Over-parametric convolution and attention mechanism-fused pleural effusion tumor cell clump segmentation network

目的 胸腔积液肿瘤细胞团块的分割对肺癌的筛查有着积极作用。胸腔积液肿瘤细胞团块显微图像存在细胞聚集、对比度低和边界模糊等问题,现有网络模型进行细胞分割时无法达到较高精度。提出一种基于UNet网络框架,融合过参数卷积与注意力机制的端到端语义分割模型DOCUNet (depthwise over-parameterized CBAM UNet)。方法 将UNet网络中的卷积层替换为过参数卷积层。过参数卷积层结合了深度卷积和传统卷积两种卷积,保证网络深度不变的同时,提高模型对图像特征的提取能力。在网络底端的过渡区域,引入结合了通道注意力与空间注意力机制的注意力模块CBAM (convolutional block attention module),对编码器提取的特征权重进行再分配,增强模型的分割能力。结果 在包含117幅显微图像的胸腔积液肿瘤细胞团块数据集上进行5折交叉实验。平均IoU (intersection over union)、Dice系数、精确率、召回率和豪斯多夫距离分别为0.858 0、0.920 4、0.928 2、0.920 3和18.17。并且与UNet等多种已存在的分割网络模型进行对比,IoU、Dice系数和精确率、召回率相较于UNet提高了2.80%、1.65%、1.47%和1.36%,豪斯多夫距离下降了41.16%。通过消融实验与类激活热力图,证明加入CBAM注意力机制与过参数卷积后能够提高网络分割精度,并能使网络更加专注于细胞的内部特征。结论 本文提出的DOCUNet将过参数卷积和注意力机制与UNet相融合,实现了胸水肿瘤细胞团块的有效分割。经过对比实验证明所提方法提高了细胞分割的精度。;Objective Lung cancer-related early detection and intervention is beneficial for lowering mortality rates. Pleural effusion symptoms,and tumor cells and tumor cell masses can be sorted out in relevant to pleural effusion and its metastatic contexts. The detection of tumor cells in pleural effusion can be recognized as an emerging screening tool for lung cancer for early-stage intervention. One of the key preprocessing steps is focused on the precise segmentation of tumor cell masses in related to pleural fluid tumor cells. However,due to severe tumor cell masses-between overlapping and adhesion,unclear cell-to-cell spacing,and unstable staining results of tumor cells in pleural effusion are challenged to be resolved using conventional staining methods,manual micrographs of unstained pleural fluid tumor clumps for cell clump segmentation derived of experienced and well-trained pathologists. But,it still has such problems of inefficiency and the inevitable miss segmentation due to its labor-intensive work. In recent years,computer vision techniques have been developing intensively for optimizing the speed and accuracy of image analysis. Traditional methods for segmenting cellular microscopic images are carried out,including thresholding and such algorithms of clustering-based,graph-based,and active contouring. However,these methods are required for image downscaling,and they have the limitations of undeveloped graphical features. Convolutional neural network(CNN) based deep learning can be used to automatically find suitable features for image segmentation tasks nowadays. The UNet is derived from the end-to-end full convolutional network (FCN) structure,and it is widely used in medical image segmentation tasks due to its unique symmetric encoder and decoder network structure to get the segmentation result relevant to location information of the segmented target,in which arbitrary size image input and equal size output image can be yielded for arbitrary size image input and equal size output image. We develop a new CNN-based UNet network structure(DOCUNet) to perform tumor cell segmentation in pleural effusion,which can be focused on the integrated depthwise over-parameterized convolution(DO-conv) and channel and spatial attention convolutional block attention module(CBAM). Method The network is developed and divided into three sections:encoder,feature enhancer,and decoder. The encoder consists of a convolution operation and a down-sampler, and a hybrid of depthwise convolution and vanilla convolution is demonstrated in terms of depthwise over-parameterized convolution(DO-conv) based convolution operation rather than vanilla convolution. In practice,to get the final image features extraction,the first stage of feature extraction is obtained by depthwise convolution along the feature dimension of the input image and followed by a vanilla convolution operation. This design improves the network's ability to extract features from cell clumps while keeping the output image size constant,and it addresses the issue of unclear features caused by severe intercellular adhesion. For the transition to the decoder,the CBAM attention module is inserted as a feature enhancer in the last layer of the encoder. The CBAM attention module is based on the channel attention mechanism,and the spatial attention mechanism is used to redistribute the weights of the encoder's high-dimensional features through suppressing other related cells-interfered background features and enhancing the network's utilization of the tumor cells'internal features. For the purpose of feature redistribution,channel and spatial-generated attention maps are pointed multiplied with the input features. The use of jump connections in the decoder allows the network to learn features at multiple scales contextual information. Our research is affiliated to Tianjin Medical University's microscopic images of tumor cell masses in pleural effusion. For the training sample set,80 percent of the 117 images collection with completed labeling is chosen in random. After data enhancement,20% of the images collection is chosen as the test sample set. The framework for building the model is chosen as Pytorch. The training is carried out on an NVIDIA RTX 3090 GPU. Each of loss function is binary cross entropy(BCE),the batch size is 4,and Adam is used as the optimizer based on an initial learning rate of 0. 003,1,and 2 of 0. 9 and 0. 999. Result To validate the proposed method's effectiveness,the network models of all the five sort of semantic segmentation networks UNet,UNet++,ResUNet,Attention-UNet,UNet3+ and U2Net are involved for its comparative experiments using the same test sample set,and five sort of measurements of intersection over union (IoU),Dice coefficient,precision,recall and Hausdorff distance,as evaluation metrics,are used to evaluate its segmentation results. For each of the five evaluation metrics,the proposed network is valued and yielded of 0. 858 0, 0. 920 4, 0. 928 2,0. 920 3 and 18. 17. Compared to UNet,first of four measures are improved by 2. 80,1. 65,1. 47 and 1. 36 percent each. The Hausdorff distance is decreased by 41. 16%. The proposed network's segmentation results are visually closer to ground truth further,and the segmentation is clearer than other cell boundary-related models to a certain extent. The SEG-GradCAM-like activation heat maps-relevant ablation experiments is demonstrated that the proposed method can improve the network's feature extraction ability,for which the network is allowed to focus on more on the internal features of tumor cells while suppressing irrelevant feature information in the image background. Conclusion To achieve effective tumor cell cluster segmentation in pleural effusion,our DOCUNet is developed in terms of an attention mechanism and a UNet-integrated depthwise over-parameterized convolution. Comparative experiments demonstrate that the proposed method can be used to improve cell segmentation accuracy and its contexts further.