Time resolved optical tomography for the detection and specification of breast disease

This thesis describes the evaluation of time-resolved optical tomography for detecting and specifying breast disease. Optical tomography involves transilluminating the breast using near infrared (NIR) light. Characteristic absorption by oxy- and deoxy-haemoglobin at NIR wavelengths can be exploited to yield oxygen saturation and blood volume information. This information may provide a distinction between the high vascularisation often associated with malignant lesions and benign or normal breast tissue. A 32 channel time-correlated single photon counting system is utilised to perform a series of investigations on both healthy volunteers and patients with pre-diagnosed lesions. Specific datatypes, extracted from a histogram of the times of flight of photons across the breast, are used to reconstruct images of the optical properties (absorption and reduced scattering coefficients). The reconstruction is performed using a non-linear, finite element based algorithm. Two patient interfaces are assessed. The first system is based on two rings of different diameters to which source and detector bundles are attached. A study involving 24 volunteers is performed. Images displaying heterogeneous features that are unique to specific healthy volunteers, and reproducible over time, are presented. Pre-diagnosed benign lesions are identified in most cases, although they are not always the most dominant feature. A single tumour is identified as a dominant increase in absorption. Additionally, the recovery of tissue post Interstitial Laser Photocoagulation (ILP) treatment of a fibroadenoma is successfully monitored in a single study. A second system based on a hemisphere filled with a coupling fluid is investigated. Preliminary investigations into the optimal optical properties of the coupling fluid and reconstruction techniques are also performed. The first investigations on healthy volunteers are presented. Initial findings suggest that this method provides superior information to the ring system due to its three dimensional capability and its ability to provide consistent coupling