Effect of Corneal Hydration on Ultrasound Velocity and Backscatter

Ronald H. Silverman, Monica S. Patel, Omer Gal, Aman Sarup, Avnish Deobhakta, Haitham Dababneh, Dan Z. Reinstein, Ernest J. Feleppa, D. Jackson Coleman

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

The cornea's acoustic properties (speed-of-sound, backscatter, attenuation) are related to its state of hydration. Our aim was to determine these properties as a function of corneal hydration using high-frequency ultrasound. Bovine corneas were suspended in a Dexsol-equivalent corneal preservation medium at 33 °C and then immersed successively in 75%, 50% and 25% medium and distilled water. Using a 38-MHz focused ultrasound transducer, we measured speed-of-sound and corneal thickness (n = 8) and stromal backscatter (n = 6) after 45-min immersion in each medium. Corneal speed-of-sound was modeled as a function of corneal thickness. We found the mean speed-of-sound to be 1605.4 ± 2.9 m/s in normotensive medium. The maximum observed speed-of-sound was 1616 m/s. As we decreased medium tonicity, the cornea swelled and the speed-of-sound decreased, reaching 1563.0 ± 2.2 m/s in water. Average corneal thickness increased from 969 ± 93 μm in 100% medium to 1579 ± 104 μm in water. Going from 100% medium to water, stromal backscatter (midband-fit) increased from -60.0 ± 0.8 dBr to -52.5 ± 3.5 dBr, spectral slope increased from -0.119 ± 0.021 to -0.005 ± 0.030 dB/MHz and attenuation coefficient decreased from 0.927 ± 0.434 to 0.010 ± 0.581 dB/cm-MHz. The observed correlation between acoustic backscatter and attenuation with the speed-of-sound offers a potential means for more accurate determination of speed-of-sound and, hence, thickness in edematous corneas. (E-mail: ros2012@med.cornell.edu).

Original languageEnglish
Pages (from-to)839-846
Number of pages8
JournalUltrasound in Medicine and Biology
Volume35
Issue number5
DOIs
StatePublished - May 2009
Externally publishedYes

Keywords

  • Backscatter
  • Cornea
  • Edema
  • Spectrum-analysis
  • Speed-of-sound
  • Ultrasound

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