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
