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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

The potential for increased tumor control probability in non–small cell lung cancer with a hypofractionated integrated boost to the gross tumor volume

Treatment outcomes in locally advanced non–small cell lung cancer (NSCLC) to date have been poor, with normal tissue toxicity often limiting the dose that can be delivered to the tumor. Treatment intensification in NSCLC via targeted dose escalation with modern delivery techniques may offer the potential for a significant increase in tumor control probability (TCP) without a clinically significant increase in organ-at-risk (OAR) toxicity. In this planning study, 20 patients were re-planned with a volumetric modulated arc therapy (VMAT) and an inhomogeneous dose distribution with iteratively escalated doses to the gross tumor volume (iGTV) (composite GTV across multiple 4-dimensional computed tomography [4DCT] phases) in a series of 20 fraction regimes. For each plan OAR doses, target coverage and predicted TCPs were collected and compared with homogenous 3-dimensional (3D) and VMAT plans, as well as with each other. In 70% of patients, it was possible to escalate to 75 Gy in 20 fractions within OAR tolerances, opening the possibility of treating these patients to a biological effective dose (BED) of 103.1 Gy{sub 10}. This planning study forms the basis of a clinical trial INTENSE (Inhomogeneous Targeted Dose Escalation in Non-Small CEll Lung Cancer), CTRIAL 15-47.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

1,2-Dibromo-4-(1,2-dibromoethyl)-cyclohexane and tris(methylphenyl) phosphate cause significant effects on development, mRNA expression, and circulating bile acid concentrations in chicken embryos

1,2-Dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH; formerly abbreviated as TBECH) and tris(methylphenyl) phosphate (TMPP; formerly abbreviated as TCP) are additive flame retardants that are detected in the environment and biota. A recent avian in vitro screening study of 16 flame retardants identified DBE-DBCH and TMPP as important chemicals for follow-up in ovo evaluation based on their effects on cytotoxicity and mRNA expression in avian hepatocytes. In this study, technical mixtures of DBE-DBCH and TMPP were injected into the air cell of chicken embryos at concentrations ranging from 0 to 54,900 ng/g and from 0 to 261,400 ng/g, respectively, to determine effects on pipping success, development, hepatic mRNA expression, thyroid hormone levels, and circulating bile acid concentrations. Both compounds were detectable in embryos at pipping and the β-DBE-DBCH isomer was depleted more rapidly than the α-isomer in tissue samples. DBE-DBCH had limited effects on the endpoints measured, with the exception of the up-regulation of two phase I metabolizing enzymes, CYP3A37 and CYP2H1. TMPP exposure caused embryonic deformities, altered growth, increased liver somatic index (LSI) and plasma bile acid concentrations, and altered mRNA expression levels of genes associated with xenobiotic and lipid metabolism and the thyroid hormone pathway. Overall, TMPP elicited more adverse molecular and phenotypic effects than DBE-DBCH albeit at concentrations several orders of magnitude greater than those detected in the environment. The increase in plasma bile acid concentrations was a useful phenotypic anchor as it was associated with a concomitant increase in LSI, discoloration of the liver tissue, and modulation of hepatic genes involved with xenobiotic and lipid metabolism. - Highlights: • DBE-DBCH and TMPP are not embryolethal to chicken embryos. • TMPP caused deformities, morphometric alterations, and increased plasma bile acids. • DBE-DBCH and TMPP altered mRNA levels of xenobiotic and lipid metabolism genes. • Elevated plasma bile acids suggest that TMPP causes liver dysfunction. • TMPP elicited more adverse molecular and phenotypic effects than DBE-DBCH.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Manipulating Aromaticity to Redirect Topochemical Polymerization Pathways

Topochemical polymerization (TCP) represents an essential route to create regio- and stereoregular polymers through solid-state transformations. Herein, we present an innovative strategy for controlling topochemical polymerization pathways by tailoring the terminal group aromaticity in the para-azaquinodimethane (AQM) ring system. Substituting phenyl groups with less aromatic furyl units extends significant spin density delocalization across the conjugated core upon thermal activation, inducing significant diradicaloid characters at furyl positions and enabling unconventional reactivities in both solution and solid states. Thermal treatment in toluene yields a unique cyclophane dimer formed via furyl-methine C-C coupling, confirmed by X-ray crystallography, while solid-state reactions produce polymers formed via both intercolumnar furyl-methine coupling and intracolumnar methine-methine coupling. The spin-center-directed mechanism underlying these transformations is validated through theoretical modeling and isotopic labeling experiments. This study highlights the prowess of aromaticity modulation in functional pro-aromatic systems, which enables the synthesis of polymers with main chain structures that are otherwise difficult to access.

Zhang, Qingsong↗
DOE OSTI2011

Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 deg. C and sintered to different temperatures (200 deg. C, 400 deg. C, 600 deg. C, 800 deg. C, 1000 deg. C and 1200 deg. C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 deg. C to 1000 deg. C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 deg. C without any additional phase other than HAP, whereas peak of {beta}-TCP (tricalcium phosphate) was observed at 1200 deg. C. Photomicrograph of TEM showed that the nanopowder sintered at 600 deg. C is composed of hydroxyapatite nanoparticles (26.0-45.6 nm), which is well in agreement with the crystallite size calculated using XRD data. TGA study showed the thermal stability of the synthesized nano-HAP powder. The BET surface area decreased with increase in sintering temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Evaluation of Wind Speed Retrieval from Continuous-Wave Lidar Measurements of a Wind Turbine Wake Using Virtual Lidar Techniques

Wind lidar technology is being extensively used in utility-scale wind turbine wake measurements because of its capabilities to capture the dominant structures of interest in the near-wake region. However, wind lidar devices provide only line-of-sight (LOS) measurements, and retrieval of horizontal wind speed from the LOS measurements of a single lidar in the wind turbine wake could introduce errors due to the assumptions used in the retrieval process. With that in mind, the goals of this paper are to estimate the errors associated with the retrieval processes and provide guidelines for best practices. To achieve these goals, virtual lidar samples are obtained with large-eddy simulations (LES) by sampling the flow field with a model of the Technical University of Denmark (DTU) SpinnerLidar. LES is chosen to simulate the neutral and unstable atmospheric boundary layer (ABL), a benchmark case of the International Energy Agency Wind Technology Collaboration Programme (IEA Wind TCP) Task 31. The precursor ABL simulation is validated with the reference data provided by the IEA Wind Task 31 benchmark case. The data from the precursor simulation is used to drive a simulation of a wind turbine submerged in the ABL. A weighting function is applied to the LES data to mimic the real DTU SpinnerLidar measurements. In the end, the virtual lidar data are processed and compared with the original LES data to estimate the errors. Results show that lidar captures mean ABL profile without any noticeable error, whereas turbulence intensity is underpredicted ~15% at hub height for the neutral case. Volume averaging by the lidar technology has a significant effect in the shear layer of a wind turbine wake.

17 WIND ENERGY↗
DOE OSTI2020

Comparison of loads from HAWC2 and OpenFAST for the IEA Wind 15 MW Reference Wind Turbine

Reference wind turbines (RWTs) that reflect the state-of-the-art of current wind energy technology are necessary in order to properly evaluate innovative methods in wind turbine design and evaluation. The International Energy Agency (IEA) Wind Technology Collaboration Platform (TCP) Task 37 has recently developed a new RWT geared towards offshore floating-foundation applications: the IEA Wind 15 MW. The model has been implemented in two aeroelastic codes, OpenFAST and HAWC2, based on an underlying common ontology. However, these toolchains result in slightly different structural parameters, and the two codes utilise different structural models. Thus, to increase the utility of the model, it is necessary to compare the aeroelastic responses. This paper compares aeroelastic loads calculated using different fidelities of the blade model in OpenFAST (ElastoDyn and BeamDyn) and HAWC2 (prismatic Timoshenko without torsion and Timoshenko with fully populated stiffness matrix), where both codes use the DTU Basic controller and the same turbulence boxes to reduce discrepancies. The aeroelastic responses to steady wind, step wind and turbulent wind (per IEC 61400-1 wind class IB) are considered. The results indicate a generally good agreement between the loads dominated by aerodynamic thrust and force, especially for the no-torsion blade models. Discrepancies were observed in other load channels, partially due to differences in the asymmetric loading of the rotor and partially due to differing closed-loop dynamics, and they will be the subject of future investigations.

17 WIND ENERGY↗
DOE OSTI2022

Metallic and complex hydride-based electrochemical storage of energy

Abstract The development of efficient storage systems is one of the keys to the success of the energy transition. There are many ways to store energy, but among them, electrochemical storage is particularly valuable because it can store electrons produced by renewable energies with a very good efficiency. However, the solutions currently available on the market remain unsuitable in terms of storage capacity, recharging kinetics, durability, and cost. Technological breakthroughs are therefore expected to meet the growing need for energy storage. Within the framework of the Hydrogen Technology Collaboration Program—H 2 TCP Task-40, IEA’s expert researchers have developed innovative materials based on hydrides (metallic or complex) offering new solutions in the field of solid electrolytes and anodes for alkaline and ionic batteries. This review presents the state of the art of research in this field, from the most fundamental aspects to the applications in battery prototypes.

Cuevas, Fermin (ORCID:0000000290555880)↗
DOE OSTI2018

Magnetic field dependence of nonlinear magnetic response and tricritical point in the monoaxial chiral helimagnet Cr 1 / 3 Nb S 2

We present a comprehensive study of the magnetization dynamics and phase evolution in the chiral helimagnet Cr 1/3 NbS 2 , which realizes a chiral soliton lattice (CSL). The magnetic field dependence of the ac magnetic response is analyzed for the first five harmonic components, M nω (H ) (n = 1–5), using a phase sensitive measurement over a frequency range, f = 11–10 000 Hz. At a critical field, the modulated CSL continuously evolves from a helicity-rich to a ferromagnetic domain-rich structure, where the crossover is revealed by the onset of an anomalous nonlinear magnetic response that coincides with extremely slow dynamics. The behavior is indicative of the formation of a spatially coherent array of large ferromagnetic domains, which relax on macroscopic time scales. The frequency dependence of the ac magnetic loss displays an asymmetric distribution of relaxation times across the highly nonlinear CSL regime, which shift to shorter time scales with increasing temperature. We experimentally resolve the tricritical point at T TCP in a temperature regime above the ferromagnetic Curie temperature which separates the linear and nonlinear magnetic regimes of the CSL at the phase transition. A comprehensive phase diagram is constructed which summarizes the features of the field and temperature dependence of the magnetic crossovers and phase transitions in Cr 1/3 NbS 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2022

Addressing Market Issues in Electrical Power Systems with Large Shares of Variable Renewable Energy

This paper reports recent findings from IEA Wind TCP Task 25, which compiles international experiences and research related to large-scale integration of wind and other renewable energy. In the paper, we address the main challenges for market integration of variable renewable energy, relating to price formation, cost recovery, balancing and other grid services. The paper gives an overview of recent scenario studies on electricity price impacts of (1) various generation, energy storage and demand types in different markets, and (2) different market designs and energy/climate policies. Studying markets with very high shares of variable renewable energy requires an improved set of analysis tools for forecasting market outcomes, estimating flexibility needs and sources, and assessing resource adequacy. Key market features need to be investigated within these improved analytical capabilities for systems transitioning to high shares of variable renewable energy, storage and flexible demand. System services that can be supported by markets will likely need to be revisited. Finally, this paper identifies open questions and suggested future market design work for supporting systems with very high shares of variable renewable energy, which are to be addressed in follow-up work of Task 25 collaborative research.

cost recovery↗
DOE OSTI2023

Improving Wind Power Market Value with Various Aspects of Diversification: Preprint

The wind generation share in many European bidding zones is already large enough to impact the market value of wind power and wind energy is getting less-than-average market price in day-ahead markets. As alternatives to investing in dedicated energy storage, there are two main ways to mitigate the decreasing market value trend, the first being different diversification measures (geographical spread, alternative wind turbine technologies, integration with solar), and the second being demand flexibility measures. Examples of these measures from some European and USA studies are given in this article, which stems from the international collaboration under IEA Wind TCP Tasks 25 and 53.

diversification↗
DOE OSTI2023

Throughput Measurements and Capacity Estimates for Quantum Connections

The throughput of conventional and quantum network connections is an important performance metric, which is typically specified by bits per second (bps) and entangled quntum bits per second (ebps), respectively. It is measured over practical quantum network connections using specialized methods, and estimated using analytical bounds for which extensive theory has been developed. For practical connections, however, these two quantities have often been hard to correlate due to the lack of measurements and estimates derived under well-characterized common conditions. They both differ significantly from the conventional network throughput of TCP which employs buffers and loss recovery mechanisms. We describe a conventional-quantum testbed that enables the comparison of these two quantities both qualitatively and quantitatively. The bps and ebps throughput is measured over fiber connections of lengths over 75 kilometers, which show that the former decreases significantly slower with distance than the latter and in a qualitatively different way. The analytic capacity estimates of ebps are derived using approximations based on light intensity measurements, and they decrease more rapidly with distance than the measured ebps throughput. These results provide qualitative insights into the conventional transport mechanisms based on buffers, and the conditions used in deriving the analytical ebps capacity estimates.

Rao, Nageswara↗
DOE OSTI2018

Internet Performance Analysis of South Asian Countries Using End-to-End Internet Performance Measurements

Internet performance is highly correlated with key economic development metrics of a region. According to World Bank, the economic growth of a country increases 1.3% with a 10% increase in the speed of the Internet. Therefore, it is necessary to monitor and understand the performance of the Internet links in the region. It helps to figure out the infrastructural inefficiencies, poor resource allocation, and routing issues in the region. Moreover, it provides healthy suggestions for future upgrades. Therefore, the objective of this paper is to understand the Internet performance and routing infrastructure of South Asian countries in comparison to the developed world and neighboring countries using end-to-end Internet performance measurements. The South Asian countries comprise nearly 32% of the Internet users in Asia and nearly 16% of the world. The Internet performance metrics in the region are collected through the PingER framework. The framework is developed by the SLAC National Accelerator Laboratory, USA and is running for the last 20 years. PingER has 16 monitoring nodes in the region, and in the last year PingER monitors about 40 sites in South Asia using the ubiquitous ping facility. The collected data is used to estimate the key Internet performance metrics of South Asian countries. The performance metrics are compared with the neighboring countries and the developed world. Particularly, the TCP throughput of the countries is also correlated with different development indices. Further, worldwide Internet connectivity and routing patterns of the countries are investigated to figure out the inconsistencies in the region. Furthermore, the performance analysis revealed that the South Asia region is 7-10 years behind the developed regions of North America (USA and Canada), Europe, and East Asia.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2010

Why Does Flow Director Cause Packet Reordering?

Intel Ethernet Flow Director is an advanced network interface card (NIC) technology. It provides the benefits of parallel receive processing in multiprocessing environments and can automatically steer incoming network data to the same core on which its application process resides. However, our analysis and experiments show that Flow Director cannot guarantee in-order packet delivery in multiprocessing environments. Packet reordering causes various negative impacts. E.g., TCP performs poorly with severe packet reordering. In this paper, we use a simplified model to analyze why Flow Director can cause packet reordering. Our experiments verify our analysis.

Wu, Wenji↗
DOE OSTI2018

Optimizing 10-Gigabit Ethernet for Networks of Workstations, Clusters, and Grids: A Case Study

Here, this paper presents a case study of the 10-Gigabit Ethernet (10GbE) adapter from Intel R . Specifically, with appropriate optimizations to the configurations of the 10GbE adapter and TCP, we demonstrate that the 10GbE adapter can perform well in local-area, storage-area, system-area, and wide-area networks. For local-area, storage-area, and system-area networks in support of networks of workstations, network-attached storage, and clusters, respectively, we can achieve over 7-Gb/s end-to-end throughput and 12-µs end-to-end latency between applications running on Linux-based PCs. For the wide-area network in support of grids, we broke the recently-set Internet2 Land Speed Record by 2.5 times by sustaining an end-to-end TCP/IP throughput of 2.38 Gb/s between Sunnyvale, California and Geneva, Switzerland (i.e., 10,037 kilometers) to move over a terabyte of data in less than an hour. Thus, the above results indicate that 10GbE may be a cost-effective solution across a multitude of computing environments.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Throughput Measurements and Profile Analysis of Cloud Networks

Cloud networks utilize virtual connections to connect virtual machines distributed across cloud sites. They are increasingly deployed due to flexible provisioning using software and cost-effectiveness in not requiring to build physical network infrastructure. However, their extensive virtualization makes it unclear how well the established practices of conventional networks translate to them. Here, we study throughput measurements over a Google Cloud network using a matching hardware emulated conventional network, which provide production and exploratory conditions, respectively. The measurements span connections representing local, cross-continental and around the Earth distances. We study the effects of parallel flows, congestion control algorithms and retransmissions on the network throughput profile expressed as a function of RTT. We compare the throughput profile of Google Cloud network with those of emulated network under various loss conditions, including those too disruptive or expensive in the former. Our analysis based on the concave-convex shape and utilization-concavity coefficients of throughput profiles indicates an overall agreement of performance between the two networks, thereby justifying the use of conventional network emulations to analyze cloud networks. In terms of practical use, our study establishes that BBR and BBRv2 alpha TCP achieve higher throughput compared to loss-based congestion control algorithms under most network configurations, especially, under losses at large RTT.

Phanekham, Derek [Southern Methodist Univ., Dallas↗
DOE OSTI2014

SU-E-T-28: A Treatment Planning Comparison of Volumetric Modulated Arc Therapy Vs. Proton Therapy for Post-Mastectomy Radiotherapy

Purpose: The delivery of post-mastectomy radiotherapy (PMRT) can be challenging for patients with left-sided breast cancer due to the PTV size and proximity to critical organs. This study investigates the use of protons for PMRT in a clinically-representative cohort of patients, and quantitatively compares volumetric modulated arc therapy (VMAT) to proton therapy to have an evidence-based rationale for selecting a treatment modality for these patients. Methods: Eight left-sided PMRT patients previously treated at our clinic with VMAT were identified for the study. PTVs included the chest wall and regional lymph nodes. Passively scattered (PS) and intensity modulated proton therapy (IMPT) plans were constructed using the Eclipse proton planning system. The resulting plans were compared to the original VMAT plan on the basis of PTV coverage; dose homogeneity index (DHI) and conformity index (CI); dose to organs at risk (OAR); tumor control probability (TCP), normal tissue complication probability (NTCP) and secondary cancer complication probability (SCCP). Differences were tested for significance using the paired Student's t-test (p<0.01). Results: All modalities produced clinically acceptable PMRT plans. The comparison demonstrated proton treatment plans provide significantly lower NTCP values for the heart and the lung while maintaining significantly better CI and DHI. At a prescribed dose of 50.4 Gy (RBE) in the PTV, the calculated mean NTCP value for the patients decreased from 1.3% to 0.05% for the whole heart (cardiac mortality) and from 3.8% to 1.1% for the lungs (radiation pneumonitis) for both proton therapy plans from VMAT plans. Both proton modalities showed a significantly lower SCCP for the contralateral breast compared to VMAT. Conclusion: All three plans (VMAT, PS, and IMPT) provide acceptable treatment plans for PMRT. However, proton therapy shows a significant advantage over VMAT with regards to sparing OARs and may be more advantageous for patients with unfavorable anatomy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

SU-E-T-324: The Influence of Patient Positioning Uncertainties in Proton Radiotherapy On Proton Range and Dose Distributions

Purpose: Proton radiotherapy allows radiation treatment delivery with high dose gradients. The nature of such dose distributions increases the influence of patient positioning uncertainties on their fidelity when compared to photon radiotherapy. The present work quantitatively analyzes the influence of setup uncertainties on proton range and dose distributions. Methods: 38 clinical passive scattering treatment fields for small lesions in the head were studied. Dose distributions for shifted and rotated patient positions were Monte Carlo-simulated. Proton range uncertainties at the 50% and 90%-dose falloff position were calculated considering 18 arbitrary combinations of maximal patient position shifts and rotations for two patient positioning methods. Normal tissue complication probabilities (NTCPs), equivalent uniform doses (EUDs) and tumor control probabilities (TCPs) were studied for organs at risk (OARs) and target volumes of eight patients. Results: We identified a median 1σ proton range uncertainty at the 50%-dose falloff of 2.8 mm for anatomy-based patient positioning and 1.6 mm for fiducial-based patient positioning as well as 7.2 mm and 5.8 mm for the 90%-dose falloff position respectively. These range uncertainties were correlated to heterogeneity indices (HIs) calculated for each treatment field (38% < R{sup 2} < 50%). A NTCP increase of more than 10% (absolute) was observed for less than 2.9% (anatomy-based positioning) and 1.2% (fiducial-based positioning) of the studied OARs and patient shifts. TCP decreases larger than 10% (absolute) were seen for less than 2.2% of the target volumes or non-existent. EUD changes were up to 178% for OARs and 35% for target volumes. Conclusion: The influence of patient positioning uncertainties on proton range in therapy of small lesions in the human brain and target and OAR dosimetry were studied. Observed range uncertainties were correlated with HIs. The clinical practice of using multiple compensator-smeared treatment beams selected to avoid distal OAR sparing is considered to be safe. J. L. was supported by a scholarship of the University of Vienna.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

The influence of patient positioning uncertainties in proton radiotherapy on proton range and dose distributions

Purpose: Proton radiotherapy allows radiation treatment delivery with high dose gradients. The nature of such dose distributions increases the influence of patient positioning uncertainties on their fidelity when compared to photon radiotherapy. The present work quantitatively analyzes the influence of setup uncertainties on proton range and dose distributions. Methods: Thirty-eight clinical passive scattering treatment fields for small lesions in the head were studied. Dose distributions for shifted and rotated patient positions were Monte Carlo-simulated. Proton range uncertainties at the 50%- and 90%-dose falloff position were calculated considering 18 arbitrary combinations of maximal patient position shifts and rotations for two patient positioning methods. Normal tissue complication probabilities (NTCPs), equivalent uniform doses (EUDs), and tumor control probabilities (TCPs) were studied for organs at risk (OARs) and target volumes of eight patients. Results: The authors identified a median 1σ proton range uncertainty at the 50%-dose falloff of 2.8 mm for anatomy-based patient positioning and 1.6 mm for fiducial-based patient positioning as well as 7.2 and 5.8 mm for the 90%-dose falloff position, respectively. These range uncertainties were correlated to heterogeneity indices (HIs) calculated for each treatment field (38% < R{sup 2} < 50%). A NTCP increase of more than 10% (absolute) was observed for less than 2.9% (anatomy-based positioning) and 1.2% (fiducial-based positioning) of the studied OARs and patient shifts. For target volumes TCP decreases by more than 10% (absolute) occurred in less than 2.2% of the considered treatment scenarios for anatomy-based patient positioning and were nonexistent for fiducial-based patient positioning. EUD changes for target volumes were up to 35% (anatomy-based positioning) and 16% (fiducial-based positioning). Conclusions: The influence of patient positioning uncertainties on proton range in therapy of small lesions in the human brain as well as target and OAR dosimetry were studied. Observed range uncertainties were correlated with HIs. The clinical practice of using multiple fields with smeared compensators while avoiding distal OAR sparing is considered to be safe.

60 APPLIED LIFE SCIENCES↗