title: Microvasculature alters the dispersion properties of shear waves--a multi-frequency MR elastography study.
abstract: 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 cs 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 ~600 µm and n=6 with ~850 µm) 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 cs was measured within a ring of ~900 µm thickness encompassing the aorta and were normalized to cs0 of the corresponding Matrigel. The frequency dependence was fit to the power law model cs ~ν(y). After scanning, optical microscopy was performed to visualize outgrowths. Results demonstrated that in presence of vascular outgrowths (1) normalized cs 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 cs 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.
authors.affiliation: Neuroscience Research Australia, Randwick, Sidney, NSW, Australia.|School of Medical Sciences, University of New South Wales, Kensington, Sidney, NSW, Australia.
authors.forename: Lauriane
authors.initials: L
authors.lastname: Jugé
authors.affiliation: Fédération de Recherche en Imagerie multimodalité (FRIM), U1148 INSERM, UFR de Médecine, University Paris Diderot, Sorbonne Paris Cité, Paris, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Petiet
authors.affiliation: BHF Centre of Excellence, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Lambert
authors.affiliation: Laboratory from inflammation to cancer in digestive diseases, UMR1149 INSERM, University Paris Diderot, Sorbonne Paris Cité, Paris, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Nicole
authors.affiliation: Laboratory of Imaging Biomarkers, UMR1149 INSERM, University Paris Diderot, Sorbonne Paris Cité, Paris, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Chatelin
authors.affiliation: Laboratory of Imaging Biomarkers, UMR1149 INSERM, University Paris Diderot, Sorbonne Paris Cité, Paris, France.|Department of Radiology, Beaujon University Hospital Paris Nord, Clichy, France.
authors.forename: Valerie
authors.initials: V
authors.lastname: Vilgrain
authors.affiliation: Laboratory of Imaging Biomarkers, UMR1149 INSERM, University Paris Diderot, Sorbonne Paris Cité, Paris, France.|Department of Radiology, Beaujon University Hospital Paris Nord, Clichy, France.
authors.forename: Bernard E
authors.initials: BE
authors.lastname: Van Beers
authors.affiliation: Neuroscience Research Australia, Randwick, Sidney, NSW, Australia.|Prince of Wales Clinical School, University of New South Wales, Kensington, Sydney, NSW, Australia.
authors.forename: Lynne E
authors.initials: LE
authors.lastname: Bilston
authors.affiliation: BHF Centre of Excellence, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
authors.forename: Ralph
authors.initials: R
authors.lastname: Sinkus
mesh_terms: D000818:Animals; D001011:Aorta / Q000033:anatomy & histology / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D066298:In Vitro Techniques; D060526:Magnetic Fields; D008297:Male; D055806:Microvessels / Q000033:anatomy & histology / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D033081:Shear Strength / Q000502:physiology
keywords: MR elastography (MRE); aortic ring model; shear wave speed (cs); structural imaging biomarkers; viscoelasticity