A major challenge of transcranial human brain photoacoustic computed tomography (PACT) is correcting for the acoustic aberration induced by the skull. Here, we present a modified universal back-projection (UBP) method, termed layered UBP (L-UBP), that can de-aberrate the transcranial PA signals by accommodating the skull heterogeneity into conventional UBP. In L-UBP, the acoustic medium is divided into multiple layers: the acoustic coupling fluid layer between the skull and detectors, the skull layer, and the brain tissue layer, which are assigned different acoustic properties. The transmission coefficients and wave conversion are considered at the fluid–skull and skull–tissue interfaces. Simulations of transcranial PACT using L-UBP were conducted to validate the method. Ex vivo experiments with a newly developed three-dimensional PACT system with 1-MHz center frequency demonstrated that L-UBP can substantially improve the image quality compared to conventional UBP.

经颅人脑光声计算机断层扫描（PACT）的主要挑战是纠正颅骨引起的声像差。在这里，我们提出了一种改进的通用反投影（UBP）方法，称为分层UBP（L-UBP），该方法可以通过将颅骨异质性容纳到常规UBP中来消除跨颅PA信号的畸变。在L-UBP中，声学介质分为多层：颅骨和检测器之间的声学​​耦合流体层，颅骨层和脑组织层，它们被分配了不同的声学属性。在流体-头骨和头骨-组织界面处考虑了传输系数和波转换。使用L-UBP进行经颅PACT的模拟以验证该方法。离体 使用新开发的中心频率为1MHz的三维PACT系统进行的实验表明，与传统的UBP相比，L-UBP可以显着改善图像质量。