Super-Resolution Posterior Ocular Microvascular Imaging Using 3-D Ultrasound Localization Microscopy With a 32X32...

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Medical Imaging

Background:

• Posterior ocular microvasculature imaging is crucial for diagnosing eye diseases.
• Current ultrasound localization microscopy (ULM) faces challenges including limited angles, sound speed variations, and low signal-to-noise ratio (SNR).

Purpose of the Study:

• To develop and validate an in-vivo three-dimensional (3-D) ultrasound localization microscopy (ULM) technique for posterior ocular microvasculature.
• To overcome limitations of restricted angles, sound speed mismatch, and low SNR in microbubble signals.

Main Methods:

• Implemented a region-dependent speed of sound (SOS) beamforming to correct phase distortions from the crystalline lens.
• Applied a 4-D non-local means filter for noise suppression and microbubble contrast enhancement.
• Utilized a 256-channel system with a 1024-element matrix array for data acquisition.

Main Results:

• Achieved a spatial resolution of 63 µm, with global resolution confirmed at approximately 59 µm via Fourier shell correlation.
• Demonstrated improved microbubble signal quality with higher normalized cross-correlation coefficients (0.67 vs. 0.60).
• Reconstructed 3-D bi-directional vessel density and flow-velocity maps, revealing detailed choroidal vascular and hemodynamic patterns.

Conclusions:

• Region-dependent SOS beamforming and spatiotemporal denoising enable high-resolution posterior ocular ULM.
• The technique offers a practical approach for quantitative 3-D assessment of retinal and choroidal microvasculature.
• This advancement holds potential for future clinical applications in diagnosing and monitoring eye conditions.