用生成模型加速新生儿重症监护室MRI,缩短扫描时间。
Diffusion Probabilistic Generative Models for Accelerated, in-NICU Permanent Magnet Neonatal MRI
- 改进网络结构与自监督去噪,适配低信噪比真实数据
- 1.5倍欠采样下重建图像满足临床诊断需求
- 无需重训练即可在两种加速率下运行,适合新生儿MRI
磁共振成像(MRI)可无创评估早年脑部发育异常。在新生儿重症监护室(NICU)使用永磁扫描仪虽能实现危重新生儿的MRI检查,但因信噪比低和接收线圈有限,导致扫描时间长。本文通过扩散概率生成模型加速NICU内新生儿MRI,建立与Aspect Imaging及Sha'are Zedek Medical Center合作的临床1特斯拉新生儿MR图像数据集,提出新训练流程:(1)改造网络以支持多分辨率;(2)用学习到的类别嵌入向量统一训练所有数据;(3)训练前进行自监督去噪;(4)通过平均后验样本重构图像。回溯性欠采样实验验证各方法有效性。由儿科神经放射科医生参与的临床读片研究显示,约1.5倍欠采样数据重建图像已具备临床可用性。结果表明,结合所有数据、去噪预训练与后验样本平均可显著提升重建质量。该生成模型将先验知识与测量模型解耦,在不重训练情况下适用于两种加速率。结论:该方法可有效缩短NICU新生儿MRI扫描时间。
原文摘要 · Abstract (English)
Purpose: Magnetic Resonance Imaging (MRI) enables non-invasive assessment of brain abnormalities during early life development. Permanent magnet scanners operating in the neonatal intensive care unit (NICU) facilitate MRI of sick infants, but have long scan times due to lower signal-to-noise ratios (SNR) and limited receive coils. This work accelerates in-NICU MRI with diffusion probabilistic generative models by developing a training pipeline accounting for these challenges. Methods: We establish a novel training dataset of clinical, 1 Tesla neonatal MR images in collaboration with Aspect Imaging and Sha'are Zedek Medical Center. We propose a pipeline to handle the low quantity and SNR of our real-world dataset (1) modifying existing network architectures to support varying resolutions; (2) training a single model on all data with learned class embedding vectors; (3) applying self-supervised denoising before training; and (4) reconstructing by averaging posterior samples. Retrospective under-sampling experiments, accounting for signal decay, evaluated each item of our proposed methodology. A clinical reader study with practicing pediatric neuroradiologists evaluated our proposed images reconstructed from 1.5x under-sampled data. Results: Combining all data, denoising pre-training, and averaging posterior samples yields quantitative improvements in reconstruction. The generative model decouples the learned prior from the measurement model and functions at two acceleration rates without re-training. The reader study suggests that proposed images reconstructed from approximately 1.5x under-sampled data are adequate for clinical use. Conclusion: Diffusion probabilistic generative models applied with the proposed pipeline to handle challenging real-world datasets could reduce scan time of in-NICU neonatal MRI.
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