Automatic lung segmentation with severe pathology plays a significant role in the clinical application, which can save physicians’ efforts to annotate lung anatomy. Since the lung has fuzzy boundary in low-dose computed tomography (CT) images, and the tracheas and other tissues generally have the similar gray value as the lung, it is a challenging task to accurately segment lung. How to extract key features and remove background features is a core problem for lung segmentation. This paper introduces a novel approach for automatic segmentation of lungs in low-dose CT images. First, we propose a contrastive attention module, which generates a pair of foreground and background attention maps to guide feature learning of lung and background separately. Second, a triplet loss is used on three feature vectors from different regions to pull the features from the full image and the lung region close whereas pushing the features from background away. Our method was validated on a clinical data set of 78 CT scans using the four-fold cross validation strategy. Experimental results showed that our method achieved more accurate segmentation results than that of state-of-the-art approaches.
Accurate lung tumor delineation plays an important role in radiotherapy treatment planning. Since the lung tumor has poor boundary in positron emission tomography (PET) images, it is a challenging task to accurately segment lung tumor. In addition, the heart, liver, bones and other tissues generally have the similar gray value as the lung tumor, therefore the segmentation results usually have high false positive. In this paper, we propose a novel and efficient fully convolutional network with a trainable compressed sensing module and deep supervision mechanism with sparse constraints to comprehensively address these challenges; and we call it fully convolutional network with sparse feature-maps composition (SFC-FCN). Our SFC-FCN is able to conduct end-to-end learning and inference, compress redundant features within channels and extract key uncorrelated features. In addition, we use deep a supervision mechanism with sparse constraints to guide the features extraction by a compressed sensing module. The mechanism is developed by driving an objective function that directly guides the training of both lower and upper layers in the network. We have achieved more accurate segmentation results than that of state-of-the-art approaches with a much faster speed and much fewer parameters.
Automatic organ localization plays a significant role in medical image segmentation. This paper introduces a novel approach for simultaneous and automatic two surface detection of renal cortex from contrast enhanced abdominal CT scans. The proposed framework is an integrated procedure consisting of three main parts: (i) cortex model training, both two shape variabilities are detected using principal components analysis from the manual annotation, and dual shape dictionaries and appearance dictionaries are constructed; (ii) outer mesh reconstruction, the initialized outer mesh is iteratively deformed to the target boundary; (iii) inner mesh reconstruction, the inner mesh can be reconstructed using the same deformation coefficients and similarity transformation of the outer mesh with the inner mesh shape dictionary. Our method was validated on a clinical data set of 37 CT scans using the leave-one-out cross validation strategy. The proposed method has improved the overall segmentation accuracy of Dice similarity coefficient to 91.95%±3.15% for renal cortex segmentation.
Accurate lung segmentation is of great significance in clinical application. However, it is still a challenging task due to its complex structures, pathological changes, individual differences and low image quality. In the paper, a novel shape dictionary-based approach, named active shape dictionary, is introduced to automatically delineate pathological lungs from clinical 3D CT images. The active shape dictionary improves sparse shape composition in eigenvector space to effectively reduce local shape reconstruction error. The proposed framework makes the shape model to be iteratively deformed to target boundary with discriminative appearance dictionary learning and gradient vector flow to drive the landmarks. The proposed algorithm is tested on 40 3D low-dose CT images with lung tumors. Compared to state-of-the-art methods, the proposed approach can robustly and accurately detect pathological lung surface.
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