Bertolo Adrien, Ferrier Jeremy, Cazzanelli Silvia, Diebolt Samuel, Tanter Mickael, Pezet Sophie, Pernot Mathieu, Osmanski Bruno-Félix, Deffieux Thomas
Physics for Medicine Paris, ESPCI Paris, INSERM, CNRS, PSL Research University, Paris, France.
Iconeus, Paris, France.
Imaging Neurosci (Camb). 2023 Nov 15;1. doi: 10.1162/imag_a_00030. eCollection 2023.
Functional ultrasound (fUS) has received growing attention in preclinical research in the past decade, providing a new tool to measure functional connectivity (FC) and brain task-evoked responses with single-trial detection capability in both anesthetized and awake conditions. Most fUS studies rely on 2D linear arrays to acquire one slice of the brain. Volumetric fUS using 2D matrix or row-column arrays has recently been demonstrated in rats and mice but requires invasive craniotomy to expose the brain due to a lack of sensitivity. In a previous study, we proposed the use of motorized linear arrays, allowing imaging through the skull in mice for multiple slices with high sensitivity. However, the tradeoff between the field of view and temporal resolution introduced by motorized scanning prevents acquiring brain-wide resting-state FC data with a sufficient volume rate for resting-state FC analysis. Here, we propose a new hybrid solution optimized and dedicated to brain-wide transcranial FC studies in mice, based on a newly developed multi-array transducer allowing simultaneous multi-slicing of the entire mouse cerebrum. We first demonstrate that our approach provides a better imaging quality compared to other existing methods. Then, we show the ability to image the whole mouse brain non-invasively through the intact skin and skull during visual stimulation under light anesthesia to validate this new approach. Significant activation was detected along the whole visual pathway, at both single and group levels, with more than 10% of augmentation of the cerebral blood volume (CBV) signal during the visual stimulation compared to baseline. Finally, we assessed resting-state FC in awake head-fixed animals. Several robust and long-ranged FC patterns were identified in both cortical and sub-cortical brain areas, corresponding to functional networks already described in previous fMRI studies. Together, these results show that the multi-array probe is a valuable approach to measure brain-wide hemodynamic activity in mice with an intact skull. Most importantly, its ability to identify robust resting-state networks is paving the way towards a better understanding of the mouse brain functional organization and its breakdown in genetic models of neuropsychiatric diseases.
在过去十年中，功能超声（fUS）在临床前研究中受到越来越多的关注，它提供了一种新工具，可在麻醉和清醒状态下通过单试验检测能力来测量功能连接性（FC）和大脑任务诱发反应。大多数fUS研究依靠二维线性阵列来获取大脑的一个切片。最近在大鼠和小鼠中已证明使用二维矩阵或行列阵列的容积fUS，但由于缺乏灵敏度，需要进行侵入性开颅手术来暴露大脑。在先前的一项研究中，我们提出使用电动线性阵列，从而能够在小鼠中透过颅骨对多个切片进行高灵敏度成像。然而，电动扫描引入的视野与时间分辨率之间的权衡使得无法以足够的容积速率获取全脑静息态FC数据用于静息态FC分析。在此，我们基于一种新开发的多阵列换能器提出了一种新的混合解决方案，该方案经过优化并专门用于小鼠全脑经颅FC研究，该换能器可对整个小鼠大脑进行同时多层切片成像。我们首先证明，与其他现有方法相比，我们的方法具有更好的成像质量。然后，我们展示了在轻度麻醉下视觉刺激期间通过完整皮肤和颅骨对整个小鼠大脑进行无创成像的能力，以验证这种新方法。在单个体和群体水平上，沿着整个视觉通路均检测到显著激活，与基线相比，视觉刺激期间脑血容量（CBV）信号增加超过10%。最后，我们评估了清醒头部固定动物的静息态FC。在皮质和皮质下脑区均识别出几种稳健且远距离的FC模式，与先前功能磁共振成像（fMRI）研究中已描述的功能网络相对应。总之，这些结果表明，多阵列探头是一种在具有完整颅骨的小鼠中测量全脑血流动力学活动的有价值方法。最重要的是，其识别稳健静息态网络的能力为更好地理解小鼠大脑功能组织及其在神经精神疾病遗传模型中的破坏铺平了道路。
