IEEE Trans Med Imaging. 2024 Aug;43(8):2937-2948. doi: 10.1109/TMI.2024.3381197. Epub 2024 Aug 1.
Oscillating Steady-State Imaging (OSSI) is a recently developed fMRI acquisition method that can provide 2 to 3 times higher SNR than standard fMRI approaches. However, because the OSSI signal exhibits a nonlinear oscillation pattern, one must acquire and combine n (e.g., 10) OSSI images to get an image that is free of oscillation for fMRI, and fully sampled acquisitions would compromise temporal resolution. To improve temporal resolution and accurately model the nonlinearity of OSSI signals, instead of using subspace models that are not well suited for the data, we build the MR physics for OSSI signal generation as a regularizer for the undersampled reconstruction. Our proposed physics-based manifold model turns the disadvantages of OSSI acquisition into advantages and enables joint reconstruction and quantification. OSSI manifold model (OSSIMM) outperforms subspace models and reconstructs high-resolution fMRI images with a factor of 12 acceleration and without spatial or temporal smoothing. Furthermore, OSSIMM can dynamically quantify important physics parameters, including R maps, with a temporal resolution of 150 ms.
振荡稳态成像 (OSSI) 是一种最近开发的 fMRI 采集方法，可提供比标准 fMRI 方法高 2 到 3 倍的 SNR。然而，由于 OSSI 信号呈现出非线性的振荡模式，因此必须采集并组合 n（例如，10）个 OSSI 图像，才能得到无振荡的 fMRI 图像，而完全采样采集会影响时间分辨率。为了提高时间分辨率并准确模拟 OSSI 信号的非线性，我们没有使用不适合数据的子空间模型，而是构建了 OSSI 信号生成的磁共振物理模型作为欠采样重建的正则化项。我们提出的基于物理的流形模型将 OSSI 采集的缺点转化为优点，并实现了联合重建和量化。OSSI 流形模型（OSSIMM）优于子空间模型，可在 12 倍加速下重建高分辨率 fMRI 图像，且无需空间或时间平滑。此外，OSSIMM 可以以 150 毫秒的时间分辨率动态量化包括 R 图在内的重要物理参数。
