Quantifying the Pattern of Retinal Vascular Orientation in Diabetic Retinopathy Using Optical Coherence Tomography Angiography

Quantitative imaging using optical coherence tomography angiography (OCTA) could provide objective tools for the detection and characterization of diabetic retinopathy (DR). In this study, we developed a novel quantitative approach using OCTA images to delineate the vessel orientation pattern of a specific region of interest, which is an orientation distribution curve depicting the probability of vessels at each angle from 0 to 360 degrees. Three quantitative metrics including vessel preferred orientation, vessel anisotropy and vessel mass were extracted from the orientation pattern and analyzed in each of eight 45° sectors at the macula. Differential retinal microvascular orientation patterns were observed between three healthy subjects and three subjects with DR. Greater variability of vessel preferred orientation (p<0.001) and vessel mass (p<0.001) was exhibited among subjects with DR than healthy in eight sectors. In the nasal-superior sector, there was a significant difference between healthy and DR subjects in preferred orientation and vessel anisotropy. The vessel mass characterized from the vascular orientation pattern was shown to be strongly correlated with the traditionally reported vessel density (p<0.00001). These preliminary results suggest the feasibility and advantage of our vessel orientation-based quantitative approach using OCTA to characterize DR-associated changes in retinal microvasculature.

Choroidal macrovessels: multimodal imaging findings and review of the literature

Background/aimsTo describe clinical and multimodal imaging features in a cohort of choroidal macrovessels.MethodsDemographics and multimodal imaging features of 16 eyes of 13 patients with choroidal macrovessels were reviewed. The multimodal imaging included colour fundus photography, fundus autofluorescence (FAF), spectral domain enhanced depth imaging optical coherence tomography (OCT), en face OCT, OCT-angiography (OCT-A), B-scan ultrasonography (US), fluorescein angiography (FFA) and indocyanine green angiography (ICGA).ResultsThree patients had bilateral involvement. On colour fundus photography, three patterns were evident (a clearly visible orange-red vessel; a track of pigmentary changes; spots of mild pigmentary changes). Vessel orientation was horizontal (11 eyes), oblique (4 eyes) or vertical (1 eye). In 2 eyes, the vessel was extra-macular. OCT in all cases showed a hyporeflective choroidal area with posterior shadowing and elevation of the overlying retina. Subretinal fluid was present in 4 eyes. FAF (12 eyes) was normal (7 eyes) or showed a hypofluorescent/hyperfluorescent track (4 eyes) or linear hyperautofluorescence (1 eye). En-face OCT (2 eyes) revealed the course of the macrovessel at the level of choroid and choriocapillaris. On OCT-A (2 eyes) the vessel had a reflectivity similar to surrounding vessels but larger diameter. B-scan US (8 eyes) showed a nodular hypoechogenic lesion. FFA (5 eyes) showed early focal hyperfluorescence (4 eyes) not increasing in later phases, or was normal (1 eye). ICGA (6 eyes) showed early hyperfluorescence of the vessel.ConclusionsChoroidal macrovessels can mimic other entities, leading to underdiagnosis. Appreciating relevant features on different imaging modalities will aid a correct diagnosis.

Morphogenesis of 3D vascular networks is regulated by tensile forces

Understanding the forces controlling vascular network properties and morphology can enhance in vitro tissue vascularization and graft integration prospects. This work assessed the effect of uniaxial cell-induced and externally applied tensile forces on the morphology of vascular networks formed within fibroblast and endothelial cell-embedded 3D polymeric constructs. Force intensity correlated with network quality, as verified by inhibition of force and of angiogenesis-related regulators. Tensile forces during vessel formation resulted in parallel vessel orientation under static stretching and diagonal orientation under cyclic stretching, supported by angiogenic factors secreted in response to each stretch protocol. Implantation of scaffolds bearing network orientations matching those of host abdominal muscle tissue improved graft integration and the mechanical properties of the implantation site, a critical factor in repair of defects in this area. This study demonstrates the regulatory role of forces in angiogenesis and their capacities in vessel structure manipulation, which can be exploited to improve scaffolds for tissue repair.

Optimization of Vessel Orientation for Robotic Coronary Artery Bypass Grafting

The availability of telemanipulation robots has not yet resulted in the emergence of a reliable endoscopic coronary bypass procedure. A major challenge in performing a closed-chest coronary operation is creating a high-quality anastomosis in a reasonable period of time. In this experimental study, the impact of distal vessel orientation on the speed and accuracy of anastomosis was quantifed. We found that vessel orientation and the relative angle of the surgical plane influence anastomosis speed, the trauma to the vessel, the accuracy of stitch placement, and the eventual achievement of hemostasis. Our results suggest that the speed and accuracy of a robotically performed anastomosis of a vessel graft to a coronary artery can be improved by making small changes in vessel orientation. Vessels should be positioned between the horizontal and diagonal orientation and inclined between the horizontal and +45. Because the 6-o'clock stitch is particularly challenging, surgeons may benefit from an orientation that moves the heel or the toe of the anastomosis away from this critical position.

MACROSCOPIC AND ANATOMICAL INVESTIGATION OF INTERLOCKED GRAIN IN ACACIA MANGIUM

Interlocked grains record change in the orientation of axial elements. In this report, vessel and fiber orientations in Acacia mangium Willd. were compared macroscopically and microscopically to analyze the interlocked grain. A method to print the cylindrical surface of a dry wood disk after bark exfoliation was devised to evaluate the stem axis and circumferential grain fluctuation and revealed circumferential heterogeneity in the vessel orientation. Fiber orientation manifested on some radial splits also was heterogeneous. A 3 mm-thick transverse plate was used to estimate vessel orientation with soft X-ray photography, which enables a wider-ranging evaluation than microscopy. Serial tangential thin plates and sections were used to measure fiber orientation angle with reflecting and polarized light microscopy, respectively, and fast Fourier transform. Both vessel and fiber orientations had a similar radial tendency and distinct inversion of the grain. However, the vessel orientation had a larger amplitude of change than fiber orientation.