Imaging gravity-induced lung water redistribution with automated inline processing at 0.55 T cardiovascular magnetic resonance

Abstract

Background Quantitative assessment of dynamic lung water accumulation is of interest to unmask latent heart failure. We develop and validate a free-breathing 3D ultrashort echo time (UTE) sequence with automated inline image processing to image changes in lung water density (LWD) using high-performance 0.55 T cardiovascular magnetic resonance (CMR). Methods Quantitative lung water CMR was performed on 15 healthy subjects using free-breathing 3D stack-of-spirals proton density weighted UTE at 0.55 T. Inline image reconstruction and automated image processing was performed using the Gadgetron framework. A gravity-induced redistribution of LWD was provoked by sequentially acquiring images in the supine, prone, and again supine position. Quantitative validation was performed in a phantom array of vials containing mixtures of water and deuterium oxide. Results The phantom experiment validated the capability of the sequence in quantifying water density (bias ± SD 4.3 ± 4.8%, intraclass correlation coefficient, ICC = 0.97). The average global LWD was comparable between imaging positions (supine 24.7 ± 3.4%, prone 22.7 ± 3.1%, second supine 25.3 ± 3.6%), with small differences between imaging phases (first supine vs prone 2.0%, p < 0.001; first supine vs second supine − 0.6%, p = 0.001; prone vs second supine − 2.7%, p < 0.001). In vivo test–retest repeatability in LWD was excellent (− 0.17 ± 0.91%, ICC = 0.97). A regional LWD redistribution was observed in all subjects when repositioning, with a predominant posterior LWD accumulation when supine, and anterior accumulation when prone (difference in anterior–posterior LWD: supine − 11.6 ± 2.7%, prone 5.5 ± 2.7%, second supine − 11.4 ± 2.9%). Global LWD maps were calculated inline within 23.2 ± 0.3 s following the image reconstruction using the automated pipeline. Conclusions Redistribution of LWD due to gravitational forces can be depicted and quantified using a validated free-breathing 3D proton density weighted UTE sequence and inline automated image processing pipeline on a high-performance 0.55 T CMR system.

Lung parenchyma transverse relaxation rates at 0.55 T

“…Note that the measurements were acquired on one single coronal slice that intersects the center of the descending aorta, and the different slices may result in different measurements due to gravitation dependence of lung water distribution. 26 …”

“…The $$$ {R}_2^{\prime } $$$ estimate from the proposed ES‐MCSE method shows less intersubject variance with higher precision than that from the reference methods. Note that the measurements were acquired on one single coronal slice that intersects the center of the descending aorta, and the different slices may result in different measurements due to gravitation dependence of lung water distribution 26 …”

“…Note that the measurements were acquired on one single coronal slice that intersects the center of the descending aorta, and the different slices may result in different measurements due to gravitation dependence of lung water distribution. 26 The ranges of R 2 and R ′ 2 (or R * 2 ) are decreased at low field; this allows flexibility in pulse sequence design, including a longer readout in spiral imaging, in multi-echo imaging, and in non-Cartesian bSSFP imaging. With a smaller R * 2 value at 0.55 T, a longer readout time up to 10 ms could be used to further improve imaging efficiency.…”

Dynamic lung water MRI during exercise stress

“…[4][5][6] MRI has recently been proposed as a promising method to noninvasively quantify lung water. 4,[7][8][9][10] MRI addresses some limitations of current clinical lung water assessments, which include invasive cardiac catheterization, semi-quantitative ultrasound, or ionizing radiation exposing computed tomography and x-ray. [11][12][13] Previous work has found that lung water MRI can depict a regional redistribution of edema, 9,14 and is associated with myocardial energetic deficits in heart failure with preserved ejection fraction (HFpEF).…”

“…4,[7][8][9][10] MRI addresses some limitations of current clinical lung water assessments, which include invasive cardiac catheterization, semi-quantitative ultrasound, or ionizing radiation exposing computed tomography and x-ray. [11][12][13] Previous work has found that lung water MRI can depict a regional redistribution of edema, 9,14 and is associated with myocardial energetic deficits in heart failure with preserved ejection fraction (HFpEF). 8 These previous studies acquired images at rest or shortly after exercise, but transient changes in lung water during exercise is yet to be imaged using MRI.…”