optimising thl-masks for the medipix-quad may, 4 th 2006 frank nachtrab
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Optimising THL-Masks for the Medipix-Quad May, 4 th 2006 Frank Nachtrab [email protected] Physikalisches Institut, Abt. IV Friedrich-Alexander-Universität Erlangen. medipix2. detector. MUROS 2.1. translation. rotation stage with. stages. object plate. - PowerPoint PPT PresentationTRANSCRIPT
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Frank Nachtrab1 04. 05. 2006Medipix2-Meeting
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Optimising THL-Masks for the Medipix-Quad
May, 4th 2006
Frank [email protected]
Physikalisches Institut, Abt. IV Friedrich-Alexander-Universität Erlangen
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Frank Nachtrab2 04. 05. 2006Medipix2-Meeting
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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
translationstagesrotation stage with
object plate
X-ray tube
medipix2detector
MUROS 2.1
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Frank Nachtrab3 04. 05. 2006Medipix2-Meeting
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Ring artefacts in CT
Problem: variations in lower threshold lead to differing counting behavior for every pixel (‘gain’)
-> ring artefacts in computed tomography
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Frank Nachtrab4 04. 05. 2006Medipix2-Meeting
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Equalisation with Noise
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Frank Nachtrab5 04. 05. 2006Medipix2-Meeting
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Equalisation using Flatfield Images
Histogram of Flatfields: THL-maskbit 0, 7; different THS→ calculate width and distance of distributions
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Frank Nachtrab6 04. 05. 2006Medipix2-Meeting
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Optimum THS - Quad
Linear fit of right boundary of bit0-distribution vs THS→ OptimumTHS (for every Chip on the Quad!)
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Frank Nachtrab7 04. 05. 2006Medipix2-Meeting
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Maskquality - Definition
Countrate independent parameter for maskquality!(lower is better; zero for a perfect detector)
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Frank Nachtrab8 04. 05. 2006Medipix2-Meeting
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Mask quality Single Chip
● All THL-Masks worse for higher thresholds● Flatfieldmasks better by a factor of ~ 1.35
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Frank Nachtrab9 04. 05. 2006Medipix2-Meeting
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Mask quality Quad
standard mask
flatfield mask
Chip 1 0.089 0.055
Chip 2 0.082 0.058
Chip 3 0.067 0.057
Chip 4 0.067 0.059
Overall 0.113 0.096
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Frank Nachtrab10 04. 05. 2006Medipix2-Meeting
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