Investigations into hyperspectral and hybrid-optical imaging for bio-applications
Lim, Hoong Ta
Date of Issue2017
School of Mechanical and Aerospace Engineering
Bio-imaging is of paramount importance in modern medical practices which can be used to acquire unique characteristics of diseases in their early stages so that medical diagnosis and treatment can begin early. This can lead to a better prognosis rate thereby offering potential possibilities for saving many lives. Two diseases, which have been at the forefront of researchers in the recent past due to their probability of cure if detected early, are colon cancer and uveal melanoma. This thesis aims to investigate the potential of two main imaging modalities, hyperspectral imaging and photoacoustic imaging, individually or by hybrid approach, for diagnosis of colon cancer and uveal melanoma, respectively. A pushbroom hyperspectral imager with user-selectable region of interest within the field of view of a video camera has been proposed and successfully demonstrated. The benefits of having user-selectable region of interest include no unwanted scanning and minimal data acquisition time. A snapshot hyperspectral video-endoscope is also developed using a custom-fabricated two-dimensional to one-dimensional fiber bundle. It converts a pushbroom hyperspectral imager into a snapshot configuration. It can be inserted into the colon for minimally invasive and in vivo investigations for the detection of cancer. The three-dimensional datacubes can provide vast amount of information, which includes the spatial features (shape and size), spectral signatures, speed and direction of the imaged samples. Further, a hyperspectral photoacoustic spectroscopy system to acquire the normalised optical absorption coefficient spectrum of highly-absorbing bio-samples is researched and developed. This allows the characterisation of healthy iris and uveal melanoma in the iris using photoacoustic method. Along this line, a probe-based hybrid-modality imaging system was also configured and its feasibility was demonstrated. The integrated system uses photoacoustic imaging and ultrasound imaging to provide complementary absorption and structural information, respectively. Gold nanocages are used as photoacoustic contrast agents, giving stronger photoacoustic signals from the iris.