Facemask and social distancing, pillars of opening up economies.

The COVID-19 pandemic has caused severe health and economic impacts globally. Strategies to safely reopen economies, travel and trade are a high priority. Until a reliable vaccine is available, non-pharmaceutical techniques are the only available means of disease control. In this paper, we aim to evaluate the extent to which social distancing (SD) and facemask (FM) use can mitigate the transmission of COVID-19 when restrictions are lifted. We used a microsimulation activity-based model for Sydney Greater Metropolitan Area, to evaluate the power of SD and FM in controlling the pandemic under numerous scenarios. The hypothetical scenarios are designed to picture feasible futures under different assumptions. Assuming that the isolation of infected cases and the quarantining of close contacts are in place, different numerical tests are conducted and a full factorial two-way MANOVA test is used to evaluate the effectiveness of the FM and SD control strategies. The main and interactive effects of the containment strategies are evaluated by the total number of infections, percentage of infections reduction, the time it takes to get the pandemic under control, and the intensity of active cases.

Optical Characterization of Neurosurgical Operating Microscopes: Quantitative Fluorescence and Assessment of PpIX Photobleaching.

Protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (5-ALA) is increasingly used as a fluorescent marker for fluorescence-guided resection of malignant gliomas. Understanding how the properties of the excitation light source and PpIX fluorescence interact with the surgical microscope is critical for effective use of the fluorescence-guided tumor resection technique. In this study, we performed a detailed assessment of the intensity of the emitted blue light and white light and the light beam profile of clinical grade operating microscopes used for PpIX visualization. These measurements revealed both recognized fluorescence photobleaching limitations and unrecognized limitations that may alter quantitative observations of PpIX fluorescence obtained with the operating microscope with potential impact on research and clinical uses. We also evaluated the optical properties of a photostable fluorescent standard with an excitation-emission profile similar to PpIX. In addition, we measured the time-dependent dynamics of 5-ALA-induced PpIX fluorescence in an animal glioma model. Finally, we developed a ratiometric method for quantification of the PpIX fluorescence that uses the photostable fluorescent standard to normalize PpIX fluorescence intensity. This method increases accuracy and allows reproducible and direct comparability of the measurements from multiple samples.

Apparent diffusion coefficient maps in the assessment of surgical patients with lumbar spine degeneration.

PURPOSE: To assess the utility of apparent diffusion coefficient (ADC) maps for the assessment of patients with advanced degenerative lumbar spine disease and describe characteristic features of ADC maps in various degenerative lumbar spinal conditions. METHODS: T1-weighted, T2-weighted and diffusion weighted (DWI) MR images of 100 consecutive patients admitted to the spinal surgery service were assessed. ADC maps were generated from DWI images using Osyrix software. The ADC values and characteristic ADC maps were assessed in the regions of interest over the different pathological entities of the lumbar spine. RESULTS: The study included 452 lumbar vertebral segments available for analysis of ADCs. Characteristic ADC map features were identified for protrusion, extrusion and sequester types of lumbar disk herniations, spondylolisthesis, reactive Modic endplate changes, Pfirrmann grades of IVD degeneration, and compromised spinal nerves. Compromised nerve roots had significantly higher mean ADC values than adjacent (p < 0.001), contralateral (p < 0.001) or adjacent contralateral (p < 0.001) nerve roots. Compared to the normal bone marrow, Modic I changes showed higher ADC values (p = 0.01) and Modic 2 changes showed lower ADC values (p = 0.02) respectively. ADC values correlated with the Pfirrmann grading, however differed from herniated and non-herniated disks of the matched Pfirrmann 3 and 4 grades. CONCLUSION: Quantitative and qualitative evaluation of ADC mapping may provide additional useful information regarding the fluid dynamics of the degenerated spine and may complement standard MRI imaging protocol for the comprehensive assessment of surgical patients with lumbar spine pathology. ADC maps were advantageous in differentiating reactive bone marrow changes, and more precise assessment of the disk degeneration state. ADC mapping of compressed nerve roots showed promise but requires further investigation on a larger cohort of patients.