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International audience; A new prototype spectral photon-counting computed tomography (SPCCT) based on a modified clinical CT system has been developed. SPCCT analysis of the energy composition of the transmitted x-ray spectrum potentially allows simultaneous dual contrast agent imaging, however, this has not yet been demonstrated with such a system. We investigated the feasibility of using this system to distinguish gold nanoparticles (AuNP) and an iodinated contrast agent. The contrast agents and calcium phosphate were imaged in phantoms. Conventional CT, gold K-edge, iodine and water images were produced and demonstrated accurate discrimination and quantification of gold and iodine concentrations in a phantom containing mixtures of the contrast agents. In vivo experiments were performed using New Zealand White rabbits at several times points after injections of AuNP and iodinated contrast agents. We found that the contrast material maps clearly differentiated the distributions of gold and iodine in the tissues allowing quantification of the contrast agents' concentrations, which matched their expected pharmacokinetics. Furthermore, rapid, repetitive scanning was done, which allowed measurement of contrast agent kinetics with high temporal resolution. In conclusion, a clinical scale, high count rate SPCCT system is able to discriminate gold and iodine contrast media in different organs in vivo.

Three-dimensional information of entire objects can be obtained by the remarkable technique of computed tomography (CT). In combination with phase sensitive X-ray imaging high contrast for soft tissue structures can be achieved as opposed to CT based on classical radiography. In this work biological samples ranging from micrometer sized single cells over multi-cellular nerve tissue to entire millimeter sized organs are investigated by use of cone-beam propagationbased X-ray phase contrast. Optimization with respect to contrast, resolution and field of view is achieved by addressing instrumentation, sample preparation and phase reconstruction techniques. By using laboratory sources functional soft tissue within the bony capsule of mouse cochleae is visualized in 3D with unprecedented image quality. At synchrotron storage rings the technique reveals more than 1000 axons running in parallel within a mouse nerve and enables doseefficient three-dimensional cellular imaging as well as two-dimensional imaging at high resolutions below 50 nm. peerReviewed

Universität Hamburg, Diss., 2001; 89 pp., (2001). doi:10.3204/DESY-THESIS-2001-001, Starting from the standard discretization of the action of the nonlinear u-model in two dimensions we compute the Wilson effective action on a coarse lattice in a one loop approximation. Two methods are considered for the integration over the constrained fluctuation field. The first one was proposed by Polyakov. It allows a straightforward extraction of the result for the running coupling constant. The drawback is a rather involved propagator for the high frequency field. This prevents a transparent extraction of its field dependence. The other way to perform the integration is the extension of the fluctuation field to the whole $R^{N +1}$. This eliminates the constraint on the fluctuation field while keeping the expansion of the propagator manageable, but one has to scrutinize an extended action. An explicit form of the effective action is given. It contains a genuine one loop contribution. Polyakov's result can still be recovered to leading order. Although the analytical form of the effective action is transparently expressed in terms of the background field, numerical investigations require an explicit dependence on the block spin. Therefore a first approximation of the background field is given, and an iterative procedure is suggested to improve its properties. A Gaussian block spin is also considered. It allows to improve the locality properties of the effective action

Hintergrund: Die Unfähigkeit nicht-wörtliche Ausdrücke richtig zu erkennen und zu benutzen ist ein seit Langem bekanntes und wichtiges Symptom der Schizophrenie. Hauptsächlich auf Läsionsstudien zu einige Arten nicht-wörtlicher Sprache beruhend, wurde das Defizit als Beleg für ein rechtshemisphärisches Defizit bei Schizophrenie gesehen (Mitchell und Crow, 2005). Nicht-wörtliche Sprache ist jedoch eine heterogene linguistische Entität, zu der Ironie, Metapher, Metonymie, Idiome und Sarkasmus zählen. Nicht-wörtliche „konkretistische“ Defizite bei Schizophrenie werden meistens als eine Einheit betrachtet; allerdings weist die neuere bildgebende Forschung bei gesunden Probanden auf unterschiedliche Verstehensprozesse für unterschiedliche Arten nicht-wörtlicher Sprache hin, wobei auch merkliche Unterschiede in der Lateralität gefunden werden konnten. Methoden: Das Ziel dieser Studie ist: (a) systematisch die Fähigkeit zum Verständnis nicht-wörtlicher Sprache in einer Stichprobe von schizophrenen Patienten unter Verwendung verschiedener Arten von nicht-wörtlichen Stimuli zu untersuchen (b) die Beziehung zu Psychopathologie und Theory-of-Mind aufzuzeigen. 30 Probanden mit einer ICD-10 Schizophrenie-Diagnose und 20 gesunde Kontrollpersonen (gematched nach Alter, Geschlecht, Bildung, Verbalem-IQ, CPT-Leistung) absolvierten eine Reihe von Tests zum Verständnis nicht-wörtlicher Sprache (Ironieverständnis, Metonymieverständnis, Sprichwortverständnis und Erklären von Sprichwörtern, Psychopathologie (Scale for the Assessment of Negative Symptoms [SANS], Scale for the Assessment of Positive Symptoms [SAPS], Positive and Negative Syndrome Scale [PANSS], Global Assessment of Functioning [GAF] scale und Neuropsychologie (Bilderordnen/TOM, Verbaler IQ, Kurzversion CPT, Digit span). Ergebnisse: Ironie- und Metonymieverständnis war bei Schizophrenie signifikant im Vergleich zu CPT-gematchten Kontrollen gemindert, obwohl nicht alle Patienten dieses Defizit aufwiesen. Der SAPS-Gesamtscore korrelierte signifikant mit dem Ironieverständnis. Im Gegensatz dazu hing das Metonymieverständnis stärker mit negativen formalen Denkstörungen zusammen. Die Interkorrelation zwischen verschiedenen Arten nicht-wörtlicher Sprache war niedriger als erwartet. Schlussfolgerung: Die Ergebnisse sind gut kompatibel mit einer Reihe von neueren Studien aus der funktionellen Bildgebung, die auf eine unterschiedliche funktionelle Neuroanatomie für verschiedene Arten und Aufgaben nicht-wörtlicher Sprache und mehr als eine pathophysiologischen Weg hinweisen. Background: The inability to identify and use nonliteral expressions correctly is a long-known and important symptom of schizophrenia. Mainly based on lesion research for some types of nonliteral language, the deficit was seen as evidence for a right hemisphere deficit in schizophrenia (Mitchell and Crow, 2005). However, nonliteral language is a heterogeneous linguistic entity that includes irony, metaphors, metonymy, idioms and sarcasm. Nonliteral "concretistic" deficits in schizophrenia are mostly seen as one entity; however newer imaging research in healthy subjects suggests different comprehension processes for different types of nonliteral language, including marked differences in laterality. Methods: The aim of this study is to: (a) systematically investigate nonliteral language comprehension skills in a schizophrenia sample using different types of nonliteral stimuli and (b) demonstrate relationship to psychopathology and Theory-of-Mind. 30 probands with ICD-10 schizophrenia and 20 healthy control subjects (matched for age, gender, education, verbal-IQ, CPT-performance) completed a nonliteral language comprehension battery (irony comprehension, metonymy comprehension, proverb comprehension and proverb explanation), psychopathology (Scale for the Assessment of Negative Symptoms [SANS], Scale for the Assessment of Positive Symptoms [SAPS], Positive and Negative Syndrome Scale [PANSS], Global Assessment of Functioning [GAF] scale and neuropsychology (picture sequencing/TOM, verbal IQ, short version CPT, digit span). Results: Irony and metonymy comprehension were significantly impaired in schizophrenia relative to the CPT-matched controls, although not all patients showed the deficit. SAPS total score was significantly correlated with irony comprehension. In contrast, metonymy comprehension was more associated with negative thought disorder. Intercorrelation between different types of nonliteral language was lower than expected. Conclusions: This is good compatible with a number of recent functional imaging studies which suggest different functional neuroanatomy for different types and tasks of nonliteral language and suggests more than one pathophysiological pathway.