Robust feature tracking is a requirement for many computer vision tasks such as indoor robot navigation. However, indoor scenes are characterized by poorly localizable features. As a result, indoor feature tracking without artificial markers is challenging and remains an attractive problem. We propose to solve this problem by constraining the locations of a large number of nondistinctive features by several planar homographies which are strategically computed using distinctive features. We experimentally show the need for multiple homographies and propose an illumination-invariant local-optimization scheme for motion refinement. The use of a large number of nondistinctive features within the constraints imposed by planar homographies allows us to gain robustness. Also, the lesser computation cost in estimating these nondistinctive features helps to maintain the efficiency of the proposed method. Our local-optimization scheme produces subpixel accurate feature motion. As a result, we are able to achieve robust and accurate feature tracking.
In this paper we present a graph cuts based segmentation technique that incorporates the domain knowledge based fuzzy inference system to find the prostate boundary more accurately. By using this prior knowledge, we increase the robustness of the algorithm at weak boundaries which are common in ultrasound images. Also in traditional graph cuts algorithm, corrections on segments will be done by user after the first run, but in the proposed method there is no user interaction after initialization and we use the priors to add hard constraints for the second run of the graph cuts.
Ultrasound imaging is a popular imaging modality due to a number of favorable properties of this modality. However, the poor quality of ultrasound images makes them a bad choice for segmentation algorithms. In this paper, we present a semi-automatic algorithm for organ segmentation in ultrasound images, by posing it as an energy minimization problem via appropriate definition of energy terms. We use graph-cuts as our optimization algorithm and employ a fuzzy inference system (FIS) to further refine the optimization process. This refinement is achieved by using the FIS to incorporate domain knowledge in order to provide additional constraints. We show that by integrating domain knowledge via FIS, the accuracy is improved significantly so that further manual refinement of object boundary is often unnecessary. Our algorithm was applied to detect prostate and carotid artery boundaries in clinical ultrasound images and shows the success of the proposed approach.
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