24 research outputs found
Counting and integrating readout for direct conversion X-ray imaging: Concept, realization and first prototype measurements
No full textA novel signal processing concept for X-ray imaging with directly converting pixelated semiconductor sensors is presented. The novelty of this approach compared to existing concepts is the combination of charge integration and photon counting in every single pixel. Simultaneous operation of both signal processing chains extends the dynamic range beyond the limits of the individual schemes and allows determination of the mean photon energy. Medical applications such as X-ray computed tomography can benefit from this additional spectral information through improved contrast and the ability to determine the hardening of the tube spectrum due to attenuation by the scanned object. A prototype chip in 0.35-micrometer technology has been successfully tested. The pixel electronics are designed using a low-swing differential current mode logic. Key element is a configurable feedback circuit for the charge sensitive amplifier which provides continuous reset, leakage current compensation and replicates the input signal for the integrator. This paper will discuss measurement results of the prototype structures and give details on the circuit design
Proceedings of the 2. Ph.D. retreat of the HPI Research School on Service-oriented Systems Engineering
No full textContents 1. Styling for Service-Based 3D Geovisualization Benjamin Hagedorn 2. The Windows Monitoring Kernel Michael Schöbel 3. A Resource-Oriented Information Network Platform for Global Design Processes Matthias Uflacker 4. Federation in SOA – Secure Service Invocation across Trust Domains Michael Menzel 5. KStruct: A Language for Kernel Runtime Inspection Alexander Schmidt 6. Deconstructing Resources Hagen Overdick 7. FMC-QE – Case Studies Stephan Kluth 8. A Matter of Trust Rehab Al-Nemr 9. From Semi-automated Service Composition to Semantic Conformance Harald Meye
Linear system models for lag in flat dynamic x-ray detectors
No full textThe detective quantum efficiency (DQE) is regarded as a suitable parameter to assess the global imaging performance of an x-ray detector. However, residual signals increase the signal-to-noise ratio and therefore artificially increase the measured DQE compared to a lag-free system. In this paper, the impact of lag on the DQE is described for two different sources of lag using linear system models. In addition to the commonly used temporal filtering model for trapping, an increase of the dark current is considered as another potential source of lag. It is shown that the assumed lag model has a crucial impact on the choice of an adequate lag estimation method. Examples are given using the direct conversion material PbO. It turns out that the most general approach is the evaluation of the temporal noise power spectrum. A new algorithm is proposed for the crucial issue of robustly estimating the power spectrum at frequency zero
