论文标题

深度学习方法,使用蒙版的图像建模进行重建,以重建不足的K空间

A Deep Learning Approach Using Masked Image Modeling for Reconstruction of Undersampled K-spaces

论文作者

Larsen, Kyler, Pal, Arghya, Rathi, Yogesh

论文摘要

磁共振成像(MRI)扫描既耗时又不稳定,因为患者长时间仍在狭窄的空间中。为了减少扫描时间,一些专家已经尝试了不足采样的K空间,试图使用深度学习来预测完全采样的结果。这些研究报告说,可以节省多达20至30分钟的扫描,这需要一个小时或更长时间。但是,这些研究都没有探索使用掩盖图像建模(MIM)预测MRI K空间缺失部分的可能性。这项研究利用了11161个从Facebook的FastMRI数据集中重建的MRI和膝关节MRI图像的K空间。这使用基线移位窗口(SWIN)和视觉变压器体系结构测试了现有模型的修改版本,该窗口和视觉变压器体系结构可在未采样的K空间上使用MIM来预测完整的K空间,从而预测完整的MRI图像。使用Pytorch和Numpy库进行修改,并发布到GitHub存储库。模型重建K空间图像后,应用了基本的傅立叶变换来确定实际的MRI图像。一旦模型达到稳态,对超参数的实验有助于实现重建图像的精确度。通过L1丢失,梯度归一化和结构相似性值评估了该模型。该模型产生了L1损耗值平均为<0.01的重建图像,训练完成后梯度归一化值<0.1。重建的K空间在训练和验证中产生了99%以上的结构相似性值,并通过完全采样的K空间进行了验证,而验证损失在0.01以下持续下降。这些数据强烈支持算法可用于MRI重建的想法,因为它们表明该模型的重建图像与原始的,完全采样的K空间非常吻合。

Magnetic Resonance Imaging (MRI) scans are time consuming and precarious, since the patients remain still in a confined space for extended periods of time. To reduce scanning time, some experts have experimented with undersampled k spaces, trying to use deep learning to predict the fully sampled result. These studies report that as many as 20 to 30 minutes could be saved off a scan that takes an hour or more. However, none of these studies have explored the possibility of using masked image modeling (MIM) to predict the missing parts of MRI k spaces. This study makes use of 11161 reconstructed MRI and k spaces of knee MRI images from Facebook's fastmri dataset. This tests a modified version of an existing model using baseline shifted window (Swin) and vision transformer architectures that makes use of MIM on undersampled k spaces to predict the full k space and consequently the full MRI image. Modifications were made using pytorch and numpy libraries, and were published to a github repository. After the model reconstructed the k space images, the basic Fourier transform was applied to determine the actual MRI image. Once the model reached a steady state, experimentation with hyperparameters helped to achieve pinpoint accuracy for the reconstructed images. The model was evaluated through L1 loss, gradient normalization, and structural similarity values. The model produced reconstructed images with L1 loss values averaging to <0.01 and gradient normalization values <0.1 after training finished. The reconstructed k spaces yielded structural similarity values of over 99% for both training and validation with the fully sampled k spaces, while validation loss continually decreased under 0.01. These data strongly support the idea that the algorithm works for MRI reconstruction, as they indicate the model's reconstructed image aligns extremely well with the original, fully sampled k space.

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