Shang Yun, Theilenberg Sebastian, Gajdošík Martin, Schreiber Laura M, Juchem Christoph
Department of Biomedical Engineering, Columbia University in the City of New York, New York, New York, USA.
Chair of Molecular and Cellular Imaging, Comprehensive Heart Failure Center, University Hospital Wuerzburg, Wuerzburg, Germany.
Magn Reson Med. 2024 Jan;91(1):91-104. doi: 10.1002/mrm.29831. Epub 2023 Aug 20.
Functional cardiac MRI scans employing balanced steady-state free precession sequences suffer from dark band artifacts in the myocardium due to B inhomogeneity. We recently introduced a novel method for the theoretical derivation of B distributions in the human heart. This study aims to simulate the B distributions in the heart across the cardiac cycle using structural MR images and validate the simulations via in vivo measured cardiac phase-specific B maps on the same subjects at 3T.
Cardiac phase-specific B field maps were acquired from eight healthy subjects at 3T. B conditions were simulated based on tissue masks created from the cardiac-phase specific structural images from the in vivo B map scan and anatomical images from a thoracic MRI scan, adopting our recently published approach. The simulations and in vivo measurements were compared by calculating the spatial correlation of their B distributions and temporal correlation of the derived spherical harmonic coefficients throughout the cardiac cycle.
The spatial comparison of B maps between the simulation and in vivo measurement indicates an overall average correlation coefficient of 0.91 across the cardiac cycle in all subjects. Both groups show consistent high-level B patterns. Temporal variations of B conditions exhibit sinusoidal characteristics and are strongly correlated between simulation and in vivo.
Theoretical simulations employing regional anatomical features were validated by direct in vivo B mapping in the same subjects. The spatial B condition throughout the cardiac cycle exhibits oscillatory characteristics due to structural distortions of cardiac motion.
采用平衡稳态自由进动序列的心脏功能磁共振成像扫描，由于磁场不均匀性，心肌会出现暗带伪影。我们最近引入了一种新方法，用于从理论上推导人体心脏中的磁场分布。本研究旨在利用结构磁共振图像模拟心动周期中整个心脏的磁场分布，并通过在3T条件下对同一受试者进行体内测量的心脏相位特异性磁场图来验证模拟结果。
在3T条件下，从8名健康受试者获取心脏相位特异性磁场图。采用我们最近发表的方法，基于从体内磁场图扫描的心脏相位特异性结构图像和胸部磁共振扫描的解剖图像创建的组织掩码来模拟磁场条件。通过计算整个心动周期中其磁场分布的空间相关性以及导出的球谐系数的时间相关性，对模拟结果和体内测量结果进行比较。
模拟结果与体内测量的磁场图的空间比较表明，所有受试者在整个心动周期中的总体平均相关系数为0.91。两组均显示出一致的高水平磁场模式。磁场条件的时间变化呈现正弦特征，并且在模拟和体内测量之间具有很强的相关性。
采用区域解剖特征的理论模拟通过对同一受试者进行直接体内磁场映射得到了验证。由于心脏运动的结构扭曲，整个心动周期中的空间磁场条件呈现出振荡特征。
