Rekonstrukcija signala iz nepotpunih merenja sa primenom u ubrzanju algoritama za rekonstrukciju slike magnetne rezonance

In dissertation a problem of reconstruction of images from undersampled measurements is considered which has direct application in creation of magnetic resonance images. The topic of the research is proposition of new regularization based methods for image reconstruction which are based on statistical Markov random field models and theory of compressive sensing. With the proposed signal model which follows the statistics of images, a new regularization functions are defined and four methods for reconstruction of magnetic resonance images are derived.У докторској дисертацији разматран је проблем реконструкције сигнала слике из непотпуних мерења који има директну примену у креирању слика магнетне резнонаце. Предмет истраживања је везан за предлог нових регуларизационих метода реконструкције коришћењем статистичких модела Марковљевог случајног поља и теорије ретке репрезентације сигнала. На основу предложеног модела који на веродостојан начин репрезентује статистику сигнала слике предложене су регуларизационе функције и креирана четири алгоритма за реконструкцију слике магнетне резонанце.U doktorskoj disertaciji razmatran je problem rekonstrukcije signala slike iz nepotpunih merenja koji ima direktnu primenu u kreiranju slika magnetne reznonace. Predmet istraživanja je vezan za predlog novih regularizacionih metoda rekonstrukcije korišćenjem statističkih modela Markovljevog slučajnog polja i teorije retke reprezentacije signala. Na osnovu predloženog modela koji na verodostojan način reprezentuje statistiku signala slike predložene su regularizacione funkcije i kreirana četiri algoritma za rekonstrukciju slike magnetne rezonance

Perceptually lossless coding of medical images - from abstraction to reality

This work explores a novel vision model based coding approach to encode medical images at a perceptually lossless quality, within the framework of the JPEG 2000 coding engine. Perceptually lossless encoding offers the best of both worlds, delivering images free of visual distortions and at the same time providing significantly greater compression ratio gains over its information lossless counterparts. This is achieved through a visual pruning function, embedded with an advanced model of the human visual system to accurately identify and to efficiently remove visually irrelevant/insignificant information. In addition, it maintains bit-stream compliance with the JPEG 2000 coding framework and subsequently is compliant with the Digital Communications in Medicine standard (DICOM). Equally, the pruning function is applicable to other Discrete Wavelet Transform based image coders, e.g., The Set Partitioning in Hierarchical Trees. Further significant coding gains are exploited through an artificial edge segmentatio n algorithm and a novel arithmetic pruning algorithm. The coding effectiveness and qualitative consistency of the algorithm is evaluated through a double-blind subjective assessment with 31 medical experts, performed using a novel 2-staged forced choice assessment that was devised for medical experts, offering the benefits of greater robustness and accuracy in measuring subjective responses. The assessment showed that no differences of statistical significance were perceivable between the original images and the images encoded by the proposed coder

Exploring the potential of two-dimensional electronic spectroscopy

Während des letzten Jahrzehntes haben multi-dimensionale ultraschnelle Spektroskopien großes Potential gezeigt, indem sie ein zunehmend breiteres experimentelles Fenster zur Untersuchung der Struktur und der Dynamiken von atomaren und molekularen Systemen auf Femtosekunden- und Pikosekunden-Zeitskalen öffneten. Die Vielseitigkeit und Bedeutung von zwei-dimensionaler elektronischer Spektroskopie beruht auf dem Gewinn an zusätzlicher Information, die man durch Ausweitung der Spektren in zwei Frequenz-Dimensionen erhält. Die vorliegende Dissertation fasst Teile unserer Anstrengungen im Bereich der zwei-dimensionalen elektronischen Spektroskopie zusammen. Der Fortschritt verlief dabei parallel auf zwei Schienen: einerseits führten Verbesserungen in der Instrumentation zu einer breiteren Anwendbarkeit der Methode. Durch die Umsetzung eines kompakten, einfach zu einrichtenden und passiv Phasen-stabilisierten Aufbaus zur Messung von zwei-dimensionalen elektronischen Spektren in drei verschiedenen Phasen-angepassten Geometrien wurde es möglich nicht nur Einzelquanten- sondern auch Doppelquanten-Kohärenzen zu studieren. Auf der anderen Seite wurden die existierenden Methoden angewandt um die elektronischen und vibronischen Dynamiken von molekularen Systemen unterschiedlicher Komplexität zu erforschen. Ein elektronisches Zwei-Level-System, dessen elektronischer Übergang an eine niederfrequente Schwingung gekoppelt ist, diente als Ausgangspunkt in unseren Untersuchungen. Das vibronische Wellenpaket, welches durch die Anregung mit einem Femtosekunden-Laserpuls erzeugt wird, manifestiert sich in oszillierenden Linienformen in zwei-dimensionalen Spektren. In einem nächsten Schritt wurden die Dynamiken der Linienformen eines Monomer-Dimer-Systems im Gleichgewicht untersucht. Es wurde gefunden, dass Exziton-Delokalisations-Effekte im Dimer die Zeitskala der spektralen Diffusion stark beeinflussen. Der Grad an Komplexität erreichte seinen Höhepunkt in der Untersuchung von Pfaden und Zeitskalen des Energietransfers in doppelwandigen zylindrischen J-Aggregaten. Die Dynamiken der Exzitonen in diesen molekularen Nanoröhrchen wurden mittels zeitlicher, energetischer und örtlicher Attribute charakterisiert. Zusätzlich wurde das Zweiexzitonen-Band von C8S3-Aggregaten mittels Doppelquanten-Kohärenz zwei-dimensionaler elektronischer Spektroskopie erforscht, mit dem Ziel ein tieferes Verständnis der elektronischen Struktur und Dynamiken in dieser Klasse von Substanzen zu gewinnen.During the last decade multi-dimensional ultrafast spectroscopies have shown great potential by opening an increasingly broad experimental window into the structure and dynamics of atomic and molecular systems on femtosecond and picosecond timescales. The versatility and significance of two-dimensional electronic spectroscopy relies on the gain of additional information obtained by spreading the spectra into two frequency dimensions. The present work summarizes part of our efforts in the field of two-dimensional electronic spectroscopy. The progress thereby ran parallel on two tracks: on the one hand, improvements in the instrumentation have led to a broader applicability of the method. By implementing a compact, easy to align, and passively phasestabilized setup for recording two-dimensional electronic spectra in three different phase-matching directions, it has become possible to study not only single-quantum but also double-quantum coherences. On the other hand, the existing methods have been applied to study the electronic and vibronic dynamics of molecular systems of varying complexity. An electronic two-level system whose electronic transition is coupled to a low-frequency vibrational mode has served as a starting point in our investigations. The vibronic wave packet that is induced by excitation with a femtosecond laser pulse manifests itself in oscillating line-shapes in the two-dimensional spectra. In a second step, the line-shape dynamics of a monomer-dimer system in equilibrium have been investigated. It was found that exciton delocalization effects in the dimer strongly influence the timescale of spectral diffusion. The degree of complexity reached its maximum in the investigation of pathways and timescales of energy transfer in double-wall cylindrical J-aggregates. Exciton dynamics in these molecular nanotubes have been characterized by temporal, energetic, and spatial properties. In addition, the double-exciton manifold of C8S3 aggregates has been studied by double-quantum two-dimensional electronic spectroscopy with the goal to gain a deeper understanding of the electronic structure and dynamics in this class of systems

Advancements and Breakthroughs in Ultrasound Imaging

Ultrasonic imaging is a powerful diagnostic tool available to medical practitioners, engineers and researchers today. Due to the relative safety, and the non-invasive nature, ultrasonic imaging has become one of the most rapidly advancing technologies. These rapid advances are directly related to the parallel advancements in electronics, computing, and transducer technology together with sophisticated signal processing techniques. This book focuses on state of the art developments in ultrasonic imaging applications and underlying technologies presented by leading practitioners and researchers from many parts of the world