Sammendrag
Capsule endoscopy is about to become an alternative to traditional colonoscopy. One uses a
wireless camera to visualize the gastrointestinal (GI) tract. A 3D model based on image sequences obtained
from wireless capsule endoscopy (WCE) can be helpful to diagnose or analyse areas of interests. We have
therefore investigated the possibility to provide enhanced viewing for gastroenterologists by reconstructing
3D shapes from WCE images. The study is done on virtual graphics-based models of human GI regions. The
shape from shading (SFS) method is applied to colon images and the quality of the reconstructed shapes is
compared with ground truth models. WCE images suffer from uneven and dim illumination due to point light
source. Therefore, we provide a method based on surface normals from reconstructed 3D models to enhance
contrast particularity in images capturing larger depths by changing the illumination from point light to
directional light. Images of different resolution are also tested to evaluate their effect on the quality of the 3D
reconstruction. We have also tested the shape from focus (SFF) method, a possibility for future WCEs, and
compared the results with SFS. Finally, enhanced images and 3D shapes recovered with both methods have
been evaluated by gastroenterologists through subjective experiments. Objective experiments indicate that
both methods are capable of reconstructing the 3D shapes of colon images successfully, but the SFF method
is better at retaining details in the reconstructed models than the SFS method. Subjective experiments show
that contrast enhanced images are highly preferred over original images. Also, having the reconstructed 3D
models in addition to the images during evaluation is found to be very useful by gastroenterologists and
sometimes even being preferred over the original image.
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