SU-E-I-79: Correction of Dark Current and Image Lag in Multi-Source Carbon Nanotube Imaging Systems

Medical Physics
C FrederickS Chang

Abstract

To correct for dark current and detector image lag in multi-source carbon nanotube (CNT) based imaging systems. CNTs can be used as a novel electron source for X-ray generation. Here a small (∼2 kV) gate voltage induces a large electric field at the CNT tip that causes field emission as opposed to thermionic emission. This enables faster switching times and allows miniaturization which aids in the development of stationary multi-source systems. These systems may encounter two key problems: dark current in non-active sources and detector lag. In damaged and perhaps end-of-life devices, sources may develop significant electron output without gate voltage, interfering with images from non-active sources. Although the output is small, it is constant, and continuous integration of detectors compared with small X-ray exposure time magnifies its contribution to the signal. A method based on binary multiplexing is developed to mitigate the dark current contributions possibly extending device lifetime. Having discrete sources, these multi-source systems have coarser angular sampling than rotating systems. This coarser sampling means that the detector signal changes more in adjacent projections than rotating systems exacerbating the effe...Continue Reading

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