Vision Transformers (ViT)s have recently become popular due to their outstanding modeling capabilities, in particular for capturing long-range information, and scalability to dataset and model sizes which has led to state-of-the-art performance in various computer vision and medical image analysis tasks. In this work, we introduce a unified framework consisting of two architectures, dubbed UNetFormer, with a 3D Swin Transformer-based encoder and Convolutional Neural Network (CNN) and transformer-based decoders. In the proposed model, the encoder is linked to the decoder via skip connections at five different resolutions with deep supervision. The design of proposed architecture allows for meeting a wide range of trade-off requirements between accuracy and computational cost. In addition, we present a methodology for self-supervised pre-training of the encoder backbone via learning to predict randomly masked volumetric tokens using contextual information of visible tokens. We pre-train our framework on a cohort of $5050$ CT images, gathered from publicly available CT datasets, and present a systematic investigation of various components such as masking ratio and patch size that affect the representation learning capability and performance of downstream tasks. We validate the effectiveness of our pre-training approach by fine-tuning and testing our model on liver and liver tumor segmentation task using the Medical Segmentation Decathlon (MSD) dataset and achieve state-of-the-art performance in terms of various segmentation metrics. To demonstrate its generalizability, we train and test the model on BraTS 21 dataset for brain tumor segmentation using MRI images and outperform other methods in terms of Dice score. Code: https://github.com/Project-MONAI/research-contributions

本文提出了一个统一的框架，它由两个体系结构组成，称为UNetFormer，具有基于3D Swin变压器的编码器和卷积神经网络和变压器的解码器。该架构的设计允许在准确性和计算成本之间满足宽范围的权衡要求。使用CT图像进行自我监督预训练，使用Medical Segmentation Decathlon（MSD）数据集进行肝和肝肿瘤分割任务的Fine-tune和测试，并使用MRI图像的BraTS 21数据集进行脑肿瘤分割，并在Dice评分方面优于其他方法。

UNetFormer: 用于三维医学图像分割的统一视觉Transformer模型和预训练框架