Magnetic resonance imaging with gradient sound respiration guide.

Xi Chen,Naoharu Kobayashi

doi:10.1371/journal.pone.0254758

Xi Chen, Naoharu Kobayashi

Open Access

https://doi.org/10.1371/journal.pone.0254758

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Abstract

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.

Highlights

Respiratory motion management is crucial for high-resolution magnetic resonance imaging (MRI) of the heart, lung, liver and kidney
The k-point navigator signal was correlated well with the diaphragm position (R2 = 0.7972; Fig 3E); there was a gradual decrease of the k-point navigator signal from the beginning to the end of the MRI scan observed, whereas Img-SG showed a similar gradual increase of the diaphragm position (Fig 3B and 3C)
Average respiration rate during the free-breathing scan, which was calculated from the trigger timings of the k-point navigator, was 13.97 ± 3.39 breaths/min (4.54 ± 1.20 sec/breath), which is higher than the respiration rate in sound-guided scans (10 breaths/min)

Summary

Introduction

Respiratory motion management is crucial for high-resolution magnetic resonance imaging (MRI) of the heart, lung, liver and kidney. The diaphragm during relaxed respiration typically moves 1–3 cm mainly in the superior-inferior direction [1,2,3,4]. Physiological monitoring using a respiration bellows is often poorly coupled with the diaphragmatic motion, which may result in inaccurate respiratory motion estimation [5,6,7]. Breath-holding is another frequently used strategy to compensate respiratory motion during MRI scans. Breath-holding limits the scan time to typically 10–20 seconds and can be challenging for patients with reduced lung function. Use of multiple breath-holds can mitigate the scan time limitation, but inconsistent diaphragm position in each breath-hold often results in residual motion artifacts [8]

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