Cortex-wide multiparametric photoacoustic microscopy based on real-time contour scanning

Area of Science:

• Neuroscience
• Biomedical Engineering
• Optical Imaging

Background:

• Cerebral hemodynamics and oxygen metabolism are critical for brain research.
• Multiparametric photoacoustic microscopy (PAM) offers comprehensive quantification using endogenous hemoglobin contrast.
• Rodent brain surface unevenness causes out-of-focus issues, leading to inaccurate PAM measurements and hindering cortex-wide analysis.

Purpose of the Study:

• To develop and validate a large-scale, high-resolution, multiparametric PAM system for accurate rodent brain imaging.
• To address the challenge of out-of-focus artifacts caused by uneven brain surfaces.
• To enable precise, real-time quantification of cerebral hemodynamics and oxygen metabolism.

Main Methods:

• Developed a multiparametric PAM system incorporating real-time surface contour extraction and scanning.
• Eliminated the need for prescan and offline contour map calculation.
• Validated the system using phantoms and live mouse brains with a thinned-skull window.

Main Results:

• The real-time contour scanning significantly improved structural image quality by correcting out-of-focus artifacts.
• Accurate measurements of hemoglobin concentration, oxygen saturation, and cerebral blood flow (CBF) were achieved across the entire mouse cortex.
• Quantitative analysis demonstrated the detrimental impact of the out-of-focus issue on hemodynamic and oxygen metabolism measurements.

Conclusions:

• The novel real-time contour scanning PAM system effectively overcomes surface topography challenges in rodent brain imaging.
• This technology enables accurate, large-scale, high-resolution multiparametric assessment of cerebral hemodynamics and oxygen metabolism.
• The findings highlight the importance of addressing out-of-focus issues for reliable brain function quantification.