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Raksha Urs, Jeffrey A Ketterling, Daniel Gross, Ronald H Silverman; Ultrasound Coherent Compound Plane-Wave Imaging of Ocular Anatomy and Blood Flow. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1689.
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© 2017 Association for Research in Vision and Ophthalmology.
Single-element mechanically scanned ultrasound transducers, common in ophthalmology, are not viable for Doppler imaging due to slow acquisition rate. Linear-array probes can be used for Doppler imaging, but they do not meet the Food and Drug Administration's (FDA) stringent exposure criteria for the eye. A recently developed linear-array based ultrasound technique called coherent compound plane-wave imaging (CCPWI) offers an enormous increase in image frame rate and depiction of blood-flow at reduced exposure intensities compared to conventional linear array imaging. Our aim was to develop and apply this technology for imaging ocular anatomy and blood-flow.
We programmed a research ultrasound platform (Verasonics Vantage 128) to perform CCPWI using a 20 MHz linear array. We measured acoustic intensity in plane-wave and conventional focused imaging modes. We developed methods to form B-mode images from phase-resolved plane-wave data acquired over multiple angles, to visualize blood-flow in real time and to depict slow-flow in the choroid offline.
Plane-wave acoustic intensity was approximately 1/3 of conventional focusing methods. Individual plane wave images could be acquired at up to 10 kHz, allowing, for instance, 1000 compound images per second (10 angles per image). Real-time vector Doppler images depicting blood-flow in the orbital vessels at intensities compliant with FDA guidelines were readily obtained. CCPWI acquired continuously for 2 seconds were post-processed to depict choroidal perfusion and flow in the central retinal and short posterior ciliary arteries over the cardiac cycle at milli-sec intervals. Blood velocities from 1 to 20 mm/s were depicted.
CCPWI represents an important advance in ocular imaging, allowing high-resolution, ultra-high speed structural and blood-flow imaging of the eye and orbit. We foresee immediate research and clinical applications of this method in the evaluation of conditions such as glaucoma, macular degeneration and ocular tumors.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
(A): Coherent Compound Plane-Wave B-Scan Image of the optic nerve head region. (B): Power Doppler Image of the same region obtained from 2000 such CCPWI B-Scans (2s of imaging at 1 kHz), depicting choroidal perfusion and blood-flow in central retinal and short posterior ciliary arteries.
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