36 research outputs found
Compact SiPM based Detector Module for Time-of-Flight PET/MR
No full textWe present a compact detector module for gamma detection in the PET part of a simultaneous ToF-PET/MR system. The module covers an area of 3.3cm x 3.3cm with 64 SiPM based readout channels. It is composed of a stack of three PCBs of identical size: The SiPMs on the topmost PCB are read out by two full-custom ASICs located on a second PCB located underneath. A third PCB at the bottom of the stack contains a local voltage regulator, an FPGA for ASIC control and data processing, and DACs to generate bias voltages for the readout ASICs and the SiPM devices. An LYSO scintillator block is optically coupled to the SiPMs for gamma to light conversion
Entwicklung einer Methode zur objektiven Bestimmung der Streulichtwahrnehmung
No full textEtwa 80 % der zur Interaktion mit der Umwelt anfallenden Informationen werden durch das visuelle System des Menschen verarbeitet. Im Laufe des natürlichen Alterungsprozesses entsteht eine Beeinträchtigung der Qualität des Sehens. Die Minderung der Sehqualität erfolgt durch physiologische Prozesse sowie pathologische Veränderungen. Die größte Beeinträchtigung entsteht durch die natürliche Alterung und die damit einhergehende Trübung der Augenlinse (Katarakt). Die Trübung der Linse führt zu einer Zunahme an intraokularem Streulicht. Die resultierende Zunahme der Streulichtwahrnehmung äußert sich in einer Abnahme der Sehleistung (Abnahme des retinalen Kontrasts) und Effekten von Blendung. Im Rahmen der vorliegenden Dissertation wurde eine Methode entwickelt, die eine quantitativ objektive Beschreibung der Streulichtwahrnehmung ermöglicht. Dazu wurde ein auf dem V-Modell basierendes generisches Prozessmodell entwickelt. Anhand dieses Modells wurde eine psychophysische Messmethode in eine objektive elektrophysiologische Messmethode transferiert. Im Entwicklungsprozess wurden Anforderungen an die Methodik abgeleitet und deren Verifikation und Validierung mittels jeweiliger Prozessschritte des Modells implementiert. Das entwickelte Konzept zur Bestimmung der Streulichtwahrnehmung basiert auf der Ermittlung der äquivalenten Schleierleuchtdichte. Dazu erfolgt die Abbildung von Kompensationsprozessen der Schleierleuchtdichte mittels visuell evozierten Potentialen. In Probandenstudien wurden die Charakteristika der zur Anwendung der Methodik notwendigen Einzelkomponenten analysiert und deren Überführung in die integrierte Messmethodik verifiziert. Abschließend wurde die entwickelte Methodik durch einen Systemvergleich mit dem Stand der Technik, dem C-Quant der Firma Oculus Optikgeräte (Oculus Optikgeräte GmbH, Wetzlar, Deutschland) validiert. Die klinische Relevanz wurde anhand der Unterscheidung zwischen drei Bereichen der Streulichtwahrnehmung, der physiologischen Streulichtwahrnehmung, physiologisch erhöhten Streulichtwahrnehmung und pathologisch erhöhten Streulichtwahrnehmung nachgewiesen.About 80% of the information from interaction with the environment is processed by the human visual system. As people age, the vision quality declines due to physiological and pathological changes. The main factor is the aging progress of the human lens, causing cataracts and increased intraocular stray light. This leads to reduced visual performance and increased glare sensitivity. This dissertation presents the development of a method for the quantitative and objective assessment of stray light perception. A generic process model based on the V-model was developed. Using this model, a psychophysical measurement principle was transferred into an objective electrophysiological measurement method. Requirements for the method were derived and their verification and validation were implemented using the respective process steps of the process model. The developed concept for evaluation the stray light perception is based on the determination the equivalent veiling luminance. Therefore, compensation processes of the veiling luminance are recorded using visual evoked potentials. In subject studies, the characteristics of the components of the concept were analyzed and their transfer into the integrated measurement method was verified. Finally, the developed methodology was validated by a system comparison with the state of the art, the C-Quant from Oculus Optikgeräte (Oculus Optikgeräte GmbH, Wetzlar, Germany). The clinical relevance of the method was demonstrated by distinguishing between three categories of stray light perception: physiological stray light perception, physiologically increased stray light perception, and pathologically increased stray light perception
First results with SiPM tiles for TOF PET based on FBK RGB-HD technology
No full textWe present the first results of timing and energy resolution of two newly developed tiles based on FBK RGB-HD SiPMs
Performance of FBK SiPMs coupled to PETA3 read-out ASIC for PET application
No full textIn this paper we show the energy and timing resolution performances of FBK SiPMs coupled to the PETA3 ASIC for PET application. We developed a measurement set-up to characterize single SiPMs coupled to scintillator exploiting the detector stack developed within the HYPERImage project. In this way we are able to characterize the combined SiPM/ASIC performance with the same signal chain (from the sensor to the ASIC board) used in the PET system. We show that using two scintillator detectors, composed of a 3x3x5mm^3 LYSO crystal coupled to a 3x3mm^2 SiPM, an intra-stack CRT of about 200ps FWHM can be obtained
La "organización que aprende" y su aporte al proceso de cambio
No full textEl presente trabajo se inicia con precisiones sobre las semejanzas y diferencias del aprendizaje individual frente al de grupos y de todo el sistema organizacional desde una perspectiva conductual, como una introducción al análisis sobre la ‘organización que aprende’ (learning organization), la cual se refiere a un tipo ideal de organización que otorga prioridad al aprendizaje de todos sus miembros y del sistema total. Además del diagnóstico y desarrollo de una ‘organización que aprende’, proporciona información sobre el instrumento Dimensions of the Learning Organization Questionnaire (DLOQ) elaborado por Watkins y Marsick (1998) con la finalidad de medir la cultura de aprendizaje, que podría ser aplicado con cualquier otro enfoque de cambio organizacional.In this article the author begins by discussing the similarity and differences between individual learning, and organizational system learning from a behavioral standpoint as an introduction to the analysis of Learning Organization, an ideal type of organization that focuses on the learning of each of its members and of the whole system. The article then presents a diagnosis and elaboration of a Learning Organization using the Dimensions of the Learning Organization Questionnaire (DLOQ), an instrument developed by Watkins and Marsick (1998) aimed at measuring the Learning Culture. This instrument can be applied in any other approach of organizational chang
A good buy: promoting probity in police procurement
No full textCorruption is a complicated concept that covers a wide array of possible situations and behaviours. Transparency International (TI) defines corruption as �the abuse of entrusted power for private gain�.3 The abuse of power by public officials may involve either a lawful or illegal exercise of authority. The personal gain may be received or merely promised. In relation to procurement, the clearest example of corruption is probably the acceptance of a bribe to ensure that a certain party�s tender is successful. Fraud, embezzlement, nepotism and cronyism are other forms of corruption are relevant in this context. What matters is not so much the nature of the act itself but rather the motivation or �spirit of corruption� (Kleinig, 1996: 166) with which it is committed. The ends sought may be organisationally approved (Newburn, 1999) and even achieved. As Kleinig suggests, �our assessment of moral worth must take our reasons into account. There is more to morality than an optimisation of outcomes� (1996: 251). Kleinig posits a wider definition of corruption (1996: 166) that includes, alongside motivations of personal benefit, corruption for organisational or divisional advantage, generally known as �noble cause corruption� (Westmarland, 2004; Miller and Blackler, 2005). Noble cause corruption might occur during procurement where there is a perception among staff that the regulatory regime causes inefficiencies for the organisation. Staff may choose to adopt unauthorised and perhaps unethical ways to circumvent the process in order to simplify or hasten the procurement process. Australian police officers interviewed by this author in 2005 commented that the bureaucratic nature of the procurement rules and the laboriousness of the implementation process often inhibited project progress. The section in which these officers worked was later found to have regularly exhibited an �apparent disregard for proper procurement and contract management processes�, including multiple breaches of applicable procurement guidelines (Ombudsman Victoria, 2009: 7). Apparently, very little personal gain was obtained through these breaches. However, one reason noble cause corruption is of concern is because it can be a �slippery slope� to personal corruption (Miller and Blackler, 2005), or at least provide a cover for it (Werner, 1983)
Reconstruction of crystal stack orientations using line-source measurements in PET
No full textThe method provides fast and robust reconstruction of stack rotations with low measuring and implementation effort, even in presence of noisy PET data. First measurements with Hyperion IID already indicate improvements to the spatial resolution using this method
