64 research outputs found
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
Fast full search block matching using subblocks and successive approximation of the error measure
No full textA fast full search block matching algorithm is developed. The matching criterion is the sum of absolute differences or the mean square error. The algorithm evaluates lower bounds for the matching criteria for subdivided blocks in order to reduce the number of search positions. It also uses the lower bounds for a fast calculation of the matching criterion for the remaining search positions. The computational complexity of the algorithm is evaluated and compared to the three-step search strategy. The search result of the algorithm is identical to the search result of the exhaustive search
Menser, P. B. (Death, 1867-06-07)
No full textAddress: 593 Vine St.Age at death: 23 Yrs887/Pg.187/1867/M W S/Ohio/Dr./F. H./Cem.Original record filed in drawer labeled 'MEIFERT-MER'
Book Reviews: Volume 6
No full textS. Hornig Priest Doing Media Research, reviewed by Eoin Devereux
Groombridge and J. Hay (eds.) The Price of Choice - Public service broadcasting in a competitive European market place, reviewed by Amanda Dunne
I. Ang Living Room Wars - Rethinking Media Audiences for a Postmodern World, reviewed by Ciaran McConaghy
S. Aronowitz, B. Martinsons and M. Menser (eds.) TechnoScience and Cyber Culture, reviewed by Brian Torod
PbO as direct conversion X-ray detector material
No full textA flat X-ray detector with lead oxide (PbO) as direct conversion material has been developed. The material lead oxide, which has a very high X-ray absorption, was analysed in detail including Raman spectroscopy and electron microscopy. X-ray performance data such as dark current, charge yield and temporal behaviour were evaluated on small functional samples. A process to cover a-Si TFT-plates with PbO has been developed. We present imaging results from a large detector with an active area of 18 x 20 cm(2). The detector has 1080 x 960 pixels with a pixel pitch of 184 mum. The linearity of detector response was verified. The NPS was determined with a total dark noise as low as 1800 electrons/pixel. The MTF was measured with two different methods: first with the analysis of a square wave phantom and second with a narrow slit. The MTF at the Nyquist frequency of 2.72 lp/mm was 50 %. We calculated first DQE values of our prototype detector plates. Full size images of anatomic and technical phantoms are shown
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