IEEE Trans Med Imaging. 2021 Mar;40(3):1032-1041. doi: 10.1109/TMI.2020.3045295. Epub 2021 Mar 2.
Anomaly detection refers to the identification of cases that do not conform to the expected pattern, which takes a key role in diverse research areas and application domains. Most of existing methods can be summarized as anomaly object detection-based and reconstruction error-based techniques. However, due to the bottleneck of defining encompasses of real-world high-diversity outliers and inaccessible inference process, individually, most of them have not derived groundbreaking progress. To deal with those imperfectness, and motivated by memory-based decision-making and visual attention mechanism as a filter to select environmental information in human vision perceptual system, in this paper, we propose a Multi-scale Attention Memory with hash addressing Autoencoder network (MAMA Net) for anomaly detection. First, to overcome a battery of problems result from the restricted stationary receptive field of convolution operator, we coin the multi-scale global spatial attention block which can be straightforwardly plugged into any networks as sampling, upsampling and downsampling function. On account of its efficient features representation ability, networks can achieve competitive results with only several level blocks. Second, it's observed that traditional autoencoder can only learn an ambiguous model that also reconstructs anomalies "well" due to lack of constraints in training and inference process. To mitigate this challenge, we design a hash addressing memory module that proves abnormalities to produce higher reconstruction error for classification. In addition, we couple the mean square error (MSE) with Wasserstein loss to improve the encoding data distribution. Experiments on various datasets, including two different COVID-19 datasets and one brain MRI (RIDER) dataset prove the robustness and excellent generalization of the proposed MAMA Net.
异常检测是指识别不符合预期模式的情况,它在各个研究领域和应用领域中都起着关键作用。现有的大多数方法都可以概括为基于异常对象检测和基于重构误差的技术。然而,由于难以定义真实世界中高多样性异常值的范围,以及无法进行推理过程,大多数方法都没有取得突破性的进展。为了解决这些不完善之处,受基于记忆的决策和视觉注意力机制的启发,我们将其作为人类视觉感知系统中选择环境信息的过滤器,在本文中,我们提出了一种基于多尺度注意力记忆和哈希寻址自动编码器网络(MAMA Net)的异常检测方法。首先,为了克服卷积算子受限固定感受野带来的一系列问题,我们提出了多尺度全局空间注意力块,可以直接作为采样、上采样和下采样函数插入到任何网络中。由于其高效的特征表示能力,网络仅使用几个级别的块就能取得有竞争力的结果。其次,我们观察到传统的自动编码器由于在训练和推理过程中缺乏约束,只能学习到一个模糊的模型,该模型对异常值的重建效果也很好。为了解决这个挑战,我们设计了一个哈希寻址记忆模块,该模块证明了异常值会产生更高的重建误差,从而进行分类。此外,我们将均方误差(MSE)与 Wasserstein 损失相结合,以改善编码数据的分布。在包括两个不同的 COVID-19 数据集和一个脑 MRI(RIDER)数据集在内的各种数据集上的实验证明了所提出的 MAMA Net 的稳健性和出色的泛化能力。