使用线性切空间对齐（LTSA）模型的自由呼吸三维心脏细胞外容积（ECV）成像
Free-breathing 3D cardiac extracellular volume (ECV) mapping using a linear tangent space alignment (LTSA) model
AI总结：
本文提出一种基于线性切空间对齐（LTSA）模型的自由呼吸三维心脏ECV成像方法，在3T下实现全心脏ECV成像，并通过在体实验验证其与二维MOLLI方法结果相当。
摘要：
目的：开发一种在3T下进行全心脏自由呼吸三维细胞外容积（ECV）成像的新方法。方法：在3T下开发了一种自由呼吸三维心脏ECV成像方法。在注射对比剂前后，使用自由呼吸心电门控反转恢复序列配合扰相梯度回波读出进行T1成像。采用基于线性切空间对齐（LTSA）模型的方法，从沿随机星堆轨迹稀疏采样的(k,t)-空间数据中重建高帧率动态图像。对注射对比剂前后的T1成像逐体素进行联合T1与发射B1估计。为考虑注射对比剂后T1随时间的变化，在对比剂注射后的T1成像中引入了线性时变T1模型。通过仿射变换对齐注射对比剂前后的T1图，生成ECV图。结果：通过在3T下对六名健康志愿者进行的在体研究，验证了所提方法的可行性。我们获得了空间分辨率为1.9×1.9×4.5 mm³、视野为308×308×144 mm³的三维ECV图，注射对比剂前后的扫描时间分别为10.1±1.4分钟和10.6±1.6分钟。所提方法获得的ECV图以及注射对比剂前后的T1图在定性和定量上均与二维MOLLI方法具有良好一致性。结论：所提方法能够在实际可行的成像时间内实现全心脏的自由呼吸三维ECV成像。所提方法估计的ECV值与现有方法得到的结果相当。关键词：心脏细胞外容积（ECV）成像，心脏T1成像，线性切空间对齐（LTSA），流形学习
英文摘要：
$\textbf{Purpose:}$ To develop a new method for free-breathing 3D extracellular volume (ECV) mapping of the whole heart at 3T. $\textbf{Methods:}$ A free-breathing 3D cardiac ECV mapping method was developed at 3T. T1 mapping was performed before and after contrast agent injection using a free-breathing ECG-gated inversion-recovery sequence with spoiled gradient echo readout. A linear tangent space alignment (LTSA) model-based method was used to reconstruct high-frame-rate dynamic images from (k,t)-space data sparsely sampled along a random stack-of-stars trajectory. Joint T1 and transmit B1 estimation was performed voxel-by-voxel for pre- and post-contrast T1 mapping. To account for the time-varying T1 after contrast agent injection, a linearly time-varying T1 model was introduced for post-contrast T1 mapping. ECV maps were generated by aligning pre- and post-contrast T1 maps through affine transformation. $\textbf{Results:}$ The feasibility of the proposed method was demonstrated using in vivo studies with six healthy volunteers at 3T. We obtained 3D ECV maps at a spatial resolution of 1.9$\times$1.9$\times$4.5 $mm^{3}$ and a FOV of 308$\times$308$\times$144 $mm^{3}$, with a scan time of 10.1$\pm$1.4 and 10.6$\pm$1.6 min before and after contrast agent injection, respectively. The ECV maps and the pre- and post-contrast T1 maps obtained by the proposed method were in good agreement with the 2D MOLLI method both qualitatively and quantitatively. $\textbf{Conclusion:}$ The proposed method allows for free-breathing 3D ECV mapping of the whole heart within a practically feasible imaging time. The estimated ECV values from the proposed method were comparable to those from the existing method. $\textbf{Keywords:}$ cardiac extracellular volume (ECV) mapping, cardiac T1 mapping, linear tangent space alignment (LTSA), manifold learning
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