Utility of optical see-through head mounted displays in augmented reality-assisted surgery: A systematic review.

This article presents a systematic review of optical see-through head mounted display (OST-HMD) usage in augmented reality (AR) surgery applications from 2013 to 2020. Articles were categorised by: OST-HMD device, surgical speciality, surgical application context, visualisation content, experimental design and evaluation, accuracy and human factors of human-computer interaction. 91 articles fulfilled all inclusion criteria. Some clear trends emerge. The Microsoft HoloLens increasingly dominates the field, with orthopaedic surgery being the most popular application (28.6%). By far the most common surgical context is surgical guidance (n=58) and segmented preoperative models dominate visualisation (n=40). Experiments mainly involve phantoms (n=43) or system setup (n=21), with patient case studies ranking third (n=19), reflecting the comparative infancy of the field. Experiments cover issues from registration to perception with very different accuracy results. Human factors emerge as significant to OST-HMD utility. Some factors are addressed by the systems proposed, such as attention shift away from the surgical site and mental mapping of 2D images to 3D patient anatomy. Other persistent human factors remain or are caused by OST-HMD solutions, including ease of use, comfort and spatial perception issues. The significant upward trend in published articles is clear, but such devices are not yet established in the operating room and clinical studies showing benefit are lacking. A focused effort addressing technical registration and perceptual factors in the lab coupled with design that incorporates human factors considerations to solve clear clinical problems should ensure that the significant current research efforts will succeed.

SERV-CT: A disparity dataset from cone-beam CT for validation of endoscopic 3D reconstruction.

In computer vision, reference datasets from simulation and real outdoor scenes have been highly successful in promoting algorithmic development in stereo reconstruction. Endoscopic stereo reconstruction for surgical scenes gives rise to specific problems, including the lack of clear corner features, highly specular surface properties and the presence of blood and smoke. These issues present difficulties for both stereo reconstruction itself and also for standardised dataset production. Previous datasets have been produced using computed tomography (CT) or structured light reconstruction on phantom or ex vivo models. We present a stereo-endoscopic reconstruction validation dataset based on cone-beam CT (SERV-CT). Two ex vivo small porcine full torso cadavers were placed within the view of the endoscope with both the endoscope and target anatomy visible in the CT scan. Subsequent orientation of the endoscope was manually aligned to match the stereoscopic view and benchmark disparities, depths and occlusions are calculated. The requirement of a CT scan limited the number of stereo pairs to 8 from each ex vivo sample. For the second sample an RGB surface was acquired to aid alignment of smooth, featureless surfaces. Repeated manual alignments showed an RMS disparity accuracy of around 2 pixels and a depth accuracy of about 2 mm. A simplified reference dataset is provided consisting of endoscope image pairs with corresponding calibration, disparities, depths and occlusions covering the majority of the endoscopic image and a range of tissue types, including smooth specular surfaces, as well as significant variation of depth. We assessed the performance of various stereo algorithms from online available repositories. There is a significant variation between algorithms, highlighting some of the challenges of surgical endoscopic images. The SERV-CT dataset provides an easy to use stereoscopic validation for surgical applications with smooth reference disparities and depths covering the majority of the endoscopic image. This complements existing resources well and we hope will aid the development of surgical endoscopic anatomical reconstruction algorithms.

Beyond Teenage and Young Adult Cancer Care: Care Experiences of Patients Aged 25-39 Years Old in the UK National Health Service.

AIMS: Adolescents and young adults aged 15-39 years with cancer face unique medical, practical and psychosocial issues. In the UK, principal treatment centres and programmes have been designed to care for teenage and young adult patients aged 13-24 years in an age-appropriate manner. However, for young adults (YAs) aged 25-39 years with cancer, little access to age-specific support is available. The aim of this study was to examine this possible gap by qualitatively exploring YA care experiences, involving patients as research partners in the analysis to ensure robust results. MATERIALS AND METHODS: We conducted a phenomenological qualitative study with YAs diagnosed with any cancer type between ages 25 and 39 years old in the last 5 years. Participants took part in interviews or focus groups and data were analysed using inductive thematic analysis. Results were shaped in an iterative process with the initial coders and four YA patients who did not participate in the study to improve the rigor of the results. RESULTS: Sixty-five YAs with a range of tumour types participated. We identified seven themes and 13 subthemes. YAs found navigating the healthcare system difficult and commonly experienced prolonged diagnostic pathways. Participants felt under-informed about clinical details and the long-term implications of side-effects on daily life. YAs found online resources overwhelming but also a source of information and treatment support. Some patients regretted not discussing fertility before cancer treatment or felt uninformed or rushed when making fertility preservation decisions. A lack of age-tailored content or age-specific groups deterred YAs from accessing psychological support and rehabilitation services. CONCLUSIONS: YAs with cancer may miss some benefits provided to teenagers and young adults in age-tailored cancer services. Improving services for YAs in adult settings should focus on provision of age-specific information and access to existing relevant support.

Fuels, power and chemical periodicity.

The insatiable-and ever-growing-demand of both the developed and the developing countries for power continues to be met largely by the carbonaceous fuels comprising coal, and the hydrocarbons natural gas and liquid petroleum. We review the properties of the chemical elements, overlaid with trends in the periodic table, which can help explain the historical-and present-dominance of hydrocarbons as fuels for power generation. However, the continued use of hydrocarbons as fuel/power sources to meet our economic and social needs is now recognized as a major driver of dangerous global environmental changes, including climate change, acid deposition, urban smog and the release of many toxic materials. This has resulted in an unprecedented interest in and focus on alternative, renewable or sustainable energy sources. A major area of interest to emerge is in hydrogen energy as a sustainable vector for our future energy needs. In that vision, the issue of hydrogen storage is now a key challenge in support of hydrogen-fuelled transportation using fuel cells. The chemistry of hydrogen is itself beautifully diverse through a variety of different types of chemical interactions and bonds forming compounds with most other elements in the periodic table. In terms of their hydrogen storage and production properties, we outline various relationships among hydride compounds and materials of the chemical elements to provide some qualitative and quantitative insights. These encompass thermodynamic and polarizing strength properties to provide such background information. We provide an overview of the fundamental nature of hydrides particularly in relation to the key operating parameters of hydrogen gravimetric storage density and the desorption/operating temperature at which the requisite amount of hydrogen is released for use in the fuel cell. While we await the global transition to a completely renewable and sustainable future, it is also necessary to seek CO2 mitigation technologies applied to the use of fossil fuels. We review recent advances in the strategy of using hydrocarbon fossil fuels themselves as compounds for the high capacity storage and production of hydrogen without any CO2 emissions. Based on these advances, the world may end up with a hydrogen economy completely different from the one it had expected to develop; remarkably, with 'Green hydrogen' being derived directly from the hydrogen-stripping of fossil fuels. This article is part of the theme issue 'Mendeleev and the periodic table'.

Metrology of crystal defects through intensity variations in secondary electrons from the diffraction of primary electrons in a scanning electron microscope.

Understanding defects and their roles in plastic deformation and device reliability is important for the development of a wide range of novel materials for the next generation of electronic and optoelectronic devices. We introduce the use of gaseous secondary electron detectors in a variable pressure scanning electron microscope for non-destructive imaging of extended defects using electron channelling contrast imaging. We demonstrate that all scattered electrons, including the secondary electrons, can provide diffraction contrast as long as the sample is positioned appropriately with respect to the incident electron beam. Extracting diffraction information through monitoring the modulation of the intensity of secondary electrons as a result of diffraction of the incident electron beam, opens up the possibility of performing low energy electron channelling contrast imaging to characterise low atomic weight and ultra-thin film materials. Our methodology can be adopted for large area, nanoscale structural characterisation of a wide range of crystalline materials including metals and semiconductors, and we illustrate this using the examples of aluminium nitride and gallium nitride. The capability of performing electron channelling contrast imaging, using the variable pressure mode, extends the application of this technique to insulators, which usually require conducting coatings on the sample surface for traditional scanning electron microscope based microstructural characterisation.

Staphylococcal lung abscess in a child with cystic fibrosis: Case report & review of literature.

With contemporary cystic fibrosis (CF) care, a lung abscess is an uncommon occurrence. We describe a case of a staphylococcal lung abscess in a teenage girl with CF who presented with a two-week history of non-specific malaise followed by two days of left posterior chest pain and fever. A chest radiograph was consistent with a left sided pulmonary abscess, which was confirmed on a CT scan of the chest. The abscess was drained under ultrasound guidance and cultured methicillin-sensitive Staphylococcus aureus. The patient responded well to antibiotic treatment with the abscess cavity showing complete radiological resolution by six weeks post drainage.

Influence of temperature on prevalence of health and welfare conditions in pigs: time-series analysis of pig abattoir inspection data in England and Wales.

The prevalence of many diseases in pigs displays seasonal distributions. Despite growing concerns about the impacts of climate change, we do not yet have a good understanding of the role that weather factors play in explaining such seasonal patterns. In this study, national and county-level aggregated abattoir inspection data were assessed for England and Wales during 2010-2015. Seasonally-adjusted relationships were characterised between weekly ambient maximum temperature and the prevalence of both respiratory conditions and tail biting detected at slaughter. The prevalence of respiratory conditions showed cyclical annual patterns with peaks in the summer months and troughs in the winter months each year. However, there were no obvious associations with either high or low temperatures. The prevalence of tail biting generally increased as temperatures decreased, but associations were not supported by statistical evidence: across all counties there was a relative risk of 1.028 (95% CI 0.776-1.363) for every 1 °C fall in temperature. Whilst the seasonal patterns observed in this study are similar to those reported in previous studies, the lack of statistical evidence for an explicit association with ambient temperature may possibly be explained by the lack of information on date of disease onset. There is also the possibility that other time-varying factors not investigated here may be driving some of the seasonal patterns.

CryoEM at 100†keV: a demonstration and prospects.

100 kV is investigated as the operating voltage for single-particle electron cryomicroscopy (cryoEM). Reducing the electron energy from the current standard of 300 or 200 keV offers both cost savings and potentially improved imaging. The latter follows from recent measurements of radiation damage to biological specimens by high-energy electrons, which show that at lower energies there is an increased amount of information available per unit damage. For frozen hydrated specimens around 300 Šin thickness, the predicted optimal electron energy for imaging is 100 keV. Currently available electron cryomicroscopes in the 100-120 keV range are not optimized for cryoEM as they lack both the spatially coherent illumination needed for the high defocus used in cryoEM and imaging detectors optimized for 100 keV electrons. To demonstrate the potential of imaging at 100 kV, the voltage of a standard, commercial 200 kV field-emission gun (FEG) microscope was reduced to 100 kV and a side-entry cryoholder was used. As high-efficiency, large-area cameras are not currently available for 100 keV electrons, a commercial hybrid pixel camera designed for X-ray detection was attached to the camera chamber and was used for low-dose data collection. Using this configuration, five single-particle specimens were imaged: hepatitis B virus capsid, bacterial 70S ribosome, catalase, DNA protection during starvation protein and haemoglobin, ranging in size from 4.5 MDa to 64 kDa with corresponding diameters from 320 to 72 Å. These five data sets were used to reconstruct 3D structures with resolutions between 8.4 and 3.4 Å. Based on this work, the practical advantages and current technological limitations to single-particle cryoEM at 100 keV are considered. These results are also discussed in the context of future microscope development towards the goal of rapid, simple and widely available structure determination of any purified biological specimen.

Evaluation of Lower-Dose Spiral Head CT for Detection of Intracranial Findings Causing Neurologic Deficits.

BACKGROUND AND PURPOSE: Despite the frequent use of unenhanced head CT for the detection of acute neurologic deficit, the radiation dose for this exam varies widely. Our aim was to evaluate the performance of lower-dose head CT for detection of intracranial findings resulting in acute neurologic deficit. MATERIALS AND METHODS: Projection data from 83 patients undergoing unenhanced spiral head CT for suspected neurologic deficits were collected. Cases positive for infarction, intra-axial hemorrhage, mass, or extra-axial hemorrhage required confirmation by histopathology, surgery, progression of findings, or corresponding neurologic deficit; cases negative for these target diagnoses required negative assessments by two neuroradiologists and a clinical neurologist. A routine dose head CT was obtained using 250 effective mAs and iterative reconstruction. Lower-dose configurations were reconstructed (25-effective mAs iterative reconstruction, 50-effective mAs filtered back-projection and iterative reconstruction, 100-effective mAs filtered back-projection and iterative reconstruction, 200-effective mAs filtered back-projection). Three neuroradiologists circled findings, indicating diagnosis, confidence (0-100), and image quality. The difference between the jackknife alternative free-response receiver operating characteristic figure of merit at routine and lower-dose configurations was estimated. A lower 95% CI estimate of the difference greater than -0.10 indicated noninferiority. RESULTS: Forty-two of 83 patients had 70 intracranial findings (29 infarcts, 25 masses, 10 extra- and 6 intra-axial hemorrhages) at routine head CT (CT dose index = 38.3 mGy). The routine-dose jackknife alternative free-response receiver operating characteristic figure of merit was 0.87 (95% CI, 0.81-0.93). Noninferiority was shown for 100-effective mAs iterative reconstruction (figure of merit difference, -0.04; 95% CI, -0.08 to 0.004) and 200-effective mAs filtered back-projection (-0.02; 95% CI, -0.06 to 0.02) but not for 100-effective mAs filtered back-projection (-0.06; 95% CI, -0.10 to -0.02) or lower-dose levels. Image quality was better at higher-dose levels and with iterative reconstruction (P < .05). CONCLUSIONS: Observer performance for dose levels using 100-200 eff mAs was noninferior to that observed at 250 effective mAs with iterative reconstruction, with iterative reconstruction preserving noninferiority at a mean CT dose index of 15.2 mGy.

Determining GaN Nanowire Polarity and its Influence on Light Emission in the Scanning Electron Microscope.

The crystal polarity of noncentrosymmetric wurtzite GaN nanowires is determined nondestructively in the scanning electron microscope using electron backscatter diffraction (EBSD). The impact of the nanowire polarity on light emission is then investigated using cathodoluminescence (CL) spectroscopy. EBSD can determine polarity of noncentrosymmetric crystals by interrogating differences in the intensity distribution of bands of the EBSD pattern associated with semipolar planes. Experimental EBSD patterns from an array of GaN nanowires are compared with theoretical patterns produced using dynamical electron simulations to reveal whether they are Ga- or N-polar or, as in several cases, of mixed polarity. CL spectroscopy demonstrates the effect of the polarity on light emission, with spectra obtained from nanowires of known polarity revealing a small but measurable shift (≈28 meV) in the GaN near band edge emission energy between those with Ga and N polarity. We attributed this energy shift to a difference in impurity incorporation in nanowires of different crystal polarity. This approach can be employed to nondestructively identify polarity in a wide range of noncentrosymmetric nanoscale material systems and provide direct comparison with their luminescence.

Implicit domain adaptation with conditional generative adversarial networks for depth prediction in endoscopy.

PURPOSE: Colorectal cancer is the third most common cancer worldwide, and early therapeutic treatment of precancerous tissue during colonoscopy is crucial for better prognosis and can be curative. Navigation within the colon and comprehensive inspection of the endoluminal tissue are key to successful colonoscopy but can vary with the skill and experience of the endoscopist. Computer-assisted interventions in colonoscopy can provide better support tools for mapping the colon to ensure complete examination and for automatically detecting abnormal tissue regions. METHODS: We train the conditional generative adversarial network pix2pix, to transform monocular endoscopic images to depth, which can be a building block in a navigational pipeline or be used to measure the size of polyps during colonoscopy. To overcome the lack of labelled training data in endoscopy, we propose to use simulation environments and to additionally train the generator and discriminator of the model on unlabelled real video frames in order to adapt to real colonoscopy environments. RESULTS: We report promising results on synthetic, phantom and real datasets and show that generative models outperform discriminative models when predicting depth from colonoscopy images, in terms of both accuracy and robustness towards changes in domains. CONCLUSIONS: Training the discriminator and generator of the model on real images, we show that our model performs implicit domain adaptation, which is a key step towards bridging the gap between synthetic and real data. Importantly, we demonstrate the feasibility of training a single model to predict depth from both synthetic and real images without the need for explicit, unsupervised transformer networks mapping between the domains of synthetic and real data.

Early transition metal-catalyzed C-H alkylation: hydroaminoalkylation for Csp3-Csp3 bond formation in the synthesis of selectively substituted amines.

Hydroaminoalkylation is a 100% atom economic method for forming Csp3-Csp3 bonds through C-H activation α to an amine and subsequent reaction with an alkene. When catalyzed by early transition metals, this reaction allows for alternative disconnections for the synthesis of structurally complex amines. This method avoids the installation of protecting groups or directing groups and does not require added oxidants, or photoredox catalysts. In this feature article, we discuss the various selectively substituted amines that can be accessed by hydroaminoalkylation, with a special focus on the development of early transition metal catalysts for their rapid, step and atom efficient assembly.

Third line treatment of advanced oesophagogastric cancer: A critical review of current evidence and evolving trends.

There is increasing evidence that treatment beyond second line provides significant survival benefit for selected advanced oesophageal and gastric adenocarcinoma patients, and important randomised controlled trials of both chemotherapy, targeted therapy and immunotherapy have recently been reported in this space. Despite this growing evidence base there are presently no formal guidelines for third line treatment available to clinicians, and as these agents move into routine clinical practice patient selection and rational sequencing of treatment will become an increasingly relevant clinical challenge. This review critically appraises the current evidence base for third line treatment and discusses patient selection, potential predictive biomarkers and future directions for third line treatment in this challenging condition.

Student perspectives on using egocentric video recorded by smart glasses to assess communicative and clinical skills with standardised patients.

INTRODUCTION: This exploratory study evaluated student perceptions of their ability to self- and peer assess (i) interpersonal communication skills and (ii) clinical procedures (a head and neck examination) during standardised patient (SP) interactions recorded by Google Glass compared to a static camera. METHODS: Students compared the Google Glass and static camera recordings using an instrument consisting of 20 Likert-type items and four open- and closed-text items. The Likert-type items asked students to rate how effectively they could assess specific aspects of interpersonal communication and a head and neck examination in these two different types of recordings. The interpersonal communication items included verbal, paraverbal and non-verbal subscales. The open- and closed-text items asked students to report on more globally the differences between the two types of recordings. Descriptive and inferential statistical analyses were conducted for all survey items. An inductive thematic analysis was conducted to determine qualitative emergent themes from the open-text questions. RESULTS: Students found the Glass videos more effective for assessing verbal (t22 = 2.091, P = 0.048) and paraverbal communication skills (t22 = 3.304, P = 0.003), whilst they reported that the static camera video was more effective for assessing non-verbal communication skills (t22 = -2.132, P = 0.044). Four principle themes emerged from the students' open-text responses comparing Glass to static camera recordings for self- and peer assessment: (1) first-person perspective, (2) assessment of non-verbal communication, (3) audiovisual experience and (4) student operation of Glass. DISCUSSION AND CONCLUSION: Our findings suggest that students perceive that Google Glass is a valuable tool for facilitating self- and peer assessment of SP examinations because of students' perceived ability to emphasise and illustrate communicative and clinical activities from a first-person perspective.

Microwaves effectively examine the extent and type of coking over acid zeolite catalysts.

Coking leads to the deactivation of solid acid catalyst. This phenomenon is a ubiquitous problem in the modern petrochemical and energy transformation industries. Here, we show a method based on microwave cavity perturbation analysis for an effective examination of both the amount and the chemical composition of cokes formed over acid zeolite catalysts. The employed microwave cavity can rapidly and non-intrusively measure the catalytically coked zeolites with sample full body penetration. The overall coke amount is reflected by the obtained dielectric loss (ε″) value, where different coke compositions lead to dramatically different absorption efficiencies (ε″/cokes' wt%). The deeper-dehydrogenated coke compounds (e.g., polyaromatics) lead to an apparently higher ε″/wt% value thus can be effectively separated from lightly coked compounds. The measurement is based on the nature of coke formation during catalytic reactions, from saturated status (e.g., aliphatic) to graphitized status (e.g., polyaromatics), with more delocalized electrons obtained for enhanced Maxwell-Wagner polarization.Catalyst deactivation by coke deposition is a major drawback in industrial processes. Here, the authors show a non-intrusive microwave cavity perturbation technique as a powerful tool to determine the nature and extent of coke accumulation in industrially-relevant zeolite catalysts.

A comparison study of complications and initial follow-up costs of transcutaneous and percutaneous bone conduction devices.

BACKGROUND: The percutaneous osseointegrated bone conduction device can be associated with more soft tissue complications when compared to the magnetic transcutaneous osseointegrated bone conduction device. This study aimed to determine whether fewer soft tissue complications may result in the transcutaneous osseointegrated bone conduction device being a lower cost option in hearing rehabilitation. METHODS: This retrospective case note review included adult patients who underwent implantation with the transcutaneous Cochlear Attract (n = 22) or percutaneous Cochlear DermaLock (n = 25) bone-anchored hearing aids between September 2013 and December 2014. The number of post-operative clinic appointments, complications and treatments undertaken, and calculated cost average, were compared between the two groups. RESULTS: Although the transcutaneous device was slightly more expensive than the percutaneous device, the percutaneous device was associated with a greater number of soft tissue complications and, as a result, the percutaneous device had significantly higher follow-up costs in the first six months following surgery. CONCLUSION: The transcutaneous osseointegrated bone conduction device may represent a more cost-effective method of hearing rehabilitation compared to the percutaneous osseointegrated bone conduction device.

Hysteretic photochromic switching of Eu-Mg defects in GaN links the shallow transient and deep ground states of the Mg acceptor.

Although p-type activation of GaN by Mg underpins a mature commercial technology, the nature of the Mg acceptor in GaN is still controversial. Here, we use implanted Eu as a 'spectator ion' to probe the lattice location of Mg in doubly doped GaN(Mg):Eu. Photoluminescence spectroscopy of this material exemplifies hysteretic photochromic switching (HPS) between two configurations, Eu0 and Eu1(Mg), of the same Eu-Mg defect, with a hyperbolic time dependence on 'switchdown' from Eu0 to Eu1(Mg). The sample temperature and the incident light intensity at 355 nm tune the characteristic switching time over several orders of magnitude, from less than a second at 12.5 K, ~100 mW/cm2 to (an estimated) several hours at 50 K, 1 mW/cm2. Linking the distinct Eu-Mg defect configurations with the shallow transient and deep ground states of the Mg acceptor in the Lany-Zunger model, we determine the energy barrier between the states to be 27.7(4) meV, in good agreement with the predictions of theory. The experimental results further suggest that at low temperatures holes in deep ground states are localized on N atoms axially bonded to Mg acceptors.

Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition.

Hydrogen is often described as the fuel of the future, especially for application in hydrogen powered fuel-cell vehicles (HFCV's). However, its widespread implementation in this role has been thwarted by the lack of a lightweight, safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amounts of hydrogen through microwave-assisted catalytic decomposition. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufactured through completely sustainable processes utilizing biomass or other renewable feedstocks.

How do children travel to school in urban India? A cross-sectional study of 5,842 children in Hyderabad.

BACKGROUND: Millions of children travel to school every day in India, yet little is known about this journey. We examined the distribution and determinants of school travel in Hyderabad, India. METHODS: We conducted a cross-sectional survey using a two-stage stratified cluster sampling design. School travel questionnaires were used to collect data from children aged 11-14 years, attending private, semi-private and government funded schools in Hyderabad. We used Google Earth to estimate the distance from home to school for each child and modelled the relationship between distance to school and mode of travel, adjusting for confounders. RESULTS: Forty five of the 48 eligible schools that were selected agreed to participate, providing a total sample of 5842 children. The response rate was 99 %. Most children walked (57 %) or cycled (6 %) to school but 36 % used motorised transport (mostly bus). The proportion using motorised transport was higher in children attending private schools (41 %) than in those attending government schools (24 %). Most (90 %) children lived within 5km of school and 36 % lived within 1km. Greater distance to school was strongly associated with the use of motorised transport. Children living close to school were much more likely to walk or cycle. CONCLUSIONS: Most children in Hyderabad walk (57 %) or cycle (6 %) to school. If these levels are to be maintained, there is an urgent need to ensure that walking and cycling are safe and pleasant. Social policies that decrease distances to school could have a large impact on road traffic injuries, air pollution, and physical activity levels.