RESUMO
OBJECTIVE: To evaluate "panoramic image stitching" for cystoscopy, a novel technique to augment a urologist's field of view transoperatively in real-time during a cystoscopic "keyhole" procedure, 3-D bladder phantoms provide a suitable setting. Thus, the objective is the evaluation of different 3-D printed bladder phantoms with respect to their ability to be used for extended experiments of panoramic cystoscopy. MATERIALS AND METHODS: Five bladder phantoms with different geometries, surface textures, stiffness and materials were assessed with rigid 0- and 30-degree lenses and a video-cystoscope regarding suitability for image stitching. For panoramic image generation, we use an established real-time stitching approach successfully applied to retrospective cystoscopy image sequences from real clinical cases. For evaluation of the experiments two quality criteria were defined, namely 'completeness' (describing the internal area of the phantom that can be stitched), and 'extension' (how far does an acquired panorama extend beyond the assumed 'equator' of the phantom). RESULTS: Panoramas of all phantom and endoscope combinations were computed. Using landmarks (south pole, north pole, equator) in the phantoms, maximum extension of the panoramas was assessed. The computed panoramas yield maximum extensions between 270o (0-degree cystoscope) and 330o (video cystoscope). Deformable phantoms yield larger panoramas than the rigid models. CONCLUSION: In can be concluded that the stitching process works quite well with all evaluated phantoms. Nevertheless, a novel phantom would be needed, combing a deformable, elliptical geometry and real-type vascular texture in the inside, that can be filled with water.
