Microbubble Backscattering Intensity Improves the Sensitivity of Three-dimensional (3D) Functional Ultrasound...

Area of Science:

• Neuroimaging
• Biophysics
• Medical Engineering

Background:

• Functional ultrasound localization microscopy (fULM) offers micron-scale brain activity mapping.
• Current fULM methods face sensitivity limitations in 3D due to sparse and noisy microbubble detections.
• Extending fULM to 3D amplifies challenges like low-frequency arrays and data sparsity.

Purpose of the Study:

• To enhance the sensitivity and robustness of 3D functional ultrasound localization microscopy.
• To address limitations in microbubble detection and localization efficiency in 3D neuroimaging.
• To develop a statistical framework integrating microbubble amplitude and count for improved functional sensitivity.

Main Methods:

• Developed a statistical framework modeling 3D microbubble arrivals as a Poisson process.
• Incorporated localization efficiency, detection probability, and backscattered amplitude into the model.
• Validated the approach using 3D microbubble advection simulations and in vivo rat brain experiments.

Main Results:

• The statistical model predicted improved functional sensitivity by integrating amplitude with count-based fULM.
• Backscattering fULM (B-fULM) demonstrated maintained sensitivity at higher microbubble concentrations where conventional fULM failed.
• B-fULM achieved significant SNR gains (18% somatosensory cortex, 61% thalamus) with preserved super-resolved spatial detail (33.4 μm).

Conclusions:

• B-fULM is a practical and sensitive advancement for super-resolved 3D functional neuroimaging.
• Integrating microbubble backscatter amplitude significantly enhances functional sensitivity in 3D fULM.
• B-fULM provides more robust and detailed mapping of neural activity compared to conventional fULM.