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Unformatted text preview: ABSTRACTS 1. High-Frequency Imaging 1.1 High-resolution parametric imaging of the vitreous, retina and choroid, Ron ald H. Silverman, 1, 2 Mark J. Ron deau, 1 R. V. Paul Chan 1 and D. Jack son Coleman, 1 1 Weill Med i cal Col lege of Cor nell Uni ver sity, New York, NY 10021 and 2 Riv er side Re search In sti tute, New York, NY 10038, s [email protected] (in vited over view). The ret ina is phys i cally and nu tri tion ally sup ported by the un der ly ing choroid, a vas cu lar tis sue that is part of the uveal tract of the eye. The ret ina and choroid are each ap prox i mately one-quar ter mil li me ter in thick ness. The ret i nal photoreceptors are one of the most met a bol - i cally ac tive sites in the hu man body and thus re quire a rich microvasculature. The photoreceptors and outer lay ers of the ret ina are ox y gen ated by dif fu sion from the un der ly - ing choroid and the in ner ret ina by the ret i nal ves sels. Dis eases of the ret ina and choroid such as small mel a no mas, di a betic retinopathy (DR) and age-re lated macular de gen er a tion (ARMD) may be associated with vascular abnormalities including ischemia, neovascular- ization, ves sel leak age and hem or rhage. This, and vitreoretinal trac tion, may re sult in blood and cel lu lar de bris en ter ing the vitreous, with potential for subsequent organization of vitreous membranes. Ultrasound (US) and optical coherence tomography (OCT) are useful and complemen- tary tech niques for eval u a tion of the ret ina, choroid and vit re ous. OCT pro vides higher res o - lution (<10 m m) than US, but is lim ited to im ag ing only the pos te rior pole (through the pu pil) un der clear me dia con di tions. It also has lim ited pen e tra tion in depth be yond the ret i nal pig - ment ep i the lium. US can be used to im age the cen tral and pe riph eral ret ina, choroid and or - bital tis sues, and is un af fected by op ti cal opac i ties. The tra di tional 10 MHz US used in ophthalmology, however, provides inadequate resolution for evaluation of the retina and choroid be cause of their thin ness in re spect to wave length (150 m m). De tec tion of early changes as so ci ated with ARMD, such as retinochoroidal per fu sion, re - or ga ni za tion of microvasculature, an a tomic changes in the macula (tears, holes, epiretinal mem branes) and vit re ous de bris, would be clin i cally use ful, es pe cially in light of new and effective treatment modalities. The central challenge for US in characterizing these tissues is their thin ness and depth. (The ax ial length of the eye is about 24 mm.) We have been ex - plor ing a num ber of ap proaches based on postpro cess ing of radio fre quen cy data to im prove US de tec tion of these changes. Scan ning is typ i cally per formed us ing a re verse arc (sec tor) scan ge om e try, avoid ing the plane of the crys tal line lens, us ing a fo cused sin gle-el e ment 20 MHz transducer. Postprocessing methods include spectral parameter imaging, nonlinear 20/40 MHz tis sue har monic im ag ing, wave let anal y sis and swept-mode color-flow im ag -...
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This note was uploaded on 08/30/2011 for the course BUSN 1003 taught by Professor Carr,r during the Spring '08 term at Arkansas State.
- Spring '08