Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States of America.
PLoS One. 2021 Jul 19;16(7):e0254758. doi: 10.1371/journal.pone.0254758. eCollection 2021.
Respiratory motion management is crucial for high-resolution MRI of the heart, lung, liver and kidney. In this article, respiration guide using acoustic sound generated by pulsed gradient waveforms was introduced in the pulmonary ultrashort echo time (UTE) sequence and validated by comparing with retrospective respiratory gating techniques. The validated sound-guided respiration was implemented in non-contrast enhanced renal angiography. In the sound-guided respiration, breathe-in and-out instruction sounds were generated with sinusoidal gradient waveforms with two different frequencies (602 and 321 Hz). Performance of the sound-guided respiration was evaluated by measuring sharpness of the lung-liver interface with a 10-90% rise distance, w10-90, and compared with three respiratory motion managements in a free-breathing UTE scan: without respiratory gating (w/o gating), 0-dimensional k-space navigator (k-point navigator), and image-based self-gating (Img-SG). The sound-guided respiration was implemented in stack-of-stars balanced steady-state free precession with inversion recovery preparation for renal angiography. No subjects reported any discomfort or inconvenience with the sound-guided respiration in pulmonary or renal MRI scans. The lung-liver interface of the UTE images for sound-guided respiration (w10-90 = 6.99 ± 2.90 mm), k-point navigator (8.51 ± 2.71 mm), and Img-SG (7.01 ± 2.06 mm) was significantly sharper than that for w/o gating (17.13 ± 2.91 mm; p < 0.0001 for all of sound-guided respiration, k-point navigator and Img-SG). Sharpness of the lung-liver interface was comparable between sound-guided respiration and Img-SG (p = 0.99), but sound-guided respiration achieved better visualization of pulmonary vasculature. Renal angiography with the sound-guided respiration clearly delineated renal, segmental and interlobar arteries. In conclusion, the gradient sound guided respiration can facilitate a consistent diaphragm position in every breath and achieve performance of respiratory motion management comparable to image-based self-gating.
呼吸运动管理对于心脏、肺、肝和肾的高分辨率 MRI 至关重要。本文介绍了在肺部超短回波时间（UTE）序列中使用脉冲梯度波形产生的声信号进行呼吸引导，并通过与回顾性呼吸门控技术进行比较进行了验证。经过验证的声控呼吸被应用于非对比增强的肾血管造影中。在声控呼吸中，吸气和呼气指令声是通过具有两个不同频率（602Hz 和 321Hz）的正弦梯度波形产生的。通过测量肺-肝界面的锐度来评估声控呼吸的性能，使用 10-90%上升距离 w10-90 进行评估，并与自由呼吸 UTE 扫描中的三种呼吸运动管理方法进行比较：无呼吸门控（w/o 门控）、0 维 k 空间导航器（k-点导航器）和基于图像的自门控（Img-SG）。声控呼吸应用于反转恢复准备的星形堆叠平衡稳态自由进动的肾血管造影中。在肺部或肾脏 MRI 扫描中，没有受试者报告对声控呼吸有任何不适或不便。声控呼吸的 UTE 图像的肺-肝界面（w10-90 = 6.99 ± 2.90mm）、k 点导航器（8.51 ± 2.71mm）和 Img-SG（7.01 ± 2.06mm）明显比无门控（17.13 ± 2.91mm;p<0.0001 用于所有的声控呼吸、k 点导航器和 Img-SG）更清晰锐利。声控呼吸和 Img-SG 的肺-肝界面锐度相当（p=0.99），但声控呼吸可更好地显示肺部血管。具有声控呼吸的肾血管造影可清晰描绘肾、节段和叶间动脉。总之，梯度声控呼吸可以在每次呼吸中保持一致的膈肌位置，并实现与基于图像的自门控相当的呼吸运动管理性能。
