My PhD Story

Spring 2002 - Spring 2005
Department of Medical Physics, Velindre Cancer Centre
Department of Medical Physics & Bioengineering, University of Wales

My research work: a Lay(wo)man's Introduction (.pdf)
Highlights from my PhD Thesis: as presented during viva (.pdf)
My PhD Story: as presented at the Royal Marsden / Institute of Cancer Research Nov 200 (.pdf)

MONTE CARLO PORTAL DOSIMETRY

Acknowledgments

I thank 
- Cancer Research Wales and Yr Ysgol Uwchradd Tregaron, for funding. 
- Geraint Lewis and Cyril Smith, for the incredible opportunities. 
- Emiliano Spezi, for the tradition of excellence. 
- Jeffrey Siebers, for co-supervising part of the work (Chapter 6). 
- Paul Keall et al. at VCU and Phil Evans et al. at ICR/RMH, for imaging facilities and helpful discussion. 
- Frank Verhaegen and Amanda Barry, for reviewing the thesis. 
- Rebecca Cufflin, for proof-reading the thesis. 
- Jonathan Giddy, for facilitating High Throughput Computing services. 
- colleagues at Velindre Cancer Centre, for friendship and tremendous support. 
- Richard Jarvis, for assistance with image acquisition. 
- Mel Jones et al., for making the phantoms. 
- Andrew Edwards, for fixing the bike. 
- colleagues in the scientific community far and near, for encouragement. 
- housekeepers and porters at Neuadd Meirionnydd, for laughter. 
- Sr Hermine, for being an inspiration still. 
- Dato Dr Sivananthan and the late Dato  Dr Pathmanathan, for medical care when I was tiny. 
- physics, for 16 years of fascination. 
- Brecon Beacons, for your contours of beauty. 
- and the ponies, for the rhythm. 
- friends and family 7000 miles away, for blessings. 
- Sayang, for sayang.

This project developed a solution for verifying external photon beam radiotherapy. The solution is based on a calibration chain for deriving portal dose maps from acquired portal images, and a calculation framework for predicting portal dose maps. Quantitative comparison between acquired and predicted portal dose maps accomplishes both geometric (patient positioning with respect to the beam) and dosimetric (2D fluence distribution of the beam) verifications. A disagreement would indicate that beam delivery had not been according to plan. The solution addresses the clinical need for verifying radiotherapy both pre-treatment (without patient in the beam) and on-treatment (with patient in the beam). Medical linear accelerators mounted with electronic portal imaging devices (EPIDs) were used to acquire portal images. Two types of EPIDs were investigated: the amorphous silicon (a-Si) and the scanning liquid ion chamber (SLIC). The EGSnrc family of Monte Carlo codes were used to predict portal dose maps by computer simulation of radiation transport in the beam-phantom-EPID configuration. Monte Carlo simulations have been implemented on several levels of High Throughput Computing (HTC), including the Grid, to reduce computation time. The solution has been tested across the entire clinical range of gantry angle, beam size (5 cm x 5 cm to 20 cm x 20 cm), beam-patient and patient-EPID separations (4 cm to 38 cm). In these tests of known beam-phantom-EPID configurations, agreement between acquired and predicted portal dose profiles was consistently within 2% of the central axis value. This Monte Carlo portal dosimetry solution therefore achieved combined versatility, accuracy and speed not readily achievable by other techniques.

Chapter 1   Introduction
Chapter 2   Electronic Portal Imaging
Chapter 3   Monte Carlo Radiation Transport
Chapter 4   Simulation of Linac Sources
Chapter 5   A Monte Carlo Solution
Chapter 6   Optimisation of Monte Carlo Simulations
Chapter 7   Practical Aspects of Image Acquisition
Chapter 8   High Throughput Computing
Chapter 9   Conclusions

Convocation / degree ceremony

That was in February 2006 at St. David's Hall. I wondered whether to attend...

If it isn't a sacrament, a ceremony is only a ceremony.
Do convocations need visibly disabled achievers to prove to the world? No! The world needs testimonies of disabled persons who aren't bitter/hardened. The world does not need testimonies of disabled persons who can study.
Of course, the noble endeavour for academic excellence deserves every reverence. This is strong enough a reason to be there.

In the end, I decided to attend because my father couldn't go up the stage and do the catwalk himself. The ceremony turned out to be a complete waste of time. I felt stupid and wondered how, people who regard themselves educated and mighty, make a fool of themselves by putting on such unnatural outfits. There was nothing solemn about the ceremony - well, Cardiff is a football city anyway:

Parents/relatives/friends cheered and whistled as they would do at football matches at the Wales Millennium Stadium.
Some graduants went up the stage in rugged jeans.
Toddlers were squeaking away through the ceremony. I love toddlers making a fuss in the church - that's a healthy sign of life and growth. But sorry, not at a convocation please.
There was nothing about academic excellence at all. It was just a mere collection of individuals feeling great about themselves, which is stupid.

I regret not to have attended the degree ceremony at the University of Surrey. Surrey would have known how to hold a p-r-o-p-e-r degree ceremony p-r-o-p-e-r-l-y, with respect and dignity. I did attend the convocation at Universiti Sains Malaysia and it was decent and respectful -- nothing like the hooligans at Cardiff University!

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My PhD Story

MONTE CARLO PORTAL DOSIMETRY

download thesis (6.3M .pdf)

Acknowledgments

Abstract

Table of contents

Convocation / degree ceremony

google th!s site