic systems for pediatric applications.” J Appl Clin Med Phys 6:88–105

Pediatric patients are at higher risk to the adverse effects from exposure to ionizing radiation than adults. The smaller sizes of the anatomy and the reduced X-ray attenuation of the tissues provide special challenges. The goal of this effort is to investigate strategies for pediatric fluoroscopy in order to minimize the radiation exposure to these individuals, while maintaining effective diagnostic image quality. Modern fluoroscopy systems are often entirely automated and computer controlled. In this paper, various selectable and automated modes are examined to determine the influence of the fluoroscopy parameters upon the patient radiation exposures and image quality. These parameters include variable X-ray beam filters, automatic brightness control programs, starting kilovolt peak levels, fluoroscopic pulse rates, and other factors. Typical values of radiation exposure rates have been measured for a range of phantom thicknesses from 5 cm to 20 cm of acrylic. Other factors that have been assessed include spatial resolution, lowcontrast discrimination, and temporal resolution. The selection menu for various procedures is based upon the examination type, anatomical region, and patient size. For pediatric patients, the automated system can employ additional filtration, special automatic brightness control curves, pulsed fluoroscopy, and other features to reduce the patient radiation exposures without significantly compromising the image quality. The benefits gained from an optimal selection of automated programs and settings for fluoroscopy include ease of operation, better image quality, and lower patient radiation exposures. PACS numbers: 87.59.-e, 87.62.+n Key words: digital fluoroscopy, pediatric radiation exposur

Value of Gadolinium-Enhanced MRI in Detection of Acute Appendicitis in Children and Adolescents

OBJECTIVE. The aim of this study was to determine both the value of gadolinium-enhanced MRI in children with suspected acute appendicitis and the best sequences for detecting acute appendicitis, to thereby decrease imaging time. MATERIALS AND METHODS. This was a retrospective review of pediatric patients with suspected appendicitis who had undergone MRI at our institution between 2010 and 2011 after an indeterminate ultrasound examination. MRI examinations included T1-weighted unenhanced and contrast-enhanced, T2-weighted, and balanced steady-state free precession (SSFP) sequences in axial and coronal planes. Sequences were reviewed together and individually by five radiologists who were blinded to the final diagnosis. Radiologists were asked to score their confidence of appendicitis diagnosis using a 5-point scale. The diagnostic performance of each MR sequence was obtained by comparing the mean area under the curve (AUC) using receiver operating characteristic (ROC) analysis. RESULTS. A total of 49 patients with clinically suspected appendicitis were included, of whom 16 received a diagnosis of appendicitis. The mean AUCs for reviewing all sequences together, contrast-enhanced sequences alone, T2-weighted sequences alone, and balanced SSFP alone were 0.984, 0.979, 0.944, and 0.910, respectively. No significant difference was observed between reviewing all sequences together versus contrast-enhanced sequences alone (p = 0.90) and T2-weighted sequences alone (p = 0.23). A significant difference was observed between contrast-enhanced sequences and balanced SSFP (p \u3c 0.03). CONCLUSION. Gadolinium-enhanced images and T2-weighted images are most helpful in the assessment of acute appendicitis in the pediatric population. These findings have led to protocol modifications that have reduced imaging time

A clinically relevant model of acute respiratory distress syndrome in human-size swine

Despite over 30 years of intensive research for targeted therapies, treatment of acute respiratory distress syndrome (ARDS) remains supportive in nature. With mortality upwards of 30%, a high-fidelity pre-clinical model of ARDS, on which to test novel therapeutics, is urgently needed. We used the Yorkshire breed of swine to induce a reproducible model of ARDS in human-sized swine to allow the study of new therapeutics, from both mechanistic and clinical standpoints. For this, animals were anesthetized, intubated and mechanically ventilated, and pH-standardized gastric contents were delivered bronchoscopically, followed by intravenous infusion of Escherichia coli-derived lipopolysaccharide. Once the ratio of arterial oxygen partial pressure (PaO(2)) to fractional inspired oxygen (F(I)O(2)) had decreased to <150, the animals received standard ARDS treatment for up to 48 h. All swine developed moderate to severe ARDS. Chest radiographs taken at regular intervals showed significantly worse lung edema after induction of ARDS. Quantitative scoring of lung injury demonstrated time-dependent increases in interstitial and alveolar edema, neutrophil infiltration, and mild to moderate alveolar membrane thickening. This pre-clinical model of ARDS in human-sized swine recapitulates the clinical, radiographic and histopathologic manifestations of ARDS, providing a tool to study therapies for this highly morbid lung disease

Non-invasive pulmonary perfusion assessment in young patients with cystic fibrosis using an arterial spin labeling MR technique at 1.5 T

OBJECT: To assess lung perfusion in young patients with cystic fibrosis (CF) using an arterial spin labeling (ASL) technique. MATERIALS AND METHODS: Perfusion imaging was performed in 5 healthy volunteers and 33 pediatric patients (13 ± 5 years) with CF using an ASL technique. Image quality was evaluated on a five-point scale (1 = excellent). Quantitative perfusion maps were calculated based on the modified Bloch equations. Perfusion differences between volunteers and CF patients and regional differences between lobes were analyzed using Student's t test. The association of perfusion values and forced expiratory volume in 1 s (FEV1) was analyzed using univariate regression analysis. RESULTS: Mean lung perfusion was 698 ± 67 ml/100g/min (range: 593-777 ml/100g/min) in volunteers and 526 ± 113 ml/100g/min (range: 346-724 ml/100g/min) in CF patients. Median image quality was 2 in volunteers and 3 in CF patients. In CF patients, significantly lower perfusion was observed in the upper lobes compared to healthy volunteers. Mean perfusion values significantly correlated with FEV1 (r = 0.84, P < 0.0001). CONCLUSION: ASL perfusion imaging provides lung perfusion assessment in young CF patients. This non-invasive functional imaging technique is worth being evaluated in the clinical monitoring of CF patients

Thoracic imaging of coronavirus disease 2019 (COVID-19) in children: a series of 91 cases

Background: Pulmonary infection with SARS-CoV-2 virus (severe acute respiratory syndrome coronavirus 2; COVID-19) has rapidly spread worldwide to become a global pandemic. Objective: To collect paediatric COVID-19 cases worldwide and to summarize both clinical and imaging findings in children who tested positive on polymerase chain reaction testing for SARS-CoV-2. Materials and methods: Data were collected by completion of a standardised case report form submitted to the office of the European Society of Paediatric Radiology from March 12 to April 8, 2020. Chest imaging findings in children younger than 18&nbsp;years old who tested positive on polymerase chain reaction testing for SARS-CoV-2 were included. Representative imaging studies were evaluated by multiple senior paediatric radiologists from this group with expertise in paediatric chest imaging. Results: Ninety-one children were included (49 males; median age: 6.1&nbsp;years, interquartile range: 1.0 to 13.0&nbsp;years, range: 9&nbsp;days–17&nbsp;years). Most had mild symptoms, mostly fever and cough, and one-third had coexisting medical conditions. Eleven percent of children presented with severe symptoms and required intensive unit care. Chest radiographs were available in 89% of patients and 10% of them were normal. Abnormal chest radiographs showed mainly perihilar bronchial wall thickening (58%) and/or airspace consolidation (35%). Computed tomography (CT) scans were available in 26% of cases, with the most common abnormality being ground glass opacities (88%) and/or airspace consolidation (58%). Tree in bud opacities were seen in 6 of 24 CTs (25%). Lung ultrasound and chest magnetic resonance imaging were rarely utilized. Conclusion: It seems unnecessary to perform chest imaging in children to diagnose COVID-19. Chest radiography can be used in symptomatic children to assess airway infection or pneumonia. CT should be reserved for when there is clinical concern to assess for possible complications, especially in children with coexisting medical conditions

Selective Heterogeneity in Exoprotease Production by <em>Bacillus subtilis</em>

Bacteria have elaborate signalling mechanisms to ensure a behavioural response that is most likely to enhance survival in a changing environment. It is becoming increasingly apparent that as part of this response, bacteria are capable of cell differentiation and can generate multiple, mutually exclusive co-existing cell states. These cell states are often associated with multicellular processes that bring benefit to the community as a whole but which may be, paradoxically, disadvantageous to an individual subpopulation. How this process of cell differentiation is controlled is intriguing and remains a largely open question. In this paper, we consider an important aspect of cell differentiation that is known to occur in the Gram-positive bacterium Bacillus subtilis: we investigate the role of two master regulators DegU and Spo0A in the control of extra-cellular protease production. Recent work in this area focussed the on role of DegU in this process and suggested that transient effects in protein production were the drivers of cell-response heterogeneity. Here, using a combination of mathematical modelling, analysis and stochastic simulations, we provide a complementary analysis of this regulatory system that investigates the roles of both DegU and Spo0A in extra-cellular protease production. In doing so, we present a mechanism for bimodality, or system heterogeneity, without the need for a bistable switch in the underlying regulatory network. Moreover, our analysis leads us to conclude that this heterogeneity is in fact a persistent, stable feature. Our results suggest that system response is divided into three zones: low and high signal levels induce a unimodal or undifferentiated response from the cell population with all cells OFF and ON, respectively for exoprotease production. However, for intermediate levels of signal, a heterogeneous response is predicted with a spread of activity levels, representing typical “bet-hedging” behaviour