Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital-Friedrich Schiller University Jena, Jena, Germany.
Neuroimage. 2012 Sep;62(3):2083-100. doi: 10.1016/j.neuroimage.2012.05.067. Epub 2012 Jun 1.
Quantitative susceptibility mapping (QSM) is a novel magnetic resonance-based technique that determines tissue magnetic susceptibility from measurements of the magnetic field perturbation. Due to the ill-posed nature of this problem, regularization strategies are generally required to reduce streaking artifacts on the computed maps. The present study introduces a new algorithm for calculating the susceptibility distribution utilizing a priori information on its regional homogeneity derived from gradient echo phase images and analyzes the impact of erroneous a priori information on susceptibility map fidelity. The algorithm, Homogeneity Enabled Incremental Dipole Inversion (HEIDI), was investigated with a special focus on the reconstruction of subtle susceptibility variations in a numerical model and in volunteer data and was compared with two recently published approaches, Thresholded K-space Division (TKD) and Morphology Enabled Dipole Inversion (MEDI). HEIDI resulted in susceptibility maps without streaking artifacts and excellent depiction of subtle susceptibility variations in most regions. By investigating HEIDI susceptibility maps acquired with the volunteers' heads in different orientations, it was demonstrated that the apparent magnetic susceptibility distribution of human brain tissue considerably depends on the direction of the main magnetic field.
定量磁化率映射（QSM）是一种基于磁共振的新技术，它通过测量磁场扰动来确定组织磁化率。由于这个问题具有不适定性，因此通常需要正则化策略来减少计算图谱上的条纹伪影。本研究介绍了一种新的算法，用于利用从梯度回波相位图像中得出的关于其区域同质性的先验信息来计算磁化率分布，并分析了错误的先验信息对磁化率图保真度的影响。该算法，即同质性增强的增量偶极子反演（HEIDI），特别关注于在数值模型和志愿者数据中重建细微的磁化率变化，并与最近发表的两种方法（阈值化 K 空间划分（TKD）和形态学增强偶极子反演（MEDI））进行了比较。HEIDI 产生的磁化率图谱没有条纹伪影，并且在大多数区域都能很好地描绘细微的磁化率变化。通过研究志愿者头部在不同方向的 HEIDI 磁化率图谱，证明了人脑组织的表观磁化率分布很大程度上取决于主磁场的方向。
