Editors' ChoiceANGIOGRAPHY

Wide-area OCT angiography gives the big picture

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Science Translational Medicine  08 Jun 2016:
Vol. 8, Issue 342, pp. 342ec90
DOI: 10.1126/scitranslmed.aag1869

Angiography—the imaging of blood vessels—is crucial for myriad disorders ranging from retinal disease to cancer. Traditionally, angiography has been accomplished through the use of injected fluorescent dyes such as fluorescein. Though fluorescence angiography does enable the visualization of blood vessels, its imaging depth can be limited; most tools visualize a two-dimensional projection of the blood vessel network instead of providing a full three-dimensional (3D) image; and imaging requires the intravenous injection of contrast agents.

Optical coherence tomography (OCT) provides real-time, 3D structural imaging of tissues. By taking advantage of the inherent motion of cells within blood vessels, OCT technologies have been extended over the past 20 years to visualize vessels within tissue without the use of dyes or labels. Starting in the mid-1990s, OCT angiography has been used to identify and measure blood vessels within the retina, as well as for applications ranging from wound healing to the dynamics of blood vessel networks within brain tumors. Until recently, however, OCT angiography imaging has largely been limited to small fields of view, on the order of a few square millimeters, and has required time-consuming mosaic-stitching approaches.

Xu et al. now demonstrate a new OCT methodology that enables both wide-area imaging of blood vessels over many square centimeters of tissue and a “zoom” mode that enables high-resolution microangiography. The authors accomplished this feat by integrating a high-speed camera, a near-infrared light source, and a new blood-flow analysis algorithm to map the 3D blood vessel network. They demonstrated large-area imaging over the entire adult human fingernail fold, where both the vasculature and the tissue structure could be simultaneously visualized. To switch to high-resolution imaging, the imaging system toggled to use an objective lens, so that regions of interest found in the wide-area view could be more closely investigated. The authors noted that the wide and zoomed imaging modes have different types of image distortion, which can be overcome through post-processing. This combination approach of wide-area assessment plus high-resolution image capture should enable rapid identification of abnormal microcirculation for a host of new clinical applications.

J. Xu et al., Scalable wide-field optical coherence tomography-based angiography for in vivo imaging applications, Biomed. Opt. Express 7, 1905–1919 (2016). [Full Text]

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