Institute of Electromagnetics and Acoustics, Department of Electronic Science, Xiamen University, Xiamen, P. R. China.
Department of Biomedical Engineering, Duke University, Durham, North Carolina.
J Biophotonics. 2019 Jul;12(7):e201800466. doi: 10.1002/jbio.201800466. Epub 2019 Mar 25.
Non-invasive photoacoustic tomography (PAT) of mouse brains with intact skulls has been a challenge due to the skull's strong acoustic attenuation, aberration, and reverberation, especially in the high-frequency range (>15 MHz). In this paper, we systematically investigated the impacts of the murine skull on the photoacoustic wave propagation and on the PAT image reconstruction. We studied the photoacoustic acoustic wave aberration due to the acoustic impedance mismatch at the skull boundaries and the mode conversion between the longitudinal wave and shear wave. The wave's reverberation within the skull was investigated for both longitudinal and shear modes. In the inverse process, we reconstructed the transcranial photoacoustic computed tomography (PACT) and photoacoustic microscopy (PAM) images of a point target enclosed by the mouse skull, showing the skull's different impacts on both modalities. Finally, we experimentally validated the simulations by imaging an in vitro mouse skull phantom using representative transcranial PAM and PACT systems. The experimental results agreed well with the simulations and confirmed the accuracy of our forward and inverse models. We expect that our results will provide better understanding of the impacts of the murine skull on transcranial photoacoustic brain imaging and pave the ways for future technical improvements.
由于颅骨的强吸声衰减、像差和混响，尤其是在高频范围 (>15 MHz)，对完整颅骨的小鼠大脑进行无创光声断层成像 (PAT) 一直是一个挑战。在本文中，我们系统地研究了鼠颅骨对光声波传播和 PAT 图像重建的影响。我们研究了由于颅骨边界处的声阻抗不匹配以及纵波和横波之间的模式转换而导致的光声波像差。还研究了颅骨内纵波和横波的混响。在逆过程中，我们重建了包含在小鼠颅骨内的点目标的颅外光声计算机断层成像 (PACT) 和光声显微镜 (PAM) 图像，显示了颅骨对两种模态的不同影响。最后，我们使用代表性的颅外 PAM 和 PACT 系统对体外鼠颅骨模型进行了实验验证，实验结果与模拟结果吻合良好，证实了我们的正、逆模型的准确性。我们期望我们的研究结果将更好地理解鼠颅骨对颅外光声脑成像的影响，并为未来的技术改进铺平道路。
