High-accuracy noninvasive continuous glucose monitoring using OCT angiography-purified blood scattering signals in human skin.

The accuracy of noninvasive continuous glucose monitoring (CGM) through near-infrared scattering is challenged by mixed scattering signals from different compartments, where glucose has a positive correlation with a blood scattering coefficient but a negative correlation with a tissue scattering coefficient. In this study, we developed a high-accuracy noninvasive CGM based on OCT angiography (OCTA)-purified blood scattering signals. The blood optical scattering coefficient (BOC) was initially extracted from the depth attenuation of backscattered light in OCT and then purified by eliminating the scattering signals from the surrounding tissues under the guidance of a 3D OCTA vascular map in human skin. The purified BOC was used to estimate the optical blood glucose concentration (BGC) through a linear calibration. The optical and reference BGC measurements were highly correlated (R = 0.94) without apparent time delay. The mean absolute relative difference was 6.09%. All optical BGC measurements were within the clinically acceptable Zones A + B, with 96.69% falling in Zone A on Parke's error grids. The blood glucose response during OGTT was mapped with a high spatiotemporal resolution of the single vessel and 5 seconds. This noninvasive OCTA-based CGM shows promising accuracy for clinical use. Future research will involve larger sample sizes and diabetic participants to confirm these preliminary findings.

Three-dimensional optical coherence digital-null deformography of multi-refractive-surface optics with nanometer sensitivity.

Knowledge of the lens deformation during the reliability test is critical for lens design and fabrication. Refractive surface distorts the optical path of probing light, and poses a great challenge to measuring the test-induced nanoscale changes of all refractive lens surfaces simultaneously. In this work, we present an optical coherence digital-null deformography (ODD). A digital null, i.e., the interference signals (including intensity and phase) of the backscattered probing light from each lens surface, was recorded prior to the test with a phase-sensitive optical coherence tomography (OCT). Then the post-test lens was physically aligned to the digital null by actuating a hexapod iteratively with a digital null alignment (DNA) method, so that the refractive distortion was matched. Finally, the changes between the aligned lens and its digital null were measured with an intensity centroid shift (ICS) at micron scale and a joint wavenumber (k)-depth (z) domain phase shift (kz-PhS) at nanoscale. We demonstrate that the proposed kz-PhS has a sensitivity of 4.15 nm and a range of 5 µm without phase wrapping; and the sensitivities of DNA are z translation 0.04 µm, x/y translation 0.24 µm, tilt 0.0003°, and rotation 0.03°. A lens drop test was performed with ODD. Circumventing refractive distortion by the null measurement, ODD can visualize the test-induced changes of all refractive surfaces non-destructively and simultaneously, and it will greatly facilitate lens design and fabrication.

Dynamic inverse SNR-decorrelation OCT angiography with GPU acceleration.

Dynamic OCT angiography (OCTA) is an attractive approach for monitoring stimulus-evoked hemodynamics; however, a 4D (3D space and time) dataset requires a long acquisition time and has a large data size, thereby posing a great challenge to data processing. This study proposed a GPU-based real-time data processing pipeline for dynamic inverse SNR-decorrelation OCTA (ID-OCTA), offering a measured line-process rate of 133 kHz for displaying OCT and OCTA cross-sections in real time. Real-time processing enabled automatic optimization of angiogram quality, which improved the vessel SNR, contrast-to-noise ratio, and connectivity by 14.37, 14.08, and 9.76%, respectively. Furthermore, motion-contrast 4D angiographic imaging of stimulus-evoked hemodynamics was achieved within a single trail in the mouse retina. Consequently, a flicker light stimulus evoked an apparent dilation of the retinal arterioles and venules and an elevation of the decorrelation value in the retinal plexuses. Therefore, GPU ID-OCTA enables real-time and high-quality angiographic imaging and is particularly suitable for hemodynamic studies.