Compressed sensing with signal averaging for improved sensitivity and motion artifact reduction in fluorine‐19 MRI,NMR in Biomedicine

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Compressed sensing with signal averaging for improved sensitivity and motion artifact reduction in fluorine‐19 MRI
NMR in Biomedicine ( IF 2.7 ) Pub Date : 2020-10-01 , DOI: 10.1002/nbm.4418
Emeline Darçot ₁ , Jérôme Yerly _{1,

2} , Tom Hilbert _{1,

3,

4} , Roberto Colotti ₁ , Elena Najdenovska _{1,

2} , Tobias Kober _{1,

3,

4} , Matthias Stuber _{1,

2} , Ruud B van Heeswijk _{1,

2}

Affiliation

Fluorine‐19 (¹⁹F) MRI of injected perfluorocarbon emulsions (PFCs) allows for the non‐invasive quantification of inflammation and cell tracking, but suffers from a low signal‐to‐noise ratio and extended scan time. To address this limitation, we tested the hypotheses that a ¹⁹F MRI pulse sequence that combines a specific undersampling regime with signal averaging has both increased sensitivity and robustness against motion artifacts compared with a non‐averaged fully sampled pulse sequence, when both datasets are reconstructed with compressed sensing. As a proof of principle, numerical simulations and phantom experiments were performed on selected variable ranges to characterize the point spread function of undersampling patterns, as well as the vulnerability to noise of undersampling and reconstruction parameters with paired numbers of x signal averages and acceleration factor x (NAx‐AFx). The numerical simulations demonstrated that a probability density function that uses 25% of the samples to fully sample the k‐space central area allowed for an optimal balance between limited blurring and artifact incoherence. At all investigated noise levels, the Dice similarity coefficient (DSC) strongly depended on the regularization parameters and acceleration factor. In phantoms, the motion robustness of an NA8‐AF8 undersampling pattern versus NA1‐AF1 was evaluated with simulated and real motion patterns. Differences were assessed with the DSC, which was consistently higher for the NA8‐AF8 compared with the NA1‐AF1 strategy, for both simulated and real cyclic motion patterns (P < 0.001). Both strategies were validated in vivo in mice (n = 2) injected with perfluoropolyether. Here, the images displayed a sharper delineation of the liver with the NA8‐AF8 strategy than with the NA1‐AF1 strategy. In conclusion, we validated the hypotheses that in ¹⁹F MRI the combination of undersampling and averaging improves both the sensitivity and the robustness against motion artifacts.

中文翻译：

具有信号平均的压缩传感可提高 19 MRI 的灵敏度并减少运动伪影

注射全氟化碳乳剂 (PFC) 的氟-19 ( ¹⁹ F) MRI 可以对炎症进行非侵入性定量和细胞追踪，但存在信噪比低和扫描时间延长的问题。为了解决这个限制，我们测试了以下假设：当重建两个数据集时，与非平均完全采样脉冲序列相比，将特定欠采样方案与信号平均相结合的¹⁹ F MRI 脉冲序列具有更高的灵敏度和针对运动伪影的鲁棒性具有压缩感知功能。作为原理证明，在选定的变量范围上进行了数值模拟和模型实验，以表征欠采样模式的点扩散函数，以及欠采样和重建参数对噪声的脆弱性，其中包含x信号平均值和加速因子x的配对数(NA x ‐AF x )。数值模拟表明，使用 25% 的样本对k空间中心区域进行完全采样的概率密度函数可以在有限模糊和伪影不相干之间实现最佳平衡。在所有研究的噪声水平下，Dice 相似系数 (DSC) 强烈依赖于正则化参数和加速因子。在体模中，使用模拟和真实运动模式评估 NA8-AF8 欠采样模式与 NA1-AF1 的运动鲁棒性。使用 DSC 评估差异，对于模拟和真实循环运动模式，NA8-AF8 的差异始终高于 NA1-AF1 策略 ( P < 0.001)。这两种策略均在注射全氟聚醚的小鼠 ( n = 2) 体内得到验证。在这里，与 NA1-AF1 策略相比，NA8-AF8 策略的图像显示出更清晰的肝脏轮廓。总之，我们验证了以下假设：在¹⁹ F MRI 中，欠采样和平均的组合提高了针对运动伪影的灵敏度和鲁棒性。

更新日期：2020-12-08

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