Schallinduzierter Kontrast in MRT-Phasenbildern : Detektion von Kalkablagerungen und erste Brustuntersuchungen von Probanden

In dieser Arbeit wurde eine neuartige Methode zur Brustkrebsdiagnose untersucht. Es wurde die Schallstrahlungskraft des Schalls mit einer Frequenz von 2,5 MHz genutzt, um Gewebe zu verrücken. Die Verschiebung liefert einen Kontrast in MRT-Phasenbildern, die mit einer bewegungssensitiven MRT-Sequenz aufgenommen wurden. Es wurden zwei Sequenzen verwendet, eine bewegungssensitive Spin-Echo Sequenz und eine bewegungssensitive Line-Scan Sequenz. Bei den Messungen wurde der Schallstrahl synchron mit der Linienaufnahme bei der Line-Scan Sequenz bewegt. Man erhielt so ein zweidimensionales Verschiebungsbild des untersuchten Objektes. Es wurden sechs Phantome untersucht, die aus gewebeimitierendem Material bestanden, in das Kalkeinschlüsse eingefügt waren. Es wurden farbkodierte Verschiebungskarten der Phantome erstellt, in denen die Kalkeinschlüsse als Regionen erhöhter Verschiebung zu erkennen waren. Die erhöhte Verschiebung entstand durch die Reflexion des Ultraschalls an den Kalkeinschlüssen. Der kleinste untersuchte und aufgefundene Kalkeinschluss hatte eine Größe von 0,4 mm3. Er war kleiner als die Voxelgröße von 1,3×1,3×4 mm3. Bei den Messungen mit der bewegungssensitiven Spin-Echo Sequenz wurden Verschiebungsgraphen erstellt. Es wurde dazu die Verschiebung entlang einer Linie an der Stelle des höchsten Schalleinflusses gegen die Tiefe im Phantom aufgetragen. Die Position der erhöhten Verschiebung stimmte mit der gemessenen Position der Kalkeinschlüsse im Phantom überein. Man konnte auch Kalkeinschlüsse auffinden, die sich hintereinander befanden. Simulationen mit der Finite Elemente Methode von einem einfachen Modell der Phantome zeigten qualitative Übereinstimmungen mit den Messungen. Dies erlaubt die Unterscheidung zwischen Kalk und Verfestigung. Es wurden die ersten Untersuchungen in vivo an drei Probanden gemacht. Bei den Messungen mit der bewegungssensitiven Spin-Echo Sequenz wurden Verschiebungsgraphen erstellt. Mit der bewegungssensitiven Line-Scan Sequenz und synchronisierter Schallstrahlbewegung erhielt man Verschiebungsbilder nicht nur von Phantomen, sondern auch von der Brust.Acoustic radiation force contrast in MR phase images - Detection of calcifications and first in vivo measurements of the breast In this work, a new method for breast cancer diagnosis was investigated. The acoustic radiation force of ultrasound with a frequency of 2.5 MHz was used to displace the tissue. The displacement leads to a contrast in magnetic resonance phase images, that are acquired with a displacement sensitive spin-echo sequence and a displacement sensitive line-scan sequence. In the measurements, the sound beam was moved synchronously with the acquisition of the lines in the line-scan sequence. Thus, a two-dimensional displacement map of the investigated object was obtained. Six tissue-mimicking phantoms with included calcifications of varying size (0.4 mm3 to 2×3×0.4 mm3) were investigated. Color coded displacement maps of the phantoms were produced where the calcifications were visible as regions with increased displacement. This increased displacement was produced by the reflection of the ultrasound at the calcification. The regions of increased displacement were larger than the calcifications because the displacement was transferred to the surrounding material by elastic coupling. The smallest inclusion found had a size of 0.4 mm3. It was smaller than the voxel size of 1.3×1.3×4 mm3. Displacement graphs were produced by plotting the displacement on a line with the highest ultrasound influence versus the depth in the phantom. The position of the increased displacement matched the measured position of the calcification in the phantom. Calcifications that were downstream from another calcification could be located. Simulations with the finite element method of a simple model of the phantoms showed a qualitative agreement with the measurements. This allows a differentiation between calcifications and stiffer lesions. First measurements in vivo of the breast were conducted on three subjects. Displacement graphs were produced from images obtained with the displacement sensitive spin-echo sequence. Displacement-weighted MR phase images of the phantoms and in vivo were obtained with the displacement sensitive line-scan sequence and synchronous movement of the ultrasound beam

Alternative strategies of nutrient acquisition and energy conservation map to the biogeography of marine ammonia-oxidizing archaea

Ammonia-oxidizing archaea (AOA) are among the most abundant and ubiquitous microorganisms in the ocean, exerting primary control on nitrification and nitrogen oxides emission. Although united by a common physiology of chemoautotrophic growth on ammonia, a corresponding high genomic and habitat variability suggests tremendous adaptive capacity. Here, we compared 44 diverse AOA genomes, 37 from species cultivated from samples collected across diverse geographic locations and seven assembled from metagenomic sequences from the mesopelagic to hadopelagic zones of the deep ocean. Comparative analysis identified seven major marine AOA genotypic groups having gene content correlated with their distinctive biogeographies. Phosphorus and ammonia availabilities as well as hydrostatic pressure were identified as selective forces driving marine AOA genotypic and gene content variability in different oceanic regions. Notably, AOA methylphosphonate biosynthetic genes span diverse oceanic provinces, reinforcing their importance for methane production in the ocean. Together, our combined comparative physiological, genomic, and metagenomic analyses provide a comprehensive view of the biogeography of globally abundant AOA and their adaptive radiation into a vast range of marine and terrestrial habitats

Soziale Prozesse in Berliner Alt- und Neubaugebieten 1982 T. 1: Ergaenzende Berichte ; Lebensweise in der Hauptstadt - Untersuchungen in Berliner Wohngebieten

IZ Sozialwissenschaften, Berlin, B 2211- GL 321 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Alternative strategies of nutrient acquisition and energy conservation map to the biogeography of marine ammonia-oxidizing archaea

Ammonia-oxidizing archaea (AOA) are among the most abundant and ubiquitous microorganisms in the ocean, exerting primary control on nitrification and nitrogen oxides emission. Although united by a common physiology of chemoautotrophic growth on ammonia, a corresponding high genomic and habitat variability suggests tremendous adaptive capacity. Here, we compared 44 diverse AOA genomes, 37 from species cultivated from samples collected across diverse geographic locations and seven assembled from metagenomic sequences from the mesopelagic to hadopelagic zones of the deep ocean. Comparative analysis identified seven major marine AOA genotypic groups having gene content correlated with their distinctive biogeographies. Phosphorus and ammonia availabilities as well as hydrostatic pressure were identified as selective forces driving marine AOA genotypic and gene content variability in different oceanic regions. Notably, AOA methylphosphonate biosynthetic genes span diverse oceanic provinces, reinforcing their importance for methane production in the ocean. Together, our combined comparative physiological, genomic, and metagenomic analyses provide a comprehensive view of the biogeography of globally abundant AOA and their adaptive radiation into a vast range of marine and terrestrial habitats