Noninvasive, in vivo imaging of blood-oxygenation dynamics within the mouse brain using photoacoustic microscopy

Abstract

Photoacoustic microscopy (PAM) has been used to obtain high-resolution, noninvasive images of the in vivo mouse brain. In this work, we exploit the high-depth and temporal resolutions of PAM to noninvasively image the blood-oxygenation dynamics of multiple cortex vessels in the mouse brain simultaneously in response to controlled hypoxic and hyperoxic challenges. These results confirm the ability of PAM to track blood oxygenation in the mouse brain, a critical aspect of imaging brain activity through the hemodynamic response.

Fig. 1

In vivo image of the mouse cortex vasculature. (a) Digital photograph of a prepared animal taken prior to imaging, depicting the 7.50 mm × 6.25 mm scanned region. (b) Noninvasive, PA image of the mouse cortex vasculature. SS: sagittal sinus; CS: coronal suture. Unlabeled arrows indicate SC cortex feeding/draining vessels. Crossed arrow points in the rostral direction. Dotted white line indicates the area over which line scanning was performed. (c) B-scan image obtained from scanning along the white dotted line in Fig. 1b. Colored arrows indicate the cross sections of the cortex vessels whose dynamic response to hypoxia and hyperoxia were tracked and plotted in Fig. 2.

Fig. 2

Dynamic vessel response profiles. Profiles acquired through a hypoxic challenge and shown in percent change of (a) ratiometric PA signals and (b) isosbestic PA signals. Each colored trace corresponds to the response profile from the respective cortex vessel indicated with the like colored arrow in Fig 1c. Dynamic vessel response profile acquired through a hyperoxic challenge and shown in percent change (c) ratiometric PA signals and (d) isosbestic PA signals. (e) Close-up of parts of the dynamic vessel responses shown in Fig. 2a.