Bhuiyan E H, Chowdhury M E H, Glover P M
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK.
Center for Magnetic Resonance Research, University of Illinois Chicago, Chicago, IL 60612, USA.
Heliyon. 2024 Jun 4;10(13):e32199. doi: 10.1016/j.heliyon.2024.e32199. eCollection 2024 Jul 15.
Prospective motion corrections in brain imaging for MRI are fairly challenging. Monitoring involuntary head movement inside MR scanner is crucial for prospective motion correction. This initial study delves into utilizing simulations to track the head's movements within an MRI scanner, achieved by measuring induced voltage changes from time-varying magnetic field gradients in head-mounted coils. The ultimate aim is to create an inventive approach for prospective motion corrections. The voltage induced in a circular coil of wire that is exposed to time-varying x-, y- and z-magnetic field gradients, is calculated for varying positions and orientations (POSE) of the coils. Similar steps are taken for a system of five coils confined to faces of a cube and it is established whether the voltage changes due to gradient pulses applied along three directions can be used to calculate the change in POSE of the set of coils. This induced voltage led to form a system of linear equations and then find a calibration matrix. Inverting the calibration matrix enables the estimation of movement parameters from the calculated voltage in the coils. Our software gives robust measurement of the six degrees of freedoms to monitor head movement accurately so far ≈0.3 mm and . By using this standard method one can identify the POSE of the coils as well head within an MR scanner. Even after, addition of noise voltage (up to 20 μV) estimated parameters does not blow up. This electromagnetic field based real-time tracking is highly accurate, non-invasive and compatible with standard MRI hardware.
磁共振成像（MRI）中大脑成像的前瞻性运动校正颇具挑战性。监测磁共振扫描仪内部的非自愿头部运动对于前瞻性运动校正是至关重要的。这项初步研究深入探讨了利用模拟来跟踪MRI扫描仪内头部的运动，这是通过测量头戴式线圈中时变磁场梯度引起的电压变化来实现的。最终目标是创建一种创新的前瞻性运动校正方法。针对线圈在不同位置和方向（POSE），计算暴露于时变x、y和z磁场梯度的圆形导线线圈中感应的电压。对于限制在立方体表面的五个线圈系统，采取类似步骤，并确定沿三个方向施加的梯度脉冲引起的电压变化是否可用于计算该组线圈的POSE变化。这种感应电压导致形成一个线性方程组，然后找到一个校准矩阵。对校准矩阵求逆能够根据线圈中计算出的电压估计运动参数。我们的软件能够对六个自由度进行稳健测量，从而精确监测头部运动，目前精度约为0.3毫米和 。通过使用这种标准方法，可以确定MR扫描仪内线圈以及头部的POSE。即使在添加噪声电压（高达20 μV）后，估计参数也不会失控。这种基于电磁场的实时跟踪高度准确、非侵入性且与标准MRI硬件兼容。
