KEYWORDS: Image segmentation, Magnetorheological finishing, Magnetic resonance imaging, Medical imaging, Bone, 3D modeling, 3D image processing, Pathology, Image processing, Current controlled current source
In this paper, we present a three-dimensional interactive segmentation method. Unlike most previous interactive
methods which largely depend on user interaction, we exploit a prior knowledge of training data to reduce the
user effort. Based on the prior knowledge, most distinguishable parts of an object are automatically segmented
and labels of some uncertain parts are queried to an user. To systematically model the problem, we combine the
hierarchical Markov random field (HMRF) framework and the active learning scheme. The HMRF framework,
proposed for the automatic manner, simultaneously reflects characteristics of local variations and their global
smoothness, while the active learning scheme improves the efficiency of interactive system. We incorporate the
active learning strategy into the editing step of the HMRF structure in order to find and modify the uncertain
parts after the automatic segmentation. Specifically, the uncertainties of local regions are firstly computed by the
label difference between segmentation candidates. Then, the graph models of the uncertain regions are updated
by the user interaction. Since the HMRF structure constrains the smoothness of local regions and the global
optimality, the segmentation is updated as a whole even though the small numbers of local parts are edited.
The proposed method is applied to the segmentation of femur and tibia in knee MR images for evaluation. The
evaluation demonstrates that the proposed method improves the segmentation efficiency more than the graph
cut based method or manual editing.
Segmentation of bone and cartilage from a three dimensional knee magnetic resonance (MR) image is a crucial
element in monitoring and understanding of development and progress of osteoarthritis. Until now, various
segmentation methods have been proposed to separate the bone from other tissues, but it still remains challenging
problem due to different modality of MR images, low contrast between bone and tissues, and shape irregularity.
In this paper, we present a new fully-automatic segmentation method of bone compartments using relevant bone
atlases from a training set. To find the relevant bone atlases and obtain the segmentation, a coarse-to-fine
strategy is proposed. In the coarse step, the best atlas among the training set and an initial segmentation are
simultaneously detected using branch and bound tree search. Since the best atlas in the coarse step is not
accurately aligned, all atlases from the training set are aligned to the initial segmentation, and the best aligned
atlas is selected in the middle step. Finally, in the fine step, segmentation is conducted as adaptively integrating
shape of the best aligned atlas and appearance prior based on characteristics of local regions. For experiment,
femur and tibia bones of forty test MR images are segmented by the proposed method using sixty training MR
images. Experimental results show that a performance of the segmentation and the registration becomes better
as going near the fine step, and the proposed method obtain the comparable performance with the state-of-the-art
methods.
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