Impact of Filling Gas on Subharmonic Emissions of Phospholipid Ultrasound Contrast Agents

Subharmonic signals backscattered from gas-filled lipid-shelled microbubbles have generated significant research interest because they can improve the detection and sensitivity of contrast-enhanced ultrasound imaging. However, the emission of subharmonic signals is strongly characterized by a temporal dependence, the origins of which have not been sufficiently elucidated. The features that influence subharmonic emissions need to be identified not only to better develop next-generation microbubble contrast agents, but also to develop more efficient subharmonic imaging (SHI) modes and therapeutic strategies. We examined the effect of microbubble filling gas on subharmonic emissions. Phospholipid shelled-microbubbles with different gaseous compositions such as sulfur hexafluoride (SF₆), octafluoropropane (C₃F₈) or decafluorobutane (C₄F₁₀), nitrogen (N₂)/C₄F₁₀ or air were insonated using a driving frequency of 10 MHz and peak negative pressure of 450 kPa, and their acoustic responses were tracked by monitoring both second harmonic and subharmonic emissions. Microbubbles were first acoustically characterized with their original gas and then re-characterized after substitution of the original gas with air, SF₆ or C₄F₁₀. A measureable change in intensity of the subharmonic emissions with a 20- to 40-min delayed onset and increasing subharmonic emissions of the order 12–18 dB was recorded for microbubbles filled with C₄F₁₀. Substitution of C₄F₁₀ with air eliminated the earlier observed delay in subharmonic emissions. Significantly, substitution of SF₆ for C₄F₁₀ successfully triggered a delay in the subharmonic emissions of the resultant agents, whereas substitution of C₄F₁₀ for SF₆ eliminated the earlier observed suppression of subharmonic emissions, clearly suggesting that the type of filling gas contained in the microbubble agent influences subharmonic emissions in a time-dependent manner. Because our agents were dispersed in air-stabilized phosphate-buffered saline, these results suggest that the diffusivity of the gas from the agent to the surrounding medium is correlated with the time-dependent evolution of subharmonic emissions.     

Improving recognition of delirium in clinical practice: a call for action

ABSTRACT: BACKGROUND: The purpose of this correspondence article is to report opinion amongst experts in the delirium field as to why, despite on-going training for all health professionals, delirium continues to be under recognised. Consensus was obtained by means of two conference workshops and an online survey of members of the European Delirium Association.Major barriers to recognition at an individual level include ignorance about the benefit of treating delirium. At an organisational level, reflecting socio-cultural attitudes, barriers include a low strategic and financial priority and the fact that delirium is an orphan condition falling between specialties.     

How does feedback from patients impact upon healthcare student clinical skill development and learning? A systematic review

Background: A key feature of health professionals’ training, irrespective of discipline, is the acquisition and application of clinical and communication skills. Despite this, little is known about the potential role of patient feedback on this process. This systematic review aimed to answer the question: How does feedback from patients impact upon healthcare student clinical skill development and learning?

Design: Systematic review of published literature.

Methods: Electronic databases were searched for studies that explored the effects of patient feedback on student learning and were published before March 2016. Eligible articles underwent methodological evaluation using the McMaster University Critical Evaluation Forms and data extraction.

Results: A total of 237 articles were retrieved following searches of electronic databases and hand searches of reference lists. Twelve (7 quantitative, 2 qualitative, 3 mixed methods) studies met the inclusion criteria. Eleven studies reported that patient feedback improved students’ clinical skills.

Conclusion: Minimal research has explored the impact of patient feedback on student learning. The research to date suggests that direct feedback from patients may be beneficial for the development of students’ communication and clinical skills; however, the wide variety of evaluation methods and the lack of validated tools for patients to provide feedback suggest that further exploration is warranted.     

Understanding and using time series analyses in addiction research

Time series analyses are statistical methods used to assess trends in repeated measurements taken at regular intervals and their associations with other trends or events, taking account of the temporal structure of such data. Addiction research often involves assessing associations between trends in target variables (e.g. population cigarette smoking prevalence) and predictor variables (e.g. average price of a cigarette), known as a multiple time series design, or interventions or events (e.g. introduction of an indoor smoking ban), known as an interrupted time series design. There are many analytical tools available, each with its own strengths and limitations. This paper provides addiction researchers with an overview of many of the methods available (GLM, GLMM, GLS, GAMM, ARIMA, ARIMAX, VAR, SVAR, VECM) and guidance on when and how they should be used, sample size det ermination, reporting and interpretation. The aim is to provide increased clarity for researchers proposing to undertake these analyses concerning what is likely to be acceptable for publication in journals such as Addiction. Given the large number of choices that need to be made when setting up time series models, the guidance emphasizes the importance of pre‐registering hypotheses and analysis plans before the analyses are undertaken.