130 research outputs found
Dynamics of finite-sized light spheres in turbulence
No full textWe report experimental results on the Lagrangian dynamics of finite-size light particles in turbulence. Using an orthogonal camera setup and 3D particle tracking, we study the velocity and acceleration statistics of rigid light spheres in a water tunnel with nearly homogeneous and isotropic turbulence. The Reynolds number (ReY) is varied from 180 to 300, and the study covers a range of size ratios (4 < D/η < 16) for marginally light spheres. We find that the normalised acceleration PDF decreases in intermittency with increasing size ratio - in qualitative agreement with the predictions of the Faxén corrected model. We also present preliminary results on the rotational dynamics of large light spheres in turbulence
Influence of photon, proton and carbon ion irradiation on differentiation, maturation and functionality of dendritic cells
No full textOptimization of carbon ion and proton treatment plans using the raster-scanning technique for patients with unresectable pancreatic cancer
No full textBackground: The aim of the thesis is to improve radiation plans of patients with locally advanced, unresectable pancreatic cancer by using carbon ion and proton beams. Patients and methods: Using the treatment planning system Syngo RT Planning (Siemens, Erlangen, Germany) a total of 50 treatment plans have been created for five patients with the dose schedule 15 × 3 Gy(RBE). With reference to the anatomy, five field configurations were considered to be relevant. The plans were analyzed with respect to dose distribution and individual anatomy, and compared using a customized index. Results: Within the index the three-field configurations yielded the best results, though with a high variety of score points (field setup 5, carbon ion: median 74 (range 48–101)). The maximum dose in the myelon is low (e.g. case 3, carbon ion: 21.5 Gy(RBE)). A single posterior field generally spares the organs at risk, but the maximum dose in the myelon is high (e.g. case 3, carbon ion: 32.9 Gy(RBE)). Two oblique posterior fields resulted in acceptable maximum doses in the myelon (e.g. case 3, carbon ion: 26.9 Gy(RBE)). The single-field configuration and the two oblique posterior fields had a small score dispersion (carbon ion: median 66 and 58 (range 62–72 and 40–69)). In cases with topographic proximity of the organs at risk to the target volume, the single-field configuration scored as well as the three-field configurations. Conclusion: In summary, the three-field configurations showed the best dose distributions. A single posterior field seems to be robust and beneficial in case of difficult topographical conditions and topographical proximity of organs at risk to the target volume. A setup with two oblique posterior fields is a reasonable compromise between three-field and single-field configurations
Helium ions for radiotherapy? Physical and biological verifications of a novel treatment modality
No full textPurpose: Modern facilities for actively scanned ion beam radiotherapy allow in principle the use of helium beams, which could present specific advantages, especially for pediatric tumors. In order to assess the potential use of these beams for radiotherapy, i.e., to create realistic treatment plans, the authors set up a dedicated He-4 beam model, providing base data for their treatment planning system TRiP98, and they have reported that in this work together with its physical and biological validations.
Methods: A semiempirical beam model for the physical depth dose deposition and the production of nuclear fragments was developed and introduced in TRiP98. For the biological effect calculations the last version of the local effect model was used. The model predictions were experimentally verified at the HIT facility. The primary beam attenuation and the characteristics of secondary charged particles at various depth in water were investigated using He-4 ion beams of 200 MeV/u. The nuclear charge of secondary fragments was identified using a Delta E/E telescope. 3D absorbed dose distributions were measured with pin point ionization chambers and the biological dosimetry experiments were realized irradiating a Chinese hamster ovary cells stack arranged in an extended target.
Results: The few experimental data available on basic physical processes are reproduced by their beam model. The experimental verification of absorbed dose distributions in extended target volumes yields an overall agreement, with a slight underestimation of the lateral spread. Cell survival along a 4 cm extended target is reproduced with remarkable accuracy.
Conclusions: The authors presented a simple simulation model for therapeutical He-4 beams which they introduced in TRiP98, and which is validated experimentally by means of physical and biological dosimetries. Thus, it is now possible to perform detailed treatment planning studies with He-4 beams, either exclusively or in combination with other ion modalities. (C) 2016 Author(s)
How to support Gen-Y consumers to start investing sustainably
No full textInvesting has become a hot topic among the younger generation since the Covid-19 crisis. However, much of its potential is still unused, as seen in a big group of the younger generation which is positive to start but procrastinates this decision. While this younger generation would like to make a positive impact with their money on the environment of the planet earth, the existing investing propositions aren’t helping them with that sustainable mission. In this thesis, I researched how Rabobank can help this group of young non-investors start investing, but with a sustainable focus. Creating a win-win situation for the non-investor who gets motivated to start investing consciously while at the same time helping them to fulfil their sustainable ambitions.To access the showcase use the following link: https://xd.adobe.com/view/1adcd6dd-4439-42e3-99e2-accc30bcbe44-4f8f/?fullscreenStrategic Product Desig
Radiation-induced motility alterations in medulloblastoma cells
No full textPhoton irradiation has been repeatedly suspected of increasing tumor cell motility and promoting locoregional recurrence of disease. This study was set up to analyse possible mechanisms underlying the potentially radiation-altered motility in medulloblastoma cells. Medulloblastoma cell lines D425 and Med8A were analyzed in migration and adhesion experiments with and without photon and carbon ion irradiation. Expression of integrins was determined by quantitative FACS analysis. Matrix metalloproteinase concentrations within cell culture supernatants were investigated by enzyme-linked immunosorbent assay (ELISA). Statistical analysis was performed using Student's t-test. Both photon and carbon ion irradiation significantly reduced chemotactic medulloblastoma cell transmigration through 8-μm pore size membranes, while simultaneously increasing adherence to fibronectin- and collagen I- and IV-coated surfaces. Correspondingly, both photon and carbon ion irradiation downregulate soluble MMP9 concentrations, while upregulating cell surface expression of proadhesive extracellular matrix protein-binding integrin α5. The observed phenotype of radiation-altered motility is more pronounced following carbon ion than photon irradiation. Both photon and (even more so) carbon ion irradiation are effective in inhibiting medulloblastoma cell migration through downregulation of matrix metalloproteinase 9 and upregulation of proadhesive cell surface integrin α5, which lead to increased cell adherence to extracellular matrix proteins
Carbon ion irradiation plus CTLA4 blockade elicits therapeutic immune responses in a murine tumor model
No full textRadiotherapy can act as an in situ vaccine, activating preventive tumor-specific immune responses in patients. Although carbon ion radiotherapy has superior biophysical properties over conventional photon irradiation, the immunological effects induced by this radiation type are poorly understood. Multiple strategies combining radiotherapy with immune checkpoint inhibition (radioimmunotherapy) to enhance antitumor immunity have been described; however, immune cell composition in tumors following radioimmunotherapy with carbon ions remains poorly explored. We developed a bilateral tumor model based on time-shifted subcutaneous injection of murine Her2+ EO771 tumor cells into immune-competent mice followed by selective irradiation of the primary tumor. αCTLA4-, but not αPD-L1-based radioimmunotherapy, induced complete tumor rejection and mediated the eradication of even non-irradiated, distant tumors. Cured mice were protected against the EO771 rechallenge, indicating long-lasting, tumor-specific immunological memory. Single-cell RNA sequencing and flow cytometric analyses of irradiated tumors revealed activation of NK cells and distinct tumor-associated macrophage clusters with upregulated expression of TNF and IL1 responsive genes. Distant tumors in the irradiated mice showed higher frequencies of naïve T cells activated upon the combination with CTLA4 blockade. Thus, radioimmunotherapy with carbon ions plus CTLA4 inhibition reshapes the tumor-infiltrating immune cell composition and can induce complete rejection even of non-irradiated tumors. Our data suggest combining radiotherapy approaches with CTLA4 blockade to achieve durable antitumor immunity. Evaluation of future radioimmunotherapy approaches should not be restricted to immunological impact at the irradiation site but should also consider systemic immunological effects on non-irradiated tumors
Förderung der integrinbasierten Meningeomzellmigration durch Bestrahlung mit Photonen, nicht jedoch durch Bestrahlung mit Kohlenstoffionen
No full textSublethal doses of photon irradiation (IR) are suspected to increase tumor cell migration and support locoregional recurrence of disease, which has already been shown in other cell lines. This manuscript describes the effect of photon and carbon-ion IR on WHO class I meningioma cell migration and provides an approach to the underlying cellular mechanisms
Out‐of‐field neutron radiation from clinical proton, helium, carbon, and oxygen ion beams
No full textBackground: In hadron therapy, out-of-field doses, which may in the long-term cause secondary cancers, are mostly due to neutrons. Very recently, 4He and 16O beams have been added to protons and 12C ions for clinical therapy. Purpose: The focus of this article is to compare secondary neutron doses produced by clinical protons, 4He, 12C, and 16O ion beams. Methods: Ambient dose equivalent, H*(10), measurements were performed, with five types of rem counters, of the neutron field produced by the four primary ions impinging on a water phantom. This experiment was performed at the Heidelberg Ion Beam Therapy Center (HIT) in the framework of the activities of the European Radiation Dosimetry Group (EURADOS). The experimental data are normalized to both unit primary particle and target dose, and are further compared to Monte Carlo (MC) simulations performed with the FLUKA and MCNP codes. Results: The intensity of the neutron field increases with ion mass, and the trend is more significant in the forward direction. The minimum H*(10) for all ions, 5μSv/Gy to 10μSv/Gy, was measured in the transverse and backward directions, whereas the maximum measured value was about 1.3 mSv/Gy for primary 16O ions in the forward direction. Additional MC simulations are presented for a more detailed analysis of the rem counters' response in the presence of heavy charged fragments. In the downstream direction, for 12C and 16O ions, approximately only 30% of the instruments' counts are due to neutrons. Conclusion: The four extended-range instruments provide reliable and consistent results, whereas the conventional rem counter underestimates H*(10) in a neutron field with a large high-energy component. FLUKA and MCNP provide consistent predictions, within a factor of 1.6 for the downstream position and lower differences in the other cases, and are in agreement with the experimental data. It was found that under certain conditions neutrons do not represent the only secondary radiation field to be monitored; the presence of charged particles affects the performance of moderator-type neutron detectors
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