Scientific Computing Department Seminars
01 Feb 2019








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Computational Mathematics and Applications seminar

Date and Time: Thursday February 21st at 2pm
Location: CR21 (R1) @ RAL (with video link to Barkla, A Block @ DL)

Speaker: Professor Martin S. Andersen, Technical University of Denmark

Title: Tomographic imaging with flat-field uncertainty


Classical methods for X-ray computed tomography (CT) are based on the assumption that the X-ray source intensity is known. In practice, however, the intensity is measured and hence uncertain. Under normal circumstances, when the exposure time is sufficiently high, this kind of uncertainty typically has a negligible effect on the reconstruction quality. However, in time- or dose-limited applications such as dynamic CT, this uncertainty may cause severe and systematic artifacts known as ring artifacts.

By modeling the measurement process and by taking uncertainties into account, it is possible to derive a convex reconstruction model that leads to improved reconstructions when the signal-to-noise ratio is low. We discuss some computational challenges associated with the model and illustrate its merits with some numerical examples based on simulated and real data.


All welcome. You are also invited to come and join us for lunch in the Rutherford restaurant beforehand.

Please let me know if you plan to attend so that the relevant security arrangements can be made. On arrival, visitors should report to the Main Rutherford Reception.

For information about travelling to the Rutherford Appleton Laboratory, please see
Parking is available if needed.

If travelling from Oxford

The Science Transit Shuttle runs every 30 minutes from various pickup points in Oxford (including the Science area) directly to RAL. Details are here:
The Thames Travel X32 bus travels between Oxford and the Harwell Campus (~ 60 minute journey, with a bus every hour).

If travelling by Train
The Thames travel X32/32A/X34 buses travel between Didcot Parkway Station and the Harwell Campus (~ 15 minute journey, with a bus every 15 minutes). Taxis are also available at Didcot Parkway Station.

For further information, contact Tyrone Rees (

+44 (0) 1235 446834


Contact: Williams, Esme (STFC,DL,SC)