论文标题

动态MRI中的数据驱动正则化参数选择

Data-driven regularization parameter selection in dynamic MRI

论文作者

Hanhela, Matti, Gröhn, Olli, Kettunen, Mikko, Niinimäki, Kati, Vauhkonen, Marko, Kolehmainen, Ville

论文摘要

在动态MRI中,通常只能使用成像方案获得足够的时间分辨率,这些成像协议在时间序列中为每个图像产生不足的数据。这导致了压缩传感(CS)的图像重建方法的流行。 CS方法中的问题之一是确定正则化参数,该参数控制数据保真度之间的平衡空间和时间正则化项。提出了针对总变化正规化参数选择的数据驱动方法,以使重建在正则化域中产生预期的稀疏水平。预期的稀疏度是从时间正则化的测量数据和空间正则化的参考图像中获得的。提出了两个配方。第一个是对参数对的2D搜索,该参数对在时间和空间正则域中都产生预期的稀疏性。在第二种方法中,使用S-Curve方法将基于稀疏性的参数选择分为两个1D搜索。使用模拟和实验性DCE-MRI评估该方法。在模拟测试案例中,这两种提出的方​​法都会产生一个接近RMSE最佳对的参数对,并且重建误差也接近最小值。在实验测试案例中,这些方法几乎产生了几乎相似的参数选择,并且重建具有很高的感知质量。两种方法都导致在模拟测试案例和实验测试用例中都可以选择时间和空间正则参数,而顺序方法在计算上更有效。

In dynamic MRI, sufficient time resolution can often only be obtained using imaging protocols which produce undersampled data for each image in the time series. This has led to the popularity of compressed sensing (CS) based image reconstruction approaches. One of the problems in CS approaches is determining the regularization parameters, which control the balance between data fidelity the spatial and temporal regularization terms. A data-driven approach is proposed for the total variation regularization parameter selection such that the reconstructions yield expected sparsity levels in the regularization domains. The expected sparsity levels are obtained from the measurement data for the temporal regularization and from a reference image for the spatial regularization. Two formulations are proposed. The first is a 2D search for a parameter pair which produces expected sparsity in both the temporal and spatial regularization domains. In the second approach, the sparsity-based parameter selection is split to two 1D searches using the S-curve method. The approaches are evaluated using simulated and experimental DCE-MRI. In the simulated test case, both proposed methods produce a parameter pair that is close to the RMSE optimal pair, and the reconstruction error is also close to minimum. In the experimental test case, the methods produce almost similar parameter selection, and the reconstructions are of high perceived quality. Both approaches lead to a highly feasible selection of the temporal and spatial regularization parameters in both the simulated and experimental test cases while the sequential method is computationally more efficient.

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