Construction rapide d'images panoramiques applicables à l'exploration cystoscopique et à l'endoscopie de fluorescence en cancérologie

Abstract : This work describes a mosaicing algorithm for constructing panoramic images of internal walls of the bladder. Time relating to the construction of panoramic images including the interesting parts must be shorter than that required by a standard cystoscopic examination. The mosaicing algorithm must be robust against lighting conditions, morphologic and texture variations relating to instruments and patient anatomy. These panoramic images could be used by a clinician for guiding further exams, storing non-redundant data and following-up evolution of lesions. The preprocessing of cystoscopic images is the first stage of the algorithm. Preprocessing consists of shading correction and fiber optics pattern attenuation occurring in fiberscope acquired images. The second stage is image registration. The chosen solution consist of cross-correlating images (using their Fourier transforms) in order to have initial translations for an iterative registration algorithm based on the sum of squared differences of images. In the third stage, images are projected in the coordinate system of the panoramic image using global transformations computed with matrices given by the iterative registration. We use a weighted average of pixel intensities to blend visible borders of images produced in the projection process. Numerical results obtained with a phantom and qualitative results obtained with real sequences show that our automatic approach is robust and allows for a fast construction of panoramic images in a period of time that is shorter than the duration of a clinical cystoscopic examination. Our experiments showed that the registration algorithm can handle geometric transformations that are larger than those existing typically in a video-sequence (90% of superposition between successive images in this case)
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Yahir Hernandez Mier. Construction rapide d'images panoramiques applicables à l'exploration cystoscopique et à l'endoscopie de fluorescence en cancérologie. Autre. Institut National Polytechnique de Lorraine, 2007. Français. ⟨NNT : 2007INPL069N⟩. ⟨tel-01752955⟩

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