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Proceedings Paper

High-frequency harmonic imaging of the eye
Author(s): Ronald H. Silverman; D. Jackson Coleman M.D.; Jeffrey A. Ketterling; Frederic L. Lizzi
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Paper Abstract

Purpose: Harmonic imaging has become a well-established technique for ultrasonic imaging at fundamental frequencies of 10 MHz or less. Ophthalmology has benefited from the use of fundamentals of 20 MHz to 50 MHz. Our aim was to explore the ability to generate harmonics for this frequency range, and to generate harmonic images of the eye. Methods: The presence of harmonics was determined in both water and bovine vitreous propagation media by pulse/echo and hydrophone at a series of increasing excitation pulse intensities and frequencies. Hydrophone measurements were made at the focal point and in the near- and far-fields of 20 MHz and 40 MHz transducers. Harmonic images of the anterior segment of the rabbit eye were obtained by a combination of analog filtering and digital post-processing. Results: Harmonics were generated nearly identically in both water and vitreous. Hydrophone measurements showed the maximum second harmonic to be -5 dB relative to the 35 MHz fundamental at the focus, while in pulse/echo the maximum harmonic amplitude was -15dB relative to the fundamental. Harmonics were absent in the near-field, but present in the far-field. Harmonic images of the eye showed improved resolution. Conclusion: Harmonics can be readily generated at very high frequencies, and at power levels compliant with FDA guidelines for ophthalmology. This technique may yield further improvements to the already impressive resolutions obtainable in this frequency range. Improved imaging of the macular region, in particular, may provide significant improvements in diagnosis of retinal disease.

Paper Details

Date Published: 12 April 2005
PDF: 10 pages
Proc. SPIE 5750, Medical Imaging 2005: Ultrasonic Imaging and Signal Processing, (12 April 2005); doi: 10.1117/12.595412
Show Author Affiliations
Ronald H. Silverman, Weill Medical College of Cornell Univ. (United States)
D. Jackson Coleman M.D., Weill Medical College of Cornell Univ. (United States)
Jeffrey A. Ketterling, Riverside Research Institute (United States)
Frederic L. Lizzi, Riverside Research Institute (United States)

Published in SPIE Proceedings Vol. 5750:
Medical Imaging 2005: Ultrasonic Imaging and Signal Processing
William F. Walker; Stanislav Y. Emelianov, Editor(s)

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