Advanced tomographic reconstruction methods for diffuse optical imaging of cerebral haemodynamic response

Diffuse Optical Tomography (DOT) is a relatively new medical imaging modality which allows the simultaneous monitoring of both oxyhaemoglobin and deoxyhaemoglobin, and this is achieved without requiring external contrast agents, because in DOT, the intrinsic absorption and scattering properties of tissue are exploited. Other important features include the fast data acquisition, the relatively low cost, the portability and compactness of the equipment and the non-ionizing radiation which is harmless to the human being. All these features make DOT, an excellent candidate for the continuous monitoring of brain oxymetry. On the other hand, DOT also presents some important disadvantages such as the low spatial resolution and the high computational power required to produce images. The aim of this research was to apply non linear signal processing techniques and analysis methods to obtain significant improvements in brain imaging. The main contributions include: the establishment of a methodology for the incorporation of functional and anatomical a priori information based on MRI scans and physiology assessments; the development of a novel method for fast image reconstruction in DOT based on the use of reduced-order models of the propagation of light; a comparative study of two model representation, namely polynomial and Radial Basis Function (RBF) reduced- order models and an investigation on the applicability of these methods in three-dimensional imaging. Several examples demonstrate the effectiveness and applicability of the new methods, including the experimental validation of the proposed algorithms. Results indicate significant improvement on the spatial resolution and localization accuracy of brain haemodynamics, but more importantly, the feasibility of real-time tomographic monitoring of brain functioning. This work is a contribution to make the use of DOT possible in clinical environments. The ultimate purpose is to develop an inexpensive noninvasive device, whose portability and compactness allows real-time monitoring of brain oxymetry at the patient's bedside for extended periods.EThOS - Electronic Theses Online ServiceGBUnited Kingdo