Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
Siemens Medical Solutions Inc., Boston, Massachusetts, USA.
Magn Reson Med. 2021 Aug;86(2):954-963. doi: 10.1002/mrm.28765. Epub 2021 Mar 25.
To reduce inflow and motion artifacts in free-breathing, free-running, steady-state spoiled gradient echo T -weighted (SPGR) myocardial perfusion imaging.
Unsaturated spins from inflowing blood or out-of-plane motion cause flashing artifacts in free-running SPGR myocardial perfusion. During free-running SPGR, 1 non-selective RF excitation was added after every 3 slice-selective RF excitations to suppress inflow artifacts by forcing magnetization in neighboring regions to steady-state. Bloch simulations and phantom experiments were performed to evaluate the impact of the flip angle and non-selective RF frequency on inflowing spins and tissue contrast. Free-running perfusion with (n = 11) interleaved non-selective RF or without (n = 11) were studied in 22 subjects (age = 60.2 ± 14.3 years, 11 male). Perfusion images were graded on a 5-point Likert scale for conspicuity of wall enhancement, inflow/motion artifact, and streaking artifact and compared using Wilcoxon sum-rank testing.
Numeric simulation showed that 1 non-selective RF excitation applied after every 3 slice-selective RF excitations produced superior out-of-plane signal suppression compared to 1 non-selective RF excitation applied after every 6 or 9 slice-selective RF excitations. In vitro experiments showed that a 30° flip angle produced near-optimal myocardial contrast. In vivo experiments demonstrated that the addition of interleaved non-selective RF significantly (P < .01) improved conspicuity of wall enhancement (mean score = 4.4 vs. 3.2) and reduced inflow/motion (mean score = 4.5 vs. 2.5) and streaking (mean score = 3.9 vs. 2.4) artifacts.
Non-selective RF excitations interleaved between slice-selective excitations can reduce image artifacts in free-breathing, ungated perfusion images. Further studies are warranted to assess the diagnostic accuracy of the proposed solution for evaluating myocardial ischemia.
减少自由呼吸、自由运行、稳态失相位梯度回波 T 加权（SPGR）心肌灌注成像中的流入和运动伪影。
流入血液或平面外运动的不饱和自旋在自由运行 SPGR 心肌灌注中会产生闪烁伪影。在自由运行 SPGR 期间，在每 3 次层选 RF 激发后添加 1 次非选择性 RF 激发，通过迫使相邻区域的磁化达到稳态来抑制流入伪影。进行 Bloch 模拟和体模实验，以评估翻转角和非选择性 RF 频率对流入自旋和组织对比的影响。在 22 名受试者（年龄=60.2±14.3 岁，11 名男性）中研究了具有（n=11）和不具有（n=11）交错非选择性 RF 的自由运行灌注。使用 5 分 Likert 量表对壁增强、流入/运动伪影和条纹伪影的可见度进行分级，并使用 Wilcoxon 总和秩检验进行比较。
数值模拟表明，与每 6 次或 9 次层选 RF 激发后施加 1 次非选择性 RF 激发相比，每 3 次层选 RF 激发后施加 1 次非选择性 RF 激发产生更好的平面外信号抑制。体外实验表明，30°翻转角产生了近乎最佳的心肌对比度。体内实验表明，添加交错非选择性 RF 可显著（P<.01）提高壁增强的可见度（平均评分=4.4 对 3.2），并减少流入/运动（平均评分=4.5 对 2.5）和条纹（平均评分=3.9 对 2.4）伪影。
在层选激发之间交错施加非选择性 RF 激发可以减少自由呼吸、无门控灌注图像中的图像伪影。需要进一步的研究来评估所提出的解决方案评估心肌缺血的诊断准确性。
Zotero 插件