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

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Signal Processing

Background:

• Functional ultrasound localization microscopy (fULM) offers micron-scale resolution for brain-wide neural activity mapping.
• Challenges in 3D fULM include limited sensitivity due to sparse microbubble (MB) detections, data sparsity, and reduced localization efficiency.

Purpose of the Study:

• To develop a novel statistical framework to enhance sensitivity and overcome limitations in 3D fULM.
• To integrate microbubble backscattered amplitude with count-based detection for improved functional neuroimaging.

Main Methods:

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

Main Results:

• Backscattering fULM (B-fULM) improves functional sensitivity, especially at high MB concentrations where conventional fULM saturates.
• B-fULM maintained sensitivity in simulations where conventional fULM failed.
• In vivo experiments showed significant SNR gains (18% in somatosensory cortex, 61% in thalamus) with B-fULM.

Conclusions:

• B-fULM provides a practical and sensitive method for super-resolved 3D functional neuroimaging.
• The integration of amplitude and count-based methods enhances the robustness of neural activity mapping.
• B-fULM preserves high spatial resolution while improving functional sensitivity.