Joint estimation of a CT-informed skull model and initial pressure distribution in transcranial photoacoustic computed tomography

Transcranial photoacoustic computed tomography (PACT) faces challenges due to skull-induced aberrations in measured pressure data. Although optimization-based image reconstruction methods have been developed to mitigate these aberrations, they require precise knowledge of skull properties that are generally unknown. Parameterized joint reconstruction (JR) methods improve computational tractability by estimating simplified skull models but only partially capture skull heterogeneity, potentially compromising modeling accuracy. Therefore, there remains a need for a reconstruction method that accounts for uncertainties in a fully heterogeneous skull model to enable accurate PACT image reconstruction in humans. In this study, a JR method for 3D transcranial PACT is developed to concurrently estimate the initial pressure distribution and CT-informed heterogeneous viscoelastic properties of the skull. The proposed approach leverages adjunct CT data and a linear relationship between CT voxel values and acoustic properties to parameterize a fully heterogeneous skull model. A gradientfree joint reconstruction method is used to estimate subject-dependent bone property parameters concurrently with the 3D initial pressure distribution. The method was systematically evaluated using realistic, full-scale 3D numerical head phantoms through in-silico studies. Results demonstrate that incorporating CT-informed heterogeneous skull modeling significantly improved image quality compared to model-based methods that assume a homogeneous skull model or a heterogeneous skull model with nominal parameter values. These findings highlight the importance of accurate skull modeling for robust transcranial PACT imaging.