Recent developments in time-of-flight PET

While the first time-of-flight (TOF)-positron emission tomography (PET) systems were already built in the early 1980s, limited clinical studies were acquired on these scanners. PET was still a research tool, and the available TOF-PET systems were experimental. Due to a combination of low stopping power and limited spatial resolution (caused by limited light output of the scintillators), these systems could not compete with bismuth germanate (BGO)-based PET scanners. Developments on TOF system were limited for about a decade but started again around 2000. The combination of fast photomultipliers, scintillators with high density, modern electronics, and faster computing power for image reconstruction have made it possible to introduce this principle in clinical TOF-PET systems. This paper reviews recent developments in system design, image reconstruction, corrections, and the potential in new applications for TOF-PET. After explaining the basic principles of time-of-flight, the difficulties in detector technology and electronics to obtain a good and stable timing resolution are shortly explained. The available clinical systems and prototypes under development are described in detail. The development of this type of PET scanner also requires modified image reconstruction with accurate modeling and correction methods. The additional dimension introduced by the time difference motivates a shift from sinogram- to listmode-based reconstruction. This reconstruction is however rather slow and therefore rebinning techniques specific for TOF data have been proposed. The main motivation for TOF-PET remains the large potential for image quality improvement and more accurate quantification for a given number of counts. The gain is related to the ratio of object size and spatial extent of the TOF kernel and is therefore particularly relevant for heavy patients, where image quality degrades significantly due to increased attenuation (low counts) and high scatter fractions. The original calculations for the gain were based on analytical methods. Recent publications for iterative reconstruction have shown that it is difficult to quantify TOF gain into one factor. The gain depends on the measured distribution, the location within the object, and the count rate. In a clinical situation, the gain can be used to either increase the standardized uptake value (SUV) or reduce the image acquisition time or administered dose. The localized nature of the TOF kernel makes it possible to utilize local tomography reconstruction or to separate emission from transmission data. The introduction of TOF also improves the joint estimation of transmission and emission images from emission data only. TOF is also interesting for new applications of PET-like isotopes with low branching ratio for positron fraction. The local nature also reduces the need for fine angular sampling, which makes TOF interesting for limited angle situations like breast PET and online dose imaging in proton or hadron therapy. The aim of this review is to introduce the reader in an educational way into the topic of TOF-PET and to give an overview of the benefits and new opportunities in using this additional information

Manifestations of Structural Dualism in the Twentieth-Century Symphony

This composer essay about the twentieth-century symphony examines the genre’s inherent concept of “structural dualism.” Structural dualism’s evolving manifestations and their interrelation are evaluated. Considering the matter from the opposite side: “What makes a symphony a symphony, regardless of the period in which it is conceived or the style it makes use of?” Emanating from the Baroque sonata, dance suite movement, and sinfonia, structural dualism was originally epitomized by the reconciliation of tonal contrasts in the Classical symphony’s sonata form. This tonal contrast shifted to thematic polarity, embodying structural dualism in the Romantic symphony’s extended sonata form, before structural dualism evolved to integrative, transformative, and—ultimately—conceptual manifestations in various appearances of the twentieth-century symphony. The study’s delineation has a twofold implication. First, it limits the observation of structural dualism to the symphony, although some reference is made to applications of the dualist principle in other genres. Second, the primarily abstract approach of evolving manifestations of the symphony’s structural dualism does not aspire to be a systematic or exhaustive representation of the genre’s twentieth-century history or repertoire. Various appearances of structural dualism will be illustrated with pioneering compositions and key esthetic statements from both composers and theorists, providing a foundation for the conclusive structural analyses in the last chapter.TABLE OF CONTENTS Abstract iii Autobiographical Note iv Acknowledgements v Table of Music Examples vii Preface viii Introduction: Structural Dualism in the Symphony 1 Chapter 1: Tonal and thematic structural dualism before the twentieth century 1.1. Defining tonal structural dualism and thematic structural dualism 4 1.2. Tonal structural dualism in the sonata form of the Classical symphony 6 1.3. Thematic structural dualism in the extended sonata form and alternative 18 formal models of the Romantic symphony Chapter 2: Manifestations of structural dualism in the twentieth-century symphony: integrative, transformative, and conceptual structural dualism 2.1. Defining “integrative,” “transformative,” and “conceptual” structural 34 dualism 2.2. Manifestations of integrative structural dualism in the twentieth-century 37 symphony 2.3. Manifestations of transformative structural dualism in the twentieth-century 51 symphony 2.4. Manifestations of conceptual structural dualism in the twentieth-century 63 symphony Chapter 3: Some examples of structural dualism in the twentieth-century symphony analyzed 3.1. Integrative structural dualism in Dmitry Shostakovich’s Fifth Symphony, 75 Movement I 3.2. Transformative structural dualism in Jean Sibelius’s Fifth Symphony, 104 Movement I 3.3. Conceptual structural dualism in Witold Lutosławski’s Second Symphony 121 Conclusion 141 Bibliography 147nrpages: 153status: accepte

Optimization of RFID Systems in Unfriendly Operating Environments

This work focused on HF RFID systems, where it was a goal to increase the reliability of the system. Especially in environments with metallic parts many problems occur. It became clear that many problems took place at the loop antenna of the RFID system. Therefore, we focussed on the design of loop antennas in order to increase the reliability of HF RFID systems. Although HF RFID systems are widely adopted by the industry, it was shown that the implementation of an RFID system for a specific environment involves a lot of design choices. Considering the loop antenna, several important design parameters have to be taken into account if we are aiming for a proper functioning HF RFID system. Metal objects in the vicinity of the loop antenna can have a high impact on the functionality of the system. In some cases a redesign of the loop antenna is needed. A redefinition of several design parameters and a solution, in terms of a new antenna concept, was proposed to take care of metal objects in the vicinity of the antenna. It has been made clear that an environment with metal objects has to be handled with care. If we only consider simple environments with one metal plate or object, we can design the loop antenna analytically. But when the environment becomes more complex, one needs a strong tool to create a reliable loop antenna for these environments. The main result of this thesis is the creation of an automated antenna design tool (AADT) which takes care of metals in the vicinity and creates an optimized loop antenna. The optimized loop antennas are based on parametric shapes and self-defined RFID goal functions. Two practical and challenging test cases served as an evaluation of the AADT in which an optimized loop antenna was implemented. In both cases, we created a reliable HF RFID system, which always met the specified requirements. At all time, measurements confirmed the simulation results.status: publishe

Trompe l’oreille. Researching innovative strategies towards “illusive” sound-process composition

A composer’s imagination reaches beyond ‘realistic’ physical laws, and aims at illusory, groundbreaking sound creations and sensations. An illusory sound process (‘trompe l’oreille’ effect, literally, ear-deceiving) can be created by breaking apart the unambiguous coherence between different musical parameters (pitch, duration, timbre, dynamic, etc.), and, consequently, rendering it diffuse, asynchronous, ambiguous, indistinct. This publication explains 'acoustic illusion' as a phenomenon and focuses on a number of experiments of the past decades. It further comments on examples from the composition practice and music literature, and suggests — through ‘hands-on’ templates — a number of strategies pertaining the use of acoustic illusion in contemporary composition.edition: 1st editionnrpages: 66status: publishe

New Feet For 5 Years A Minute. An artistic research into groundbreaking spatial-temporal experiences in the cross discipline of architecture and music

Architect dr. Jo Van Den Berghe en componist dr. Jeroen D’hoe vinden elkaar in het artistiek onderzoeksproject New Feet for 5 Years a Minute. De synesthesie tussen architectuur en muziek tast grenzen af en genereert nieuwe architecturale en muzikale compositiemogelijkheden die de waarnemer meenemen in een wervelende beleving van ruimte en klank, getimede leegte en plaatselijk ontgrensde tijd. Dit provocatief klank-beeld-verhaal werkt bewust ontregelend op het net- en trommelvlies van de waarnemer.nrpages: 66status: publishe

New Feet for 5 years a minute

Architect Jo Van Den Berghe en componist Jeroen D’hoe vinden elkaar in het artistiek onderzoeksproject NEW FEET FOR 5 YEARS A MINUTE (Associatie K.U.Leuven i.s.m. Concertgebouw Brugge). De synesthesie tussen architectuur en muziek tast grenzen af en genereert nieuwe architecturale en muzikale compositiemogelijkheden die de toeschouwer meenemen in een wervelende beleving van ruimte en klank, ge-time-de leegte en plaatselijk ontgrensde tijd.status: publishe

New Feet for 5 Years a Minute

Presentation and dissemination of the transdisciplinary research project New Feet for 5 Years a Minute (OPK 07/47). This presentation has been an elaborated combination of an opening lecture, an exhibition of the research process (sketches, scale models, draft compositions), and a concert by Spectra Ensemble (conductor Filip Rathé),combined with a mobile installation on the main stage of Concertgebouw Brugge.status: publishe