The Swedish National 7T Facility, Lund University Bioimaging Center, Lund University, Klinikgatan 32, BMC D11, 22242, Lund, Sweden.
Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg- Eppendorf, Hamburg, Germany.
BMC Med Imaging. 2020 Dec 9;20(1):128. doi: 10.1186/s12880-020-00523-x.
Ultra-high field magnetic resonance imaging (MR) may be used to improve intracranial blood flow measurements. However, standard cardiac synchronization methods tend to fail at ultra-high field MR. Therefore, this study aims to investigate an alternative synchronization technique using Doppler ultrasound.
Healthy subjects (n = 9) were examined with 7T MR. Flow was measured in the M1-branch of the middle cerebral artery (MCA) and in the cerebral aqueduct (CA) using through-plane phase contrast (2D flow). Flow in the circle of Willis was measured with three-dimensional, three-directional phase contrast (4D flow). Scans were gated with Doppler ultrasound (DUS) and electrocardiogram (ECG), and pulse oximetry data (POX) was collected simultaneously. False negative and false positive trigger events were counted for ECG, DUS and POX, and quantitative flow measures were compared.
There were fewer false positive triggers for DUS compared to ECG (5.3 ± 11 vs. 25 ± 31, p = 0.031), while no other measured parameters differed significantly. Net blood flow in M1 was similar between DUS and ECG for 2D flow (1.5 ± 0.39 vs. 1.6 ± 0.41, bias ± 1.96SD: - 0.021 ± 0.36) and 4D flow (1.8 ± 0.48 vs. 9 ± 0.59, bias ± 1.96SD: - 0.086 ± 0.57 ml). Net CSF flow per heart beat in the CA was also similar for DUS and ECG (3.6 ± 2.1 vs. 3.0 ± 5.8, bias ± 1.96SD: 0.61 ± 13.6 μl).
Gating with DUS produced fewer false trigger events than using ECG, with similar quantitative flow values. DUS gating is a promising technique for cardiac synchronization at 7T.
超高场磁共振成像（MR）可用于改善颅内血流测量。然而，标准的心脏同步方法在超高场 MR 中往往会失效。因此，本研究旨在探讨一种使用多普勒超声的替代同步技术。
健康受试者（n=9）在 7T MR 下进行检查。使用平面相位对比（2D 流）测量大脑中动脉（MCA）M1 分支和脑导水管（CA）的血流。使用三维三向相位对比（4D 流）测量 Willis 环的血流。扫描与多普勒超声（DUS）和心电图（ECG）同步，并同时采集脉搏血氧仪数据（POX）。对 ECG、DUS 和 POX 进行假阴性和假阳性触发事件计数，并比较定量流量测量值。
与 ECG 相比，DUS 的假阳性触发更少（5.3±11 对 25±31，p=0.031），而其他测量参数无显著差异。M1 的净血流在 2D 流（1.5±0.39 对 1.6±0.41，偏倚±1.96SD：-0.021±0.36）和 4D 流（1.8±0.48 对 9±0.59，偏倚±1.96SD：-0.086±0.57）之间使用 DUS 和 ECG 时相似。CA 中每搏的净 CSF 流量也相似，DUS 和 ECG 分别为 3.6±2.1 和 3.0±5.8（偏倚±1.96SD：0.61±13.6 μl）。
与使用 ECG 相比，DUS 产生的假触发事件更少，且流量值相似。DUS 门控是超高场心脏同步的一种有前途的技术。
