Department of Physics

Postgraduate research profiles


Ngie Ung

Phone: (+61 4) 0117 1640


Start date

Feb 2008

Submission date

Feb 2012

Ngie Ung


Adaptation of margins and tolerances: Quantifying the consequences of machine- and patient- related uncertainties in external beam radiotherapy for prostate cancer.


Radiotherapy is important mode of treatment for prostate cancer. Over the past decades, there have been tremendous changes and improvement in the technologies of radiotherapy using linear accelerators. This study specifically look into the adaptation of margins and tolerances to uncertainties in external beam radiotherapy of prostate cancer. In the first stage of this project, comparison will be made on the treatment plans for prostate cancer radiotherapy generated prior and after installation of MLCs in linear accelerators. This part of study will be further extended by introducing MLC errors into 3D conformal radiotherapy and intensity-modulation radiotherapy (IMRT) treatment plans for prostate cancer. The second part of this study will investigate the effect of mechanical uncertainties of the linear accelerators in the tracking algorithm for image-guidance radiotherapy (IGRT) of prostate using fiducial markers. This also includes the investigation of uncertainties in the coincidence of treatment and imaging isocentre. In the final part of the study, the extent of prostate motion and treatment margins will be investigated under different positioning strategies. Formulas for prostate margin will be modeled using the results obtained in the first and second part of the study. This part of study will give us the information on the differences of margins produced by different positioning strategies with different machine- as well as patient-related uncertainties and this information will enhance the knowledge on delineation of planning target volume (PTV) during prostate radiotherapy.

Why my research is important

Adaptation of treatment based on machine- and patient-related uncertainties (and models of uncertainties) allows prostate radiotherapy treatment for individuals to be customized for optimal clinical outcome. Margins and tolerances of treatment which are personalized for every patient will direct quality improvement measures in radiation therapy.


  • Malaysian Ministry of Higher Education
  • University of Malaya


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