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Acknowledgements

Abstract

About the Author

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Improving the Precision of Leg Ulcer Area Measurement with Active Contour Models

 


 

 

 

Timothy David Jones

 

 

 

 

A submission presented in partial fulfilment of the

requirements of the University of Glamorgan/Prifysgol Morgannwg

for the degree of Doctor of Philosophy

 

 

This work was carried out in collaboration with

the Royal National Hospital for Rheumatic Diseases, Bath

and the University Hospital of Wales, Cardiff

 

 

 

 

May 1999

 

 

 

 

"But a Samaritan, as he travelled, came where the man was; and when he saw him, he took pity on him. He went to him and bandaged his wounds, pouring on oil and wine."

Luke 10:33-34

 

 

 

Acknowledgements

I extend warm and hearty gratitude to Prof. B. F. Jones for his supervision and helpful guidance throughout the duration of this project. His careful oversight and concern have been of great benefit to me through a long and sometimes arduous journey. I deeply appreciate the patience and understanding he has shown and in particular for inspiring me to focus the work and complete this thesis.

I would also like to take this opportunity to extend my thanks to both of my second supervisors, Dr. Peter Plassmann and Dr. S. J. Rees, for providing helpful suggestions and advice.

I gratefully acknowledge the assistance of Prof. E. F. J. Ring of the Royal National Hospital for Rheumatic diseases in Bath and Dr. K. G. Harding of the University Hospital of Wales, Cardiff for allowing access to patients and for providing images of leg ulcers.

I am also grateful to Dr. Wyn Williams for his help with variational calculus and to Dr. David Jones for assisting in the design of the manual delineation experiments. Thanks also to Dr. Jamal Ameen for casting a critical eye over the statistical analyses.

This work was partly funded by the Higher Education Funding Council of Wales (HEFCW) under the Development of Research (DevR) initiative.

 

 

Abstract

A leg ulcer is a chronic wound of the skin that, at best, takes many months to fully heal and causes great distress to the patient. Treating leg ulcers places a large financial burden upon the National Health Service in the United Kingdom, estimated to be in excess of £300M annually. Measurement of the size of leg ulcers is a guide to assessing the progress of wound healing, and the use of non-invasive measurement techniques avoids damaging or infecting the wound. The area of a leg ulcer is currently measured by presenting a human observer with a captured video image of a wound, who then uses a mouse or pointing device to delineate the wounded region. Typically, the standard deviation of area measurements taken this way is approximately 5% of the wound area. In addition, different observers can show a bias difference in their area measurements from 3% to 25% of the wound area. It is proposed to reduce the incidence of such errors by using an active contour model to improve the delineation. Four different models are developed by adapting and applying several contributions made to the active contour model paradigm. Novel features include an external force that acts normally, but not tangentially, to the boundary, a new external energy term that promotes homogeneity of the gray level at the edge of the wound and the application of the minimax principle for setting the parameters of an active contour model with piecewise b-spline curves. The algorithms provide the physician with a new and practical tool for producing area measurements with improved precision and are semi-automatic, requiring only a manual delineation to start the algorithm. In most cases, measurement precision is improved by application of the algorithms. Many wounds give rise to measurable bias differences between average manual area measurements and the corresponding algorithmic area measurements, typically averaging 3% to 4% of wound area. With some wounds the bias magnitude can exceed 10% as a result of the contour partly deviating from the true edge of the wound and following a false edge.

 

 

About the Author

Tim D. Jones currently holds the distinguished position of Research Fellow (is that one lump or two ?) with the School of Computing at the University of Glamorgan. In 1993 he obtained the B. Eng. and M. Eng. Degrees in Electrical and Electronic Engineering, graduating with first class honours and a distinction respectively. He received the degree of Doctor of Philosophy in Computing (do you want 'fries' with that ?) from the University of Glamorgan in August 1999. His current research interests are watching television and anything else that requires little enthusiasm or effort (well, that's what doing a Ph. D. did to me, what did yours do to you!?) Dr. Jones is a trustee and secretary of an independent Christian Charity called SWITCH that is committed to the practise of 'Radical Christianity', i.e. a gospel that includes social concern as well as Evangelical and Charismatic principles, ethics and doctrine.

 

 

Errata

This is the perpetually-expanding section

(1) Appendix A, Equation 17

The last row of the matrix should read [-1 -12 7 6]

(2) References

Author surname in the alphabetically-ordered list should read Berriss

 

 

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