Statistical aspects of elastic scattering spectroscopy with applications to cancer diagnosis

Elastic scattering spectroscopy (ESS), is a non-invasive and real-time in vivo optical diagnosis technique sensitive to changes in the physical properties of human tissue, and thus able to detect early cancer and precancerous changes. This thesis focuses on the statistical issue on how to eliminate irrelevant variations in the high-dimensional ESS spectra and extract the most useful information to enable the classification of tissue as normal or abnormal. Multivariate statistical methods have been used to tackle the problems, among which principal component discriminant analysis and partial least squares discriminant analysis are the most explored throughout the thesis as general tools for supervised dimension reduction and classification. Customized multivariate methods are proposed in the specific context of ESS. When ESS spectra are measured in vivo by a hand-held optical probe, differences in the angle and pressure of the probe are a major source of variability between the spectra from replicate measurements. A customized spectral pre-treatment called error removal by orthogonal subtraction (EROS) is designed to ameliorate the effect of this variability. This pre-treatment reduces the complexity and increases both the accuracy and interpretability of the subsequent classification models when applied to early detection of cancer risk in Barrett’s oesophagus. For the application of ESS to diagnosis of sentinel lymph node metastases in breast cancer, an automated ESS scanner was developed to take measurements from a larger area of tissue to produce ESS images for cancer diagnosis. Problems arise due to the existence of background area in the image with considerable between-node variation and no training data available. A partially supervised Bayesian multivariate finite mixture classification model with a Markov random field spatial prior in a reduced dimensional space is proposed to recognise the background area automatically at the same time as distinguishing normal from metastatic tissue.EThOS - Electronic Theses Online ServiceGBUnited Kingdo