Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Optimising THL-Masks for the Medipix-Quad Frank Nachtrab Physikalisches Institut, Abt. IV Friedrich-Alexander-Universität Erlangen
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Medipix2 CT setup in Erlangen Three translation stages (1 µm resolution) One rotation stage (0.1 degree resolution) MUROS 2.1 Distances: – Focus-detector: 768mm – Focus-object plate: 635mm Tungsten X-ray tube: – standard diagnostic tube – tube voltage 40 – 125 kV translation stages rotation stage with object plate X-ray tube medipix2 detector MUROS 2.1
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Ringartefacts in CT Problem: variations in lower threshold lead to differing counting behavior for every pixel (gain) -> ringartefacts in computed tomography
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Equalisation with Noise
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Equalisation using Flatfields Histogram of Flatfields: THL-maskbit 0, 7; different THS calculate width and distance of distributions
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Optimum THS linear fit of right boundary of bit0-distribution vs THS OptimumTHS (for every Chip on the Quad!)
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Maskquality - Definition Countrate independent parameter for maskquality! (lower is better; zero for a perfect detector)
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Maskquality Single Chip THL-Masks worse for higher thresholds Flatfieldmasks better by a factor of ~ 1.35
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg Maskquality Quad StandardmaskFlatfieldmask Chip Chip Chip Chip Overall
Frank Nachtrab Medipix2-Meeting Physikalisches Institut Universität Erlangen-Nürnberg