Systematic evaluation and plan quality assessment of the Leksell® gamma knife® lightning dose optimizer.

To compare stereotactic radiosurgery (SRS) plan quality metrics of manual forward planning (MFP) and Elekta Fast Inverse Planning™ (FIP)-based inversely optimized plans for patients treated with Gamma Knife®. Clinically treated, MFP SRS plans for 100 consecutive patients (115 lesions; 67 metastatic and 48 benign) were replanned with the FIP dose optimizer based on a convex linear programming formulation. Comparative plans were generated to match or exceed the following metrics in order of importance: Target Coverage (TC), Paddick Conformity Index (PCI), beam-on time (BOT), and Gradient Index (GI). Plan quality metrics and delivery parameters between MFP and FIP were compared for all lesions and stratified into subgroups for further analysis. Additionally, performance of FIP for multiple punctate (<4 mm) metastatic lesions on a subset of cases was investigated. A Wilcoxon signed-rank test for non-normal distributions was used to assess the statistical differences between the MFP and FIP treatment plans. Overall, 76% (87/115) of FIP plans showed a statistically significant improvement in plan quality compared to MFP plans. As compared to MFP, FIP plans demonstrated an increase in the median PCI by 1.1% (p<0.01), a decrease in GI by 3.7% (p< 0.01), and an increase in median number of shots by 74% (p< 0.01). TC and BOT were not statistically significantly different between MFP and FIP plans (p>0.05). FIP plans showed a statistically significant increase in use of 16 mm (p< 0.01) and blocked shots (p< 0.01), with a corresponding decrease in 4 mm shots (p< 0.01). Use of multiple shots per coordinate was significantly higher in FIP plans (p<0.01). The FIP optimizer failed to generate a clinically acceptable plan in 4/115 (3.5%) lesions despite optimization parameter changes. The mean optimization time for FIP plans was 5.0 min (Range: 1.0 - 10.0 min). In the setting of multiple punctate lesions, PCI for FIP was significantly improved (p<0.01) by changing the default low-dose/BOT penalty optimization setting from a default of 50/50 to 75-85/40. FIP offers a significant reduction in manual effort for SRS treatment planning while achieving comparable plan quality to an expert planner-substantially improving overall planning efficiency. FIP plans employ a non-intuitive increased use of blocked sectors and shot-in-shot technique to achieve high quality plans. Several FIP plans failed to achieve clinically acceptable treatments and warrant further investigation.

Overwintering fires in boreal forests.

Forest fires are usually viewed within the context of a single fire season, in which weather conditions and fuel supply can combine to create conditions favourable for fire ignition-usually by lightning or human activity-and spread1-3. But some fires exhibit 'overwintering' behaviour, in which they smoulder through the non-fire season and flare up in the subsequent spring4,5. In boreal (northern) forests, deep organic soils favourable for smouldering6, along with accelerated climate warming7, may present unusually favourable conditions for overwintering. However, the extent of overwintering in boreal forests and the underlying factors influencing this behaviour remain unclear. Here we show that overwintering fires in boreal forests are associated with hot summers generating large fire years and deep burning into organic soils, conditions that have become more frequent in our study areas in recent decades. Our results are based on an algorithm with which we detect overwintering fires in Alaska, USA, and the Northwest Territories, Canada, using field and remote sensing datasets. Between 2002 and 2018, overwintering fires were responsible for 0.8 per cent of the total burned area; however, in one year this amounted to 38 per cent. The spatiotemporal predictability of overwintering fires could be used by fire management agencies to facilitate early detection, which may result in reduced carbon emissions and firefighting costs.

Adoption of Lightning Safety Best-Practices Policies in the Secondary School Setting.

CONTEXT: Lightning-related injuries are among the top 10 causes of sport-related death at all levels of sport, including the nearly 8 million athletes participating in US secondary school sports. OBJECTIVE: To investigate the adoption of lightning safety policies and the factors that influence the development of comprehensive lightning safety policies in United States secondary schools. DESIGN: Cross-sectional study. SETTING: Secondary school. PATIENTS OR OTHER PARTICIPANTS: Athletic trainers (ATs). MAIN OUTCOME MEASURE(S): An online questionnaire was developed based on the "National Athletic Trainers' Association Position Statement: Lightning Safety for Athletics and Recreation" using a health behavior model, the precaution adoption process model, along with facilitators of and barriers to the current adoption of lightning-related policies and factors that influence the adoption of lightning policies. Precaution adoption process model stage (unaware for need, unaware if have, unengaged, undecided, decided not to act, decided to act, acting, maintaining) responses are presented as frequencies. Chi-square tests of associations and prevalence ratios with 95% CIs were calculated to compare respondents in higher and lower vulnerability states, based on data regarding lightning-related deaths. RESULTS: The response rate for this questionnaire was 13.43% (n = 365), with additional questionnaires completed via social media (n = 56). A majority of ATs reported maintaining (69%, n = 287) and acting (6.5%, n = 27) a comprehensive lightning safety policy. Approximately 1 in 4 ATs (25.1%, n = 106) described using flash to bang as an evacuation criterion. Athletic trainers practicing in more vulnerable states were more likely to adopt a lightning policy than those in less vulnerable states (57.4% versus 42.6%, prevalence ratio [95% CI] = 1.16 [1.03, 1.30]; P = .009). The most commonly cited facilitator and barrier were a requirement from a state high school athletics association and financial limitations, respectively. CONCLUSIONS: A majority of ATs related adopting (eg, maintaining and acting) the best practices for lightning safety. However, many ATs also indicated continued use of outdated methods (eg, flash to bang).

Calculation of transient potential rise on the wind turbine struck by lightning.

A circuit model is proposed in this paper for calculating the transient potential rise on the wind turbine struck by lightning. The model integrates the blade, sliding contact site, and tower and grounding system of the wind turbine into an equivalent circuit. The lightning current path from the attachment point to the ground can be fully described by the equivalent circuit. The transient potential responses are obtained in the different positions on the wind turbine by solving the circuit equations. In order to check the validity of the model, the laboratory measurement is made with a reduced-scale wind turbine. The measured potential waveform is compared with the calculated one and a better agreement is shown between them. The practical applicability of the model is also examined by a numerical example of a 2 MW Chinese-built wind turbine.

Lightning safety of animals.

This paper addresses a concurrent multidisciplinary problem: animal safety against lightning hazards. In regions where lightning is prevalent, either seasonally or throughout the year, a considerable number of wild, captive and tame animals are injured due to lightning generated effects. The paper discusses all possible injury mechanisms, focusing mainly on animals with commercial value. A large number of cases from several countries have been analyzed. Economically and practically viable engineering solutions are proposed to address the issues related to the lightning threats discussed.

Next-generation pulse oximetry. Focusing on Masimo's signal extraction technology.

Pulse oximeters are used to determine trends in patients' blood oxygen saturation and to warn of dangerous saturation levels. But conventional pulse oximetry has some inherent limitations. For example, it has difficulty monitoring patients who are moving or who have poor perfusion; it is also subject to interference from certain visible and infrared light sources. Over the past several years, a number of companies have developed advanced signal-processing techniques that allow pulse oximeters to overcome many of these limitations. We refer to such new technologies as next-generation pulse oximetry. In this Evaluation, we focus on the first next-generation technology to have reached the market: Masimo Corporation's Signal Extraction Technology (SET). We designed our study of Masimo SET to address the main question that needs to be asked of any next-generation technology: How well does it compare to conventional pulse oximetry? Specifically, how well does it perform when a patient is moving or being moved, when a patient is poorly perfused, or when certain types of light strike the sensor while it is attached to or detached from the patient? We also examined one type of sensor used with this product, comparing it to conventional tape-on sensors for comfort and durability. Several other next-generation pulse-oximeter products have become available since we began this study. We are currently evaluating these products and will publish our findings in the near future. A list of the products, including a brief description of each, is included in this article. Pulse oximeters are used to determine trends in patients' blood oxygen saturation and to warn against dangerous saturation levels. These monitors are often vital in helping to ensure patient safety, especially for critically ill patients, pediatric patients, and neonates. But conventional pulse oximetry has some inherent limitations--most significantly, it has difficulty monitoring patients who are moving or who have poor perfusion. Although gradual improvements have been made to the technology, only recently has it advanced to the point where it has really begun to overcome these limitations. A number of manufacturers have developed advanced signal-processing algorithms that allow pulse oximeters to "read through" motion and conditions of poor perfusion. The first of these "next-generation" pulse-oximeter technologies that reached the market was Masimo Corporation's Signal Extraction Technology (SET). We tested that product in this Evaluation. In this Overview, we'll tell you about conventional pulse oximetry and its shortfalls, next-generation technology and how it's designed to improve on the old methods, and how we approached our Evaluation of Masimo SET.