Kaidi Liang
Position
Medical Physics MSc Thesis Student (Clinical)
Qualifications
MSc Part I (Medical Physics), University of Canterbury
Contact Details
Room: 813, Physics and Astronomy
Phone: +64 3 364 2987
Internal Phone: 7544
Email: kaidi.liang@pg.canterbury.ac.nz
Phone: +64 9 373 7599 ext 88833
Email: klia014@aucklanduni.ac.nz
Research
A fibre optics approach to radiation dosimetry, collaboration with the Biophotonics Lab at the University of Auckland, 2011 – 2012
Supervisors: Juergen Meyer and Frederique Vanholsbeeck
Profile
Kaidi Liang graduated from the University of Auckland in 2010 with Bachelor of Technology in Medical Physics and Imaging Technologies, focusing on optics, imaging and other applications of physics in medicine. In the same year he began his MSc in Medical Physics from the University of Canterbury.
The challenge in radiation therapy is to deliver a precise dose of radiation to the target. Several dosimetric techniques are available to measure the ionizing radiation, but they have limitations. In particular, the non-tissue equivalence of the detector housing and the sensitive volume leads to perturbations of the beam fluence and necessitates correction factors. Another constraint placed on the conventional dosimetric techniques is the limited resolution. The above are an issue in small field dosimetry or when high dose gradients are presents, such as in e.g. micro beam radiotherapy. The aim of this project, as a proof of principle, is to develop a fibre optics setup that accurately measures the radiation beam profile and the absolute radiation energy imparted in the given sample. The approach is quasi-calorimetric in nature and is based on one fundamental principle; the energy imparted by the radiation beam is converted into heat in the medium and as the temperature increases, the optical properties of the water also change - effectively a change in the refractive index. If the relationship between the temperature and refractive index is known then the absolute change in refractive index can be related to the temperature change, hence the radiation dose delivered into the phantom. This refractive index can be measured through interferometry by passing a laser beam through the irradiated medium and combined with a reference arm to form an interference pattern to determine the change in the optical path length of the laser beam. The main goal of the project is to investigate the feasibility of a transportable fibre optics setup capable of measuring the dose profile in a water phantom.
