论文标题
与完全卷积网络的语义分割的自适应特征重组和重新校准
Adaptive feature recombination and recalibration for semantic segmentation with Fully Convolutional Networks
论文作者
论文摘要
完全卷积的网络在高效的同时,已经在图像语义分割方面取得了显着的结果。这种效率是由于在单个前向通过中分割几个体素的能力而产生的。因此,特征图中的单元与同一位置的体素之间存在直接的空间对应关系。在卷积层中,内核跨越所有通道,并从中提取信息。我们观察到,通过增加通道的数量随后进行压缩的线性重组可能会增强其判别能力。此外,并非所有特征地图都与所预测的类具有相同的相关性。为了学习渠道间的关系并重新校准了抑制较小相关的通道,在与卷积神经网络的图像分类中提出了挤压和激发块。但是,这并不能很好地适应用于完全卷积网络的分割,因为它们同时分割了几个对象,因此功能映射可能仅在某些位置包含相关信息。在本文中,我们提出了特征的重组和空间自适应的重新校准块,该块适用于使用完全卷积的网络-SEGSE块进行语义分割。通过考虑跨通道信息以及空间相关性,可以重新校准特征图。实验结果表明,重组和重新校准改善了竞争性基线的结果,并在三个不同的问题上概括了:脑肿瘤分割,中风半支柱估计和缺血性中风病变结果预测。在这三个应用程序中,获得的结果具有竞争力或优于最新技术。
Fully Convolutional Networks have been achieving remarkable results in image semantic segmentation, while being efficient. Such efficiency results from the capability of segmenting several voxels in a single forward pass. So, there is a direct spatial correspondence between a unit in a feature map and the voxel in the same location. In a convolutional layer, the kernel spans over all channels and extracts information from them. We observe that linear recombination of feature maps by increasing the number of channels followed by compression may enhance their discriminative power. Moreover, not all feature maps have the same relevance for the classes being predicted. In order to learn the inter-channel relationships and recalibrate the channels to suppress the less relevant ones, Squeeze and Excitation blocks were proposed in the context of image classification with Convolutional Neural Networks. However, this is not well adapted for segmentation with Fully Convolutional Networks since they segment several objects simultaneously, hence a feature map may contain relevant information only in some locations. In this paper, we propose recombination of features and a spatially adaptive recalibration block that is adapted for semantic segmentation with Fully Convolutional Networks - the SegSE block. Feature maps are recalibrated by considering the cross-channel information together with spatial relevance. Experimental results indicate that Recombination and Recalibration improve the results of a competitive baseline, and generalize across three different problems: brain tumor segmentation, stroke penumbra estimation, and ischemic stroke lesion outcome prediction. The obtained results are competitive or outperform the state of the art in the three applications.