PARALLELPROJ -- An open-source framework for fast calculation of projections in tomography

In this article, we introduce, a novel open-source framework designed for efficient parallel computation of projections in tomography leveraging either multiple CPU cores or GPUs. This framework efficiently implements forward and back projection functions for both sinogram and listmode data, utilizing Joseph's method, which is further extended to encompass time-of-flight (TOF) PET projections. Our evaluation involves a series of tests focusing on PET image reconstruction using data sourced from a state-of-the-art clinical PET/CT system. We thoroughly benchmark the performance of the projectors in non-TOF and TOF, sinogram, and listmode employing multi CPU-cores, hybrid CPU/GPU, and exclusive GPU mode. Moreover, we also investigate the timing of non-TOF sinogram projections calculated in STIR (Software for Tomographic Image Reconstruction) which recently integrated parallelproj as one of its projection backends. Our results indicate that the exclusive GPU mode provides acceleration factors between 25 and 68 relative to the multi-CPU-core mode. Furthermore, we demonstrate that OSEM listmode reconstruction of state-of-the-art real-world PET data sets is achievable within a few seconds using a single consumer GPU.Comment: 15 pages with 6 figures (first figure is tikz generated from joseph.tex) and 1 table. All figures and tables are at the end of the manuscrip

Analysis and simulation of photon scattering and neutron capture gamma spectra

Within this thesis two twin experiments consisting of neutron capture and photon scattering on the neighbour isotopes 77Se / 78Se and 195Pt / 196Pt have been analysed to gain qualitative and quantitative information about the photon strength function and level density in the respective compound nuclei. For the analysis and simulation of both experimental types a new Monte Carlo simulation using a fast and efficient, extreme statistical treatment of radiative nuclear deexcitations, was developed. Furthermore the influence of fluctuations of transition widths on photon scattering were investigated and quantified. It could be shown that those lead to an enhancement of elastic scattering processes. The data analysis of both twin experiments reveals non-Lorentzian extra E1 photon strength below the neutron separation energy

Description of dipole strength in heavy nuclei in conformity with their quadrupole degrees of freedom

In conformity to new findings about the widespread occurrence of triaxiality arguments are given in favor of a description of the giant dipole resonance in heavy nuclei by the sum of three Lorentzians. This TLO parameterization allows a strict use of resonance widths {\Gamma} in accordance to the theoretically founded power law relation to the resonance energy. No additional variation of {\Gamma} with the photon energy and no violation of the sum rule are necessary to obtain a good agreement to nuclear photo-effect, photon scattering and radiative capture data. Photon strength other than E1 has a small effect, but the influence of the level density on photon emission probabilities needs further investigation.Comment: Presented at the 3rd International Workshop on Compound Nuclear Reactions and Related Topics at Prague, 2011, to be published via the EPJ Web of Conference

Study of surface changes on industrial glasses with AFM, FE-SEM, EDX, SNMS and LM : Part 2. Surface changes by water drop etching, annealing at atmosphere and flame treatment

One of the possible defects in sputter coating layers are cone shaped rods which originate from the float glass surface on the atmosphere side. The glass surface had been etched by wax-like corrosion droplets and holes were formed into the glass skin after washing. This results in inhomogeneity on the surface, which induces an inhomogenous deposition pattern of the material on the surface during the process of sputtering. In contrast, the tin bath side is shown to be an ideal coating surface without any inhomogen eity. In some eases however, it could not be bent above the glass transition temperature (Tg) in air due to formation of bloom patterns, which make the glass milky. Our studies revealed that phase separation is the ultimate cause of the observed bloom formation. In addition, sulphur flakes and needle-like nanocrystallites were detected on the tin bath side as well as hexagonal nanocrystallites on the atmosphere side of the annealed float glass. It was also found that flame treatment of borosilieate and lead crystal glasses induced two changes on the glass surfaces. These are precipitation of evaporation products and phase separation beneath the glass skin. The samples were studied by a combination of field emission scanning electron microscopy (FE-SEM) with different accelerating voltages and atomic force microscopy (AFM)

Blood Product Supply on Germany: The Impact of Apheresis and Pooled Platelet Concentrates

Background: In Germany, about 60% of all produced platelet concentrates (PCs) are apheresis PCs (APCs). Ongoing discussions on APC reimbursement and costs might lead to a potential shift in pooled PC (PPC)/APC production. Objective of this analysis was to build a comprehensive model from the societal perspective to evaluate consequences associated with shifts in platelet supply and demand. Methods: Literature search, desktop researches on platelet supply and demand. Model calculations, time horizon one year: model input from the Paul Ehrlich -Institute, data 2013. Base case: 19.2% of annual whole blood donations (WBDs) were used for production of 38.5% PPCs, decay of 46,218 PCs (8.0%). Scenarios calculated: variation in PPC proportion of 10-100%. Results: Base case: during PPC production 41,957-83,913 red blood cell concentrates (RBCCs) are estimated to be lost, which corresponds to 1-2% of annual RBCCs in Germany. Scenarios were calculated for a production of 60-100% PPCs: loss is estimated to be 1.5-5.0% of annual RBCCs (65,430-218,099), decay 54,189-69,022 PCs (9.4-12.0%). Conclusion: Production of different blood components is interlinked and sensitive to unidimensional decisions. Increasing PPC proportion has negative impact on the RBCC production and on the antigen-matched APC donor pool. Completion of the model calculations to predict the optimal PPC/APC proportion would require evidence on the number of refractory patients, donor pool sizes, and incidences of diseases requiring platelet transfusions. (C) 2016 S. Karger GmbH, Freibur

Percutaneous aortic valve replacement: valvuloplasty studies in vitro

Objective: Valvuloplasty of the aortic valve is currently used in selected patients for severe calcified aortic valve disease, but clinical effectiveness is low and complication rate remains high. In this study, the total particle load after valvuloplasty and the embolization risk of calcific debris into the coronary arteries was analyzed in an in vitro model. Methods: Three highly calcified human aortic leaflets have been sutured into a porcine annulus (N=9). Both coronary arteries were separated and each was anastomized to a silicon line, which was drained off into a measuring beaker. Then valvuloplasty was performed (Thyshak II, 20mm, 1.5atm). After removal of the balloon, 100ml of sodium chloride solution irrigated the ascending aorta. After passing through the separated coronary arteries, the solution was filtered (filter size 0.45μm), dried, and the total amount of particles was analyzed microscopically. Results: Nine experiments were analyzed. After valvuloplasty, all hearts showed a median of 18 particles larger than 1mm in the coronary arteries (range 0-307). The amount of particles smaller than 1mm was 6574 (median, range 2207-14200). In five cases, coronary arteries were completely occluded by bulky particles. Conclusion: This study demonstrated a large amount of calcific particles after valvuloplasty with a consequently high risk for coronary embolic events in case of highly calcified aortic valves. In times of valvuloplasty rediscovering as part of transcatheter valve implantation, the risk of embolization should be taken into consideration and filtering techniques have to be develope

Resolution enhancement, noise suppression, and joint T2* decay estimation in dual-echo sodium-23 MR imaging using anatomically-guided reconstruction

Purpose: Sodium MRI is challenging because of the low tissue concentration of the 23 Na nucleus and its extremely fast biexponential transverse relaxation rate. In this article, we present an iterative reconstruction framework using dual-echo 23Na data and exploiting anatomical prior information (AGR) from high-resolution, low-noise, 1 H MR images. This framework enables the estimation and modeling of the spatially-varying signal decay due to transverse relaxation during readout (AGRdm), which leads to images of better resolution and reduced noise resulting in improved quantification of the reconstructed 23Na images. Methods: The proposed framework was evaluated using reconstructions of 30 noise realizations of realistic simulations of dual echo twisted projection imaging (TPI) 23 Na data. Moreover, three dual echo 23 Na TPI brain data sets of healthy controls acquired on a 3T Siemens Prisma system were reconstructed using conventional reconstruction, AGR and AGRdm. Results: Our simulations show that compared to conventional reconstructions, AGR and AGRdm show improved bias-noise characteristics in several regions of the brain. Moreover, AGR and AGRdm images show more anatomical detail and less noise in the reconstructions of the experimental data sets. Compared to AGR and the conventional reconstruction, AGRdm shows higher contrast in the sodium concentration ratio between gray and white matter and between gray matter and the brain stem. Conclusion: AGR and AGRdm generate 23 Na images with high resolution, high levels of anatomical detail, and low levels of noise, potentially enabling high-quality 23 Na MR imaging at 3T.Comment: 19 pages, 8 figures, 2 table

Study of surface changes on industrial glasses with AFM, FE-SEM, EDX, SNMS and LM : Part 1. Glass skin and corrosion

By combining different analytieal techniques, including modern high resolution imaging tools such as field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), new phenomena in the surface, near surface and bulk structure of various industrial glasses (without any cleaning process) have been diseovered. Investigations of soda-lime-silica container glass and lead silicate glass tubings exposed to atmospheric and to dried air are presented. The results of the first part of this paper can be explained with an SiO2 rich skin on the glass, which can protect the glass against the attack of external media. If the skin was mechanically injured, inhomogeneous corrosion products on pm scale grew around the injured site after exposure to humid air for times between days up to one year. Microchannels were formed through the injured site due to restricted ion exchange, followed by a local increase of the pH value and consequently the dissolution of the glass network. Finally some stress in the glass, yielded during manufacture, can be partially released and the cutting behaviour is improved. Faster cooling results in a thinner skin and the ions in the glass are able to migrate to the surface more easily when surrounded by some reactive media. Slower cooling results in thicker skin and wax-like droplets instead of erystallites are formed on the surface at a later stage in humid air. The wax-like droplets can etch the glass skin locally, followed by the growth of inhomogeneous corrosion products similar to the injury induced corrosion. If the fresh glass surface was hot-end treated, the quality of the adjacent coating layer depended strongly on the thickness of the skin