Automated motion-artifact correction in an OCTA image using tensor voting approach

Dynamic 3D imaging of cerebral blood flow in awake mice using self-supervised-learning-enhanced optical coherence Doppler tomography

Cerebral blood flow (CBF) is widely used to assess brain function. However, most preclinical CBF studies have been performed under anesthesia, which confounds findings. High spatiotemporal-resolution CBF imaging of awake animals is challenging due to motion artifacts and background noise, particularly for Doppler-based flow imaging. Here, we report ultrahigh-resolution optical coherence Doppler tomography (µODT) for 3D imaging of CBF velocity (CBFv) dynamics in awake mice by developing self-supervised deep-learning for effective image denoising and motion-artifact removal. We compare cortical CBFv in awake vs. anesthetized mice and their dynamic responses in arteriolar, venular and capillary networks to acute cocaine (1 mg/kg, i.v.), a highly addictive drug associated with neurovascular toxicity. Compared with awake, isoflurane (2-2.5%) induces vasodilation and increases CBFv within 2-4 min, whereas dexmedetomidine (0.025 mg/kg, i.p.) does not change vessel diameters nor flow. Acute cocaine decreases CBFv to the same extent in dexmedetomidine and awake states, whereas decreases are larger under isoflurane, suggesting that isoflurane-induced vasodilation might have facilitated detection of cocaine-induced vasoconstriction. Awake mice after chronic cocaine show severe vasoconstriction, CBFv decreases and vascular adaptations with extended diving arteriolar/venular vessels that prioritize blood supply to deeper cortical capillaries. The 3D imaging platform we present provides a powerful tool to study dynamic changes in vessel diameters and morphology alongside CBFv networks in the brain of awake animals that can advance our understanding of the effects of drugs and disease conditions (ischemia, tumors, wound healing).

Development of a multi-scene universal multiple wavelet-FFT algorithm (MW-FFTA) for denoising motion artifacts in OCT-angiography in vivo imaging

Optical coherence tomography angiography (OCTA) images suffer from inevitable micromotion (breathing, heartbeat, and blinking) noise. These image artifacts can severely disturb the visibility of results and reduce accuracy of vessel morphological and functional metrics quantization. Herein, we propose a multiple wavelet-FFT algorithm (MW-FFTA) comprising multiple integrated processes combined with wavelet-FFT and minimum reconstruction that can be used to effectively attenuate motion artifacts and significantly improve the precision of quantitative information. We verified the fidelity of image information and reliability of MW-FFTA by the image quality evaluation. The efficiency and robustness of MW-FFTA was validated by the vessel parameters on multi-scene in vivo OCTA imaging. Compared with previous algorithms, our method provides better visual and quantitative results. Therefore, the MW-FFTA possesses the potential capacity to improve the diagnosis of clinical diseases with OCTA.

Ultrasonic technologies in imaging and drug delivery

Ultrasonic technologies show great promise for diagnostic imaging and drug delivery in theranostic applications. The development of functional and molecular ultrasound imaging is based on the technical breakthrough of high frame-rate ultrasound. The evolution of shear wave elastography, high-frequency ultrasound imaging, ultrasound contrast imaging, and super-resolution blood flow imaging are described in this review. Recently, the therapeutic potential of the interaction of ultrasound with microbubble cavitation or droplet vaporization has become recognized. Microbubbles and phase-change droplets not only provide effective contrast media, but also show great therapeutic potential. Interaction with ultrasound induces unique and distinguishable biophysical features in microbubbles and droplets that promote drug loading and delivery. In particular, this approach demonstrates potential for central nervous system applications. Here, we systemically review the technological developments of theranostic ultrasound including novel ultrasound imaging techniques, the synergetic use of ultrasound with microbubbles and droplets, and microbubble/droplet drug-loading strategies for anticancer applications and disease modulation. These advancements have transformed ultrasound from a purely diagnostic utility into a promising theranostic tool.

Effect of intravitreal dexamethasone implant versus ranibizumab on vessel density in branch retinal vein occlusion

PURPOSE

This study aimed to compare the effect of intravitreal dexamethasone implant with that of ranibizumab on vessel density (VD) in eyes with branch retinal vein occlusion (BRVO).

METHODS

Sixty-three eyes of 63 patients with superotemporal BRVO treated either with intravitreal dexamethasone implant (DEX group, n = 31) or ranibizumab (RNB group, n = 32) were prospectively enrolled. Swept-source optical coherence tomography angiography 6 × 6 mm scans of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) in all eyes were analyzed.

RESULTS

The mean baseline VD of the SCP and the DCP was similar between groups in all quadrants (p > 0.05 for all). At 12 months, the VD of the SCP in the parafoveal superior and temporal quadrants was significantly higher in the RNB group than in the DEX group (p = 0.002 and p = 0.001, respectively). The VD of the DCP in the parafoveal temporal, nasal, and superior quadrants was significantly higher in the RNB group than in the DEX group (p < 0.05 for all). Further, there was a statistically significant positive correlation between the improvement of visual acuity and increased VD of the SCP and the DCP in the parafoveal temporal quadrant in both groups (R = 0.589, p = 0.001 and R = 0.455, p = 0 .017, respectively).

CONCLUSION

Our findings support that ranibizumab does not inhibit collateral vessel formation in eyes with superotemporal BRVO compared to dexamethasone implant. VD and vessel formation can positively affect the vision prognosis in long-term follow-up.