Department of Radiology, University Medical Centre Utrecht, 3584CX, Utrecht, the Netherlands.
Magn Reson Med. 2018 Jan;79(1):593-599. doi: 10.1002/mrm.26651. Epub 2017 Feb 28.
Robust fat suppression is essential in bilateral breast MRI at 7 Tesla. The lack of good fat suppression can result in errors when calculating the enhancement curve from dynamic contrast-enhanced acquisitions. In this work we propose discretized frequency shimming to improve the quality of fat suppression by exploiting the capabilities of a parallel transmit setup.
With discretized frequency shimming, different resonance frequencies are used for the different transmitters of the radiofrequency coil. This can be particularly useful for frequency-selective radiofrequency pulses, such as water excitation. The potential of this method has been investigated by simulations on seven acquired B maps. Prospective experiments on phantoms and four healthy volunteers were performed to illustrate the performance of discretized frequency shimming.
Simulations show a decrease in off-resonance excitation for all subjects when discretized frequency shimming is used. This decrease is highly subject-dependent, but can result in up to 30% better fat suppression, as observed in phantom and volunteer experiments.
Discretized frequency shimming improves fat suppression in bilateral breast MRI at 7 Tesla. Magn Reson Med 79:593-599, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
在 7 特斯拉双侧乳腺 MRI 中，稳健的脂肪抑制至关重要。如果动态对比增强采集的增强曲线计算中缺乏良好的脂肪抑制，可能会导致错误。在这项工作中，我们提出了离散频率调谐，通过利用并行传输设置的功能来提高脂肪抑制的质量。
通过离散频率调谐，为射频线圈的不同发射器使用不同的共振频率。这对于诸如水激发之类的频率选择射频脉冲特别有用。通过对七个采集的 B 图进行模拟研究，研究了该方法的潜力。对四个健康志愿者的前瞻性实验说明了离散频率调谐的性能。
模拟结果表明，使用离散频率调谐时，所有受试者的离共振激发均减少。这种减少高度依赖于个体，但可以在体模和志愿者实验中观察到高达 30%的更好的脂肪抑制效果。
离散频率调谐可改善 7 特斯拉双侧乳腺 MRI 的脂肪抑制效果。磁共振医学杂志 79:593-599, 2018。© 2017 国际磁共振学会。
