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A. Chabi, R.H. Silverman, D.J. Coleman; Comparative High Resolution Imaging of the Posterior Coats by OCT and 20 MHz Ultrasound . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3626.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Optical coherence tomography (OCT) is capable of high-resolution imaging of the posterior coats, and has become a useful tool for evaluation of the retina and macula. 10 MHz ultrasound has long been used in the evaluation of the posterior pole of the eye, but at significantly lower resolution than OCT. Advances in ultrasound technology, however, are now allowing use of higher frequencies, with concomitant improvement in resolution. In this report we describe comparative images of the posterior coats in normal eyes and in disease. Method: We imaged normal eyes with 10 and 15 MHz PZT transducers, and a 20 MHz lithium niobate transducer, all with comparable apertures and focal lengths. 20 MHz ultrasound and OCT images were also acquired on a series of patients with macular holes, nevi, and tumors. Results: 20 MHz images allowed differentiation of the retina, choroid and sclera. In addition, at 20 MHz the retina showed banding patterns suggesting internal structure comparable in many respects to that seen in OCT and histology. 20 MHz ultrasound images provided less axial resolution than OCT, but deeper penetration, allowing visualization of orbital tissues as well as the retina, choroids and sclera. Conclusions: 20 MHz imaging of the posterior coats appears to be on the threshold for resolution of the internal layers of the retina. Conventionally formatted B-mode images showing the entire globe may not allow full appreciation of the resolution capabilities at 20 MHz. While not providing the resolution of OCT, ultrasound can be used in the presence of optical opacity and provides deeper penetration.
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