71 research outputs found
Motion Correction of Whole-Body PET Data with a Joint PET-MRI Registration Functional
Respiratory motion is known to degrade image quality in PET imaging. The necessary acquisition time of several minutes per bed position will inevitably lead to a blurring effect due to organ motion. A lot of research has been done with regards to motion correction of PET data. As full-body PET-MRI became available recently, the anatomical data provided by MRI is a promising source of motion information. Current PET-MRI-based motion correction approaches, however, do not take into account the available information provided by PET data. PET data, though, may add valuable additional information to increase motion estimation robustness and precision.In this work we propose a registration functional that is capable of performing motion detection in gated data of two modalities simultaneously. Evaluation is performed using phantom data. We demonstrate that performing a joint registration of both modalities does improve registration accuracy and PET image quality.<br
The Energy Materials in-Situ Laboratory Berlin (EMIL) at BESSY II
The Helmholtz Center Berlin (HZB) and the Max-Planck Society (MPG) strengthen
their research in renewable energies with the implementation of the joint
Energy Material in-Situ Lab Berlin (EMIL) at the third generation light source
BESSY II. The new facility is dedicated to the in-situ and in-system x-ray
analysis of materials and devices for photovoltaic applications, (photo-)
catalytic processes, energie conversion and storage. To obtain a comprehensive
understanding of the involved materials, spectroscopic methods with x-rays
from the soft- up to the hard x-ray regime reveal an almost complete picture
of their chemical and electronic properties. The contribution presents the
layout of the x-ray beamlines and their performance in terms of photon flux,
energy resolution and spot sizes
Beamline design and performance
The Energy Materials In-Situ Laboratory Berlin (EMIL) at BESSY-II is currently
under construction. Two canted undulators for soft- and hard X-rays will be
installed into the BESSY II storage ring in one straight section, complex
beamlines with more than twenty optical elements will be set up and a new
laboratory building attached to BESSY II will host three endstations and a
large UHV-transfer system connecting various HV- and UHV-deposition systems.
The undulators, UE48 and U17, provide a broad energy spectrum of 80 - 10000
eV, of which the harder radiation (>700 eV) is provided by a cryogenic in-
vacuum device. Three monochromators (two plane grating monochromators (PGM)
and one LN2-cooled double crystal monochromator (DCM)) disperse the radiation
into separate pathways of 65 m length, while downstream of the monochromators
split-mirror chambers distribute the photon beam to one (or simultaneously to
two) of five upcoming endstations. Three of these endstations are designed for
the full energy range with spatial overlap of the soft and hard foci, whereas
one endstation (PEEM) uses only the soft and another one (PINK) only the hard
branch, respectively
Staphylococcus massiliensis isolated from human blood cultures, Germany, 2017-2020
Clinical and laboratory data on newly described staphylococcal species is rare, which hampers decision-making when such
pathogens are detected in clinical specimens. Here, we describe Staphylococcus massiliensis detected in three patients at a
university hospital in southwest Germany. We report the discrepancy of microbiological fndings between matrix-assisted
laser desorption/ionization time-of-fight mass spectrometry, 16S-rRNA polymerase chain reaction, and whole-genome
sequencing for all three isolates. Our fndings highlight the diagnostic pitfalls pertinent to novel and non-model organisms
in daily microbiological practice, in whom the correct identifcation is dependent on database accuracy
Suppression of electrical breakdown phenomena in liquid TriMethyl Bismuth based ionization detectors
Organometallic liquids provide good properties for ionization detectors.
TriMethyl Bismuth (TMBi) has been proposed as a detector medium with charge and
Cherenkov photon readout for Positron Emission Tomography. In this work, we
present studies for the handling of TMBi at different electric fields and under
different environmental conditions to find applicable configurations for the
suppression of electrical breakdowns in TMBi at room temperature. A simple
glass cell with two electrodes filled with TMBi was constructed and tested
under different operation conditions. Working at the vapour pressure of TMBi at
room temperature of about 40 mbar and electric fields of up to 20 kV/cm in
presence of a small oxygen contamination we found the formation of a discharge
channel in the liquid and a steady increase in the current. Further reduction
of pressure by pumping caused the TMBi to boil and a spontaneous combustion.
Eliminating the oxygen contamination led the TMBi under the same condition to
only decompose. When operating the setup under an argon atmosphere of 1 bar we
did not observe breakdowns of the electrical potential up to field strengths of
20 kV/cm. Still, in presence of a small oxygen contamination fluctuating
currents in the nA range were observed, but no decomposition or combustion. We
conclude from our experiments that TMBi at room temperature in a pure argon
atmosphere of 1 bar remains stable against electrical breakdown at least up to
electric field strengths of 20 kV/cm, presumably because the formation of
gaseous TMBi was prevented.Comment: 14 page, 8 figure
Mechanistic interrogation of combination Bevacizumab/dual PI3K/mTOR inhibitor response in Glioblastoma implementing novel MR and PET imaging biomarkers.
Purpose:
Resistance to bevacizumab (BEV) in glioblastoma (GBM) is believed to occur via activation of molecular networks including the mTOR/PI3K pathway. Implementing an MRI/PET molecular imaging biomarker approach, we sought to interrogate response to combining BEV with the mTOR/PI3K inhibitor BEZ235.
Methods:
Tumors were established by orthotopically implanting U87MG-luc2 in mice. Animals were treated with BEZ235 and/or BEV, and imaged using diffusion weighted-MRI, T2 weighted (T2w), and T2* weighted (T2*w) before and following delivery of superparamagnetic iron oxide (SPIO) contrast. Maps for changes in relaxation rates: ΔR2, ΔR2* and apparent diffusion coefficient (ADC) were calculated. Vessel Size Index (VSI) and micro vessel density index (MDI) were derived. 3´-deoxy-3´-[18F]fluorothymidine ([18F]FLT)- and O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) PET was further performed and tumor endothelium/proliferation markers assessed by immunohistochemistry.
Results:
Treatment with BEV resulted in a pronounced decrease in tumor volume (T2w MRI). No additive effect on tumour volume was observed in BEV/BEZ235 combination compared with BEV monotherapy. Ki67 proliferation index staining and [18F]FLT uptake studies were used to support observations. Using ΔR2* and ΔR2 values respectively, BEZ235 + BEV combination significantly reduced tumor microvessel volume in comparison to BEV alone. Decreased MDI was further observed in the combination group; supported by von Willebrand Factor (vWF) immunohistochemistry. We observed decreased [18F]FET uptake following BEV, but failed to observe further reduced [18F]FET uptake in the combination cohort. vWF IHC analysis showed mean tumor vessel size increased in all cohorts. Conclusions: Assessing MR imaging biomarker parameters together with [18F]FET and [18F]FLT PET, informed drug combination mechanism of action and provided clues as to potential clinical response. Translation of a BEZ35/BEV combination regimen could support reduction of peritumoral edemaobviating the requirement for steroids. Implementing hypothesis driven molecular imaging studies facilitates the interrogation of drug response in the pre-clinic. These data may more accurately predict the clinical potential of novel therapeutic approaches in oncology
Thymidine Metabolism as Confounding Factor of 3'-Deoxy-3'-[18F]Fluorothymidine Uptake after Therapy in a Colorectal Cancer Model.
Non-invasive monitoring of tumor therapy response helps in developing personalized treatment strategies. Here, we performed sequential positron emission tomography (PET) and diffusion-weighted magnetic resonance imaging (DW-MRI) to evaluate changes induced by a FOLFOX-like combination chemotherapy in colorectal cancer (CRC) xenografts, to identify the cellular and molecular determinants of these imaging biomarkers. Methods: Tumor bearing CD1 nude mice, engrafted with FOLFOX-sensitive Colo205 CRC xenografts, were treated with FOLFOX (5 fluorouracil, leucovorin and oxaliplatin) in weekly intervals. On d1, d2, d6, d9 and d13 of therapy, tumors were assessed by in vivo imaging and ex vivo analyses. In addition, HCT116 xenografts, which did not respond to the FOLFOX treatment, were imaged on d1 of therapy. Results: In Colo205 xenografts, FOLFOX induced a profound increase in uptake of the proliferation PET tracer 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), which was accompanied by increases in markers for proliferation (Ki67, TK1) and for activated DNA damage response (DDR; ÎłH2AX), whereas the effect on cell death was minimal. As tracer uptake was unaltered in the HCT116 model, these changes appear to be specific for tumor response. Conclusion: We demonstrate that [18F]FLT PET can non-invasively monitor molecular alterations induced by a cancer treatment, including thymidine metabolism and DDR. The cellular or imaging changes may not, however, be directly related to therapy response as assessed by volumetric measurements
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