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Microvasculature alters the dispersion properties of shear waves – a multi‐frequency MR elastography study
Author(s) -
Jugé Lauriane,
Petiet Anne,
Lambert Simon A.,
Nicole Pascal,
Chatelin Simon,
Vilgrain Valerie,
Van Beers Bernard E.,
Bilston Lynne E.,
Sinkus Ralph
Publication year - 2015
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3438
Subject(s) - materials science , magnetic resonance elastography , dispersion (optics) , shear waves , nuclear magnetic resonance , shear (geology) , elastography , biomedical engineering , optics , physics , ultrasound , composite material , acoustics , medicine
Magnetic Resonance Elastography (MRE) uses macroscopic shear wave propagation to quantify mechanical properties of soft tissues. Micro‐obstacles are capable of affecting the macroscopic dispersion properties of shear waves. Since disease or therapy can change the mechanical integrity and organization of vascular structures, MRE should be able to sense these changes if blood vessels represent a source for wave scattering. To verify this, MRE was performed to quantify alteration of the shear wave speed c s due to the presence of vascular outgrowths using an aortic ring model. Eighteen fragments of rat aorta included in a Matrigel matrix (n=6 without outgrowths, n=6 with a radial outgrowth extent of ~600µm and n=6 with ~850µm) were imaged using a 7 Tesla MR scanner (Bruker, PharmaScan). High resolution anatomical images were acquired in addition to multi‐frequency MRE (ν = 100, 115, 125, 135 and 150 Hz). Average c s was measured within a ring of ~900µm thickness encompassing the aorta and were normalized to c s0 of the corresponding Matrigel. The frequency dependence was fit to the power law model c s ~ν y . After scanning, optical microscopy was performed to visualize outgrowths. Results demonstrated that in presence of vascular outgrowths (1) normalized c s significantly increased for the three highest frequencies (Kruskal‐Wallis test, P = 0.0002 at 125 Hz and P = 0.002 at 135 Hz and P = 0.003 at 150 Hz) but not for the two lowest (Kruskal‐Wallis test, P = 0.63 at 100 Hz and P = 0.87 at 115 Hz), and (2) normalized c s followed a power law behavior not seen in absence of vascular outgrowths (ANOVA test, P < 0.0001). These results showed that vascular outgrowths acted as micro‐obstacles altering the dispersion relationships of propagating shear waves and that MRE could provide valuable information about microvascular changes. Copyright © 2015 John Wiley & Sons, Ltd.