Intraocular Pressure–dependent Corneal Elasticity Measurement Using High-frequency Ultrasound

2019 ◽  
Vol 41 (5) ◽  
pp. 251-270 ◽  
Author(s):  
Laurentius O. Osapoetra ◽  
Dan M. Watson ◽  
Stephen A. McAleavey
Keyword(s):  
Intraocular Pressure ◽  
High Resolution ◽  
High Frequency ◽  
Wave Speed ◽  
Biomechanical Properties ◽  
Single Element ◽  
High Frequency Ultrasound ◽  
Spatially Resolved ◽  
Corneal Biomechanical Properties ◽  
Frequency Ultrasound

Measurement of corneal biomechanical properties can aid in predicting corneal responses to diseases and surgeries. For delineation of spatially resolved distribution of corneal elasticity, high-resolution elastography system is required. In this study, we demonstrate a high-resolution elastography system using high-frequency ultrasound for ex-vivo measurement of intraocular pressure (IOP)-dependent corneal wave speed. Tone bursts of 500 Hz vibrations were generated on the corneal surface using an electromagnetic shaker. A 35-MHz single-element transducer was used to track the resulting anti-symmetrical Lamb wave in the cornea. We acquired spatially resolved wave speed images of the cornea at IOPs of 7, 11, 15, 18, 22, and 29 mmHg. The IOP dependence of corneal wave speed is apparent from these images. Statistical analysis of measured wave speed as a function of IOP revealed a linear relation between wave speed and IOP cs = 0.37 + 0.22 × IOP, with the coefficient of determination R2 = 0.86. We also observed depth-dependent variations of wave speed in the cornea, decreasing from anterior toward posterior. This depth dependence is more pronounced at higher IOP values. This study demonstrates the potential of high-frequency ultrasound elastography in the characterization of spatially resolved corneal biomechanical properties.

Efficiency Control Cellulite Treatment Using High-Frequency Ultrasound Visualization of High Resolution

10.12737/5809 ◽  
2014 ◽  
Vol 8 (1) ◽  
pp. 1-2
Author(s):  
Белков ◽  
P. Belkov ◽  
Безуглый ◽  
A. Bezuglyy ◽  
Круглова ◽  
...  
Keyword(s):  
High Resolution ◽  
Human Skin ◽  
High Frequency ◽  
Subcutaneous Tissue ◽  
Control Group ◽  
Objective Data ◽  
High Frequency Ultrasound ◽  
Functional Parameters ◽  
Efficiency Control ◽  
Frequency Ultrasound

To describe ultrasonographic image of human skin with cellulite, the authors used high-frequency ultrasound visualization of the skin with a frequency of 22 MHz using a system DUB (tpm GmbH Germany). The skin on the thigh in 15 patients with cellulite and in 10 patients in the control group was examined. The differences in thickness and acoustic density of dermis and subcutaneous tissue between the group of patients with cellulite and in control were described. Objective data of high frequency ultrasound allow to quantify morphological and functional parameters of the skin in the dynamics and results of cellulite correction.

scholarly journals ZnO thin-film optimization towards the fabrication of high-frequency ultrasound transducers

2021 ◽  
Author(s):  
◽  
Ihab Sinno
Keyword(s):  
Zinc Oxide ◽  
High Frequency ◽  
Oxide Films ◽  
Single Element ◽  
High Deposition Rate ◽  
Ultrasound Transducers ◽  
Metal Contacts ◽  
High Frequency Ultrasound ◽  
Zinc Oxide Films ◽  
Frequency Ultrasound

<p>Zinc oxide is a popular wide bandgap semiconductor material with versatile electrical and optical properties. In its wurtzite crystal form, this semiconductor is piezoelectric, and has material properties that make it an attractive candidate for fabricating high frequency ultrasound transducers. This thesis describes the development of an RF sputtering process for creating zinc oxide films with thicknesses ranging from 3μm to 10μm, aiming for transducer frequencies of 300MHz to 1 GHz. Sputtering parameters are optimized to meet the dual requirements of a c-axis film orientation while maintaining a high deposition rate. These constraints and the dimensional characteristics of the utilized sputtering system, such as the short substrate-to-target distance, introduce high levels of strain in the deposited zinc oxide films. Various anneal procedures are developed to reduce film strain and optimize the resulting microstructure. It is found that annealing temperatures > 600°C eliminate the inherent film strain, but simultaneously result in the dewetting of the bottom metal contact, making this thermal treatment unsuitable for device processing. As an alternative to traditional metal contacts used in ultrasound transducers, the use of highly doped zinc oxide contacts is then investigated. It is shown that aluminium doped zinc oxide contacts provide an improved seed layer for device growth while eliminating the dewetting problems associated with metal contacts at high anneal temperatures. In addition, the use of such transparent conductive oxide contacts can lead to novel ultrasound applications, which benefit from the integration of optical and acoustic imaging in a single lens. A proof of concept all-zinc oxide single element ultrasound transducer structure is finally fabricated, to highlight the potential of an integrated optical-acoustic lens design.</p>

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

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.

High Frequency Ultrasound for High Resolution Skin Imaging

Frequenz ◽  
2001 ◽  
Vol 55 (1-2) ◽  
Author(s):  
Michael Vogt ◽  
Katharina Kaspar ◽  
Peter Altmeyer ◽  
Klaus Hoffmann ◽  
Stephan El Gammal
Keyword(s):  
High Resolution ◽  
High Frequency ◽  
High Frequency Ultrasound ◽  
Skin Imaging ◽  
Frequency Ultrasound

Mechanical Deformation of Peripapillary Retina in Response to Acute Intraocular Pressure Elevation

2022 ◽  
Author(s):  
Sunny Kwok ◽  
Manqi Pan ◽  
Nicholas Hazen ◽  
Xueliang Pan ◽  
Jun Liu
Keyword(s):  
Intraocular Pressure ◽  
High Frequency ◽  
Mechanical Deformation ◽  
Ultrasound Elastography ◽  
Radial Compression ◽  
High Shear ◽  
High Frequency Ultrasound ◽  
Tangential Strain ◽  
Frequency Ultrasound ◽  
Peripapillary Retina

Abstract Elevated intraocular pressure (IOP) may cause mechanical injuries to the optic nerve head (ONH) and the peripapillary tissues in glaucoma. Previous studies have reported the mechanical deformation of the ONH and the peripapillary sclera (PPS) at elevated IOP. The deformation of the peripapillary retina (PPR) has not been well-characterized. Here we applied high-frequency ultrasound elastography to map and quantify PPR deformation, and compared PPR, PPS and ONH deformation in the same eye. Whole globe inflation was performed in ten human donor eyes. High-frequency ultrasound scans of the posterior eye were acquired while IOP was raised from 5 to 30 mmHg. A correlation-based ultrasound speckle tracking algorithm was used to compute pressure-induced displacements within the scanned tissue cross-sections. Radial, tangential, and shear strains were calculated for the PPR, PPS, and ONH regions. In PPR, shear was significantly larger in magnitude than radial and tangential strains. Strain maps showed localized high shear and high tangential strains in PPR. In comparison to PPS and ONH, PPR had greater shear and a similar level of tangential strain. Surprisingly, PPR radial compression was minimal and significantly smaller than that in PPS. These results provide new insights into PPR deformation in response of IOP elevation, suggesting that shear rather than compression was likely the primary mode of IOP-induced mechanical insult in PPR. High shear, especially localized high shear, may contribute to the mechanical damage of this tissue in glaucoma.

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