Contrast Enhancement of the Right Ventricle during Coronary CT Angiography – Is It Necessary?

Purpose

It is unclear if prolonged contrast media injection, to improve right ventricular visualization during coronary CT angiography, leads to increased detection of right ventricle pathology. The purpose of this study was to evaluate right ventricle enhancement and subsequent detection of right ventricle disease during coronary CT angiography.

Materials and Methods

472 consecutive patients referred for screening coronary CT angiography were retrospectively evaluated. Every patient underwent multidetector-row CT of the coronary arteries: 128x 0.6mm coll., 100-120kV, rot. time 0.28s, ref. mAs 350 and received an individualized (P3T) contrast bolus injection of iodinated contrast medium (300 mgI/ml). Patient data were analyzed to assess right ventricle enhancement (HU) and right ventricle pathology. Image quality was defined good when right ventricle enhancement >200HU, moderate when 140-200HU and poor when <140HU.

Results

Good image quality was found in 372 patients, moderate in 80 patients and poor in 20 patients. Mean enhancement of the right ventricle cavity was 268HU±102. Patients received an average bolus of 108±24 ml at an average peak flow rate of 6.1±2.2 ml/s. In only three out of 472 patients (0.63%) pathology of the right ventricle was found (dilatation) No other right ventricle pathology was detected.

Conclusion

Right ventricle pathology was detected in three out of 472 patients; the dilatation observed in these three cases may have been picked up even without dedicated enhancement of the right ventricle. Based on our findings, right ventricle enhancement can be omitted during screening coronary CT angiography.     

Genomic Heritability: What Is It?

Whole-genome regression methods are being increasingly used for the analysis and prediction of complex traits and diseases. In human genetics, these methods are commonly used for inferences about genetic parameters, such as the amount of genetic variance among individuals or the proportion of phenotypic variance that can be explained by regression on molecular markers. This is so even though some of the assumptions commonly adopted for data analysis are at odds with important quantitative genetic concepts. In this article we develop theory that leads to a precise definition of parameters arising in high dimensional genomic regressions; we focus on the so-called genomic heritability: the proportion of variance of a trait that can be explained (in the population) by a linear regression on a set of markers. We propose a definition of this parameter that is framed within the classical quantitative genetics theory and show that the genomic heritability and the trait heritability parameters are equal only when all causal variants are typed. Further, we discuss how the genomic variance and genomic heritability, defined as quantitative genetic parameters, relate to parameters of statistical models commonly used for inferences, and indicate potential inferential problems that are assessed further using simulations. When a large proportion of the markers used in the analysis are in LE with QTL the likelihood function can be misspecified. This can induce a sizable finite-sample bias and, possibly, lack of consistency of likelihood (or Bayesian) estimates. This situation can be encountered if the individuals in the sample are distantly related and linkage disequilibrium spans over short regions. This bias does not negate the use of whole-genome regression models as predictive machines; however, our results indicate that caution is needed when using marker-based regressions for inferences about population parameters such as the genomic heritability.     

Is It Easy to Stop RNA Polymerase?

Cdk2 has been viewed as a key cell cycle regulator that is essential for S phase progression. The recent discovery that Cdk2 is not required for cell proliferation in mice now shows that other factors must be able to replace Cdk2 in stimulating DNA replication. Experiments performed in Xenopus egg extracts identify the mitotic protein kinases Cdk1/Cyclin B and Cdk1/Cyclin A as likely candidates. These observations raise the intriguing possibility that Cdk1 normally participates in genome duplication in wild type cells.     

Why Is the Substomatal Chamber as Large as It Is?

The rate of CO(2) uptake by the mesophyll is examined as a function of the size of the substomatal chamber. Using the techniques of classical electric circuit analysis and a model in which the uptake is linear in the ambient CO(2) concentration, it is shown that the optimal chamber radius is several times larger than is the pore radius. This is somewhat larger than necessary for the reduction of transpirational water loss, and it offers an explanation for the otherwise inexplicably large size of the chamber.     

Microtubule Flux: What Is It Good for?

During mitosis in a eukaryotic cell, microtubule subunits continuously move towards spindle poles. A new study has revealed that inhibiting this microtubule flux in mammalian cells has no major effects on chromosome movements; it does, however, increase the probability of erroneous chromosome segregation.     

Candida africana: Is It a Fungal Pathogen?

Twelve years ago, Candida africana was proposed as new species within the Candida albicans species complex, and since then has raised much controversy regarding whether or not it should be considered a separate species from C. albicans. Although its taxonomic status is still a matter of debate, this yeast differs from C. albicans by a number of phenotypic, genotypic, pathogenic and clinical characteristics that make this fungus particularly interesting to study. Current epidemiological and clinical data suggest that C. africana has a worldwide distribution, is particularly adapted to colonize/infect human vaginal mucosa, and may also be responsible for most serious diseases involving other human organs. In this review, we will discuss the current knowledge about C. africana, highlighting its role in human infections, thus providing a complete clinical picture in order to understand if this yeast can be considered an important pathogen.     

Healthcare-Associated Candidemia: Is It a Distinct Syndrome?

Candidemia historically has represented a nosocomial infection rather than one that can present in the emergency department. However, many pathogens traditionally thought confined to the hospital setting now are frequently seen in persons presenting to the emergency department. This phenomenon led to the creation of the notion of the healthcare-associated infection. Healthcare-associated infections reflect an intermediate status between community-acquired and nosocomial processes and describe a select subgroup of persons with community-onset infection but an ongoing interaction with the healthcare system. The question necessarily therefore arises regarding the potential role for yeast as pathogens in healthcare-associated bloodstream infection. Several studies have specifically explored this issue. Each of the studies illustrate that community-onset candidemia does, in fact occur, and most subjects with such infections meet the criteria for a healthcare-associated syndrome. Although methodologically limited, these analyses reveal that healthcare-associated candidemia clearly exists but remains a rare occurrence.     

Is the edTPA the Right Choice for Evaluating Teacher Readiness?

The purpose of this article is to describe and analyze the edTPA, a performance assessment created by the Stanford Center for Assessment, Learning, and Equity (SCALE) and administered by Pearson, Inc., to assess the professional readiness of student teachers. We challenge claims made in support of using this assessment, specifically within the context of arts teacher preparation programs, and we address areas of immediate critical concern to make alternative recommendations.     

Evidence-Based Laboratory Medicine: Is It Working in Practice?

The principles of Evidence-Based Medicine have been established for about two decades, with the need for evidence-based clinical practice now being accepted in most health systems around the world. These principles can be employed in laboratory medicine. The key steps in evidence-based practice, namely (i) formulating the question; (ii) searching for evidence; (iii) appraising evidence; (iv) applying evidence; and (v) assessing the experience are all accepted but, as yet, translation into daily clinical and laboratory practice has been slow. Furthermore, the demand for evidence-based laboratory medicine (EBLM) has been slow to develop.There are many contrasting observations about laboratory medicine, for example (i) there is too much testing vs insufficient testing; (ii) testing is expensive vs laboratories are expected to generate income; and (iii) test results have little impact on outcomes vs test results are crucial to clinical decision making. However, there is little evidence to support any of these observations. Integrating the principles of EBLM into routine practice will help to resolve some of these issues by identifying (a) where laboratory medicine fits into the care pathway; (b) where testing is appropriate; (c) the nature and quality of evidence required to demonstrate the clinical utility of a test; (d) how the test result impacts on clinical actions; (e) where changes in the care pathway will occur; and (f) where benefit/value can be achieved. These answers will help to establish the culture of EBLM in clinical and laboratory practice.     

Peak Waste: When Is It Likely to Occur?

Population and per capita gross domestic product (GDP) projections are used to estimate total global municipal solid waste (MSW) generation over the twenty‐first century. Some projections for global population suggest that it will peak this century. Waste generation rates per capita generally increase with affluence, although in the most affluent countries there is also a trend toward dematerialization. The confluence of these factors means that at some point in the future total global waste generation could possibly peak. To determine when peak waste might occur, we used the shared‐socioeconomic pathway scenarios (used in Intergovernmental Panel on Climate Change [IPCC] studies) combined with estimates of municipal solid waste (MSW) generation rates, extrapolated from our work for the World Bank. Despite the expectation that total MSW generation in Organisation for Economic Co‐operation and Development (OECD) and high‐income countries will peak mid‐century, with current trajectories global peak waste is not expected before 2100. The peak could be moved forward to around 2075 and reduced in intensity by some 30% if a more aggressive sustainability growth scenario were followed, rather than the current business‐as‐usual scenario. Further, the magnitude of peak waste is sensitive to the intensity of waste generation; it could vary from 7.3 to 10.9 megatonnes per day under the sustainability scenario. The timing of peak waste will substantially depend on the development of cities in Sub‐Saharan Africa, where population growth rates are more than double the rest of the world.