Quantification of Lung Stiffness Using Magnetic Resonance Elastography (MRE): Clinical Validation for Smokers

: Tobacco-related pathologies are the most preventable diseases. The purpose is to provide personalized cartography of smoker lung stiffness using non-irradiating imaging modalities, MRI and MRE (magnetic resonance imaging/elastography). Thirty-four smokers were divided into five groups distributed with a range of pack-years (PY) of 10. All patients underwent three imaging tests (CT: computed tomography, MRI, MRE) to make possible measurements of lung density, with two modalities (CT, MR), and stiffness. CT lung density was measured using the Hounsfield number. MR density was obtained from a fast gradient echo sequence and validated with an in vitro 3D abdominal phantom. The MRE test was performed with a motion-encoding gradient (Z direction), a spin-echo echo-planar sequence and four offsets. A pneumatic driver (frequency: 50 Hz) was placed on the right lung and four axial phase images were recorded. Post-processing was then performed to record a personalized stiffness cartography. CT density significantly increased in relation to PY, showing denser tissue for the heavy smokers. As MR density acquisition is less accurate than CT, a slight increase in lung density was obtained. MRE tests revealed a significant increase in stiffness with pack-year. Patient-specific lung stiffness showed inhomogeneous distribution of values. MRE could provide a personalized cartography of stiffness for regular uptake of the lung's mechanical behavior in smokers. The stiffness could become a biomarker for preventing future lung disease. MRE test could be an alternative to CT test for the follow-up of smokers.