Microscopic multifrequency MR elastography for mapping viscoelasticity in zebrafish

Abstract

Purpose The zebrafish (Danio rerio) has become an important animal model in a wide range of biomedical research disciplines. Growing awareness of the role of biomechanical properties in tumor progression and neuronal development has led to an increasing interest in the noninvasive mapping of the viscoelastic properties of zebrafish by elastography methods applicable to bulky and nontranslucent tissues. Methods Microscopic multifrequency MR elastography is introduced for mapping shear wave speed (SWS) and loss angle (φ) as markers of stiffness and viscosity of muscle, brain, and neuroblastoma tumors in postmortem zebrafish with 60 µm in‐plane resolution. Experiments were performed in a 7 Tesla MR scanner at 1, 1.2, and 1.4 kHz driving frequencies. Results Detailed zebrafish viscoelasticity maps revealed that the midbrain region (SWS = 3.1 ± 0.7 m/s, φ = 1.2 ± 0.3 radian [rad]) was stiffer and less viscous than telencephalon (SWS = 2.6 ± 0. 5 m/s, φ = 1.4 ± 0.2 rad) and optic tectum (SWS = 2.6 ± 0.5 m/s, φ = 1.3 ± 0.4 rad), whereas the cerebellum (SWS = 2.9 ± 0.6 m/s, φ = 0.9 ± 0.4 rad) was stiffer but less viscous than both (all p < .05). Overall, brain tissue (SWS = 2.9 ± 0.4 m/s, φ = 1.2 ± 0.2 rad) had similar stiffness but lower viscosity values than muscle tissue (SWS = 2.9 ± 0.5 m/s, φ = 1.4 ± 0.2 rad), whereas neuroblastoma (SWS = 2.4 ± 0.3 m/s, φ = 0.7 ± 0.1 rad, all p < .05) was the softest and least viscous tissue. Conclusion Microscopic multifrequency MR elastography‐generated maps of zebrafish show many details of viscoelasticity and resolve tissue regions, of great interest in neuromechanical and oncological research and for which our study provides first reference values.

Ex vivo magnetic resonance elastography of the small bowel in Crohn’s disease

“…The consistency of our method was confirmed in a wellcharacterized tissue-mimicking phantom providing values in agreement with shear oscillatory rheometry (47). Due to this consistency, tabletop MRE was used in previous studies (41,(48)(49)(50) as a reference method and was employed here without further calibration. Shear wave speed c, shear wave penetration rate a, and damping ratio γ were determined as surrogate markers of stiffness, viscosity, and dissipation, respectively.…”

Liquid-Liver Phantom

“…In THE and MRE, plane shear waves were introduced by a vibration plate immersed in the phantom while tabletop MRE induced cylindrical waves in a glass tube. Tabletop MRE in cylindrical samples has been used as a reference method in many studies 37–40 . The experimental setups are illustrated in Figure 1.…”

“…Tabletop MRE in cylindrical samples has been used as a reference method in many studies. [37][38][39][40] The experimental setups are illustrated in Figure 1.…”

Mechanical properties of breast, kidney, and thyroid tumours measured by AFM: Relationship with tissue structure

“…Our findings on the mechanical properties of breast, kidney, and thyroid tumour tissue will allow the development of similar biomaterials, in order to elucidate the role of stiffness and viscosity for metastatic spread depending on cancer subtype. With the progress of in vivo techniques to characterise the viscoelastic properties of soft tissues with a higher spatial resolution, namely SWE(51) and microscopic Magnetic Resonance Elastography (MRE)(52)(53)(54), the mechanical properties of the tumour could then be used as an in vivo predictive marker of bone metastasis formation.In conclusion, this study elucidated the modification of the viscoelastic properties of tumour tissue from different types of cancer. While the elastic modulus of breast tumour tissue increased compared to the normal surrounding tissue, various effects were observed for kidney thyroid tissue depending on the type, structure and composition of the tumour.…”