The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

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Present and Future of Surface-Enhanced Raman Scattering

The study group.

Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Optical Coherence Tomography of the Human Retina

Importance The retinal vasculature is involved in many ocular diseases that cause visual loss. Although fluorescein angiography is the criterion standard for evaluating the retina vasculature, it has risks of adverse effects and known defects in imaging all the layers of the retinal vasculature. Optical coherence tomography (OCT) angiography can image vessels based on flow characteristics and may provide improved information. Objective To investigate the ability of OCT angiography to image the vascular layers within the retina compared with conventional fluorescein angiography. Design, Setting, and Participants In this study, performed from March 14, 2014, through June 24, 2014, a total of 5 consecutive, overlapping B-scan OCT angiography images composed of 216 A-scans were obtained at 216 discrete positions within a region of interest, typically a 2 × 2-mm area of the retina. The flow imaging was based on split-spectrum amplitude decorrelation angiography (SSADA), which can dissect layers of vessels in the retina. These distinct layers were compared with the fluorescein angiograms in 12 healthy eyes from patients at a private practice retina clinic to evaluate the ability to visualize the radial peripapillary capillary network. The proportion of the inner vs outer retinal vascular layers was estimated by 3 masked readers and compared with conventional fluorescein angiograms of the same eyes. Main Outcomes and Measures Outcome measures were visualization of the radial peripapillary capillary network in the fluorescein and SSADA scans and the proportion of the inner retinal vascular plexus vs the outer retinal capillary plexus as seen in SSADA scans that would match the fluorescein angiogram. Results In none of the 12 eyes could the radial peripapillary capillary network be visualized completely around the nerve head by fluorescein angiography, whereas the network was readily visualized in the SSADA scans. The fluorescein angiograms were matched, with a mean proportion of the inner vascular plexus being 95.3% (95% CI, 92.2%-97.8%) vs 4.7% (95% CI, 2.6%-5.7%) for the outer capillary plexus from the SSADA scans. Conclusions and Relevance Fluorescein angiography does not image the radial peripapillary or the deep capillary networks well. However, OCT angiography can image all layers of the retinal vasculature without dye injection. Therefore, OCT angiography, and the findings generated, have the potential to affect clinical evaluation of the retina in healthy patients and patients with disease.

https://jamanetwork.com/journals/jamaophthalmology/articlepdf/1910581/eoi140088.pdf

Retinal Vascular Layers Imaged by Fluorescein Angiography and Optical Coherence Tomography Angiography

The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

Measurement of intraocular distances by backscattering spectral interferometry

Angiography of Optic Disc Perfusion in Glaucoma with a 70 kHz Spectral OCT

Label-Free Optical Micro-Angiography for Functional Imaging of Microcirculations within Tissue Beds In Vivo

Radial Peripapillary Capillary Plexus Perfusion and Regional Visual Field Loss in Glaucoma

Optimizing and fully understanding the dynamic culture conditions in tissue engineering could accelerate
exploration of this new technique into a promising therapy in the medical field. Scaffolds used in tissue
engineering usually are highly porous with various pore architecture depending on techniques that
manufacture them. Perfusing culture fluid through a scaffold in a bioreactor has proven efficient in
enhancing the exchange of nutrients and gas within cell-scaffold constructs. Upon perfusion, flowing fluid
in pores inevitably produces shear stress on the wall of the pores, which will in turn induce cellular
response for the cells possessing mechanotransducers. Thus, establishing a relationship between perfusion
rate, fluid shear stress and pore architecture in a 3-dimensional cell culture environment is a challenging
task faced by tissue engineers because the same inlet flow rate could induce local variation of flow rate
within the pores. Until recently, there is no proper non-destructive monitoring technique available that is
capable of measuring flow rate in opaque thick objects. In this study, chitosan scaffolds with altered pore
architectures were manufactured by freeze-drying or porogen leaching out or alkaline gelation techniques.
Doppler optical coherence tomography (DOCT) has been used to differentiate the flow rate pattern within
scaffolds which have either elongating pore structure or homogeneous round pore structure. The structural
and flow images have been obtained for the scaffolds. It is found that pore interconnectivity is critically
important in obtaining a steady flow under a given inlet flow rate. In addition, different internal pore
structures affect local flow rate pattern.

Yali Jia

Papers

Angiography of Optic Disc Perfusion in Glaucoma with a 70 kHz Spectral OCT

Label-Free Optical Micro-Angiography for Functional Imaging of Microcirculations within Tissue Beds In Vivo

Radial Peripapillary Capillary Plexus Perfusion and Regional Visual Field Loss in Glaucoma

The study of effects of pore architecture in chitosan scaffolds on the fluid flow pattern by Doppler OCT

OCT Angiography of Macular Ganglion Cell Complex Circulation in Glaucoma