With balanced spatial resolution, imaging depth, and functional sensitivity, photoacoustic tomography (PAT) hold great promise for human brain imaging. However, the strong acoustic attenuation and aberration of the human skull (∼8 mm thick) are longstanding technical challenges for PAT of the human brain. In this work, we numerically investigated the impacts of the stratified human skull on photoacoustic wave propagation (i.e., the forward model) and PAT image formation (i.e., the inverse model). We simulated two representative transcranial PAT implementations: photoacoustic computed tomography (PACT) and photoacoustic macroscopy (PAMac). In the forward model, we simulated the detailed photoacoustic wave propagation from a point or line source through a digital human skull. The wave attenuation, refraction, mode conversation, and reverberation were thoroughly investigated. In the inverse model, we reconstructed the transcranial PACT and PAMac images of a point or line target enclosed by the human skull. Our results demonstrate that transcranial PAMac suffers mainly from wave reverberation within the skull, leading to prolonged signal duration and reduced axial resolution. Transcranial PACT is more susceptible to the skull’s acoustic distortion, mode conversion, and reverberation, which collectively lead to strong image artifacts and deteriorated spatial resolutions. We also found that PACT with a ring-shaped transducer array shows more tolerance of the skull’s adverse impacts and can provide more accurate image reconstruction. Our results suggest that incorporating the skull’s geometry and acoustic properties can improve transcranial PAT image reconstruction. We expect that our results have provided a more comprehensive understanding of the acoustic impact of the human skull on transcranial PAT.

中文翻译：

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人颅骨对经颅光声成像的声学影响

具有平衡的空间分辨率，成像深度和功能灵敏度，光声层析成像（PAT）对于人脑成像具有广阔的前景。然而，人类颅骨的强声衰减和像差（约8毫米厚）是人类大脑PAT的长期技术挑战。在这项工作中，我们数值研究了分层的人类头骨对光声波传播（即正向模型）和PAT图像形成（即，逆模型）。我们模拟了两种代表性的经颅PAT实施：光声计算机断层扫描（PACT）和光声宏观检查（PAMac）。在正向模型中，我们模拟了从点或线源通过数字化人类头骨传播的详细光声波。彻底研究了波的衰减，折射，模式转换和混响。在逆模型中，我们重建了人类头骨包围的点或线目标的经颅PACT和PAMac图像。我们的研究结果表明，经颅PAMac主要受颅骨内波混响的影响，从而导致信号持续时间延长和轴向分辨率降低。经颅PACT更容易受到颅骨声学失真，模式转换和混响的影响，这会共同导致强烈的图像伪像和恶化的空间分辨率。我们还发现带有环形换能器阵列的PACT显示出对颅骨不利影响的更大耐受力，并且可以提供更准确的图像重建。我们的结果表明，合并头骨的几何形状和声学特性可以改善经颅PAT图像的重建。我们希望我们的结果对人颅骨对经颅PAT的声学影响提供了更全面的了解。我们的结果表明，合并头骨的几何形状和声学特性可以改善经颅PAT图像的重建。我们希望我们的结果对人颅骨对经颅PAT的声学影响提供了更全面的了解。我们的结果表明，合并头骨的几何形状和声学特性可以改善经颅PAT图像的重建。我们希望我们的结果对人颅骨对经颅PAT的声学影响提供了更全面的了解。