Department of Neurology, Perelman School of Medicine, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA.
NVIDIA GmbH, Einsteinstraße 172, Munich 81677, Germany; German Center for Vertigo and Balance Disorders, LMU Klinikum, Munich 81377, Germany.
Neuroimage. 2022 Jul 15;255:119170. doi: 10.1016/j.neuroimage.2022.119170. Epub 2022 Apr 1.
Strong magnetic fields from magnetic resonance (MR) scanners induce a Lorentz force that contributes to vertigo and persistent nystagmus. Prior studies have reported a predominantly horizontal direction for healthy subjects in a 7 Tesla (T) MR scanner, with slow phase velocity (SPV) dependent on head orientation. Less is known about vestibular signal behavior for subjects in a weaker, 3T magnetic field, the standard strength used in the Human Connectome Project (HCP). The purpose of this study is to characterize the form and magnitude of nystagmus induced at 3T.
Forty-two subjects were studied after being introduced head-first, supine into a Siemens Prisma 3T scanner. Eye movements were recorded in four separate acquisitions over 20 min. A biometric eye model was fitted to the recordings to derive rotational eye position and then SPV. An anatomical template of the semi-circular canals was fitted to the T2 anatomical image from each subject, and used to derive the angle of the B magnetic field with respect to the vestibular apparatus.
Recordings from 37 subjects yielded valid measures of eye movements. The population-mean SPV ± SD for the horizontal component was -1.38 ± 1.27 deg/sec, and vertical component was -0.93 ± 1.44 deg/sec, corresponding to drift movement in the rightward and downward direction. Although there was substantial inter-subject variability, persistent nystagmus was present in half of subjects with no significant adaptation over the 20 min scanning period. The amplitude of vertical drift was correlated with the roll angle of the vestibular system, with a non-zero vertical SPV present at a 0 degree roll.
Non-habituating vestibular signals of varying amplitude are present in resting state data collected at 3T.
磁共振（MR）扫描仪产生的强磁场会引起洛伦兹力，导致眩晕和持续的眼球震颤。先前的研究报告称，在 7 特斯拉（T）MR 扫描仪中，健康受试者的主要方向为水平方向，慢相速度（SPV）取决于头部方向。在较弱的 3T 磁场中，即人类连接组计划（HCP）中使用的标准强度，对于受试者的前庭信号行为知之甚少。本研究旨在描述在 3T 下诱导的眼球震颤的形式和幅度。
42 名受试者在被引入西门子 Prisma 3T 扫描仪时首先仰卧。在 20 分钟的 4 次独立采集过程中记录眼球运动。使用生物计量眼球模型拟合记录，得出旋转眼球位置，然后得出 SPV。从每个受试者的 T2 解剖图像拟合半规管解剖模板，并用于得出 B 磁场相对于前庭装置的角度。
来自 37 名受试者的记录得出了有效的眼球运动测量值。水平成分的人群平均 SPV±SD 为-1.38±1.27 度/秒，垂直分量为-0.93±1.44 度/秒，对应于向右和向下的漂移运动。尽管存在很大的个体间变异性，但在 20 分钟的扫描期间，一半的受试者出现了持续的眼球震颤，没有明显的适应。垂直漂移的幅度与前庭系统的滚动角度相关，在 0 度滚动时存在非零垂直 SPV。
在 3T 采集的静息状态数据中存在幅度不同的非习惯性前庭信号。
