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The hybrid K+/Ca2+ sensor based on laser scanned silicon transducer for multi-component analysis
(2002)
The optimization of light output and energy resolution of scintillators is of special interest for the development of high resolution and high sensitivity PET. The aim of this work is to obtain statistically reliable results concerning optimal surface treatment of scintillation crystals and the selection of reflector material. For this purpose, raw, mechanically polished and etched LSO crystals (size 2×2×10 mm3) were combined with various reflector materials (Teflon tape, Teflon matrix, BaSO4) and exposed to a 22Na source. In order to ensure the statistical reliability of the results, groups of 10 LSO crystals each were measured for all combinations of surface treatment and reflector material. Using no reflector material the light output increased up to 551±35% by mechanical polishing the surface compared to 100±5% for raw crystals. Etching the surface increased the light output to 441±29%. The untreated crystals had an energy resolution of 24.6±4.0%. By mechanical polishing the surface it was possible to achieve an energy resolution of 13.2±0.8%, by etching of 14.8±0.7%. In combination with BaSO4 as reflector material the maximum increase of light output has been established to 932±57% for mechanically polished and 895±61% for etched crystals. The combination with BaSO4 also caused the best improvement of the energy resolution up to 11.6±0.2% for mechanically polished and 12.2±0.3% for etched crystals. Relating to the light output there was no significant statistical difference between the two surface treatments in combination with BaSO4. In contrast to this, the statistical results of the energy resolution have shown the combination of mechanical polishing and BaSO4 as the optimum.
We are developing an X-ray computed tomography (CT) system which will be combined with a high resolution animal PET system. This permits acquisition of both molecular and anatomical images in a single machine. In particular the CT will also be utilized for the quantification of the animal PET data by providing accurate data for attenuation correction. A first prototype has been built using a commercially available plane silicon diode detector. A cone-beam reconstruction provides the images using the Feldkamp algorithm. First measurements with this system have been performed on a mouse. It could be shown that the CT setup fulfils all demands for a high quality image of the skeleton of the mouse. It is also suited for soft tissue measurements. To improve contrast and resolution and to acquire the X-ray energy further development of the system, especially the use of semiconductor detectors and iterative reconstruction algorithms are planned.
In: Advances in intelligent computing in engineering : proceedings of the 9.International EG-ICE Workshop ; Darmstadt, (01 - 03 August) 2002 / Martina Schnellenbach-Held ... (eds.) . - Düsseldorf: VDI-Verl., 2002 .- Fortschritt-Berichte VDI, Reihe 4, Bauingenieurwesen ; 180 ; S. 1-35 The paper describes a novel way to support conceptual design in civil engineering. The designer uses semantical tools guaranteeing certain internal structures of the design result but also the fulfillment of various constraints. Two different approaches and corresponding tools are discussed: (a) Visually specified tools with automatic code generation to determine a design structure as well as fixing various constraints a design has to obey. These tools are also valuable for design knowledge specialist. (b) Extensions of existing CAD tools to provide semantical knowledge to be used by an architect. It is sketched how these different tools can be combined in the future. The main part of the paper discusses the concepts and realization of two prototypes following the two above approaches. The paper especially discusses that specific graphs and the specification of their structure are useful for both tool realization projects.