A GPU Tool for Efficient, Accurate, and Realistic Simulation of Cone Beam CT Projections

Simulation of x-ray projection images plays an important role in cone beam CT (CBCT) related research projects. A projection image contains primary signal, scatter signal, and noise. It is computationally demanding to perform accurate and realistic computations for all of these components. In this work, we develop a package on GPU, called gDRR, for the accurate and efficient computations of x-ray projection images in CBCT under clinically realistic conditions. The primary signal is computed by a tri-linear ray-tracing algorithm. A Monte Carlo (MC) simulation is then performed, yielding the primary signal and the scatter signal, both with noise. A denoising process is applied to obtain a smooth scatter signal. The noise component is then obtained by combining the difference between the MC primary and the ray-tracing primary signals, and the difference between the MC simulated scatter and the denoised scatter signals. Finally, a calibration step converts the calculated noise signal into a realistic one by scaling its amplitude. For a typical CBCT projection with a poly-energetic spectrum, the calculation time for the primary signal is 1.2~2.3 sec, while the MC simulations take 28.1~95.3 sec. Computation time for all other steps is negligible. The ray-tracing primary signal matches well with the primary part of the MC simulation result. The MC simulated scatter signal using gDRR is in agreement with EGSnrc results with a relative difference of 3.8%. A noise calibration process is conducted to calibrate gDRR against a real CBCT scanner. The calculated projections are accurate and realistic, such that beam-hardening artifacts and scatter artifacts can be reproduced using the simulated projections. The noise amplitudes in the CBCT images reconstructed from the simulated projections also agree with those in the measured images at corresponding mAs levels.Comment: 21 pages, 11 figures, 1 tabl

Oceans and human health : navigating changes on Canada’s coasts

Ocean conditions can affect human health in a variety of ways that are often overlooked and unappreciated. Oceans adjacent to Canada are affected by many anthropogenic stressors, with implications for human health and well-being. Climate change further escalates these pressures and can expose coastal populations to unique health hazards and distressing conditions. However, current research efforts, education or training curriculums, and policies in Canada critically lack explicit consideration of these ocean–public health linkages. The objective of this paper is to present multiple disciplinary perspectives from academics and health practitioners to inform the development of future directions for research, capacity development, and policy and practice at the interface of oceans and human health in Canada. We synthesize major ocean and human health linkages in Canada, and identify climate-sensitive drivers of change, drawing attention to unique considerations in Canada. To support effective, sustained, and equitable collaborations at the nexus of oceans and human health, we recommend the need for progress in three critical areas: (i) holistic worldviews and perspectives, (ii) capacity development, and (iii) structural supports. Canada can play a key role in supporting the global community in addressing the health challenges of climate and ocean changes

Investigating the contribution of peri-domestic transmission to risk of zoonotic malaria infection in humans

Background: In recent years, the primate malaria Plasmodium knowlesi has emerged in human populations throughout South East Asia, with the largest hotspot being in Sabah, Malaysian Borneo. Control efforts are hindered by limited knowledge of where and when people get exposed to mosquito vectors. It is assumed that exposure occurs primarily when people are working in forest areas, but the role of other potential exposure routes (including domestic or peri-domestic transmission) has not been thoroughly investigated. Methodology/Principal Findings: We integrated entomological surveillance within a comprehensive case-control study occurring within a large hotspot of transmission in Sabah, Malaysia. Mosquitoes were collected at 28 pairs households composed of one where an occupant had a confirmed P. knowlesi infection within the preceding 3 weeks (“case”) and an associated “control” where no infection was reported. Human landing catches were conducted to measure the number and diversity of mosquitoes host seeking inside houses and in the surrounding peri-domestic (outdoors but around the household) areas. The predominant malaria vector species was Anopheles balabacensis, most of which were caught outdoors in the early evening (6pm - 9pm). It was significantly more abundant in the peri-domestic area than inside houses (5.5-fold), and also higher at case than control households (0.28±0.194 vs 0.17±0.127, p<0.001). Ten out of 641 An. balabacensis tested were positive for simian malaria parasites, but none for P. knowlesi. Conclusions/Significance: This study shows there is a possibility that humans can be exposed to P. knowlesi infection around their homes. The vector is highly exophagic and few were caught indoors indicating interventions using bednets inside households may have relatively little impact

SARS-CoV Antibody Prevalence in All Hong Kong Patient Contacts

A total of 1,068 asymptomatic close contacts of patients with severe acute respiratory (SARS) from the 2003 epidemic in Hong Kong were serologically tested, and 2 (0.19%) were positive for SARS coronavirus immunoglobulin G antibody. SARS rarely manifests as a subclinical infection, and at present, wild animal species are the only important natural reservoirs of the virus

Effectiveness of a mobile smoking cessation service in reaching elderly smokers and predictors of quitting

<p>Abstract</p> <p>Background</p> <p>Different smoking cessation programmes have been developed in the last decade but utilization by the elderly is low. We evaluated a pilot mobile smoking cessation service for the Chinese elderly in Hong Kong and identified predictors of quitting.</p> <p>Methods</p> <p>The Mobile Smoking Cessation Programme (MSCP) targeted elderly smokers (aged 60 or above) and provided service in a place that was convenient to the elderly. Trained counsellors provided individual counselling and 4 week's free supply of nicotine replacement therapy (NRT). Follow up was arranged at 1 month by face-to-face and at 3 and 6 months by telephone plus urinary cotinine validation. A structured record sheet was used for data collection. The service was evaluated in terms of process, outcome and cost.</p> <p>Results</p> <p>102 governmental and non-governmental social service units and private residential homes for the elderly participated in the MSCP. We held 90 health talks with 3266 elderly (1140 smokers and 2126 non-smokers) attended. Of the 1140 smokers, 365 (32%) received intensive smoking cessation service. By intention-to-treat, the validated 7 day point prevalence quit rate was 20.3% (95% confidence interval: 16.2%–24.8%). Smoking less than 11 cigarettes per day and being adherent to NRT for 4 weeks or more were significant predictors of quitting. The average cost per contact was US$54 (smokers only); per smoker with counselling: US$168; per self-reported quitter: US$594; and per cotinine validated quitter: US$827.</p> <p>Conclusion</p> <p>This mobile smoking cessation programme was acceptable to elderly Chinese smokers, with quit rate comparable to other comprehensive programmes in the West. A mobile clinic is a promising model to reach the elderly and probably other hard to reach smokers.</p

Cellular heterogeneity of pluripotent stem cell-derived cardiomyocyte grafts is mechanistically linked to treatable arrhythmias

Preclinical data have confirmed that human pluripotent stem cell-derived cardiomyocytes (PSC-CMs) can remuscularize the injured or diseased heart, with several clinical trials now in planning or recruitment stages. However, because ventricular arrhythmias represent a complication following engraftment of intramyocardially injected PSC-CMs, it is necessary to provide treatment strategies to control or prevent engraftment arrhythmias (EAs). Here, we show in a porcine model of myocardial infarction and PSC-CM transplantation that EAs are mechanistically linked to cellular heterogeneity in the input PSC-CM and resultant graft. Specifically, we identify atrial and pacemaker-like cardiomyocytes as culprit arrhythmogenic subpopulations. Two unique surface marker signatures, signal regulatory protein α (SIRPA)+CD90−CD200+ and SIRPA+CD90−CD200−, identify arrhythmogenic and non-arrhythmogenic cardiomyocytes, respectively. Our data suggest that modifications to current PSC-CM-production and/or PSC-CM-selection protocols could potentially prevent EAs. We further show that pharmacologic and interventional anti-arrhythmic strategies can control and potentially abolish these arrhythmias

Psychosocial Risk Factors in Disordered Gambling: A Descriptive Systematic Overview of Vulnerable Populations

Background: Gambling is a behaviour engaged in by millions of people worldwide; for some, gambling can become a severely maladaptive behaviour, and previous research has identified a wide range of psychosocial risk factors that can be considered important for the development and maintenance of disordered gambling. Although risk factors have been identified, the homogeneity of risk factors across specific groups thought to be vulnerable to disordered gambling is to date, unexplored. Methods: To address this, the current review sought to conduct a systematic overview of literature relating to seven vulnerable groups: young people and adolescents, older adults, women, veterans, indigenous peoples, prisoners, and low socio-economic/income groups. Results: Multiple risk factors associated with disordered gambling were identified; some appeared consistently across most groups, including being male, co-morbid mental and physical health conditions, substance use disorders, accessibility and availability of gambling, form and mode of gambling, and experience of trauma. Further risk factors were identified that were specific to each vulnerable group. Conclusion: Within the general population, certain groups are more vulnerable to disordered gambling. Although some risk factors are consistent across groups, some risk factors appear to be group specific. It is clear that there is no homogenous pathway in to disordered gambling, and that social, developmental, environmental and demographic characteristics can all interact to influence an individual’s relationship with gambling

Calcified Algae for Tissue Engineering.

This book presents the latest advances in marine structures and related biomaterials for applications in both soft- and hard-tissue engineering, as well as controlled drug delivery

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio