BiCFormer: Swin Transformer based model for classification of benign and malignant pulmonary nodules

Abstract Pulmonary cancer is one of the most common and deadliest cancers worldwide, and the detection of benign and malignant nodules in the lungs can be an important aid in the early diagnosis of lung cancer. Existing convolutional neural networks inherit their limitations by extracting global contextual information, and in most cases prove to be less efficient in obtaining satisfactory results. Transformer-based deep learning methods have obtained good performance in different computer vision tasks, and this study attempts to introduce them into the task of computed tomography (CT) image classification of lung nodules. However, the problems of sample scarcity and difficulty of local feature extraction in this field. To this end, we are inspired by Swin Transformer to propose a model named BiCFormer for the task of classifying and diagnosing CT scan images of lung nodules. Specifically, first we introduce a multi-layer discriminator generative adversarial network module for data augmentation to assist the model in extracting features more accurately. Second, unlike the encoder of traditional Transformer, we divide the encoder part of BiCFormer into two parts: bi-level coordinate (BiC) and fast-partial-window (FPW). The BiC module has a part similar to the traditional channel attention mechanism is able to enhance the performance of the model, and is more able to enhance the representation of attention object features by aggregating features along two spatial directions. The BiC module also has a dynamic sparse attention mechanism that filters out irrelevant key-value pairs in rough regions, allowing the model to focus more on features of interest. The FPW module is mainly used to reduce computational redundancy and minimize feature loss. We conducted extensive experiments on the LIDC-IDRI dataset. The experimental results show that our model achieves an accuracy of 97.4% compared to other studies using this dataset for lung nodule classification, making it an effective and competitive method.