Allain, B.; (2012) Re-localisation of microscopic lesions in their macroscopic context for surgical instrument guidance. Doctoral thesis , UCL (University College London).

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Abstract

Optical biopsies interrogate microscopic structure in vivo with a 2mm diameter miniprobe placed in contact with the tissue for detection of lesions and assessment of disease progression. After detection, instruments are guided to the lesion location for a new optical interrogation, or for treatment, or for tissue excision during the same or a future examination. As the optical measurement can be considered as a point source of information at the surface of the tissue of interest, accurate guidance can be difficult. A method for re-localisation of the sampling point is, therefore, needed. The method presented in this thesis has been developed for biopsy site re-localisation during a surveillance examination of Barrett’s Oesophagus. The biopsy site, invisible macroscopically during conventional endoscopy, is re-localised in the target endoscopic image using epipolar lines derived from its locations given by the tip of the miniprobe visible in a series of reference endoscopic images. A confidence region can be drawn around the relocalised biopsy site from its uncertainty that is derived analytically. This thesis also presents a method to improve the accuracy of the epipolar lines derived for the biopsy site relocalisation using an electromagnetic tracking system. Simulations and tests on patient data identified the cases when the analytical uncertainty is a good approximation of the confidence region and showed that biopsy sites can be re-localised with accuracies better than 1mm. Studies on phantom and on porcine excised tissue demonstrated that an electromagnetic tracking system contributes to more accurate epipolar lines and re-localised biopsy sites for an endoscope displacement greater than 5mm. The re-localisation method can be applied to images acquired during different endoscopic examinations. It may also be useful for pulmonary applications. Finally, it can be combined with a Magnetic Resonance scanner which can steer cells to the biopsy site for tissue treatment.

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