A Skull-Removed Chronic Cranial Window for Ultrasound and Photoacoustic Imaging of the Rodent Brain.

Xuanhao Wang,Chaoyi Chen,Wen He,Lu Yin,Yan Luo,Cheng Ma,Yuwen Chen,Tengfei Yu

doi:10.3389/fnins.2021.673740

Abstract

Ultrasound and photoacoustic imaging are emerging as powerful tools to study brain structures and functions. The skull introduces significant distortion and attenuation of the ultrasound signals deteriorating image quality. For biological studies employing rodents, craniotomy is often times performed to enhance image qualities. However, craniotomy is unsuitable for longitudinal studies, where a long-term cranial window is needed to prevent repeated surgeries. Here, we propose a mouse model to eliminate sound blockage by the top portion of the skull, while minimum physiological perturbation to the imaged object is incurred. With the new mouse model, no craniotomy is needed before each imaging experiment. The effectiveness of our method was confirmed by three imaging systems: photoacoustic computed tomography, ultrasound imaging, and photoacoustic mesoscopy. Functional photoacoustic imaging of the mouse brain hemodynamics was also conducted. We expect new applications to be enabled by the new mouse model for photoacoustic and ultrasound imaging.

Highlights

Ultrasound imaging (USI) and photoacoustic imaging (PAI) are two rapidly developing imaging technologies for neuroscience (Xu and Wang, 2006; Xia et al, 2014; Moran and Thomson, 2020)
The mice were euthanized for histopathology, in which thin sections of the brains were stained with hematoxylin and eosin (H&E) and investigated under a microscope
The effectiveness of the model was validated by the photoacoustic computed tomography (PACT) imaging experiment. 20 coronal plane slices was acquired from frontal lobe to mid brain with a step of 250 μm, and 3 typical layers were shown with the zoomed view of the cranial cavity (Figure 4)

Summary

Introduction

Ultrasound imaging (USI) and photoacoustic imaging (PAI) are two rapidly developing imaging technologies for neuroscience (Xu and Wang, 2006; Xia et al, 2014; Moran and Thomson, 2020). USI visualizes internal brain structures via sound reflection (Rabut et al, 2019), while Doppler signals convey important functional information about blood flow (Demene et al, 2016). Photoacoustic microscopy (PAM) and photoacoustic computed tomography (PACT) have been developed to provide a wide range of image resolution, depth, and field of view (FOV), offering a rather scalable imaging modality for various applications. Both USI and PAI suffer from a significant reduction in signal quality when ultrasound signals pass through the skull. USI suffers a worse situation than PAI due to the round-trip signal path, yet in PAI, a reduction of signal strength is caused by the blockage of the excitation light by the skull (Yang et al, 2016)

Methods

Results

Conclusion