344 research outputs found
Inter- and intrafractional 4D dose accumulation for evaluating ΔNTCP robustness in lung cancer.
BACKGROUND AND PURPOSE
Model-based selection of proton therapy patients relies on a predefined reduction in normal tissue complication probability (NTCP) with respect to photon therapy. The decision is necessarily made based on the treatment plan, but NTCP can be affected when the delivered treatment deviates from the plan due to delivery inaccuracies. Especially for proton therapy of lung cancer, this can be important because of tissue density changes and, with pencil beam scanning, the interplay effect between the proton beam and breathing motion.
MATERIALS AND METHODS
In this work, we verified whether the expected benefit of proton therapy is retained despite delivery inaccuracies by reconstructing the delivered treatment using log-file based dose reconstruction and inter- and intrafractional accumulation. Additionally, the importance of two uncertain parameters for treatment reconstruction, namely deformable image registration (DIR) algorithm and α/β ratio, was assessed.
RESULTS
The expected benefit or proton therapy was confirmed in 97% of all studied cases, despite regular differences up to 2 percent point (p.p.) NTCP between the delivered and planned treatments. The choice of DIR algorithm affected NTCP up to 1.6 p.p., an order of magnitude higher than the effect of α/β ratio.
CONCLUSION
For the patient population and treatment technique employed, the predicted clinical benefit for patients selected for proton therapy was confirmed for 97.0 % percent of all cases, although the NTCP based proton selection was subject to 2 p.p. variations due to delivery inaccuracies
Physician-assisted death in psychiatric practice in the Netherlands
BACKGROUND: In 1994 the Dutch Supreme Court ruled that in exceptional
instances, physician-assisted suicide might be justifiable for patients
with unbearable mental suffering but no physical illness. We studied
physician-assisted suicide and euthanasia in psychiatric practice in the
Netherlands. METHODS: In 1996, we sent questionnaires to 673 Dutch
psychiatrists - about half of all such specialists in the country - and
received 552 responses from the 667 who met the study criteria (response
rate, 83 percent). We estimated the annual frequencies of requests for
physician-assisted suicide by psychiatrists and actual instances of
assistance. RESULTS: Of the respondents, 205 (37 percent) had at least
once received an explicit, persistent request for physician-assisted
suicide and 12 had complied. We estimate there are 320 requests a year i
Accounting for aboveground carbon storage in shrubland and woodland ecosystems in the Great Basin
Improving the accuracy of carbon accounting in terrestrial ecosystems is critical for understanding carbon fluxes associated with land cover change, with significant implications for global carbon cycling and climate change. Semi‐arid ecosystems account for an estimated 45% of global terrestrial ecosystem area and are in many locations experiencing high degrees of degradation. However, aboveground carbon accounting has largely focused on tropical and forested ecosystems, while drylands have been relatively neglected. Here, we used a combination of field estimates, remotely sensed data, and existing land cover maps to create a spatially explicit estimate of aboveground carbon storage within the Great Basin, a semi‐arid region of the western United States encompassing 643,500 km2 of shrubland and woodland vegetation. We classified the region into seven distinct land cover categories: pinyon‐juniper woodland, sagebrush steppe, salt desert shrub, low sagebrush, forest, non‐forest, and other/excluded, each with an associated carbon estimate. Aboveground carbon estimates for pinyon‐juniper woodland were continuous values based on tree canopy cover. Carbon estimates for other land cover categories were based on a mean value for the land cover type. The Great Basin ecosystems contain an estimated 295.4 Tg in aboveground carbon, which is almost double the previous estimates that only accounted for forested ecosystems in the same area. Aboveground carbon was disproportionately stored in pinyon‐juniper woodland (43.7% carbon, 16.9% land area), while the shrubland systems accounted for roughly half of the total land area (49.1%) and one‐third of the total carbon. Our results emphasize the importance of distinguishing and accounting for the distinctive contributions of shrubland and woodland ecosystems when creating carbon storage estimates for dryland regions
Waterstofwijk Plan voor waterstof in Hoogeveen
In dit publieke rapport wordt waterstof als een aanvullende mogelijkheid voor verduurzaming van de warmtevoorziening in woonwijken gepresenteerd. Het demonstratieproject Waterstofwijk Hoogeveen dient hierbij als rode draad. Voor andere wijken zal per geval bekeken moeten worden of de waterstofoptie echt past bij de betreffende wijk
Forest biodiversity, carbon sequestration, and wood production: modeling synergies and trade-offs for ten forest landscapes across Europe
Original ResearchEurope’s forests provide vital habitat for biodiversity and essential ecosystem services
whose provision must be sustained or enhanced over the coming century. However,
the potential to secure or increase forest ecosystem services, while securing the
habitat requirements of taxa remains unclear, especially within the context of uncertain
climate and socio-economic developments. To tease out the associated trade-offs
and synergies, we used 10 case study landscapes within nine countries throughout
Europe. Starting with the current status of the forests in the case study landscapes,
we simulated forest development 100 years into the future. Simulations were embedded
in three combined climate and socio-economic frame scenarios based on global and
European policies which varied in their climate change mitigation efficiency. Scenarios
were translated into country specific projections of climate variables, and resultant
demands for wood products. Forest management regimes were projected to vary in
response to these scenarios at local scales. The specific combinations of alternative
forest management practices were based on parallel research and input from local forest
stakeholders. For each case study, a specific forest growth simulator was used. In
general, the climate scenarios applied did not cause fundamentally different ecosystem
service outputs at the case study level. Our results revealed almost no reduction in outcomes for biodiversity indicators with an increase in wood production, and in some
cases synergistic results occurred when diversity was actively promoted as part of the
management concept. Net carbon uptake was not strongly correlated with biodiversity,
indicating that biodiversity-friendly forest management doesn’t need to curtail carbon
sequestration. Notably, we obtained heterogeneous results for the relation between
sustainable wood production and net carbon uptake. Most scenarios resulted in a
more or less reduced net carbon uptake over the long term, often due to stand age
class distribution shifts. Levels of sustainable wood production varied widely during
the simulation period, from significant increases (Sweden, Lithuania) to minor changes
(Slovakia, Turkey) and slight decreases (Ireland, Netherlands). We place our results
within the larger context of European forest policy and the challenges of simulating and
contrasting forest biodiversity and the ecosystem services that societies depend on outcomes for biodiversity indicators with an increase in wood production, and in some
cases synergistic results occurred when diversity was actively promoted as part of the
management concept. Net carbon uptake was not strongly correlated with biodiversity,
indicating that biodiversity-friendly forest management doesn’t need to curtail carbon
sequestration. Notably, we obtained heterogeneous results for the relation between
sustainable wood production and net carbon uptake. Most scenarios resulted in a
more or less reduced net carbon uptake over the long term, often due to stand age
class distribution shifts. Levels of sustainable wood production varied widely during
the simulation period, from significant increases (Sweden, Lithuania) to minor changes
(Slovakia, Turkey) and slight decreases (Ireland, Netherlands). We place our results
within the larger context of European forest policy and the challenges of simulating and
contrasting forest biodiversity and the ecosystem services that societies depend oninfo:eu-repo/semantics/publishedVersio
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