论文标题
3D CNN中的本地旋转不变性
Local Rotation Invariance in 3D CNNs
论文作者
论文摘要
局部旋转不变(LRI)图像分析在许多应用中,尤其是在任意旋转时发生的局部组织结构的医学成像中,尤其是在医学成像中。 LRI在纹理分析中构成了几个突破的基石,包括局部二进制模式(LBP),最大响应8(MR8)和可进入的滤纸。最近提出了全球旋转不变性卷积神经网络(CNN),但在深度学习的背景下,LRI很少研究。 LRI设计允许学习过滤器核算所有方向,从而使可训练的参数和训练数据与标准的3D CNN相比大大降低。在本文中,我们提出和比较了几种具有方向灵敏度的LRI CNN的方法。两种方法使用方向通道(对旋转内核的响应),要么通过明确旋转内核或使用可靠的过滤器来使用方向通道。这些取向通道构成了数据的局部旋转模化表示。跨取向的局部汇总会产生LRI图像分析。可进入的过滤器用于实现3D旋转的精细,有效的采样以及可训练的参数和操作的减少,这要归功于涉及固体球形谐波(SH)的参数表示,这些谐波(SH)是SH的产物,这些SH的产物与相关的径向介绍。我们研究了第三个策略,以获得基于旋转不适式的secs secs shs shs shs shs shs shs sh的第三个策略。评估了所提出的方法,并将其与3D数据集上的标准CNN进行了比较,包括由旋转模式组成的合成纹理体积和CT中的肺结核分类。结果显示了LRI图像分析的重要性,同时导致可训练参数的急剧减少,超过了接受数据增强的训练的标准3D CNN。
Locally Rotation Invariant (LRI) image analysis was shown to be fundamental in many applications and in particular in medical imaging where local structures of tissues occur at arbitrary rotations. LRI constituted the cornerstone of several breakthroughs in texture analysis, including Local Binary Patterns (LBP), Maximum Response 8 (MR8) and steerable filterbanks. Whereas globally rotation invariant Convolutional Neural Networks (CNN) were recently proposed, LRI was very little investigated in the context of deep learning. LRI designs allow learning filters accounting for all orientations, which enables a drastic reduction of trainable parameters and training data when compared to standard 3D CNNs. In this paper, we propose and compare several methods to obtain LRI CNNs with directional sensitivity. Two methods use orientation channels (responses to rotated kernels), either by explicitly rotating the kernels or using steerable filters. These orientation channels constitute a locally rotation equivariant representation of the data. Local pooling across orientations yields LRI image analysis. Steerable filters are used to achieve a fine and efficient sampling of 3D rotations as well as a reduction of trainable parameters and operations, thanks to a parametric representations involving solid Spherical Harmonics (SH), which are products of SH with associated learned radial profiles.Finally, we investigate a third strategy to obtain LRI based on rotational invariants calculated from responses to a learned set of solid SHs. The proposed methods are evaluated and compared to standard CNNs on 3D datasets including synthetic textured volumes composed of rotated patterns, and pulmonary nodule classification in CT. The results show the importance of LRI image analysis while resulting in a drastic reduction of trainable parameters, outperforming standard 3D CNNs trained with data augmentation.