Purpose

T_1ρ dispersion quantification can potentially be used as a cardiac magnetic resonance index for sensitive detection of myocardial fibrosis without the need of contrast agents. However, dispersion quantification is still a major challenge, because T_1ρ mapping for different spin lock amplitudes is a very time consuming process. This study aims to develop a fast and accurate T_1ρ mapping sequence, which paves the way to cardiac T_1ρ dispersion quantification within the limited measurement time of an in vivo study in small animals.

Methods

A radial spin lock sequence was developed using a Bloch simulation-optimized sampling pattern and a view-sharing method for image reconstruction. For validation, phantom measurements with a conventional sampling pattern and a gold standard sequence were compared to examine T_1ρ quantification accuracy. The in vivo validation of T_1ρ mapping was performed in N = 10 mice and in a reproduction study in a single animal, in which ten maps were acquired in direct succession. Finally, the feasibility of myocardial dispersion quantification was tested in one animal.

Results

The Bloch simulation-based sampling shows considerably higher image quality as well as improved T_1ρ quantification accuracy (+ 56%) and precision (+ 49%) compared to conventional sampling. Compared to the gold standard sequence, a mean deviation of − 0.46 ± 1.84% was observed. The in vivo measurements proved high reproducibility of myocardial T_1ρ mapping. The mean T_1ρ in the left ventricle was 39.5 ± 1.2 ms for different animals and the maximum deviation was 2.1% in the successive measurements. The myocardial T_1ρ dispersion slope, which was measured for the first time in one animal, could be determined to be 4.76 ± 0.23 ms/kHz.

Conclusion

This new and fast T_1ρ quantification technique enables high-resolution myocardial T_1ρ mapping and even dispersion quantification within the limited time of an in vivo study and could, therefore, be a reliable tool for improved tissue characterization.

中文翻译：

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使用 k 空间加权图像对比度和 Bloch 模拟优化径向采样模式对小鼠进行快速心肌 T1ρ 映射

目的

T _1ρ色散量化可以潜在地用作心脏磁共振指数，用于敏感检测心肌纤维化而无需造影剂。然而，色散量化仍然是一个主要挑战，因为不同自旋锁振幅的T _1ρ映射是一个非常耗时的过程。本研究旨在开发一种快速准确的T _1ρ映射序列，为在小动物体内研究的有限测量时间内进行心脏T _1ρ色散量化铺平道路。

方法

使用 Bloch 模拟优化的采样模式和用于图像重建的视图共享方法开发了径向自旋锁定序列。为了验证，比较了具有常规采样模式和金标准序列的体模测量以检查T _1ρ量化精度。T _1ρ映射的体内验证在N  = 10 只小鼠中进行，并在单个动物的繁殖研究中进行，其中直接连续获得了 10 个图。最后，在一只动物身上测试了心肌分散量化的可行性。

结果

与传统采样相比，基于 Bloch 模拟的采样显示出更高的图像质量以及改进的T _1ρ量化准确度 (+ 56%) 和精度 (+ 49%)。与金标准序列相比，观察到平均偏差为 - 0.46 ± 1.84%。体内测量证明心肌T _1ρ映射的高重现性。不同动物的左心室平均T _{1ρ为 39.5 ± 1.2 ms，连续测量的最大偏差为 2.1%。}在一只动物中首次测量的心肌T _{1ρ离散斜率可以确定为4.76±0.23 ms/kHz。}

结论

这种新的快速T _1ρ量化技术能够在体内研究的有限时间内实现高分辨率心肌T _1ρ映射甚至离散量化，因此可以成为改进组织表征的可靠工具。