Magnetic resonance elastography of the lungs: A repeatability and reproducibility study

Abstract

Lung diseases are one of the leading causes of death worldwide, from which four million people die annually. Lung diseases are associated with changes in the mechanical properties of the lungs. Several studies have shown the feasibility of using magnetic resonance elastography (MRE) to quantify the lungs' shear stiffness. The aim of this study is to investigate the reproducibility and repeatability of lung MRE, and its shear stiffness measurements, obtained using a modified spin echo‐echo planar imaging (SE‐EPI) MRE sequence. In this study, 21 healthy volunteers were scanned twice by repositioning the volunteers to image right lung both at residual volume (RV) and total lung capacity (TLC) to assess the reproducibility of lung shear stiffness measurements. Additionally, 19 out of the 21 volunteers were scanned immediately without moving the volunteers to test the repeatability of the modified SE‐EPI MRE sequence. A paired t‐test was performed to determine the significant difference between stiffness measurements obtained at RV and TLC. Concordance correlation and Bland–Altman's analysis were performed to determine the reproducibility and repeatability of the SE‐EPI MRE‐derived shear stiffness measurements. The SE‐EPI MRE sequence is highly repeatable with a concordance correlation coefficient (CCC) of 0.95 at RV and 0.96 at TLC. Similarly, the stiffness measurements obtained across all volunteers were highly reproducible with a CCC of 0.95 at RV and 0.92 at TLC. The mean shear stiffness of the lung at RV was 0.93 ± 0.22 kPa and at TLC was 1.41 ± 0.41 kPa. TLC showed a significantly higher mean shear stiffness (P = 0.0004) compared with RV. Lung MRE stiffness measurements obtained using the SE‐EPI sequence were reproducible and repeatable, both at RV and TLC. Lung shear stiffness changes across respiratory cycle with significantly higher stiffness at TLC than RV.

Magnetic resonance elastography for estimating in vivo stiffness of the abdominal aorta using cardiac‐gated spin‐echo echo‐planar imaging: a feasibility study

“…5 To date, MRE has been used to measure the stiffness in various organs, including the brain, [6][7][8] breast, 9,10 skeletal muscle, 11,12 heart, 13,14 kidney 15 and lung. 16,17 Aortic stiffness is known to be closely associated with a variety of cardiovascular comorbidities, such as systemic arterial hypertension 18 and abdominal aortic aneurysm (AAA). 19 Recent development in aortic MRE has demonstrated that it is feasible to measure in vivo aortic stiffness in the healthy aorta [20][21][22] as well as in the aorta with abnormalities.…”

“…These encouraging results and the versatility of MRE have stimulated considerable research advancing this novel technique towards more clinical applications 5 . To date, MRE has been used to measure the stiffness in various organs, including the brain, 6–8 breast, 9,10 skeletal muscle, 11,12 heart, 13,14 kidney 15 and lung. 16,17 …”

Free‐breathing MR elastography of the lungs: An in vivo study

“…This decrease in lungs density might be attributed to the degeneration of elastic fibers in the alveolar ducts. 15 In previous studies conducted by Mariappan et al and Fakhouri et al, 10,22,23 only the right lung was scanned to avoid artifacts caused by the heart motion in the left lung. However, in this study both the right and left lungs were scanned by using SE-spiral and SE-EPI sequences.…”

“…Several studies have shown the feasibility of quantifying lung’s shear stiffness by using MRE 10,21,22 . Those studies were performed on the right lung only during breathhold at residual volume, midpoint of tidal volume, and at total lung capacity 10,23 . It was shown that MRE was capable of detecting significant differences in lung’s shear stiffness across the respiratory cycle 10,23 .…”

Advances and Future Direction of Magnetic Resonance Elastography

“…It was demonstrated that the change in shear stiffness was observed due to change in airway opening pressure. Recently, the reproducibility of lung MRE was studied using an SE-EPI MRE sequence in 15 healthy volunteers 123 . Good reproducibility of lung MRE-derived stiffness measurements was observed in RV (R2=0.88) and TLC (R2=0.96).…”