Retinal oxygen kinetics imaging and analysis (ROKIA) based on the integration and fusion of structural-functional imaging

Abstract

The retina is one of the most metabolically active tissues in the body. The dysfunction of oxygen kinetics in the retina is closely related to the disease and has important clinical value. Dynamic imaging and comprehensive analyses of oxygen kinetics in the retina depend on the fusion of structural and functional imaging and high spatiotemporal resolution. But it's currently not clinically available, particularly via a single imaging device. Therefore, this work aims to develop a retinal oxygen kinetics imaging and analysis (ROKIA) technology by integrating dual-wavelength imaging with laser speckle contrast imaging modalities, which achieves structural and functional analysis with high spatial resolution and dynamic measurement, taking both external and lumen vessel diameters into account. The ROKIA systematically evaluated eight vascular metrics, four blood flow metrics, and fifteen oxygenation metrics. The single device scheme overcomes the incompatibility of optical design, harmonizes the field of view and resolution of different modalities, and reduces the difficulty of registration and image processing algorithms. More importantly, many of the metrics (such as oxygen delivery, oxygen metabolism, vessel wall thickness, etc.) derived from the fusion of structural and functional information, are unique to ROKIA. The oxygen kinetic analysis technology proposed in this paper, to our knowledge, is the first demonstration of the vascular metrics, blood flow metrics, and oxygenation metrics via a single system, which will potentially become a powerful tool for disease diagnosis and clinical research.

Fig. 1.

Instrumentation of ROKIA.

Fig. 2.

The pipeline of stabilized laser speckle angiography.

Fig. 3.

The maximum intensity projection of SPI along X-axis and Y-axis. (a) X-axis; (b) Y-axis.

Fig. 4.

Retina perfusion images obtained by different algorithms. (a) A typical retina perfusion image with motion artifact; (b) The perfusion image that directly uses registration algorithms; (c) The perfusion image obtained by the method proposed in this section.

Fig. 5.

The pipeline of vascular metrics measurement. Abbreviations: SLSA:stabilized laser speckle angiography; PI,perfusion image; ED,external diameter; LD, lumen diameter.

Fig. 6.

Comparison of vascular cross-sections in 548 nm images and perfusion images. (a) 548 nm image, the yellow solid line box and the blue solid line box mark the representative venous and arterial regions, respectively; (b) Enlarged view of the venous region in the 548 nm image and perfusion image, in which the red line marks the vein in the 548 nm image, and the green line marks the vein in the perfusion image; (c) The cross-sections of retinal veins, the red curve is the cross-section of the vein in the 548 nm image, and the green curve is the cross-section of the vein in the perfusion image;(d) Perfusion image, the yellow dotted box and the blue dotted box mark the representative venous and arterial regions, respectively; (e) Enlarged view of the arterial region in the 548 nm image and perfusion image, in which the red line marks the artery in the 548 nm image, and the green line marks the artery in the perfusion image; (f) The cross-sections of retinal artery, the red curve is the cross-section of the artery in the 548 nm image, and the green curve is the cross-section of the artery in the perfusion image.

Fig. 7.

A representative pulsatility derived from a healthy subject. A to B represents the systole phase and B to C represents the diastole phase.

Fig. 8.

Workflow of the ROKIA pipeline. Abbreviations: ED,external diameter ; LD, lumen diameter; $\mathrm{S}{\mathrm{O}}_2$ , retinal oxygen saturation; ${\mathrm{C}}_{\mathrm{O}2}$ , retinal oxygen concentration; BFV, retinal blood flow velocity; RBF, retinal blood flow; WT, wall thickness; WLR, wall-to-lumen ratio; A, artery; V, vein; $\mathrm{D}{\mathrm{O}}_2$ , oxygen delivery; $\mathrm{M}{\mathrm{O}}_2$ , oxygen metabolism; OEF, oxygen extraction fraction. A representative video is provided to demonstrate the dynamic velocity measurement results, as shown in Visualization 1.

Fig. 9.

Results of Retinal Oxygen Kinetics Imaging in a healthy subject. (a) The image at 548 nm. (b) The image at 605 nm. (c) The $\mathrm{S}{\mathrm{O}}_2$ map. (d) The ${\mathrm{C}}_{\mathrm{O}2}$ map. (e) The BFV image. (f) The RBF image. (g) The ED map. (h) The LD map. (i) The pulsatilities in arteries and veins. (j) The standard artery-vein mapping labelledby an experienced ophthalmologist on color fundus image. The red ’A’ represents arteries, and the ’V’ represents veins. Abbreviations: ED, external diameter ; LD, lumen diameter; $\mathrm{S}{\mathrm{O}}_2$ , retinal oxygen saturation; ${\mathrm{C}}_{\mathrm{O}2}$ , retinal oxygen concentration; BFV, retinal blood flow velocity; RBF, retinal blood flow; WT, wall thickness; WLR, wall-to-lumen ratio; A, artery; V, vein; CFI, color fundus image.