Dose to pelvic lymph nodes in image based high dose rate brachytherapy of carcinoma cervix

AimThe aim of this study is to analyse the dosimetry to the pelvic lymph nodes and its correlation to point B using CT based high dose rate brachytherapy of carcinoma cervix.BackgroundConventionally, dose to pelvic lymph nodes from intracavitary brachytherapy was reported by point B and by the reference points of the lymphatic trapezoid.Materials and methods30 consecutive CT based high dose rate applications were reviewed between February and March 2016. The high risk clinical target volume and the organs at risk and the pelvic nodal groups were contoured. DVH parameters for the right and left obturator nodal group, right and left external iliac nodal group and right and left internal iliac nodal group were recorded. Right and left point B doses were also recorded.ResultsOn analysis of the combined dose, it was found that all the DVH parameters were significantly different from point B, except the D100 obturator and D2cc internal iliac lymph node. There was a significant correlation between all DVH parameters and point B, except D2cc, D1cc and D0.1cc of external iliac. The obturator group received the highest dose contribution from brachytherapy. The mean D90 dose received per fraction for the obturator, external iliac and internal iliac nodes was 2.7 Gy, 1.17 Gy and 1.41 Gy, respectively.ConclusionsThere is a significant dose contribution to the pelvic lymph nodal groups during intracavitary brachytherapy. There is a low degree of correlation between point B dose and dosimetric parameters of the individual nodal groups. Hence, it is important to analyse the dose delivered to individual nodal groups during intracavitary brachytherapy, at least in patients with enlarged lymph nodes to calculate the cumulative dose delivered.     

The Impact of the Deepwater Horizon: The Evolving International Legal Regime for Offshore Accidental Pollution Prevention,Preparedness, and Response

The Deepwater Horizon incident in the Gulf of Mexico has ignited unprecedented global attention and debate on and global review of the efficiency and effectiveness of the existing international regimes governing offshore operations; particularly, accidental pollution prevention, preparedness, and response mechanisms. This article looks at these developments.     

Climatic niche of the Saker Falcon Falco cherrug: predicted new areas to direct population surveys in Central Asia

Accurate species distribution data across remote and extensive geographical areas are difficult to obtain. Here, we use bioclimatic envelope models to determine climatic constraints on the distribution of the migratory Saker Falcon Falco cherrug to identify areas in data-deficient regions that may contain unidentified populations. Sakers live at low densities across large ranges in remote regions, making distribution status difficult to assess. Using presence-background data and eight bioclimatic variables within a species distribution modelling framework, we applied MaxEnt to construct models for both breeding and wintering ranges. Occurrence data were spatially filtered and climatic variables tested for multicollinearity before selecting best fit models using the Akaike information criterion by tuning MaxEnt parameters. Model predictive performance tested using the continuous Boyce index (B) was high for both breeding (B_TEST = 0.921) and wintering models (B_TEST = 0.735), with low omission rates and minimal overfitting. The Saker climatic niche was defined by precipitation in the warmest quarter in the breeding range model, and mean temperature in the wettest quarter in the wintering range model. Our models accurately predicted areas of highest climate suitability and defined the climatic constraints on a wide-ranging rare species, suggesting that climate is a key determinant of Saker distribution across macro-scales. We recommend targeted population surveys for the Saker based on model predictions to areas of highest climatic suitability in key regions with distribution knowledge gaps, in particular the Qinghai-Tibet plateau in western China. Further applications of our models could identify protected areas and reintroduction sites, inform development conflicts, and assess the impact of climate change on distributions.     

Liver Selective Internal Radiation Therapy with 90Y resin microspheres: Comparison between pre-treatment activity calculation methods

Different methods to calculate ⁹⁰Y resin microspheres activity for Selective Internal Radiation Therapy (SIRT) were compared. Such comparison is not yet available and is needed in clinical practice to optimize patient specific treatment planning.32 ^99mTc-macroagregates (MAA) evaluations were performed, followed by 26 treatments. Four methods to calculate ⁹⁰Y-activity were applied retrospectively: three based on Body Surface Area and one based on MIRD formalism, partition model (PM). Relationships between calculated activities, lung breakthrough (LB), the activity concentration ratio between lesions and healthy liver (T/N) and tumour involvement were investigated, where lobar and whole liver treatments were analysed separately.Without attenuation correction, overestimation of LB was 65%. In any case, the estimated lungs' doses remained below 30 Gy. Thus, the maximal injectable activity (MIA) is not limited by lungs' irradiation. Moreover, LB was not significantly related to T/N, neither to tumour involvement nor radiochemical purity (RP).Differences in calculated activity with the four methods were extremely large, in particular they were greater between BSA-based and PM activities for lobar treatments (from −85% to 417%) compared to whole liver treatments (from −49% to 61%). Two values of T/N ratio were identified as thresholds: for BSA-based methods, healthy liver doses are much higher than 30 Gy when T/N < 3; for PM, tumour doses are higher than 120 Gy when T/N > 4.As PM accounts for uptake ratio between normal and tumour liver, this method should be employed over BSA-based methods.     

Home range sizes of two Hawaiian honeycreepers: implications for proposed translocation efforts

Prior to the reintroduction of a species, managers need an understanding of the expected behavior of the species in the new habitat. How a species uses its habitat and how much space individuals require are particularly important when conservation lands are limited. Critically endangered Maui Parrotbills (Kiwikiu, Pseudonestor xanthophrys) once occupied a variety of habitats on the Hawaiian islands of Maui and Moloka‘i, but, due to habitat loss and disease, are now restricted to a fraction of their former range. To prevent their extinction, reintroducing parrotbills to historically occupied native, mesic forest on the leeward slopes of Haleakalā is considered a critical recovery action. Managers have selected Nakula Natural Area Reserve (NAR) as the site of translocation and restoration efforts are currently underway to support this goal. In addition, other species, including endemic Maui ‘Alauahio (Maui Creeper, Paroreomyza montana), may recolonize these forests naturally as the habitat improves. However, estimates of the home range sizes of focal species are needed so that managers can estimate how many individuals might be able to occupy new habitats. Our objective therefore was to estimate the home range sizes of parrotbills and ‘alauahio at three sites within their current ranges to provide estimates of typical habitat and space use patterns. Using resightings of color‐banded birds from 2007 to 2014, we calculated home ranges using minimum convex polygons and kernel density estimators. Depending on estimation technique, parrotbill home ranges were estimated to encompass 9.29 ± 1.29 (SE) ha or 9.63 ± 1.51 ha, and pairs occupied ranges of 11.8 ha or 14.5 ha. ‘Alauahio home ranges were 0.85 ± 0.09 ha or 0.87 ± 0.08 ha in size. Home range sizes varied among study sites for both species, likely reflecting the influence of local habitat attributes and quality on movement patterns and space use. Although we do not know how these species will behave in the new habitat, our estimates of home range size provide guidance for managers planning the reintroduction of parrotbills to Nakula NAR.     

EGSnrc application for IMRT planning

The aim of this study was to describe a detailed instruction of intensity modulated radiotherapy (IMRT) planning simulation using BEAMnrc-DOSXYZnrc code system (EGSnrc package) and present a new graphical user interface based on MATLAB code (The MathWorks) to combine more than one. 3ddose file which were obtained from the IMRT plan.This study was performed in four phases: the commissioning of Varian Clinac iX6 MV, the simulation of IMRT planning in EGSnrc, the creation of in-house VDOSE GUI, and the analysis of the isodose contour and dose volume histogram (DVH) curve from several beam angles. The plan paramaters in sequence and control point files were extracted from the planning data in Tan Tock Seng Hospital Singapore (multileaf collimator (MLC) leaf positions – bank A and bank B, gantry angles, coordinate of isocenters, and MU indexes).VDOSE GUI which was created in this study can display the distribution dose curve in each slice and beam angle. Dose distributions from various MLC settings and beam angles yield different dose distributions even though they used the same number of simulated particles. This was due to the differences in the MLC leaf openings in every field. The value of the relative dose error between the two dose ditributions for “body” was 51.23 %. The Monte Carlo (MC) data was normalized with the maximum dose but the analytical anisotropic algorithm (AAA) data was normalized by the dose in the isocenter.In this study, we have presented a Monte Carlo simulation framework for IMRT dose calculation using DOSXYZnrc source 21. Further studies are needed in conducting IMRT simulations using EGSnrc to minimize the different dose error and dose volume histogram deviation.     

城乡交错带景感生态规划的基本思路与实现

传统城市规划方法多集中在城市用地、人口规模和交通优先等方面,而较少关注城市环境质量和环境福利。要构筑一个与未来居民生活品质相适应的城市形态,城市生态规划就必须考虑更多样化的数据基础和可获得性的技术,尤其是居民对这些规划的实际感受,合理和科学的规划需要综合分析城市生态系统,包括自然和人为因素。一个新的概念和理论"景感生态学"能够将城市规划蓝图与人类感知相耦合。景感生态规划理应包括人类对规划的各种感知需求,包括视觉、听觉、味觉、嗅觉和触觉等。本文秉承景感生态学的基本理论,以西集镇为执行案例,探索性地针对城乡交错带开展景感生态规划,以阐明将居民感觉信息融入生态规划过程的挑战性和重要性。     

Mechanisms for the inclusion of cumulative impacts in conservation decision-making are sensitive to vulnerability and irreplaceability in a stochastically simulated landscape

It is commonly understood that the cumulative impact of increased habitat destruction on biological systems does not scale linearly. Despite this, current environmental decision-making strategies often fail to incorporate these non-linearities because impact assessments are regularly performed independently without considering contributions to future cumulative impacts, which are, instead, externalised to the environment. Here we used a stochastic modelling framework to examine the effect of three decision-making strategies – externalised, individually-borne and shared cumulative costs – on the number of species driven to extinction by the development of a region. We also tested how different levels of vulnerability (quantified as the correlation between development benefits and species richness) and irreplaceability (expressed as the average area of occupancy of an assemblage) influence the outcomes of development. Overall, the inclusion of cumulative impacts in our simulations resulted in the destruction of fewer patches and, as a consequence, more modest benefits obtained from developments. Moreover, these patterns were strongest when cumulative costs were shared by all developers. The most striking finding was that the distinction between decision-making strategies was highest in landscapes of high vulnerability and irreplaceability. Environmental decision-makers are recommended to commit to a strategy for incorporating the cumulative costs of development because, as this study suggests, this affects the endpoints of conservation and development considerably; especially in the most vulnerable and irreplaceable landscapes.