Exploring MR regression patterns in rectal cancer during neoadjuvant radiochemotherapy with daily T2- and diffusion-weighted MRI

Background To date, only limited magnetic resonance imaging (MRI) data are available concerning tumor regression during neoadjuvant radiochemotherapy (RCT) of rectal cancer patients, which is a prerequisite for adaptive radiotherapy (RT) concepts. This exploratory study prospectively evaluated daily fractional MRI during neoadjuvant treatment to analyze the predictive value of MR biomarkers for treatment response. Methods Locally advanced rectal cancer patients were examined with daily MRI during neoadjuvant RCT. Contouring of the tumor volume was performed for each MRI scan by using T2- and diffusion-weighted-imaging (DWI)-sequences. The daily apparent-diffusion coefficient (ADC) was calculated. Volumetric and functional tumor changes during RCT were analyzed and correlated with the pathological response after surgical resection. Results In total, 171 MRI scans of eight patients were analyzed regarding anatomical and functional dynamics during RCT. Pathological complete response (pCR) could be achieved in four patients, and four patients had a pathological partial response (pPR) following neoadjuvant treatment. T2- and DWI-based volumetry proved to be statistically significant in terms of therapeutic response, and volumetric thresholds at week two and week four during RCT were defined for the prediction of pCR. In contrast, the average tumor ADC values widely overlapped between both response groups during RCT and appeared inadequate to predict treatment response in our patient cohort. Conclusion This prospective exploratory study supports the hypothesis that MRI may be able to predict pCR of rectal cancers early during neoadjuvant RCT. Our data therefore provide a useful template to tailor future MR-guided adaptive treatment concepts

Measurements of the Delta(1232) Transition Form Factor and the Ratio sigma_n\sigma_p From Inelastic Electron-Proton and Electron-Deuteron Scattering

Measurements of inclusive electron-scattering cross sections using hydrogen and deuterium targets in the region of the Delta(1232) resonance are reported. A global fit to these new data and previous data in the resonance region is also reported for the proton. Transition form factors have been extracted from the proton cross sections for this experiment over the four-momentum transfer squared range 1.64 < Q^2 < 6.75 (GeV/c)^2 and from previous data over the range 2.41 < Q^2 < 9.82 (GeV/c)^2. The results confirm previous reports that the Delta(1232) transition form factor decreases more rapidly with Q^2 than expected from perturbative QCD. The ratio of sigma _n \sigma_p in the \Delta(1232) resonance region has been extracted from the deuteron data for this experiment in the range 1.64 < Q^2 < 3.75 (GeV/c)^2 and for a previous experiment in the range 2.4 < Q^2 < 7.9 (GeV/c)^2. A study has been made of the model dependence of these results. This ratio sigma_n\sigma_p for \Delta(1232) production is slightly less than unity, while sigma_n\sigma_p for the nonresonant cross sections is approximately 0.5, which is consistent with deep inelastic scattering results.Comment: 10 figures. 42 pages, including figures. submitted to Physical Review

Die Nutzung neuer und erneuerbarerEnergiequellen in Entwicklungsländern

On the occasion of the United Nations Conference on New and Renewable Sources of Energy in Nairobi August 1981, each of the participating countries submitted- a national paper which describes the energy scene and the role of new and renewable sources of energy in the respective country. In the following study 47 national papers from developing countries and 16 national papers from industrialized countries have been analyzed. The aim of this analysis was to find out how important the new and renewable sources of energy in the developing and the developed countries are and what possible fields for an effective north-south cooperation exist. The analysis consists of the following steps: - Extracting of relevant informations and data from the national papers and tabulating them in a uniform manner (to be found in Volume 2 of this study). - Determination of fields for bilateral cooperation between developed and developing countries from the view point of the developing countries. - Classification of developing countries with regard to oil and coal resources, hydropower potential and firewood situation. - Detailed analysis of 10 representative developing countries. - Analysis of the industrialized nations with regard to energy policy, cooperation with developing countries and state of art of the technologies for using new and renewable sources of energy. At present nearly all developing countries consume considerable amounts of renewables, especially firewood and dung. Most of these countries want to introduce various other new and renewable sources of energy on the basis of new and efficient technologies. But there exist various economic, financial, infrastructural, socio-cultural and other constraints. To overcome these constraints an enormous self-help and a much more intensive cooperation with industrialized countries in the fields of energy planning,education,development of infrastructure,research and technical development is necessary

Accurate measurement of hydrodynamic interactions between a particle and walls

International audienceA new experimental setup allows the measurement of hydrodynamic interactions between the walls of a vessel and a particle moving along a three-dimensional trajectory in a viscous fluid. The vertical motion of the particle is measured with an accuracy of 50 nm using laser interferometry, while its horizontal movements are controlled with an accuracy of 20 μm by displacing the vessel in the horizontal direction so as to keep the sphere in the fixed vertical laser beam. Three axisymmetric closed containers are used as examples: two vertical cylinders (with flat and convex lens-shaped lower walls) and a cone. Various effects of combined creeping flow hydrodynamic interactions between the particle and walls are observed

Experimental Investigation of the Hydrodynamic Interactions between a Sphere and a Large Spherical Obstacle

The hydrodynamic interactions between a spherical particle embedded in a very viscous fluid and a large close spherical obstacle are investigated experimentally. The displacement of the particle is followed by laser interferometry with a 100 nm resolution. The large obstacle is either convex, plane or concave. The experimental results for the drag coefficient on the particle are compared to the theoretical results written as three terms expansions for small gaps, viz. the result of Cox and Brenner (1967) for a plane obstacle, the result of Jeffrey (1982) and Jeffrey and Onishi (1984) for a convex obstacle and an extension of Cooley and O'Neill (1969) for a concave obstacle. Excellent agreement is found between the experimental and the theoretical results for all cases

Precise measurement of particle-wall hydrodynamic interactions at low Reynolds number using laser interferometry

International audienceThe motion of a spherical particle (with radius 1 to 6 mm) in a viscous fluid is measured using laser interferometry. The typical sensitivity on the measured displacement of the sphere is of the order of 50 nm. The particle is moving on the axis of a closed cylinder. The hydrodynamic interactions between the particle and the walls of the cylinder are compared with the theoretical result of Sano [J. Phys. Soc. Jpn. 56, 2713 (1987)] valid for a very small sphere. The agreement is excellent for the smallest sphere used in the experiment. The experiment also agrees with the result from the theory of lubrication when the sphere is close to a plane end wall. The effect of the particle roughness appears at small distances. Laser interferometry appears as a useful tool to study particle–wall hydrodynamic interactions when the geometry is cumbersome