Melbourne Brain Centre Imaging Unit, The University of Melbourne, Australia; Department of Biomedical Engineering, The University of Melbourne, Australia.
Melbourne Neuropsychiatry Centre, The University of Melbourne, Australia; Department of Medicine and Radiology, The University of Melbourne, Australia.
Neuroimage. 2021 May 1;231:117701. doi: 10.1016/j.neuroimage.2020.117701. Epub 2021 Jan 20.
Quantitative susceptibility mapping (QSM) is a novel MR technique that allows mapping of tissue susceptibility values from MR phase images. QSM is an ill-conditioned inverse problem, and although several methods have been proposed in the field, in the presence of a wide range of susceptibility sources, streaking artifacts appear around high susceptibility regions and contaminate the whole QSM map. QSMART is a post-processing pipeline that uses two-stage parallel inversion to reduce the streaking artifacts and remove banding artifact at the cortical surface and around the vasculature.
Tissue and vein susceptibility values were separately estimated by generating a mask of vasculature driven from the magnitude data using a Frangi filter. Spatially dependent filtering was used for the background field removal step and the two susceptibility estimates were combined in the final QSM map. QSMART was compared to RESHARP/iLSQR and V-SHARP/iLSQR inversion in a numerical phantom, 7T in vivo single and multiple-orientation scans, 9.4T ex vivo mouse data, and 4.7T in vivo rat brain with induced focal ischemia.
Spatially dependent filtering showed better suppression of phase artifacts near cortex compared to RESHARP and V-SHARP, while preserving voxels located within regions of interest without brain edge erosion. QSMART showed successful reduction of streaking artifacts as well as improved contrast between different brain tissues compared to the QSM maps obtained by RESHARP/iLSQR and V-SHARP/iLSQR.
QSMART can reduce QSM artifacts to enable more robust estimation of susceptibility values in vivo and ex vivo.
定量磁化率映射（QSM）是一种新颖的磁共振技术，可从磁共振相位图像中绘制组织磁化率值。QSM 是一个病态逆问题，尽管该领域已经提出了几种方法，但在存在广泛的磁化率源的情况下，条纹伪影出现在高磁化率区域周围，并污染整个 QSM 图。QSMART 是一种后处理管道，它使用两级并行反演来减少条纹伪影，并去除皮质表面和血管周围的带状伪影。
通过使用 Frangi 滤波器从幅度数据生成血管驱动的掩模，分别估计组织和静脉磁化率。对背景场去除步骤使用空间相关滤波，并且在最终的 QSM 图中组合两个磁化率估计值。在数值体模、7T 体内单和多方向扫描、9.4T 离体小鼠数据以及 4.7T 体内诱导局灶性缺血的大鼠脑中，将 QSMART 与 RESHARP/iLSQR 和 V-SHARP/iLSQR 反演进行了比较。
与 RESHARP 和 V-SHARP 相比，空间相关滤波在靠近皮质的相位伪影抑制方面表现更好，同时保留了没有脑边缘侵蚀的感兴趣区域内的体素。与 RESHARP/iLSQR 和 V-SHARP/iLSQR 获得的 QSM 图相比，QSMART 成功减少了条纹伪影，并提高了不同脑组织之间的对比度。
QSMART 可以减少 QSM 伪影，从而更稳健地在体内和体外来估计磁化率值。
