PDF(Pubmed)
Abstract：
To address the challenges posed by fat-water chemical shift artifacts and relaxation rate discrepancies to quantitative susceptibility mapping (QSM) outside the brain, and to generate accurate susceptibility maps of the head-and-neck at 3 and 7 Tesla.
Simultaneous Multiple Resonance Frequency (SMURF) imaging was extended to 7 Tesla and used to acquire head-and-neck gradient echo images at both 3 and 7 Tesla. Separated fat and water images were corrected for Type 1 (displacement) and Type 2 (phase discrepancy) chemical shift artefacts, and for the bias resulting from differences in T1 and T2∗ relaxation rates, recombined and used as the basis for QSM. A novel phase signal-based masking approach was used to generate head-and-neck masks.
SMURF generated well-separated fat and water images of the head-and-neck. Corrections for chemical shift artefacts and relaxation rate differences removed overestimation of the susceptibility values, blurring in the susceptibility maps, and the disproportionate influence of fat in mixed voxels. The resulting susceptibility maps showed high correspondence between the paramagnetic areas and the locations of fatty tissues and the susceptibility estimates were similar to literature values. The proposed masking approach was shown to provide a simple means of generating head-and-neck masks.
Corrections for Type 1 and Type 2 chemical shift artefacts and for fat-water relaxation rate differences, mainly in T1 , were shown to be required for accurate susceptibility mapping of fatty-body regions. SMURF made it possible to apply these corrections and generate high-quality susceptibility maps of the entire head-and-neck at both 3 and 7 Tesla.
Simultaneous Multiple Resonance Frequency (SMURF) imaging was extended to 7 Tesla and used to acquire head-and-neck gradient echo images at both 3 and 7 Tesla. Separated fat and water images were corrected for Type 1 (displacement) and Type 2 (phase discrepancy) chemical shift artefacts, and for the bias resulting from differences in T1 and T2∗ relaxation rates, recombined and used as the basis for QSM. A novel phase signal-based masking approach was used to generate head-and-neck masks.
SMURF generated well-separated fat and water images of the head-and-neck. Corrections for chemical shift artefacts and relaxation rate differences removed overestimation of the susceptibility values, blurring in the susceptibility maps, and the disproportionate influence of fat in mixed voxels. The resulting susceptibility maps showed high correspondence between the paramagnetic areas and the locations of fatty tissues and the susceptibility estimates were similar to literature values. The proposed masking approach was shown to provide a simple means of generating head-and-neck masks.
Corrections for Type 1 and Type 2 chemical shift artefacts and for fat-water relaxation rate differences, mainly in T1 , were shown to be required for accurate susceptibility mapping of fatty-body regions. SMURF made it possible to apply these corrections and generate high-quality susceptibility maps of the entire head-and-neck at both 3 and 7 Tesla.
摘要：
目的：为了解决由脂肪-水化学位移伪影和弛豫率差异对脑外定量磁化率图（QSM）带来的挑战，并在3和7特斯拉时生成准确的头颈部磁化率图。
方法：同时多共振频率（SMURF）成像扩展到7特斯拉，并用于在3和7特斯拉下采集头颈部梯度回波图像。针对1型（位移）和2型（相位差异）化学位移伪影校正了分离的脂肪和水图像，对于T1和T2*松弛率差异导致的偏差，重组并用作QSM的基础。一种新颖的基于相位信号的掩蔽方法用于生成头颈部面罩。
结果：SMURF生成了头颈部分离良好的脂肪和水图像。对化学位移伪影和弛豫率差异的校正消除了对磁化率值的高估，在磁化率图中模糊，以及混合体素中脂肪的不成比例的影响。所得的磁化率图显示顺磁性区域与脂肪组织位置之间的高度对应关系，磁化率估计与文献值相似。所提出的掩蔽方法被证明提供了生成头颈面罩的简单方法。
结论：对1型和2型化学位移伪影和脂肪-水松弛率差异的校正，主要在T1，被证明是准确绘制脂肪体区域磁化率所必需的。SMURF使得应用这些校正成为可能，并在3和7特斯拉生成整个头颈部的高质量磁化率图。
方法：同时多共振频率（SMURF）成像扩展到7特斯拉，并用于在3和7特斯拉下采集头颈部梯度回波图像。针对1型（位移）和2型（相位差异）化学位移伪影校正了分离的脂肪和水图像，对于T1和T2*松弛率差异导致的偏差，重组并用作QSM的基础。一种新颖的基于相位信号的掩蔽方法用于生成头颈部面罩。
结果：SMURF生成了头颈部分离良好的脂肪和水图像。对化学位移伪影和弛豫率差异的校正消除了对磁化率值的高估，在磁化率图中模糊，以及混合体素中脂肪的不成比例的影响。所得的磁化率图显示顺磁性区域与脂肪组织位置之间的高度对应关系，磁化率估计与文献值相似。所提出的掩蔽方法被证明提供了生成头颈面罩的简单方法。
结论：对1型和2型化学位移伪影和脂肪-水松弛率差异的校正，主要在T1，被证明是准确绘制脂肪体区域磁化率所必需的。SMURF使得应用这些校正成为可能，并在3和7特斯拉生成整个头颈部的高质量磁化率图。
