Acoustic impacts of the human skull on transcranial photoacoustic imaging

Posted on 22.02.2021 - 14:32
With balanced high spatial resolution and deep penetration as well as functional sensitivity, photoacoustic tomography (PAT) is promising for human brain imaging. However, due to the strong acoustic attenuation of the human skull (~8 mm thick) and the acoustic impedance mismatch between brain and skull, non-invasive PAT of the human brain with an intact skull remains technically challenging. In this work, we numerically investigated the impacts of the stratified human skull on the photoacoustic wave propagation (i.e., the forward model) and the PAT image reconstruction (i.e., the inverse model). In the forward model, we simulated the detailed photoacoustic wave propagation from a point or line source inside the brain through a digital human skull model. The wave attenuation, refraction, mode conversation, and reverberation within the skull was investigated. We simulated different signal detection strategies by two representative transcranial PAT implementations: photoacoustic computed tomography (PACT) and photoacoustic macroscopy (PAMac). In the inverse model, we reconstructed the transcranial PACT and PAMac images of a point target enclosed by the human skull. Our results demonstrate that the human skull has substantial impacts on transcranial PAT. Transcranial PAMac suffers mainly from wave reverberation within the skull, leading to prolonged signal duration and thus reduced axial resolution. Transcranial PACT is more susceptible to the skull’s acoustic distortion, mode conversion, and reverberation, which collectively lead to increased image artifacts and deteriorated spatial resolution in both lateral and axial dimensions. We also found that compared with the linear transducer array, PACT with the ring-shaped transducer array is superior in reconstructing the accurate target position and more tolerant of the skull’s adverse impacts. Our results indicate that incorporation of the skull’s geometry and acoustic parameters can improve the transcranial PACT image reconstruction with reduced image artifacts. Our results provide a more comprehensive understanding of the acoustic impacts of the human skull on transcranial photoacoustic imaging.

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Liang, Bingyang; Wang, Shaomeng; Shen, Fei; Liu, Qing Huo; Gong, Yubin; Yao, Junjie (2021): Acoustic impacts of the human skull on transcranial photoacoustic imaging. The Optical Society. Collection. https://doi.org/10.6084/m9.figshare.c.5271155.v1
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AUTHORS (6)

Bingyang Liang
Shaomeng Wang
Fei Shen
Qing Huo Liu
Yubin Gong
Junjie Yao

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