Abstract
.Large-scale, high-resolution imaging of cerebral hemodynamics is essential for brain research. Uniquely capable of comprehensive quantification of cerebral hemodynamics and oxygen metabolism in rodents based on the endogenous hemoglobin contrast, multiparametric photoacoustic microscopy (PAM) is ideally suited for this purpose. However, the out-of-focus issue due to the uneven surface of the rodent brain results in inaccurate PAM measurements and presents a significant challenge to cortex-wide multiparametric recording. We report a large-scale, high-resolution, multiparametric PAM system based on real-time surface contour extraction and scanning, which avoids the prescan and offline calculation of the contour map required by previously reported contour-scanning strategies. The performance of this system has been demonstrated in both phantoms and the live mouse brain through a thinned-skull window. Side-by-side comparison shows that the real-time contour scanning not only improves the quality of structural images by addressing the out-of-focus issue but also ensures accurate measurements of the concentration of hemoglobin (), oxygen saturation of hemoglobin (), and cerebral blood flow (CBF) over the entire mouse cortex. Furthermore, quantitative analysis reveals how the out-of-focus issue impairs the measurements of , , and CBF.
Highlights
Providing the unique contrast of optical absorption and excellent scalability of spatial resolution and tissue penetration depth, photoacoustic imaging has emerged as an enabling technology for brain research.[1,2] Capitalizing on the optical absorption of hemoglobin, multiparametric photoacoustic microscopy (PAM) is uniquely capable of comprehensive characterization of the cerebral vasculature in vivo.[3]
The side-by-side comparison of raster scan and contour scan was further performed in vivo
The entire mouse cortex was first imaged using raster scan to show the influence of the out-of-focus issue on the measurements of microvascular structure and function (i.e., concentration of hemoglobin (CHb), sO2, and cerebral blood flow (CBF))
Summary
Providing the unique contrast of optical absorption and excellent scalability of spatial resolution and tissue penetration depth, photoacoustic imaging has emerged as an enabling technology for brain research.[1,2] Capitalizing on the optical absorption of hemoglobin, multiparametric photoacoustic microscopy (PAM) is uniquely capable of comprehensive characterization of the cerebral vasculature in vivo.[3] statistical, spectroscopic, and correlation analysis of the same dataset allows simultaneous quantification of the total concentration of hemoglobin (CHb), oxygen saturation of hemoglobin (sO2), and cerebral blood flow (CBF) at the microscopic level.[4] combing these hemodynamic measurements enables the quantification of the cerebral metabolic rate of oxygen.[5]. The out-of-focus issue compromises the image resolution and signal-to-noise ratio (SNR).[7,8]
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