Ged Ridgway


I'm a final year PhD student within the Centre for Medical Image Computing at University College London. CMIC is an interdisciplinary centre within the departments of Computer Science and Medical Physics & Bioengineering. I have been supervised by Professor Derek Hill, Dr Sébastien Ourselin, and Professor Nick Fox, who is at the Dementia Research Centre within the Institute of Neurology at UCL. I am also supervised by Dr Brandon Whitcher, who is based at GlaxoSmithKline. GSK, together with the EPSRC fund my PhD through a CASE Studentship. For further information, please download my CV in PDF format.


My research project is Longitudinal MR Imaging of Dementia — the use of three-dimensional structural Magnetic Resonance Imaging, together with computational image analysis and statistical methods, to investigate the chronological behaviour of dementias such as Alzheimer's Disease. Example applications include:

The work involves techniques from image processing and analysis, machine learning, and statistics, including topics such as:

The image below illustrates a simple example; it shows the cerebral atrophy over one year in an AD patient. In particular it highlights two alternative ways to visualise (and to quantify) structural change over time:

  1. The residual differences following low-dimensional (e.g. rigid or affine) image registration
  2. Measures derived from the displacement field of a high-dimensional warp between the images
Other alternatives include:

Longitudinal MR Imaging of Alzheimer's Disease — Example

An example of a patient with probable Alzheimer's Disease [anonymised data from the DRC, ION, UCL]. (a) Sections of a 3D T1-weighted MR Image. (b) The same, from a scan taken one year later, rigidly registered to the first. (c) A subtraction image indicating structural changes over time. (d) The determinant of the Jacobian matrix from a high-dimensional registration between the images — brighter colours indicate tissue expansion; darker, contraction or loss.

Analysis of local measures of change (such as the above Jacobian determinants) among a group of subjects, perhaps divided into sub-groups such as patient and control, requires that the different subjects be spatially normalised into correspondence — a challenging task due to the natural anatomical variability in the human brain. Furthermore, statistical analysis, and necessary preprocessing such as data-reduction, should take into account the different factors (or "modes") of variation: spatial, temporal, and individual (perhaps including nested factors such as different subjects within certain sub-groups).


Journal articles

Ridgway, G.; Omar, R.; Ourselin, S.; Hill, D.; Warren, J. & Fox, N.
Issues with threshold masking in voxel-based morphometry of atrophied brains.
(Code available)
Tofts, P. S.; Jackson, J. S.; Tozer, D. J.; Cercignani, M.; Keir, G.; Macmanus, D. G.; Ridgway, G. R.; Ridha, B. H.; Schmierer, K.; Siddique, D.; Thornton, J. S.; Wroe, S. J. & Fox, N. C.
Imaging cadavers: Cold FLAIR and noninvasive brain thermometry using CSF diffusion.
Magn Reson Med
2008, 59, 190-195
Ridgway, G. R.; Henley, S. M. D.; Rohrer, J. D.; Scahill, R. I.; Warren, J. D. & Fox, N. C.
Ten simple rules for reporting voxel-based morphometry studies.
2008, 40, 1429-1435
Camara, O.; Schnabel, J. A.; Ridgway, G. R.; Crum, W. R.; Douiri, A.; Scahill, R. I.; Hill, D. L. G. & Fox, N. C.
Accuracy assessment of global and local atrophy measurement techniques with realistic simulated longitudinal Alzheimer's disease images.
2008, 42, 696-709
Henley, S. M. D.; Wild, E. J.; Hobbs, N. Z.; Warren, J. D.; Frost, C.; Scahill, R. I.; Ridgway, G. R.; MacManus, D. G.; Barker, R. A.; Fox, N. C. & Tabrizi, S. J.
Defective emotion recognition in early HD is neuropsychologically and anatomically generic.
2008, 46, 2152-2160
Camara, O.; Schweiger, M.; Scahill, R.; Crum, W.; Sneller, B.; Schnabel, J.; Ridgway, G.; Cash, D.; Hill, D. & Fox, N.
Phenomenological Model of Diffuse Global and Regional Atrophy Using Finite-Element Methods.
Medical Imaging, IEEE Transactions on
2006, 25, 1417-1430

Conference papers

Modat, M., Ridgway, G., Taylor, Z., Hawkes, D., Fox, N. & Ourselin, S.
A Parallel-friendly Normalised Mutual Information Gradient for Free-Form Deformation.
SPIE Medical Imaging
(Please email for pre-print)
Ridgway, G.; Camara, O.; Scahill, R.; Crum, W.; Whitcher, B.; Fox, N. & Hill, D.
Longitudinal Voxel-Based Morphometry with Unified Segmenation: Evaluation on simulated Alzheimer's disease.
Medical Image Understanding and Analysis
2007, 201-205
(Please email for pre-print)
Camara, O.; Scahill, R.; Crum, W.; Schnabel, J.; Ridgway, G.; Hill, D. & Fox, N.
Evaluation of local and global atrophy measurement techniques with simulated Alzheimer's disease images.
Medical Image Understanding and Analysis
2007, 16-20
(MIUA Best Paper Award)
(Please email for pre-print)
Camara, O.; Scahill, R. I.; Schnabel, J. A.; Crum, W. R.; Ridgway, G. R.; Hill, D. L. G. & Fox, N. C.
Accuracy assessment of global and local atrophy measurement techniques with realistic simulated longitudinal data.
Med Image Comput Comput Assist Interv
2007, 10, 785-792
Camara-Rey, O.; Sneller, B. I.; Ridgway, G. R.; Garde, E.; Fox, N. C. & Hill, D. L. G.
Simulation of acquisition artefacts in MR scans: effects on automatic measures of brain atrophy.
Med Image Comput Comput Assist Interv
2006, 9, 272-280

Conference abstracts/posters

Ridgway, G. R.; Whitcher, B.; Hill, D. L. G. & Fox, N. C.
Longitudinal Multivariate Tensor- and Searchlight-Based Morphometry Using Permutation Testing.
14th annual meeting of the Organization for Human Brain Mapping
(NIH Travel Award)
Nichols, T.; Ridgway, G.; Webster, M. & Smith, S.
GLM Permutation - Nonparametric inference for arbitrary general linear models.
14th annual meeting of the Organization for Human Brain Mapping
Ridgway, G. R.; Scahill, R. I.; Hill, D. L. G. & Fox, N. C.
A Comparison of Voxel Compression Mapping and Longitudinal Voxel-Based Morphometry.
13th annual meeting of the Organization for Human Brain Mapping
Scahill, R.; Ridgway, G.; Black, R.; Grundman, M.; Hill, D. & Fox, N.
ICAD IC-104-01 Regional distribution of grey matter changes in Abeta (AN1792) immunized patients with AD: A voxel-based morphometry analysis.
Alzheimer's & Dementia: The Journal of the Alzheimer's Association
2006, 2, 654-654
Ridgway, G.; Fox, N. & Hill, D.
Looking for patterns in brain atrophy - principal component analysis of structural MR images.
MIAS-IRC Spring-School, Oxford



Other contributions

I frequently offer help on the mailing lists for SPM and FSL, have helped to edit parts of the SPM WikiBook, and have contributed to CMIC's internal Wiki.


Ged Ridgway
Centre for Medical Image Computing
Department of Medical Physics
Malet Place Engineering Building
University College London
Gower Street
London WC1E 6BT
United Kingdom

Tel: +44 (0) 20 7679 0218
Fax: +44 (0) 20 7679 0225
Email: Ged(dot)Ridgway(at)gmail(dot)com

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