Annual Report 2007 - The Australian Nanotechnology Network

Mrs. Xiaoxia Yin (University of Adelaide) – visit to Reading University and
Cambridge University in the U.K.
Xiaoxia is a Postgraduate student and her area of interest is Nanotechnology Driven Advances
in Terahertz Cancer 3D Computed Tomography
The work for this visit will specifically enhance Adelaide’s National T-ray Facility by providing
a 3-D tomographic imaging, based on the non-ionizing and coherent detection characteristics of
terahertz radiation (T-rays), with an aim to achieve images of developing tumors using novel
nanoscale terahertz imaging contrast agents.
Her application was supported by her supervisor Prof Derek Abbot and by Dr Sillas Hadjiloucas
from the University of Reading.
RE: Progress Report in relation to Ms Xiaoxia (Sunny) Yin stay at Cambridge University
This is a report of the work accomplished by Mrs Xiaoxia (Sunny) Yin during my stay at
Cambridge University as I conducted research in the summer term of 2007 as part of my
ARCNN Fellowship (travel and subsistence visiting Scholarship). The scholarship has provided
research training to me while at the same time facilitated collaboration with Professor Lynn
Gladden (Department of Chemical Engineering, Cambridge University) and the Centre for
Biomedical Engineering, Department of Electrical and Electronic Engineering, University of
Adelaide in the area of signal and imaging processing for THz QCL transient spectroscopy.
During my stay at Cambridge, we had long discussions on wavelet decomposition schemes and
the use of an inverse Radon transform algorithm in relation to the imaging processing of THz
QCL transients. Issues related to hardware performance of THz QCL imaging as well as to
experimental techniques were clarified. The use of wavelet based ramp filtered projection was
also discussed and back projection of the filtered sinograms was also considered. The THz QCL
imaging system was applied for the measured data in Cambridge. This experimental procedure
was important to help me further understand the principle of THz QCL for imaging.
As for the specific project regarding THz QCL imaging, we study the local reconstruction of the
region-of-interest (ROI) from a 3D terahertz imaging obtained via a quantum cascade laser
(QCL). It is an important step in the understanding wavelet based techniques and traditional
filtered back projection (FBP) to map terahertz local measurements for deep resolution. The
advantage of local reconstruction is the reduction in the measurement time. Difficulties with the
limited projection angles and image noise, make the development of accurate algorithms
particularly challenging. Segmentation algorithms are
applied on the reconstructed images with low contrast. The
resultant segments from the local reconstructed images are
compared with the the back ground truth to explore the
ability of a QCL to image target object, polystyrene, with
complex contours (a clown's head with hole inside). The
target segments are adjusted via changing the size of the
exposure regions, which means the smaller exposure cannot
reveal a full reconstructed segment. It is found that 3D local
reconstructions of the target (hole) using a QCL take on a
number of different shapes since the various contours of the
target physically distort the measured optical parameters of
the object. Local computed tomography via wavelet is
suitable for the image reconstruction in terahertz frequency
range with lower image quality, which results in lower
misclassification after s egmentation, compared to traditional FBP algorithms.
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