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Ultrasound imaging boasts cutting-edge technologies
Advances in ultrasound imaging can assist in monitoring vitreous and choroidal changes over time.
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Improvements in imaging resolution are one of the advancements in ultrasound technology that have enabled physicians to more accurately evaluate vitreoretinal diseases, according to a surgeon.
Precise imaging is increasingly important as macular and retinal diseases have come under more intense scrutiny with the rise of anti-angiogenic therapeutic options, D. Jackson Coleman, MD, FACS, said.
Important developments include wavelet technology, swept mode imaging, harmonic techniques and advanced pulse mode technology, Dr. Coleman said at Columbia University’s Imaging and Visual Diagnostics: State of the Art meeting in New York.
While the advent of optical coherence tomography (OCT) has dominated the imaging field, ultrasound is an important technology in certain cases, he said.
OCT is most effective in retinal and vitreoretinal traction imaging, Dr. Coleman said. Ultrasound, in contrast, can be useful in imaging choroidal structure and flow, opaque eyes and eyes with trauma, tumors or vitreous hemorrhage, he said.
“With these new techniques, we’re treating patients better, the effectiveness of drugs is better, and we think that these techniques will be allowing us to keep pace with developments in OCT,” Dr. Coleman said.
Wavelet imaging
Wavelet imaging uses a different process than other ultrasound technologies. It works by examining both time and frequency domains for the best time and frequency localizations, Dr. Coleman said. It identifies choroidal microarchitecture and stratifies dry and wet age-related macular degeneration, he said.
A typical scan shows that a wavelet of a normal, healthy choroid has a marked difference in the drusen and retinal blood vessel compared with abnormal wet AMD. Patterns in the choroid can assist in determining that, he said.
“What we hope is that we’re going to not only be able to see the difference between wet and dry AMD, but we can also begin to look at the changes between dry and wet, so they we can treat those patients earlier,” Dr. Coleman said.
Swept mode imaging
Swept mode imaging evaluates true blood flow in the choroid.
It is similar to Doppler imaging, Dr. Coleman said, in that it has color flow information that assists in making accurate measurements. He said swept mode imaging allows for high spatial resolution, but it provides lower sensitivity than Doppler imaging and flow data at arbitrary points of the cardiac cycle.
Dr. Coleman suggested using a sample beamwidth for at least one cardiac cycle to help address the latter problem.
Other advances
Harmonic ultrasound imaging causes pressure disturbances in a fluid medium, Dr. Coleman said. This technique improves resolution and signal-to-noise ratio in choroidal imaging.
Pulse mode technology creates an image by averaging the amplitude of acoustic emission made by the primary ultrasound beam’s sweep of frequency, Dr. Coleman said. It provides improved evaluation of vitreoretinal traction and gradation of vitreous opacification, he said.
Contrast agents have cardiovascular applications and are used by orthopedic surgeons, but they have not yet been approved by the U.S. Food and Drug Administration for ophthalmic use, Dr. Coleman said.
These agents are usually gas-filled lipid microspheres that have better signal-to-noise ratios for backscatter by blood, he said. With use of harmonic and subharmonic imaging, the imaging can show an increase in signal-to-noise ratio.
“I think in the near future, these will be used,” he said.
For more information:
- D. Jackson Coleman, MD, FACS, can be reached at Weill Medical College of Cornell University, Department of Ophthalmology, 520 E. 70th St., New York, NY 10021; 212-746-5588; fax: 212-746-8732; e-mail: djcole@med.cornell.edu. Ocular Surgery News could not confirm whether Dr. Coleman has a direct financial interest in the products mentioned in this article or if he is a paid consultant for any companies mentioned.
- Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.