Department of Radiology, Weill Cornell Medical College, New York, New York, USA.
Department of Biomedical Engineering, Cornell University, Ithaca, New York, USA.
Magn Reson Med. 2017 Sep;78(3):1080-1086. doi: 10.1002/mrm.26475. Epub 2016 Oct 3.
We assessed the accuracy of quantitative susceptibility mapping in a gadolinium balloon phantom with a large range of susceptibility values and imaging resolutions at 1.5 and 3 Tesla (T).
The phantom contained sources with susceptibility values of 0.4, 0.8, 1.6, and 3.2 ppm and was imaged at isotropic resolutions of 0.7, 0.8, 1.2, and 1.8 mm. Numerical simulations were performed to match the experimental findings. Voxel sensitivity effects were used to explain the susceptibility underestimations.
Both phantom data and simulation demonstrated that systematic underestimation of the susceptibility values increased with voxel size, field strength, and object susceptibility.
The underestimation originates from the signal formation in a voxel, which can be described by the voxel sensitivity function. The amount of underestimation is thus affected by imaging resolution, magnitude contrast, image filtering, and details of the susceptibility inclusions such as the susceptibility value and geometry. High-resolution imaging is therefore needed for accurate reconstruction of QSM values, especially at higher susceptibilities. Magn Reson Med 78:1080-1086, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
我们在钆气球体模中评估了定量磁化率映射在大范围磁化率值和在 1.5 和 3T 下的不同成像分辨率的准确性。
该体模包含磁化率值为 0.4、0.8、1.6 和 3.2ppm 的源，在各向同性分辨率为 0.7、0.8、1.2 和 1.8mm 下进行成像。进行数值模拟以匹配实验结果。采用体素灵敏度效应来解释磁化率的低估。
体模数据和模拟均表明，磁化率值的系统低估随体素尺寸、场强和物体磁化率的增加而增加。
这种低估源于体素中的信号形成，可以用体素灵敏度函数来描述。因此，低估的程度受成像分辨率、幅度对比、图像滤波以及磁化率夹杂物的详细信息（如磁化率值和几何形状）的影响。因此，为了准确重建 QSM 值，特别是在较高磁化率下，需要高分辨率成像。
磁共振医学 78:1080-1086, 2017。© 2016 国际磁共振学会。
