Dietrich Benjamin E, Brunner David O, Wilm Bertram J, Barmet Christoph, Gross Simon, Kasper Lars, Haeberlin Maximilian, Schmid Thomas, Vannesjo S Johanna, Pruessmann Klaas P
Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
Skope Magnetic Resonance Technologies, Zurich, Switzerland.
Magn Reson Med. 2016 Apr;75(4):1831-40. doi: 10.1002/mrm.25770. Epub 2015 May 14.
MR image formation and interpretation relies on highly accurate dynamic magnetic fields of high fidelity. A range of mechanisms still limit magnetic field fidelity, including magnet drifts, eddy currents, and finite linearity and stability of power amplifiers used to drive gradient and shim coils. Addressing remaining errors by means of hardware, sequence, or signal processing optimizations, calls for immediate observation by magnetic field monitoring. The present work presents a stand-alone monitoring system delivering insight into such field imperfections for MR sequence and system analysis.
A flexible NMR field probe-based stand-alone monitoring system, built on a software-defined-radio approach, is introduced and used to sense field dynamics up to third-order in space in a selection of situations with different time scales.
Highly sensitive trajectories are measured and successfully used for image reconstruction. Further field perturbations due to mechanical oscillations and thermal field drifts following demanding gradient use and external interferences are studied.
A flexible and versatile monitoring system is presented, delivering camera-like access to otherwise hardly accessible field dynamics with nanotesla resolution. Its stand-alone nature enables field analysis even during unknown MR system states.
磁共振成像的形成和解读依赖于高保真度的高精度动态磁场。一系列机制仍在限制磁场的保真度，包括磁体漂移、涡流以及用于驱动梯度线圈和匀场线圈的功率放大器的有限线性度和稳定性。通过硬件、序列或信号处理优化来解决剩余误差，需要通过磁场监测进行即时观测。本研究提出了一种独立监测系统，可深入了解此类磁场缺陷，用于磁共振序列和系统分析。
介绍了一种基于灵活的核磁共振场探头的独立监测系统，该系统基于软件定义无线电方法构建，并用于在具有不同时间尺度的一系列情况下感知高达空间三阶的场动态。
测量了高灵敏度轨迹，并成功用于图像重建。研究了在使用苛刻梯度和外部干扰后，由于机械振荡和热场漂移导致的进一步场扰动。
提出了一种灵活通用的监测系统，以纳米特斯拉分辨率提供类似相机的方式来获取原本难以获取的场动态。其独立性质使得即使在未知的磁共振系统状态下也能进行场分析。
