The Australian Optical Society 

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  • 19 Feb 2019
  • 2:30 PM - 4:30 PM
  • New Horizons, G29, 20 Research Way, Clayton

2:30 pm - 3:00 pm: Dr. Thomas Li (University of Canterbury, NZ)

Title (Part 1):  Improving Signal to Noise by Near-Field Dual-Energy X-ray Phase Retrieval (~20 Mins)

Title (Part 2):  Machine Learning Image Classification and Segmentation for Road and Dental Applications (~5 Mins)


(Part1) Propagation-based phase contrast imaging and phase retrieval can improve the signal to noise ratio (SNR). This is of great importance for applications in medicine and biology. However, for phase retrieval from one energy measurement, assumptions must be made about the object. To avoid those assumptions, we use two measurements collected at the same propagation distance but with different X-ray energies. Phase retrieval is then performed by incorporating the Alvarez Macovski model that models the X-ray interaction as photoelectric and Compton scattering. We show that a Multi-grid Linear Iterative phase retrieval method keeps similar spatial resolution, reduces phase contrast fringes, while improves the SNR by a factor of 2 to 10 corresponds to an X-ray dosage reduction of 4 to 100. Furthermore, it allows us to separate our object into two known projected material thickness.

(Part 2) An overview about Thomas' work with the New Zealand Transportation Authority (NZTA) for labelling road surfaces and road signs, and his collaboration in Australia regarding AI dental check-up through image processing and machine learning.

3:00 pm – 3.30 pm: Dr. Matthew Dimmock (Monash University)

Title: Validation of a Geant4 model of the X-ray Fluorescence Micro-probe at the Australian synchrotron


A Geant4 Monte Carlo simulation of the X-ray Fluorescence Micro-probe (XFM) end-station at the Australian Synchrotron has been developed. The simulation is required for optimization of the scan configuration and reconstruction algorithms. As part of the simulation process, a Gaussian beam model was developed to describe the beam evolution as a function of propagation distance. Experimental validation of this simulation has tested the efficacy for use of the low-energy physics models in Geant4 for this synchrotron-based technique. The observed spectral distributions calculated in the 384 pixel Maia detector, positioned in the standard back-scatter configuration, were compared with those obtained from experiments performed at three incident X-ray beam energies: 18.5, 11.0 and 6.8 keV. Discrepancies were quantified in the multiple-scatter tail of the Compton continuum.

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