Inverse Problems and Imaging Seminars

2nd Semester, 2011/12

• 15th
  March
  2012 Adjoint Techniques in Optical Tomography
  Kernel Prieto (School of Mathematics, University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

• 8th
  March
  2012 Level Set Methods for Inverse Scattering (II): Shape evolution by level set functions.
  Oliver Dorn (School of Mathematics, University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  I plan to continue the discussion from last week's seminar and present more details on how to choose level set functions and how to evolve these in order to solve shape reconstruction problems.

• 1st
  March
  2012 Level Set Methods for Inverse Scattering (I): Shape representation by level set functions.
  Oliver Dorn (School of Mathematics, University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  I will give a brief and very informal introduction in the use of level set functions for inverse scattering and image reconstruction. The 'classical level set representation of shapes' is presented and motivated this week which has been used intensively in the literature for different shape evolutions problems, such as shape reconstruction, shape optimization and image segmentation applications. This is the first of a few talks which I plan to present on this topic based on interest and feedback of the audience. These talks are in a completely 'ad hoc' style presented mainly at the blackboard.

• 23rd
  February
  2012 The generalised Radon transform on ellipses: strain measurement and seismic imaging
  Bill Lionheart (School of Mathematics, University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  The Radon transform can be generalized to the integral on families of curves - often called the Funk-Radon transform. Integrals over families of ellipses arise in two dimensional seismic reflection imaging (and similar techniques such as ground penetrating radar) where the wave speed is assumed constant. The extraction of strain measurements from diffraction patterns of polycrystaline materials also involves the ellipse Radon transform. We shall consider cases in which an explicit inversion formula is available as well as a PDE that characterizes the range.

Previous events

• 3rd
  Nov
  2011 Permeability estimation using two-phase flow equations and 4D seismics
  Salomao Chissonde, CEAS and SEAES, University of Manchester
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  In this work the equations of fluid flow in porous media are used in combination with time-lapse changes in pressure and saturation and 4D seismic results for estimating the absolute permeability in reservoirs. The derived fluid flow differential equations are discretized and solved using Matlab, additional parameters such as mobility, and fractional flow are also considered. This work integrates different disciplines, mathematics, computer programming, geophysics and reservoir engineering. These together serve as tools to predict reservoir performance and to optimize the hydrocarbon recovery and field profit by reducing the uncertainty and by generating updated integrated models.

• 27nd
  Oct
  2011 On seismic travel times, X-rays and magic squares
  Oliver Dorn (School of Mathematics, University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  In the seminar, I will give an example of an inverse problem which occurs in three different applications where it asks for three different solutions!

• 6th
  Oct
  2011 Factorization method in Electrical Impedance Tomography
  Russel Miller (School of Mathematics)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  TBA

• 29th
  Sept
  2011 We will try to arrange for a Live Video Broadcast of the External Event: Inverse Problems Seminar at Newton Institute, Cambridge. (Gunther Uhlmann, University of Irvine, will talk about 'Cloaking: Science meets Science Fiction').
  
  
  Time 5:00pm, Frank Adam Room 2, School of Mathematics, Alan Turing Building
  Abstract

  Cloaking: science meets science fiction
  Uhlmann, G (Washington)
  Thursday 29 September 2011, 17:00-18:00
  Seminar Room 1, Newton Institute, Cambridge
  Abstract
  We describe recent theoretical and experimental progress on making objects invisible to detection by electromagnetic waves, acoustic waves and quantum waves. We emphasize the method of transformation optics. For the case of electromagnetic waves, Maxwell's equations have transformation laws that allow for design of electromagnetic materials that steer light around a hidden region, returning it to its original path on the far side. Not only would observers be unaware of the contents of the hidden region, they would not even be aware that something was being hidden. The object, which would have no shadow, is said to be cloaked. We recount some of the history of the subject and discuss some of the issues involved.

• 22nd
  Sept
  2011 The Sensitivity in Electrical Impedance Tomography
  Michael Crabb (School of Mathematics)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  TBA

• 27th
  May
  2010 High Performance Visualizing (and tightly coupling high performance reconstruction) for the Next Generation of 3D volumes
  Martin Turner and George Leaver
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  The EPSRC funded "Multiscale x-ray imaging facility for monitoring and modelling structural evolution in situ" project has created the multi-scale from macro to nano Henry Moseley X-Ray Imaging Facility, launched in June 2009. A multitude of different objects have been scanned creating new insights across the faculties. To build the next generation of visualization system Research Computing have looked at bids from IBM, HP and Dell. "These three bids represent three creative ways to construct the next generation of tightly connected HPC and HPV over highly interconnected datasets for the $ 4K^3 $ models required." We will present hardware options and software available for developing and building this system and ask for use cases from researchers to help them exploit their algorithms to the next stage. Details will be given of the pre-project that has just completed with the development of a scalable visualization package built on the UK National supercomputing facility run by NAG, a CRAY XT5 (www.hector.ac.uk).

• 20th
  May
  2010 xtreme-End Remote Scientific Visualization Show-and-Tell
  External event, see abstract.
  
  Time 2:00-4:00pm, Kilburn Building, Room 1:10.
  Abstract

  No Inverse Problems and Imaging seminar in the Alan Turing Bldg this day. Instead: Invitation to participate in the related workshop/show-and-tell event with company AVS Europe organized by M. Turner in the Kilburn Bldg.
  
  Abstract for that event: With the company AVS Europe we will present and discuss recent work including: CRAY HECToR integration of remote visualization, ParaFEM-Viewer, Erasmus funded Unstructured Volume rendering, and EU IP training and reports back from AVS user group in Switzerland and AVS in the CS Advanced MSc course.

• 29th
  April
  2010 Multi-Sheet Rebinning Methods for Real Time Tomography
  Marta Betcke (University College London)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  The high speed of data acquisition in the new cone beam scanners, like Rapiscan RTT, is achieved through using a stationary ring of sources, which replaces the slowly rotating gantry. To accommodate the stationary ring of sources in the design, it was necessary to divert from the 4th generation CT geometry. The resulting new geometry requires new different reconstruction algorithms than those devised for the standard cone beam CT. In this talk I present a novel type of rebinning methods for the RTT scanner geometry. The new methods generalise the idea of rebinning to a single surface to rebinning to multiple surfaces and provide a family of provably optimal methods. The multi-sheet surface is a natural fit for the RTT scanner geometry. The new methods utilise this property along with the linearity of the Radon transform to reconstruct superimposed images on the multi-sheet surface, which are subsequently deconvolved in the axial direction through solving of a series of small systems of equations for each transaxial pixel independently, therewith constituting a highly parallelisable and efficient method. I will discuss a simplified variant of the multi-sheet method, which can be implemented in a more efficient way while its performance remains very close to the optimal method. Finally, I will show performance of the two-sheet rebinning method on the RTT80 data.

• 22nd
  April
  2010 CO2 injection and characterization of compartmentalized reservoirs
  Rossmary Villegas (School of Chemical Engineering, University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  One popular technique for enhanced oil recovery is to inject CO2 through injection wells into an active reservoir in order to enhance hydrocarbon production rates at the production wells. During this process, it is important to simulate and monitor the gas or fluid flow in the reservoir from the available data. We present a new approach for the simulation of such CO2 injection processes. This approach is in particular useful in those cases where channels of certain rock types are present in the reservoir. Our algorithm is able to reconstruct complicated channels and the corresponding permeability distributions simultaneously from production and CO2 injection data. For the characterization we use a compositional model which takes into account the interaction between the injected CO2 and the gas or fluid in the reservoir. Also the incorporation of additional 4D seismic data is discussed. In the shape reconstruction approach, an implicit representation of the shapes (channels) by a level set technique is used in order to be able to incorporate interfaces in the model. Numerical results are presented which demonstrate the performance and main concepts of this algorithm.

• 18th March
  2010 Scatter in an uncollimated x-ray CT machine based on a Geant4 Monte Carlo simulation
  Nicola Wadeson (University of Manchester)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  A high-speed motionless-gantry x-ray CT machine has been developed by Rapiscan Systems Ltd. to eliminate mechanical rotation, allowing for 3D images to be collected in real time. The nature of the design limits the possibility of detector collimation which has implications in the reconstructed image due to scattered photons. A Monte Carlo computer simulation of the x-ray machine has been developed, using the Geant4 software toolkit, to analyse the behaviour of both Rayleigh and Compton scattered photons. An overview of the system and the simulation will be presented along with results obtained for typical airport baggage and medical applications.

• 11th March
  2010 Passive mmwave/THz radiometric imaging and inverse problems in electronic beam-forming
  Neil Salmon (QinetiQ)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  Passive millimetre wave (20 to 300 GHz) and THz (0.1 THz to 30 THz) imaging radiometry offers capabilities for real-time all weather imaging, personnel security screening and remote atmospheric sounding. Examples of imagery to demonstrate these capabilities will be presented together with the fundamentals of radiometry. However, the deployment scenarios for these applications require the use of planar geometry electronic beam-forming technology, as conventional quasi-optical systems are too bulky and heavy. Fortunately, recent advances in electronic technology mean this architecture of imager can now be realised and collaborative work with QinetiQ in the Alan Turing building of the Physics and Astronomy department now sets out to demonstrate this experimentally. This shift in technology brings new requirements for algorithm innovation to create images from directly sampled and correlated radiometric electric fields from aperture arrays. Some basics of how this inversion problem is currently viewed will be presented.

• 4th
  March
  2010 Can Fritz John help with Laminography?
  Bill Lionheart (School of Mathematics)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  In 1939 Fritz John wrote an influential paper that set the scene for 3D x-ray CT and drew the attention of the world to Radon's earlier work. In this paper he shows how the integrals of a function over lines satisfy a partial differential equation (John's equation) and hence how if data is known on some sets of lines it can be deduced for a larger set by solving a boundary value problem. This paper deserves to be revisited. In problems such as laminography where a thin sheet is x-rayed from limited range of directions and other limited data problems the paper certainly shows that some data sets are non-redundant. I expect this has implication to a range of limited data problems, for example tomography using a transmission electron microscope and who knows perhaps astronomy or other problems.That is where the audience participation comes in. The talk will only use advanced calculus so should be reasonably accessible.

• 25th February
  2010 Early breast cancer detection using microwaves and a level set inversion strategy
  Oliver Dorn (School of Mathematics)
  
  Time 2:00pm, Frank Adams Room 1, School of Mathematics, Alan Turing Building
  Abstract

  During recent years, the use of microwaves has been discussed as a tool for the early detection of breast cancer. The gold standard for breast screening is still mammography, even though it suffers from well-known limitations: lack of sensitivity (it misses up to 15% of tumors), low specificity (it gives rise to a large amount of false positive readings), and the exposure to potentially dangerous radiation. The use of microwaves as a complementary screening tool might help to avoid or improve some of these limitations. However, even though antenna development for this new technology has been advancing well, and several prototypes have been built worldwide, the development of efficient inversion algorithms for reliably extracting the desired information from the gathered microwave data has not kept pace. Major difficulties are the potentially low contrast in electromagnetic parameters between a malignant or benign tumor and the surrounding fibroglandular tissue in a dense breast, and the comparatively long wavelength of microwaves which both challenge the mathematical tools which are employed for the inversion. In the talk, we will present a recently developed structural inversion technique which makes use of a level set representation of shapes for estimating simultaneously the main structure of the complex breast and giving information regarding the existence, location and size of a hidden tumour from microwave data. Numerical experiments in 2D are presented which show that this technique is able to provide stable reconstructions for realistic breast phantoms (based on MRI images) from simulated 2D data. Some criteria are given on size and characteristics of a hidden tumour to be reliably detected by this technique. This is joint work with N. Irishina, M. Moscoso and D. Alvarez, Universidad Carlos III de Madrid, Spain.

Previous Forums

• 
  
  2006 - 2008
  The Inverse Problems and Imaging Seminar has formerly been called the MIMS FORUM. Seminar talks which have been given in the MIMS FORUM during previous semesters are listed below.
  
  
   
  
• 29
  Apr
  2008
  Lab based X-ray Nanotomography system for non invasive multiscale imaging from composite materials to biological samples -with resolution from mm to sub 50 nm
  S. H . Lau, Xradia Inc
  3 - 4pm, D13 Material Science Centre
   
  
• 28
  Apr
  2008
  Inverse problems in Positron Emission Tomography
  Julian Matthews
  2 - 3pm, Frank Adams 1, Alan Turing Building
   
  
• 20
  Mar
  2008
  The development of Tomographic Energy Dispersive Diffraction Imaging
  Bob Cernik
  10 - 11am, Frank Adams 2, Alan Turing Building
   
  
• 23
  Nov
  2007
  Dissecting Dinosaurs
  Phil Manning
  11 - 12pm, Frank Adams 1, Alan Turing Building
   
  
• 23
  Oct
  2007
  In-treatment X-ray Cone-beam Tomography for Guiding Radiotherapy: Developments at the Christie Hospital
  Chris Moore and Tom Marchant
  3 - 4pm, Frank Adams 2, Alan Turing Building
   
  
• 10
  Sept
  2007
  Ultra-fast tomography using off-the-shelf graphics cards
  Guillem Pratx
  3:30-4:30 pm, Frank Adams room 1, Alan Turing Building
   
  
• 12
  June
  2007
  Truncated Projections and Region-of-Interest Reconstruction in Classical X-Ray Computed Tomography
  Rolf Clackdoyle
  1:45-2:45 pm, M12, MSS Building
   
  This forum will be part of a British Inverse Problems Society one day meeting on "Challenges in tomography: Medical Imaging, Material Science and Airport Security". More information
  Abstract ( click to view)

  In computed tomography, an x-ray projection is truncated if the detector is not large enough to capture the image of the sample being scanned. In certain cases it is possible to accurately reconstruct a subset of the sample (a region-of-interest) even if some of the projections are truncated. The current understanding of region-of-interest reconstruction will be presented.

• 20
  March
  2007
  Hough transform for severely limited data in industrial tomography
  Eugenio P. A. Constantino
  2 - 3 pm, M12, MSS Building.
  
• 12
  Feb
  2007
  Image analysis for computerised tomography
  Dan Öberg
  2 - 3 pm, M12, MSS Building.
  
• 8
  Nov
  2006
  Nanotomography and diffraction contrast tomography at the European synchrotron
  Greg Johnson
  1 - 2 pm, M12, MSS Building.
  
• 20
  Sep
  2006
  New Dynamic (4D) Image Reconstruction Methods for Positron Emission Tomography
  Andrew Reader
  2 - 3pm, O10, MSS Building
  

Further information

For further information or to be added to the seminar mailing list, please contact Oliver Dorn.