Background: The coronavirus disease 2019 (COVID-19) pandemic has disrupted university teaching globally. The mental health impacts on international university students have been overlooked.Aims: This study examined the differences in COVID-19-related stressors and mental health impacts between international university students studying in the UK or USA who returned to their home country or region (returnees) and those who stayed in their institution country (stayers), and identified COVID-19-related stressors and coping strategies that were predictors of mental health.Method: An online questionnaire survey was conducted from April 28 through May 12, 2020 using an exponential, non-discriminative snowball sampling strategy (registered at the National Institutes of Health: NCT04365361).Results: A total of 124 full-time international university students (36.3% male) were included: 75.8% had returned to their home country or region for reasons related to COVID-19; 77.4% were pursuing a bachelor's program, and 53.2% were in programs with practicum component. 84.7% of all students had moderate-to-high perceived stress, 12.1% had moderate-to-severe symptoms of anxiety and depression, and 17.7% had moderate-to-severe symptoms of insomnia. Compared with returnees, stayers had significantly higher stress from COVID-19-related stressors such as personal health and lack of social support (Cohen's d: 0.57–1.11), higher perceived stress [10-item Perceived Stress Scale (PSS-10)] {22.6 ± 6.2 vs. 19.1 ± 6.1, β [95% confidence interval (CI)]: 4.039 (0.816, 7.261), Cohen's d: 0.52}, and more severe insomnia symptoms [Insomnia Severity Index (ISI)] [11.8 ± 6.1 vs. 7.6 ± 5.2, β (95% CI): 3.087 (0.262, 5.912), Cohen's d: 0.45], with moderate-to-large effect sizes. Compared with males, females reported significantly higher stress from uncertainties about academic program (Cohen's d: 0.45) with a small effect size. In the total sample, stress related to academics (e.g., personal attainment, uncertainties about academic program, and changes in teaching/learning format), health (including personal health and health of family and friends), availability of reliable COVID-19-related information, and lack of social support predicted more negative mental health impacts. Resilience, positive thinking, and exercise were predictors of less severe mental health impacts.Conclusions: Stayers experienced more adverse mental health impacts than returnees. We call on educators and mental health professionals to provide appropriate support for international students, particularly the stayers, during the pandemic.

A quality assurance method was developed to investigate the effects of residual target motion for hypofractionated spine radiosurgery. The residual target motion (target movement between successive image-guided corrections) was measured on-line via dual x-ray imagers for patients treated with CyberKnife (Accuray, Inc., Sunnyvale, CA), a robotic linear accelerator with intrafractional image-tracking capability. The six degree-of-freedom characteristics of the residual target motion were analyzed, the effects of such motion on patient treatment delivery were investigated by incorporating the probability distribution of the residual motion into the treatment planning dose calculations, and deviations of the doses from those originally planned were calculated. Measurements using a programmable motion phantom were also carried out and compared with the static treatment plan calculations. It was found that the residual target motions were patient specific and typically on the order of 2 mm. The measured dose distributions incorporating the residual target motion also exhibited 2.0 mm discrepancy at the prescription isodose level when compared with the static treatment plan calculations. For certain patients, residual errors introduced significant uncertainties (-1 Gy) for the dose delivered to the spinal cord, especially at the high dose levels covering a small volume of the spinal cord (e.g., 0.1 cc). In such cases, stringent cord constraints and frequent monitoring of the target position should be implemented.

Rapid delivery of multiple shots or isocenters is one of the hallmarks of Gamma Knife radiosurgery. In this study, we investigated whether the temporal order of shots delivered with Gamma Knife Perfexion would significantly influence the biological equivalent dose for complex multi-isocenter treatments. Twenty single-target cases were selected for analysis. For each case, 3D dose matrices of individual shots were extracted and single-fraction equivalent uniform dose (sEUD) values were determined for all possible shot delivery sequences, corresponding to different patterns of temporal dose delivery within the target. We found significant variations in the sEUD values among these sequences exceeding 15% for certain cases. However, the sequences for the actual treatment delivery were found to agree (<3%) and to correlate (R² = 0.98) excellently with the sequences yielding the maximum sEUD values for all studied cases. This result is applicable for both fast and slow growing tumors with α/β values of 2 to 20 according to the linear-quadratic model. In conclusion, despite large potential variations in different shot sequences for multi-isocenter Gamma Knife treatments, current clinical delivery sequences exhibited consistent biological target dosing that approached that maximally achievable for all studied cases.