Non-linear emissions from microbubbles introduced to the vasculature for exposure to focused ultrasound are routinely monitored for assessment of therapy and avoidance of irreversible tissue damage. Yet the bubble-based mechanistic source for these emissions, under subresonant driving at typical therapeutic pressure amplitudes, may not be well understood. In the study described here, dual-perspective high-speed imaging at 210,000 frames per second (fps), and shadowgraphically at 10 Mfps, was used to observe cavitation from microbubbles flowing through a 500-mm polycarbonate capillary exposed to focused ultrasound of 692 kHz at therapeutically relevant pressure amplitudes. The acoustic emissions were simultaneously collected via a broadband calibrated needle hydrophone system. The observations indicate that periodic bubble-collapse shock waves can dominate the non-linear acoustic emissions, including subharmonics at higher driving amplitudes. Contributions to broadband emissions through variance in shock wave amplitude and emission timings are also identified. Possible implications for in vivo microbubble cavitation detection, mechanisms of therapy and the conventional classification of cavitation activity as stable or inertial are discussed. (

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Objective: To explore ethics education needs in Canadian Neonatal Perinatal Medicine (NPM) training programs. Methods: A retrospective review of NPM trainees' performance at the National NPM Objective Structured Clinical Examination (OSCE) was undertaken for 2012 to 2017 and two distinct cross-sectional online surveys were carried out. One survey targeted recently graduated neonatologists (RGNs) who completed 2 years' training in a Canadian NPM program between 2010 and 2015; the other survey was sent to Canadian NPM training program directors (PDs). The domains of interest were: perception of education, ethics and communication topics, educational strategies, assessment of trainees' competencies, and barriers to neonatal ethics education. Results: NPM trainees generally performed less well in stations involving ethics and communication relative to other domains on the National OSCE. Forty-seven RGNs (44.3%) and 12 PDs (92.3%) completed the survey. Over 90% of PDs and RGNs agreed on the importance of training in ethics and communication. Both groups highly valued training on topics related to communication. Preferred teaching strategies were experiential: observation and feedback. PDs mentioned the importance of using validated tools to regularly and formally assess trainees. They recognized challenges in regard to financial resources, physical space, and faculty training in patient-physician communication. Conclusions: National OSCE results indicate the need to improve neonatal ethics and communication training in Canadian NPM programs. RGNs and PDs identified important topics, as well as teaching and evaluation strategies. These results can be used to develop a training program for ethics and communication in NPM.

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