van der Heide Oscar, Sbrizzi Alessandro, van den Berg Cornelis A T
Computational Imaging Group for MR Diagnostics and Therapy, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan 100, 3583 CX Utrecht, Netherlands; Department of Radiology, Division of Imaging and Oncology, University Medical Center Utrecht, Heidelberglaan 100, 3583 CX Utrecht, Netherlands.
Computational Imaging Group for MR Diagnostics and Therapy, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan 100, 3583 CX Utrecht, Netherlands; Department of Radiology, Division of Imaging and Oncology, University Medical Center Utrecht, Heidelberglaan 100, 3583 CX Utrecht, Netherlands.
Magn Reson Imaging. 2023 Jun;99:7-19. doi: 10.1016/j.mri.2023.01.017. Epub 2023 Jan 25.
MR Spin TomogrAphy in Time-domain ("MR-STAT") is quantitative MR technique in which multiple quantitative parameters are estimated from a single short scan by solving a large-scale non-linear optimization problem. In this work we extended the MR-STAT framework to non-Cartesian gradient trajectories. Cartesian MR-STAT and radial MR-STAT were compared in terms of time-efficiency and robustness in simulations, gel phantom measurements and in vivo measurements. In simulations, we observed that both Cartesian and radial MR-STAT are highly robust against undersampling. Radial MR-STAT does have a lower spatial encoding power because the outer corners of k-space are never sampled. However, especially in T2, this is compensated by a higher dynamic encoding power that comes from sampling the k-space center with each readout. In gel phantom measurements, Cartesian MR-STAT was observed to be robust against overfitting whereas radial MR-STAT suffered from high-frequency artefacts in the parameter maps at later iterations. These artefacts are hypothesized to be related to hardware imperfections and were (partially) suppressed with image filters. The time-efficiencies were higher for Cartesian MR-STAT in all vials. In-vivo, the radial reconstruction again suffered from overfitting artefacts. The robustness of Cartesian MR-STAT over the entire range of experiments may make it preferable in a clinical setting, despite radial MR-STAT resulting in a higher T1 time-efficiency in white matter.
时域磁共振自旋断层扫描（“MR-STAT”）是一种定量磁共振技术，通过解决大规模非线性优化问题，从单次短扫描中估计多个定量参数。在这项工作中，我们将MR-STAT框架扩展到非笛卡尔梯度轨迹。在模拟、凝胶体模测量和体内测量中，对笛卡尔MR-STAT和径向MR-STAT的时间效率和稳健性进行了比较。在模拟中，我们观察到笛卡尔和径向MR-STAT对欠采样都具有高度稳健性。径向MR-STAT的空间编码能力较低，因为k空间的外角从未被采样。然而，特别是在T2中，这被每次读出时对k空间中心采样所带来的更高动态编码能力所补偿。在凝胶体模测量中，观察到笛卡尔MR-STAT对过拟合具有稳健性，而径向MR-STAT在后期迭代的参数图中存在高频伪影。这些伪影被认为与硬件缺陷有关，并通过图像滤波器（部分）得到抑制。在所有样品瓶中，笛卡尔MR-STAT的时间效率更高。在体内，径向重建再次受到过拟合伪影的影响。尽管径向MR-STAT在白质中导致更高的T1时间效率，但在整个实验范围内，笛卡尔MR-STAT的稳健性可能使其在临床环境中更具优势。
