Ex Vivo Evaluation of Mouse Brain Elasticity Using High-Frequency Ultrasound Elastography

Abstract Optical coherence tomography (OCT) and high-frequency ultrasound (HFUS), two established imaging modalities in the field of dermatology, were evaluated and compared regarding their applicability for visualization of skin tissue morphology and quantification of murine intradermal structures. The accuracy and reproducibility of both methods were assessed ex vivo and in vivo using a standardized model for intradermal volumes based on injected soft tissue fillers. OCT revealed greater detail in skin morphology, allowing for detection of single layers due to the superior resolution. Volumetric data measured by OCT (7.9 ± 0.3 μl) and HFUS (7.7 ± 0.5 μl) were in good agreement and revealed a high accuracy when compared to the injected volume of 7.98 ± 0.8 µl. In vivo, OCT provided a higher precision (relative SD: 26% OCT vs. 42% HFUS) for the quantification of intradermal structures, whereas HFUS offered increased penetration depth enabling the visualization of deeper structures. A combination of both imaging technologies might be valuable for tumor assessments or other dermal pathologies in clinical settings.

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In vivo imaging of swimming micromotors using hybrid high-frequency ultrasound and photoacoustic imaging

10.1101/2020.06.15.148791 ◽

2020 ◽

Author(s):

Azaam Aziz ◽

Joost Holthof ◽

Sandra Meyer ◽

Oliver G. Schmidt ◽

Mariana Medina-Sánchez

Keyword(s):

High Frequency ◽

Imaging System ◽

Ex Vivo ◽

Photoacoustic Imaging ◽

Imaging Techniques ◽

High Frequency Ultrasound ◽

Living Organisms ◽

And Function ◽

Frequency Ultrasound

AbstractThe fast evolution of medical micro- and nanorobots in the endeavor to perform non-invasive medical operations in living organisms boosted the use of diverse medical imaging techniques in the last years. Among those techniques, photoacoustic (PA) tomography has shown to be promising for the imaging of microrobots in deep-tissue (ex vivo and in vivo), as it possesses the molecular specificity of optical techniques and the penetration depth of ultrasound imaging. However, the precise maneuvering and function control of microrobots, in particular in living organisms, demand the combination of both anatomical and functional imaging methods. Therefore, herein, we report the use of a hybrid High-Frequency Ultrasound (HFUS) and PA imaging system for the real-time tracking of magnetically driven micromotors (single and swarms) in phantoms, ex vivo, and in vivo (in mice bladder and uterus), envisioning their application for targeted drug-delivery.

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Regional variation of corneal stromal deformation measured by high-frequency ultrasound elastography

Experimental Biology and Medicine ◽

10.1177/15353702211029283 ◽

2021 ◽

pp. 153537022110292

Author(s):

Sunny Kwok ◽

Nicholas Hazen ◽

Keyton Clayson ◽

Xueliang Pan ◽

Jun Liu

Keyword(s):

Intraocular Pressure ◽

Cross Section ◽

High Frequency ◽

Regional Variation ◽

Corneal Stroma ◽

Ultrasound Elastography ◽

High Frequency Ultrasound ◽

Intraocular Pressure Elevation ◽

Shear Strains ◽

Frequency Ultrasound

The cornea’s mechanical response to intraocular pressure elevations may alter in ectatic diseases such as keratoconus. Regional variations of mechanical deformation in normal and keratoconus eyes during intraocular pressure elevation have not been well-characterized. We applied a high-frequency ultrasound elastography technique to characterize the regional deformation of normal and keratoconus human corneas through the full thickness of corneal stroma. A cross-section centered at the corneal apex in 11 normal and 2 keratoconus human donor eyes was imaged with high-frequency ultrasound during whole globe inflation from 5 to 30 mmHg. An ultrasound speckle tracking algorithm was used to compute local tissue displacements. Radial, tangential, and shear strains were mapped across the imaged cross-section. Strains in the central (1 mm surrounding apex) and paracentral (1 to 4 mm from apex) regions were analyzed in both normal and keratoconus eyes. Additional regional analysis was performed in the eye with severe keratoconus presenting significant thinning and scarring. Our results showed that in normal corneas, the central region had significantly smaller tangential stretch than the paracentral region, and that within the central region, the magnitudes of radial and shear strains were significantly larger than that of tangential strain. The eye with mild keratoconus had similar shear strain but substantially larger radial strains than normal corneas, while the eye with severe keratoconus had similar overall strains as in normal eyes but marked regional heterogeneity and large strains in the cone region. These findings suggested regional variation of mechanical responses to intraocular pressure elevation in both normal and keratoconus corneas, and keratoconus appeared to be associated with mechanical weakening in the cone region, especially in resisting radial compression. Comprehensive characterization of radial, tangential, and shear strains through corneal stroma may provide new insights to understand the biomechanical alterations in keratoconus.

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