Auswirkungen der Bildgebungsdosis auf das Sekundärkrebsrisiko bei bildgeführter Strahlentherapie von Kindern mit Morbus Hodgkin

Hintergrund Die moderne Strahlentherapie bietet die Möglichkeit der hochpräzisen Behandlung von Tumorerkrankungen. Um diese Präzision bestmöglich umzusetzen, ist eine bildgeführte Strahlentherapie zur Lagerungsverifikation der Patienten heutzutage Standard. Je nach Frequenz und Technik ist der dadurch entstehende zusätzliche Dosisbeitrag allerdings nicht zu vernachlässigen. In dieser Arbeit werden die potentiellen Folgen dieser zusätzlichen Dosis an einem pädiatrischen Kollektiv bestehend aus M. Hodgkin Patienten evaluiert. Dies wird zum einen in Bezug auf die Planqualität durchgeführt, zum anderen im Hinblick auf die Entwicklung eines Sekundärkarzinoms. Methodik Auf Basis von acht Bestrahlungsplänen pädiatrischer Patienten mit M. Hodgkin, die retrospektiv analysiert wurden, wurden auf Grundlage verschiedener täglicher Bildgebungsszenarien die zusätzliche Bildgebungsdosis zum Bestrahlungsplan addiert. Dabei wurden verschiedene Energien (kV/MV) sowie planare und CBCT Techniken verwendet und im Hinblick auf das Sekundärkrebsrisiko für Mamma und Lunge miteinander verglichen. Die Berechnungen des zusätzlichen Sekundärkrebsrisikos beruhen dabei auf mathematischen Modellen. Des Weiteren wurde der Einfluss der zusätzlichen Bildgebung auf die Risikoorganschonung durch eine Analyse der dosimetrischen Planqualität durchgeführt. Ergebnisse Das Kollektiv zeigt untereinander starke Abweichungen zwischen den einzelnen Plänen, sodass eher eine Einzelfallbetrachtung stattfinden sollte. Dennoch zeigen sich bei allen acht Patienten ähnliche Tendenzen. Die kV-Bildgebung beeinflusst die Planqualität, v.a. in Bezug auf die Risikoorgan-schonung nur marginal, auch bei der Verwendung täglicher Volumenaufnahmen Ausgehend von einem Erkrankungsalter für den Sekundärtumor von 50 Jahren findet sich das geringste zusätzliche Risiko bei täglicher kV-Bildgebung mit 200° Rotationsaufnahmen (0,02 Fälle pro 104 Patientenjahren (PY) für die Lunge und 0,07-0,08 Fälle pro 104 PY für die Mamma). Leicht erhöhte Risikowerte erhält man für Verifikationsaufnahmen der selben Energie mit 360° Rotation (0,08 Fälle pro 104 PY für die Lunge und 0,44-0,57 Fälle pro 104 PY für die Mamma). Sollte keine kV-Bildgebung möglich sein, können zur täglichen Lagekontrolle auch planare 6MV Verifikationsaufnahmen angewandt werden, da auch hierbei das zusätzliche Risiko lediglich um 0,1 Fälle pro 104 PY für die Lunge und < 1 Fall pro 104 PY für die Mamma steigt. Eine tägliche Lagerungsverifikation mittels Volumenaufnahmen (360°) im MV-Bereich resultiert in nicht vernachlässigbar hohen zusätzlichen Dosen. Auch das zusätzliche Sekundärkrebsrisiko steigt dabei auf 0,7-0,8 Fälle pro 104 PY für die Lunge und 3 Fälle pro 104 PY für die Mamma. Diese Werte steigen bei Erhöhung des Erkrankungsalters von 50 auf 70 Jahre weiter an, was das Risiko für die Lunge um den Faktor 4 erhöht, bei einer Erhöhung des Alters auf 90 Jahre um den Faktor 12. Schlussfolgerung Bei einer täglichen Bildgebung mit kV-CBCT-Verifikationsaufnahmen führt die zusätzliche Bildgebungsdosis zu vertretbaren zusätzlichen Sekundärkrebsrisiken sowie immer noch adäquater Planqualität, weshalb tägliche Volumenaufnahmen im kV-Bereich durchaus empfehlenswert sind. Bei nicht vorhandener kV-Modalität empfiehlt sich die Lagekontrolle im MV-Bereich durch tägliche Achsen-Aufnahmen, nicht jedoch durch tägliche CBCTs. Eine Risikoreduktion kann man durch das Verwenden einer Teil-(200°) anstelle einer Vollrotation (360°) der CBCTs erreichen: das Risiko eines Mamma-Karzinoms kann dabei um den Faktor 7 gesenkt werden, da sich bei einer 200° Rotation die Gantry dorsal des Patienten bewegt und die Mamma somit erheblich geschont wird.Background Modern radiation therapy offers the possibility of very precise tumor treatment. To implement this precision at its best, image guided radiation therapy has become the standard to verify the patients’ position. However, depending on the frequency and technique, the additional radiation dose is not negligible. In this study the potential consequences of this imaging dose are evaluated considering a pediatric collective of patients with M. Hodgkin. This is done to evaluate the plan quality and the probability of development of secondary cancer. Methods Based on eight treatment plans of pediatric patients with M. Hodgkin, which were analyzed retrospectively, the additional imaging dose of different daily imaging scenarios was added to the treatment plan. Different energies (kV/MV) as well as planar and CBCT techniques were used and compared regarding secondary cancer risk for breast and lungs. The calculations of the additional cancer risk are based on mathematical modeling. Moreover, the influence of the additional imaging dose to reduce the organs at risk was assessed by analyzing the dosimetrical plan quality. Results There exists a huge variability between the single plans of the collective; as such an individual assessment should be preferred. However, all eight patients show similar tendencies. The influence of the kV-imaging on the plan quality, especially regarding the minimization of radiation to organs at risk, is just marginal, even with the use of daily volumetric images. Assuming the development of a secondary cancer at age 50, the lowest additional risk occurs with daily kV-imaging with a 200° rotation (0.02 cases per 104 patient years (PY) for the lungs and 0.07-0.08 cases per 104 PY for the breast). A 360° rotation with the same energy increases the risk slightly (0.08 cases per 104 PY for the lungs and 0.44-0.57 cases per 104 PY for the breast). If no kV-modality is available, planar 6MV verification images can be applied to control the patients’ position daily, as the additional risk merely increases about 0.1 cases per 104 PY for the lungs and < 1 cases per 104 PY. Daily positioning verification using 3D imaging with MV energies results in non-negligible high doses. Also, the additional secondary cancer risk increases to 0.7-0.8 cases per 104 PY for the lungs and 3 cases per 104 PY for the breast. These values increase if an older attained age of 70 years is considered; the risk rises by a factor of 4 for the lungs, with an attained age of 90 years the risk rises even by a factor of 12. Conclusions Daily imaging using kV CBCTs results in an acceptable additional secondary cancer risk as well as still appropriate plan quality. As such daily 3D imaging with kV energies is advisable. If no kV modality is available, positioning verification with MV energies should be done using planar images but not daily CBCTs. The risk can be reduced by using a partial (200°) rotation instead of a complete rotation (360°). For breast cancer the risk can be lowered by a factor of 7 as for a 200° rotation the gantry moves dorsal to the patient and the breast can be spared substantially

Microstructure modification of EB-pvd gadolinium zirconate thermal barrier coatings and the effect on their resistance against siliceous CMAS melts

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Microstructure modification of EB-pvd gadolinium zirconate thermal barrier coatings and the effect on their resistance against siliceous CMAS melts

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Формирование предпринимательских умений студентов инженерного вуза

Представлена методика формирования предпринимательских умений студентов инженерного вуза на основе практико-ориентированной подготовки, способствующей внедренческой деятельности инженера в современных условиях. Проведен анализ состояния проблемы формирования предпринимательских умений в России. Определены педагогические условия, способствующие формированию готовности студентов технического университета к комплексной инженерной деятельности. Сформулировано понятие предпринимательской компетенции инженера. Обосновано эффективное применение метода проектов для формирования предпринимательских умений студентов инженерного вуза. Представлена модель формирования предпринимательских умений студентов инженерного вуза с учетом проектной деятельности инженера.The developing methods of entrepreneurial competences of engineering students, based on the practice-oriented training to encourage an implemental activity of an engineer in the modern context has been presented in the report. The analysis of the problem of entrepreneurial competencies development in Russia has been carried out. The pedagogical conditions encouraging the commitment of the technical university students for an integrated engineering activity has been defined. The concept of entrepreneurial competencies of an engineer has been stated. An effective appliance of project methods to develop entrepreneurial competences of the engineering university students has been proved. There has been presented the development model of entrepreneurial competences of engineering students

Investigation of erosion behavior of EB-PVD-TBCs and sacrificial coatings after CMAS infiltration

Aero-engines operating in sand laden environments often encounter severe problems with thermal barrier coatings (TBCs) due to erosion damage. Since the turbine entry temperatures are raising, the life-time of TBC coatings as well as its thermal conductivity are additionally influenced by molten sand (calcium-magnesium-alumino-silicate/ CMAS). Few attempts have been made in understanding the combined impact of both erosion and CMAS effects [1,2]. Wellman and Nicholls [1] have found that a fully CMAS infiltrated electron-beam physical vapor deposited (EB-PVD) TBC behaves like a continuum during erosion and slightly improves its erosion behavior under room temperature compared to pure TBC. Development of CMAS resistant coatings has been a hot topic for the last two decades and one of the proposed method is the application of sacrificial oxide layers such as Al2O3, MgO, Sc2O3 et al. [3], on top of the TBCs. These sacrificial layers chemically react with the CMAS and modify the melting temperature or the viscosity of CMAS and thus the infiltration of CMAS into the TBC is inhibited. Since both damage mechanisms (erosion and corrosion) occur parallel and competitively in a turbine, this study focuses on deeper understanding of the erosion behavior of CMAS-infiltrated 7wt.-% yttria stabilized zirconia (7YSZ) TBCs. 400 µm thick 7YSZ coatings with two different microstructures were produced by EB-PVD. Additionally, sacrificial Al2O3 coatings were also applied on the top of 7YSZ by means of suspension plasma spraying (SPS) and suspension high velocity oxy-fuel spraying (SHVOF) using water-based suspensions. CMAS infiltration experiments were carried out at 1250 °C using different CMAS compositions and different infiltration times. Erosion tests were realized at room temperature in an in-house erosion test rig and evaluated partly by confocal microscopy. Microstructural examinations as well as crack identification before and after testing were carried out using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Infiltrated TBCs behaved as a continuum material during erosion exposure which lead mainly to surface spallation. Furthermore, the CMAS infiltration in the TBCs and partly the sintering effect at 1250 °C lead to a network of vertical cracks. These vertical cracks are weak areas where severe erosion occurs. The different TBC microstructures, infiltration times and CMAS compositions strongly influence the erosion behavior of the TBC. In case of alumina top coats the microstructure and especially the presence of porosity in the coating has strongly influenced the CMAS infiltration depth, the erosion behavior, and the stability of the entire coating system. [1] R.G. Wellman, J.R. Nicholls, Erosion, corrosion and erosion–corrosion of EB PVD thermal barrier coatings, Tribology International. 41 (2008) 657–662. doi:10.1016/j.triboint.2007.10.004. [2] S. Rezanka, D.E. Mack, G. Mauer, D. Sebold, O. Guillon, R. Vaßen, Investigation of the resistance of open-column-structured PS-PVD TBCs to erosive and high-temperature corrosive attack, Surface and Coatings Technology. 324 (2017) 222–235. doi:10.1016/j.surfcoat.2017.05.003. [3] A.K. Rai, R.S. Bhattacharya, D.E. Wolfe, T.J. Eden, CMAS-Resistant Thermal Barrier Coatings (TBC), International Journal of Applied Ceramic Technology. 7 (2010) 662–674. doi:10.1111/j.1744-7402.2009.02373.x

Метод CRAMM - комплексный подход к оценке рисков

The article shows the use of the method CRAMM for risk management and research of information security systems

Автоматическое закорачивание отдельных фаз линий для ликвидации дуговых коротких замыканий

During the last few years high power diode laser arrays have become well established for direct material processing due to their high efficiency of more than 50%. But standard broad-area waveguide designs are susceptible to modal instabilities and filamentations resulting in low beam qualities. The beam quality increases by more than a factor of four by using tapered laser arrays, but so far they suffer from lower efficiencies. Therefore tapered lasers are mainly used today as single emitters in external resonator configurations. With increased output power and lifetime, they will be much more attractive for material processing and for pumping of fiber amplifiers. High efficiency tapered mini bars emitting at a wavelength of 980 nm are developed, and in order to qualify the bars, the characteristics of single emitters and mini bars from the same wafer have been compared. The mini bars have a width of 6 mm with 12 emitters. The ridge waveguide tapered lasers consist of a 500 µm long ridge and a 2000 µm long tapered section. The results show very similar behavior of the electro-optical characteristics and the beam quality for single emitters and bars. Due to different junction temperatures, different slope efficiencies were measured: 0.8 W/A for passively cooled mini bars and 1.0 W/A for actively cooled mini-bars and single emitters. The threshold current of 0.7 A per emitter is the same for single emitters and emitter arrays. Output powers of more than 50 W in continuous wave mode for a mini bar with standard packaging demonstrates the increased power of tapered laser bars

Investigation of CMAS resistance of SPS- and SHVOF-alumina topcoats on EB-PVD 7YSZ layers

Thermal barrier coatings (TBCs) undergo severe degradation by interaction with molten calcium-magnesium-aluminum-silicate (CMAS) minerals that are found mainly in volcanic ashes (VA) or desert sands. After the infiltration of the CMAS, chemical reactions, diffusion and phase transformation can lead to residual stress, cracks and spallation and thus significantly shorten the life-time of the components. As the state-of-the-art material 7 wt.-% Y2O3 stabilized ZrO2 (7YSZ) offers limited resistance to the CMAS attack, development of CMAS-resistant TBCs has undergone intense research during the last decades. One of the proposed approaches is the application of a sacrificial layer on top of the TBC which reacts with the molten CMAS/VA to crystalline phases and in this way inhibits further infiltration by sealing the gaps and pores. Al2O3 is one candidate for such a sacrificial layer which exhibits good CMAS resistance by formation of arresting phases. However, EB‑PVD Al2O3-topcoats suffer locally from cracks that arise from crystallization and sintering shrinkage, thereby providing only a discontinuous protection against CMAS infiltration due to their characteristic morphology. Even though the alumina is a candidate material, the coating density and the arrangement of porosity has been found to be a critical factor for restricting CMAS infiltration. In this work alumina coatings were sprayed on top of EB‑PVD 7YSZ TBCs using suspension plasma spraying (SPS) and suspension high velocity oxygen fuel spraying (SHVOF) starting from an aqueous suspension containing fine dispersed Al2O3 (d50 about 2.3 µm). The spray parameters were optimized in order to produce Al2O3 topcoats with homogeneous distributed porosity from very porous (porosity about 30 %) to denser (porosity about 10-15 %). These coatings were tested under CMAS attack by performing infiltration experiments at 1250 °C for different time intervals from 5 min to 10 hours. One Island volcanic ash from the Eyjafjallajökull volcano (IVA) and two types of synthetic CMAS compositions were tested in this study. The infiltration kinetics and reaction products were studied by SEM, energy-dispersive spectroscopy (EDS) and x-ray diffraction (XRD). It was observed that the microstructure and especially the presence of the porosity in the Al2O3 coatings strongly influenced the CMAS infiltration kinetics. Due to its high and non-uniform porosity, CMAS/VA melt infiltrated the 100 µm thick, very porous alumina SPS‑coating inhomogeneously and reached the subjacent 7YSZ layer already after one hour of annealing at 1250°C. Additionally, it was found that the infiltration kinetics varies also with the chemical composition of the CMAS/VA. Different crystalline phases such as anorthite, spinel or others were formed as reaction products of the SPS‑Alumina-TBC with the CMAS/VA-melt. The exact phases and its location depend on the used CMAS/VA composition. Furthermore, the annealing time has a major influence on the presence of the various phases. The infiltration kinetics of the SHVOF‑coatings was different due to a change in morphology. The current experiments clearly demonstrate that CMAS/VA mitigation depends on the interplay between morphology of the coating which dictates the driving force for infiltration, the reaction speed between alumina and the deposit, and the deposit chemistry

Development of EBCs and T/EBC multi-layer coatings: Challenges and implications

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