Four-dimensional imaging using a one-dimensional transducer array combining photoacoustic signals with ultrasonic timecoding
Phys. Rev. Applied 26, 034037 – Published 17 September, 2026
DOI: https://doi.org/10.1103/tkjq-xb7z
Abstract
Photoacoustic imaging (PAI) enables high optical contrast at ultrasonic imaging depths; however, real-time volumetric imaging remains challenging due to the complexity of two-dimensional arrays or the slow mechanical scanning of one-dimensional arrays. In this study, we propose a strategy for scan-free four-dimensional imaging that combines photoacoustic signals with ultrasonic timecoding (PAUTC). For targets possessing both optical absorption and acoustic impedance contrast, we utilize a 1D array to acquire volumetric images in a single data acquisition. By synchronizing pulsed optical excitation with orthogonal ultrasound emissions, elevational spatial information is encoded into temporal delays of scattered ultrasound and subsequently combined with the photoacoustic signals. This encoding strategy enables single-shot 3D reconstruction, without the need for 1D array scanning or complex 2D array detection. We theoretically demonstrate that the spatial resolution of the PAUTC method is mainly determined by the effective bandwidth of the 1D array and provide an analytic expression for the resolution. The performance of the PAUTC method is validated through simulations and experiments. PAUTC restores elevational clarity and achieves volumetric imaging of complex 3D structures with optical and acoustic impedance contrast properties, whereas conventional photoacoustic tomography fails due to the lack of elevational resolution missing in a 1D array. Phantom experiments validate the effectiveness of PAUTC in reconstructing complex 3D structures. Furthermore, real-time 4D imaging is demonstrated by quantitatively tracking a moving microbead at a frame rate of 10 Hz. With the efficient continuous volumetric imaging capability, PAUTC might hold promise for applications in hemodynamic monitoring, fluid dynamics characterization, tracking exogenous dual-contrast agents, guiding interventional metallic needles, and superresolution imaging.
