基于改进的Mask R-CNN的染色体图像分割框架

针对染色体图像的人工分割耗时费力且当前自动分割方法精度不佳的问题，基于改进的Mask R-CNN提出了一种染色体图像分割框架——Mask Oriented R-CNN，引入方向信息对染色体图像进行实例分割。首先，新增有向包围框回归分支，以预测紧实包围框并获取方向信息；然后，提出新的交并比（IoU）度量——角度加权交并比（AwIoU），从而结合方向信息与边的关系以改进冗余包围框的判据；最后，实现有向卷积通路结构，通过拷贝掩模分支通路并依据实例的方向信息选择训练路径来减少掩模预测中的干扰。实验结果表明，相较于基准模型Mask R-CNN，Mask Oriented R-CNN在IoU阈值为0.5时的平均精度均值指标提升了10.22个百分点，IoU阈值为0.5~0.95时的平均指标提升了4.91个百分点。研究结果显示，Mask Oriented R-CNN框架相较于基准模型取得了更好的染色体图像分割结果，有助于实现染色体图像自动分割。

Chromosome image segmentation framework based on improved Mask R-CNN

The manual segmentation of chromosome images is time-consuming and laborious, and the accuracy of current automatic segmentation methods is not poor. Therefore, based on improved Mask R-CNN (Mask Region-based Convolutional Neural Network), a chromosome image segmentation framework named Mask Oriented R-CNN (Mask Oriented Region-based Convolutional Neural Network) was proposed, which introduced orientation information to perform instance segmentation of chromosome images. Firstly, the regression branch of oriented bounding boxes was added to predict the compact bounding boxes and obtain orientation information. Secondly, a novel Intersection-over-Union (IoU) metric called AwIoU (Angle-weighted Intersection-over-Union) was proposed to improve the criterion of redundant bounding boxes by combining the relationship between the orientation information and edges. Finally, the oriented convolutional path structure was realized to reduce the interference in mask prediction by copying the path of mask branch and selecting the training path according to the orientation information of the instances. Experimental results show that compared with the baseline model Mask R-CNN, Mask Oriented R-CNN has the mean average precision increased by 10.22 percentage points when the IoU threshold is 0.5, and the mean metric increased by 4.91 percentage points when the IoU threshold is from 0.5 to 0.95. Experimental results show that the Mask Oriented R-CNN framework achieves better segmentation results than the baseline model in chromosome image segmentation, which is helpful to achieve automatic segmentation of chromosome images.