Document Detail

High-frequency ultrasonic imaging of the anterior segment using an annular array transducer.
MedLine Citation:
PMID:  17141314     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: Very high-frequency ultrasound (VHFU; >35 megahertz [MHz]) allows imaging of anterior segment structures of the eye with a resolution of less than 40 microm. The low focal ratio of VHFU transducers, however, results in a depth of field (DOF) of less than 1 mm. The aim was to develop a high-frequency annular array transducer for ocular imaging with improved DOF, sensitivity, and resolution compared with conventional transducers.
DESIGN: Experimental study.
PARTICIPANTS: Cadaver eyes, ex vivo cow eyes, in vivo rabbit eyes.
METHODS: A spherically curved annular array ultrasound transducer was fabricated. The array consisted of 5 concentric rings of equal area, had an overall aperture of 6 mm, and a geometric focus of 12 mm. The nominal center frequency of all array elements was 40 MHz. An experimental system was designed in which a single array element was pulsed and echo data were recorded from all elements. By sequentially pulsing each element, echo data were acquired for all 25 transmit-and-receive annuli combinations. The echo data then were focused synthetically and composite images were produced. Transducer operation was tested by scanning a test object consisting of a series of 25-microm diameter wires spaced at increasing range from the transducer. Imaging capabilities of the annular array were demonstrated in ex vivo bovine, in vivo rabbit, and human cadaver eyes.
MAIN OUTCOME MEASURES: Depth of field, resolution, and sensitivity.
RESULTS: The wire scans verified the operation of the array and demonstrated a 6.0-mm DOF, compared with the 1.0-mm DOF of a conventional single-element transducer of comparable frequency, aperture, and focal length. B-mode images of ex vivo bovine, in vivo rabbit, and cadaver eyes showed that although the single-element transducer had high sensitivity and resolution within 1 to 2 mm of its focus, the array with synthetic focusing maintained this quality over a 6-mm DOF.
CONCLUSIONS: An annular array for high-resolution ocular imaging has been demonstrated. This technology offers improved DOF, sensitivity, and lateral resolution compared with single-element fixed focus transducers currently used for VHFU imaging of the eye.
Ronald H Silverman; Jeffrey A Ketterling; D Jackson Coleman
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2006-11-30
Journal Detail:
Title:  Ophthalmology     Volume:  114     ISSN:  1549-4713     ISO Abbreviation:  Ophthalmology     Publication Date:  2007 Apr 
Date Detail:
Created Date:  2007-04-02     Completed Date:  2007-04-12     Revised Date:  2014-09-21    
Medline Journal Info:
Nlm Unique ID:  7802443     Medline TA:  Ophthalmology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  816-22     Citation Subset:  IM    
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MeSH Terms
Anterior Eye Segment / ultrasonography*
Ciliary Body / ultrasonography*
Image Enhancement
Iris / ultrasonography*
Lens, Crystalline / ultrasonography*
Sensitivity and Specificity
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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